<<

PIONEER EXTENDED MISSIONS PLAN

Document No. PC-1001

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

AMES RESEARCH CENTER

MOFFETT FIELD, 94035

MAY 20,1981

REVISION 1 NOVEMBER 30,1982

REVISION 2 JUNE 15, 1990 DISTRIBUTION NASA HEADQUARTERS

Code SL Code SF

W. T. Huntress, Jr. J. W. Dyer H. C. Brinton C. L. Jackson F. Carr J. Sperans A. Merwarth D. Okerson Code SFP

Code SS R. 0. Fimmel R. W. Jackson L. J. Demas L. E. Lasher W. V. Jones D. W. Lozier J. C. Ling J. R. Phillips T. W. Perry M.A. Smith M. N. Wirth

CodeD

D. L. Compton K. A. Hessenius

CodeS

J. C. Sharp P. Dyal JET PROPULSION LABORATORY A. Berman D. Bray E. Burke N. Moninger R. Ryan L. Shaw BENDIX FIELD ENGINEERING CORPQRATION

R. Campo R. Chavez K. Jednorozec B. Karas R.Mann T.Quinn T. Young SAN JOSE STATE UNNERSITY FOUNDATION

L. Colin ~-- .;

ii DISIRffiUTION- INVESTIGATORS

PIONEER 6-9 PIONEER ORBITER

John Mihalov Guest·lnyesti ~tors (ContcD

PIONEER 10/11 R. E. Daniell M. Dryer John D. Anderson L. Elson Aaron Barnes E. G. Fontheim R. Walker Fillius J. L. Fox D. Intriligator J. C. Gerard· Darrell L. Judge E. W. Greenstadt Frank B. McDonald R. Greeley John A. Simpson M. Harel Edward J. Smith W. Hoegy James A. Van Allen S. Kumar S. S. Limaye. M. B. McElroy R. Meier Principal Investigators P. Morgan P.MougUUs-Mark Aaron Barnes L. J. Paxton Larry H. Brace R E. Revercomb· Paul A. Ooutier J. M. Rodriguez Ray Klebesadel P. Rodriguez Arvydas Kliore B. Schizgal William C. Knudsen N. Sheeley H. B. Niemann J. A. Slavin Gordon H. Pettengill C. W. Smith Christopher T. Russell D. Smith A. Ian F. Stewart P. G. Steffes Robert J. Strangeway D. L. Turcotte F. W. Taylor W. T. Vestrand Larry D. Travis D. R. Wimams D. W'mske Guest lnyestiptors R. Wolff R~Woo J. M. Ajello A. Young J. Anderson Y. Yung K. A. Anderson J. Appleby Interdisciplinazy Scientists G. Balmino W. J. Borucki Siegfried J. Bauer S. W. Bougher Donald M. Hunten C. Bowin S. R Brecht Andrew Nagy D. L. Carpenter · James.Pollack R. T. Dancy Nelson Spencer P. E. Oark

iii NATIONAL AERONAUTICS AND SPACE ADMINISTRATION AMES RESEARCH CENTER . MOFFETT FIELD, CALIFORNIA 94035 PIONEER EXTENDED MISSIONS PLAN MAY 20,1981 REVISION 1 NOVEMBER 30, 1982 REVISION 2 JUNE 15, 1990 APPROVED:

W. Vernon Jones /ll Program Scientist ~~ Lawrence Colin bct11~~ Scientist Pioneer Venus Pro~ Scientist ·~~-rl ~Ann C. Merwarth ~21!t1"an!# (Acnng) · Pioneer Project Manager PJ.:ogram Manager, Headquarters Chief, Pioneer Missions Office

~~W~_.W.Dyer F A. CaiT e;uty Chief, Spa~;:: Division eputy Director, S<'lar System Exploration Division, Headquarters

Wesley ·• Huntress, Director, . Exploration Division, Headquarters <;;;;; Z?tb /~ Dale L. Compton . Director of Ames Research Center

iy NATIONALAERONAUTICSANDSPACEAD~STRATION

AMES RESEARCH CENTER

MOFFETT FIELD, CALIFORNIA

PIONEER EXTENDED MISSIONS PLAN

PIONEER DOCUMENT PC-1001

MAY 20,1981

REVISION 1 NOVEMBER 30, 1982

REVISION 2 JUNE 15, 1990

This document is a part of the Documentation which is controlled by the Pioneer Project Office, Ames Research Center, Moffett Field, California. As such it is requested that no copies be made by any individual of any pages within.

To be placed on the distribution list for additional official' versions of this document, address your request to:

Pioneer Project Manager NASNAmes Research Center Mail Stop 244-14 Moffett Field, California 94035

v NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

AMES RESEARCH CENTER

MOFFETT FIELD, CALIFORNIA 94035

DOCUMENT NO. PC-1001

PIONEER EXTENDED MISSIONS PLAN

TABLE OF CONTENTS

1. SCOPE ...... 1

2. BACKGROUND AND ORIGINAL MISSION OBJECTIVES ...... 2 2.1 Pioneers 6, 7, 8 and 9 ...... 2 2.2 Pioneers 10 and 11 ...... 2 2.3 Pioneer Venus (Pioneers 12 and 13) ...... 3 2.3.1 Pioneer Venus Orbiter (Pioneer 12) ...... 3 2.3.2 (Pioneer 13) ...... 4

3. MISSION OBJECTIVES FOR EXTENDED MISSIONS ...... 5 3.1 Pioneers 6, 7, 8 and 9 ...... 5 3.2 Pioneers 10 and 11 ...... 5 3.3 Pioneer Venus Orbiter (Pioneer 12) ...... 6

4. TRAJECTORIES/MISSION PROFILES ...... 9 4.1 Pioneers 6, 7, 8 and 9 ...... 9 4.2 Pioneers 10 and 11 ...... 9 4.3 Pioneer Venus Orbiter (Pioneer 12) ...... 10

5. ...... 11 5.1 Pioneers 6, 7, 8 and 9 ...... 11 5.1.1 Systems Description ...... 11 5.1.2 Systems Status ...... 11 5.2 Pioneers 10 and 11 ...... ; ...... 12 5.2.1 Systems Description ...... 12 5.2.2 Systems Status ...... 13 5.3 Pioneer Venus Orbiter (Pioneer 12) ...... 13 5.3.1 Systems Description ...... 13 5.3.2 Systems Status ...... 14

6. SCIENTIFIC INVESTIGATIONS ...... 15 6.1 Pioneers 6, 7, and 8 ...... 15 6.1.1 Single-Axis Fluxgate (GSFC) ...... 15

vi TABLE OF CONTENTS (CONTD) ~ Page

6.1.2 Faraday-Cup Probe (MIT) ...... 15 6.1.3 Solar Plasma Detector (ARC) ...... 16 6.1.4 Telescope (UC) ...... 17 6.1.5 Electric Field Detector (TRW) ...... 17 6.2 Pioneers 10 and 11 ...... 18 6.2.1 Helium Vector Magnetometer (JPUHVM) Instrument ...... 18 6.2.2 Plasma Analyzer (ARC/PA) Instrument ...•...... 18 6.2.3 Charged Particle (UC/CPI) Instrument ...... , .... . 19 6.2.4 Geiger Tube Telescope (UI/GTT} Instrument...... 19 6.2.5 Cosmic Ray Telescope (GSFC/CRT) Instrument ...... 20 6.2.6 Trapped Detector (UCSD/TRD) Instrument ...... 21 6.2.7 Ultraviolet Photometer (USC/UV) Instrument ...... •...... 21 6.2.8 Imaging Photopolarimeter (UA/IPP) Instrument ...... 22 6.2.9 Detector (LaRC/MD} Instrument ...... 22 6.2.10 Radiometric Science ...... 23 6.2.10.1 Search for Undetected Planets of the Solar System ...... ·...... 23 6.2.10.2 Detection of Gravity Waves ...... 23 6.3 Pioneer Venus Orbiter (Pioneer 12) ...... 23 6.3.1 Radar Mapper (MIT/ORAD) Instrument ...... : ...... 23 6.3.2 Neutral Mass Spectrometer (GSFC/ONMS) Instrument ...... 24 6.3.3 Retarding Potential Analyzer (LPARL/ORPA) Instrument ...... 24 6.3.4 Ion Mass Spectrometer (GSFC/OIMS) Instrument ...... 25 6.3.5 Electron Temperature Probe (GSFC/OETP) Instrument...... 26 6.3.6 Ultraviolet Spectrometer (UC/OUVS) Instrument ...... 26 a 6.3.7 Photopolarimeter (GISS/OCPP) Instrument ...... 27 6.3.8 Magnetometer (UCLNOMAG) Instrument ...... 28 6.3.9 Plasma Analyzer (ARC/OP A) Instrument ...... 28 6.3.10 Electric Field Detector (UCLAJOEFD) Instrument ...... 29 6.3.11 Gamma Ray Burst Detector (LASL/OGBD) InstrumenL ...... 30 6.3.12 Groundbased ( Science) Investigators· ...... 30 6.3.12.1 Pioneer Venus. Orbiter Radio Studies...... 30 6.3.12.2 Pioneer Venus Orbiter Doppler Radio Tracking .. , ...... 31 6.3.12.3 Atmospheric Drag Experiment (LRC/OAD) ...... 31 6.3.13 Interdisciplinary ScieDtists ...... -...... 32 6.3.14 Guest Investigator Program ...... 32

7.0 OPEAATIONS ...... 34' 7.1 Guidelines ...... 34 7.1.1 Pioneers 6-8 ...... - ...... ~ . 34 7.1.2 Pioneer 10 and 11 ...... - ...... 34 7.1.3 Pioneer Venus Orbiter (Pioneer 12) ...... 34 7.2 Planning and Development...... · ...... 35 7.3 Flight Operations ...... 36 7.4 Data Processing and Distribution ...... • 37 7.4.1 Pioneers 6-8 ...... 37 7.4.2 Pioneers-10 and 11 ...... 37 7.4.3 Pioneer Venus Orbiter (Pioneer 12) ...... 37 ~

vii TABLE OF CONTENTS (CONTD)

7.5 Scientific Data Analyses and Reporting ...... 37 7.5.1 Data Analysis Activities ...... 37 7~5.2 Data Archiving ...... 38 8. MANAGEMENT ...... : ...... 39 8.1 General ...... ·...... 39 8.2 Scientific Policy ...... 39 8.3 Missions Management ...... 39 8.4 Project Control...... 40

9. RESOURCES ...... 42 9.1 Tracking and Data Acquisition ...... 42 9.2 Ground Data System ...... 42 9.2.1 NASCOM ...... 43 9.2.2 l1oneer Mission Computer Center ...... 43 9.2.3 Pioneer Mission Operations Center ...... 43 9.2.4 Navigation Data System ...... 43 9.2.5 Unified Abstract Data System (UADS) ...... 44 9.3 Manpower ...... 44 9.3.1 Management and Technical Direction ...... 44 9.3.2 Flight Operations and Data Processing and Distribution ...... 44 9.3.3 Support ...... 44 9.3.3.1 DSN Scheduling and Coordination ...... 44 9.3.3.2 Nayiga~i<;>n Support: ...... 44 9.3.4 Scientific Investigators ...... 44 9.3.4.1 Pioneers 6, 7, and 8 ...... 45 9.3.4.2 Pioneers 10 and 11 ...... 45 9.3.4.3 Pioneer Venus Orbiter (Pioneer 12) ...... 45 9.4 Funding ...... 45

TABLES

4.1-1 PIONEER 6-9 ORBITAL CHARACTERISTICS ...... 9

4.2-1 HELIOCENTRIC RADIUS OF PIONEER 10 AND 11, AU ...... 10

6-1 ACfiVE PRINCIPAL INVESTIGATORS ...... 33

9.3-1 MANPOWER, AMES RESEARCH CENTER ...... 46

viii ILLUSTRATIONS

FIGURE 2-1 PIONEER MISSION PHASES

FIGURE 4.1-1 HELIOCENTRIC PLOT OF PIONEERS 6-9 IN ORBIT

FIGURE 4.2-1 SOLAR SYSTEM OUTBOUND SPACECRAFT

FIGURE 4.3-1 . PIONEER VENUS ORBITER PERIAPSIS ALTITUDE PROFILE: 1980-1992

FIGURE 4.3-2 ORBITAL DYNAMICS OF PIONEER VENUS ORBITER: 1980-1992

FIGURE 5.1-1 PIONEER 6-9 SPACECRAFT

FIGURE 5.2-1 PIONEER 10 AND 11 SPACECRAFT

FIGURE 5.3-1 PIONEER VENUS ORBITER SPACECRAFT

FIGURE 8.3-1 PIONEER FUNCTIONAL ORGANIZATION

FIGURE 9.2-1 PIONEER GROUND DATA SYSTEM CONFIGURATION

FIGURE 9.2.2-1 COMPUTER CONFIGURATION FOR PIONEER MISSION OPERATIONS

APPENDICES

Appendix A: · Pioneer Venus Orbiter Guest Investigators

AppendixB: Pioneer Missions Tracking Requirements and Science Objectives

ix LIST OF ABBREVIATIONS

A angstrom(s) ac alternating current A-hr Ampere-hour(s) AMU Atomic Mass Units ARC Ames Research Center AU (s) bps bits per second em centimeter(s) CMD command de direct current deg or 0 degree(s) DSN Deep e electron E energy E/q energy per unit charge EDR Experimenter Data Record EM Extended Mission eV electron volt(s) F fahrenheit ft foot, feet GISS Goddard Institute for Space Studies gm gram(s) GSFC Goddard Space Flight Center HSDL high speed data line Hz Hertz (cycles/second) IDR Intermediate Data Record in. or" inch(es) IR infrared JPL Jet Propulsion Laboratory K Kelvin kbits thousand bits keV thousand electron volts kHz kilohertz km kilometer(s) kV kilovolts LaRC LASL Los Alamos Scientific Laboratory lb pound(s) m meter(s) MDR Master Data Record MeV million electron volts MHz megahertz min or' minute(s) MIT Massachusetts Institute of Technology mm millimeter(s) mr milliradian( s) msormsec millisecond(s) N north NASCOM NASA Communications (Network) NASA National Aeronautics and Space Administration NCS Network Control System

X LIST OF ABBREVFATIONS. (CONTD)

Ni~Cad Nicket-Cadmium nm: nanometer(s) NOAA National! Oceanic and1Atmospheric Achnihistration. NSSDC National Space Science Data Center nT nanotesla(s) NTI Nishikawa-'Fakimizawa-Tago ODP· OrThit Determination Program OMOP Orbital Mission Opet:ations Pl'annihg (Committee) oss: Office·

xi Document No. PC-1001 Original Issue: 20 May 1981 Revision:(1): 11/30/82 (2): 06/15/90 1. SCOPE

This document constitutes the plan for the Pioneer 6-12 extended missions to further explore the immediate environment of Venus, the solar interplanetary environment, its outer regions and beyond. All seven of the Pioneer spacecraft have completed their primary missions. This plan is for the acquisition and scientific analyses of data to add to humanity's understanding of the , its interaction with Venus, and its evolution and interaction with the as it expands outward from the . The acquisition and analysis of data for adding to the knowledge and understanding of the physical properties of comets is also included. This plan summarizes the objec-tives being pursued, the scientific investigations to be performed in pursuit of these objectives, and the operations and management plans. A description of the resources allocated to implement this plan and a detailed justification for allocation of DSN resources are also included.

1 Document No. PC-1001 Originallssue: 20 May 1981 Revision:(l): 11/30/82 (2): 06/15/90 2. BACKGROUND AND ORIGINAL MISSION OBJECTIVES

The following sections outline the original mission objectives, formal mission phases, and present status of the Pioneer series of spacecraft. Figure 2-1 illustrates the timelines of mission phases for the spacecraft.

2.1 Pioneers 6, 7, 8 and 9

The primary nlission objectives for Pioneers 6, 7, 8 and 9 were to conc;Iuct scientific observations of interplanetary phenomena beyond the influence of . Specifically, the on-board scientific instruments were to measure the characteristics of interplanetary , plasma, magnetic field, electric , and cosmic rays. These objectives were achieved by all four spacecraft during their 6-month primary missi'ons. The launch dates were December 16, 1965, August 17, 1966, December 13, 1967 and November 8, 1968 for Pioneers 6, 7, 8 and 9, respectively. The spacecraft continue to travel in their heliocentric orbits at approximately 1 AU radius, and, except for Pioneer 9, some instru-ments continue to operate on each spacecraft. Radio transceivers on the three remaining spacecraft are still functioning, and the spacecraft continue to transmit and provide data when tracking time is available. The Pioneer 6 through 9 spacecraft were.designed and constructed in the early 1960's by STL, now TRW, at Redondo Beach, California, for NASA Ames Research Center.

2.2 Pioneers 10 and 11

The general mission objectives of Pioneers 10 and 11 included: exploring the beyond the orbit of ; investigating the nature of the belt and assessing its hazards to outer planet missions; exploring the environment of ; finding the extent .of the and describing the interstellar medium; and, if Pioneer 10 attained its Jovian scientific objectives, exploring the Saturnian environment (). The formal Primary Mission for Pioneer 10 was completed following its Jupiter encounter on December 3, 1973; since then it has pursued the interplanetary objectives of its Heliospheric Mission. Pioneer 11 was retargeted for flyby in 1974, although its Primary Mission ended with Jupiter encounter on December 9, 1974. Until its encounter with Saturn on September 1, 1979 it was in a "Saturn Extension" mission phase, with the Pioneer 11 Heliospheric Mission commencing thereafter. Since September 1979, the two spacecraft have proceeded in generally opposite directions toward the solar system boundary, and continue to transmit data on interplanetary phenomena and properties of galactic and extragalactic cosmic rays. The absence of detection of the heliosphere boundary by either Pioneer 10 or 11 would appear to indicate that the boundary of our heliosphere is more extensive than previously envisioned.

Pioneers 10 and 11 were designed and built by TRW Systems Group, Redondo Beach, California, for Ames Research Center in the early 1970's. Launch of Pioneer 10 occurred on March 2, 1972, slightly under two'and a half years after the spacecraft contract award. Pioneer 11 was launched on AprilS, 1973.

2 Document No. PC-1001 Originallssue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 2.3 Pioneer Venus (Pioneers 12 and 13)

2.3.1 Pioneer Venus Orbiter (Pioneer 12)

The numerous scientific objectives of Pioneer 12's primary mission fell into the following general categories: composition and structure of the Venus atmos-phere at all levels; composition and structure of ; atmospheric thermal balance and temperature structure; dynamics of atmospheric circulation, flow, and convection; iono-spheric composition and solar wind interaction; survey of the solar wind at times of comet passage; and properties of the planet's surface and interior.

In <~:ddition to the preceding planetary scientific·objectives, systematic observations of several comets were made using the OUVS (Orbiter Ultra-Violet Spectrometer) instrument between April, 1984 and May, 1987. The comets observed and dates of observations were as follows:

Comet Observation Dates

Encke Apri113 to Apri116, 1984

Giacobini-Zinner September 8 to September 15, 1985

Halley December 27, 1985 to March 9, 1986

Wilson March 13 to May 2, 1987 ~ NTT April 8, 1987

McNaught November 19 to November 24, 1987

The scientific objectives of these comet observations with the OUVS were:

(a) Determine the cometary water evolution rate and its variation

(b) . Determine carbon/oxygen/hydrogen ratios and their variation

(c) Search for evidence of rotation of the comet nucleus

(d) Image the Lyman-Alpha coma

The Pioneer Venus Orbiter mission began at orbit insertion on December 4, 1978. The primary mission was designated to last for one Venus Sidereal day (243 days) from orbit insertion to August 4, 1979. Subsequently, the mission of the Pioneer Venus Orbiter was redefined into three phases detailed in Table 2.3.1-1.

3 DocumentNo.. PC-1001; Originat'Issue: 20 May 1981. Revision:(!): 11/30/82:·. (2): 06/15/90' TABLE 2.3.1-1. PVO MISSION PHASES,

Period~

I From orbit:insertion (!December 4, 1978) to mid 1980. (Low Altitude) Periapsi~ altitude controlledto lie between 140 km, and;250.km.

Il Mid. 19 80 to .mid 199 L Periapsis altitude not (High Altitude) controlled. Altitude of periapsis rose to a maximum of2309 km on July 4, 1986. Phase II will be. arbitrarily defined to end when periapsis.altitude falls to 1000 km around mid 1991..

Ill Mid· 1991 to re-entry arourid.August/September, (Re-Entcy). 1992. Control of periapsis altitude resumed, to the extent remaining propellant permits, during· final: months of the mission.

The Pioneer Venus Orbiter has completed all of the detailed objectives of1 Phase I! and· is now in Phase ll providing new data from hitherto inaccessible regions in the Venus/solar wind interactive region. New data on solar: cycle effects. on, the· structure of: the Venus middle and upper atmosphere and the· is also being acquired;

The Pioneer Venus Orbiter was designed• and· assembled by the Hugnes.Aircraft Company, ELSegundo, California, in.the mid.:. 1970'-s for Ames Research.€enter; The spacecraft was launched on May 20; 1978. ·

23.2' Pioneer Venus Multiprobe (Pioneer ·1:3)..

The objectives of the Multi probe were to investigate the composition. and' dynamics of Venus' atmosphere by means of instruments carried to the surface at;four! widely separated. locations on the planet. Also, the physical. parameters. of the· cloud: particles.and.the radiative heat transfer were measured as functions of altitude. The: Multiprobe Bus carried.instruments to report neutral' and ion.c.ompositions.of the: atmosphere at altitudes below the Orbiter's closest approach, and· above the Probes',' activation.

The Multiprobe part of the Pioneer Venus. Mission was completed:J)ecember. 9; 1978. . Document No. PC-1 00 I Original Issue : 20 May 1981 Revision:(l): 11/30/82 (2): 06/15/90 3. MISSION OBJECTIVES FOR EXTENDED MISSIONS Following are objectives of the Extended Flight Missions for the Pioneers 6, 7, 8, 9, 10, 11 and 12 spacecraft:

3.1 Pioneers 6, 7, 8 and 9 Pioneers 6-9 have operated for 21 to 24 years in solar orbit, and except for Pioneer 9, appear capable for several more years of continued service. Objectives of these oldest operating Pioneer Spacecraft are: (a) To provide measurements of characteristics of the solar wind and electric field when aligned with other selected solar wind monitoring instruments.

(b) To observe the ultimate longevity and failure modes of the aging flight components, such as solar panels, sun sensors, data handling systems, radio transmitters, etc. (Pioneer 6-9 were launched in 1965-1968).

These objectives are secondary to those given below for Pioneers 10-12.

3.2 Pioneers 10 and 11 Pioneers 10 and 11 continue in pursuit of an originally designated prime mission objective of the Project: to explore the outer regions of the Solar System; to define the Solar System's interaction with its external environment; to determine the spatial distribution and flow patterns of solar and galactic cosmic rays; to find the boundary of the heliosphere; and to observe the interstellar medium. Pioneers 10 and 11 have so far shown the heliospheric boundary with the interstellar medium to be much more distant than previously expected. Pioneer 10's power and communi­ cations effectiveness are now projected to 60 AU, more than twice the pre-launch estimate. Modulation of cosmic rays and detailed measurements of the solar wind indicate that the boundary of our heliosphere may be approximately 50-100 AU from the Sun. Pioneer 11 's excursion to Saturn and faster declining power supply may limit its ability to operate to about 40 AU.

Inference as to the extent of the heliosphere is sought by monitoring the solar modulation of cosmic ray intensities and ultraviolet scans of changing atomic interactions with sunlight which result from incursion of extra-solar particles into the heliosphere, and by direct measurement of densities and energy spectra of electrons and ions as functions of regression from the Sun. Pioneers 10 and 11 will continue the characterization of the solar wind and its interactions (or lack of responsiveness) with planets and their magnetosheaths, of the gradient in cosmic particle density with distance from the Sun, and (from Pioneer 11) of the gradient of dust particle density with distance from the Sun.

The extreme range of Pioneer 10 from Earth will make possible sensitive searches for gravity waves and for a possible undiscovered planet.

Pioneers 10 and 11, together with the two Voyagers and other spacecraft closer to the Sun, provide a widely space-diversified set of observations with which to better understand the coronal expansion process. Pioneer 10 passed 48.1 AU in January, 1990 close to the downwind direction from the Sun (anti-solar apex direction)

5 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 relative to its interstellar motion, and was receding from the Sun at about 2.7 AU/year.

Pioneer 11 was 29.8 AU from the Sun in January, 1990, and was proceeding outward at 2.48 AU/year within the quadrant of the interstellar upwind direction (solar apex direction) near the ecliptic plane. Voyagers I and II are dispersed on either side of Pioneer ll's escape trajec-tory, with Voyager I very near the interstellar wind longitude but 40° above it in latitude.

For many years to come, these four escaping spacecraft will be mankind's only probes beyond Jupiter.

3.3 Pioneer Venus Orbiter (Pioneer 12)

Objectives of data collection of the Pioneer Venus Orbiter take advantage of the changing orientation of the orbit relative to Venus, the for evaluating solar interactions with Venus' atmosphere relative to the solar cycle, and future possibilities for contributing to other missions. The spacecraft will remain in orbit through a complete solar cycle, after which it will approach, and enter, the ' southern hemisphere in late 1992. Specific objectives are to provide:

(a) In-situ sampling of the solar wind and Venusian ionosphere and their - interactions through a range of intermediate altitudes (0.1 through 0.4 planet radii) at low latitudes.

The volume containing the in-situ sampling includes the nose and elongated tail of the nonmagnetic planet's disturbance in the solar wind, and will become accessible through gradual rotation of the orbit's line of apsides through the ecliptic parallel due to solar gravitation. Hypotheses on thermal and chemical interactions between the solar wind and both the ionosphere and the neutral atmosphere of Venus being developed from analyses of present data from the Orbiter can be con-firmed or greatly strengthened by the anticipated additional data. Correlation with data taken by Russian spacecraft near sub-solar and wake regions around Mars will be attempted. Also, modeling of Venus' interaction with the solar wind is expected to provide important insights needed for interpretation of corresponding in-situ sampling from any future cometary flyby~.

(b) Measurement of the vertical structure of the day-side and night-side ionosphere and neutral atmosphere through an entire solar cycle.

By means of radio occultation the structure of the electron density in the ionosphere can be measured from the ionopause to well below the main peak, and the thermal structure of the upper neutral atmosphere can be probed from about 90 to 40 km altitude. Since this technique is independent of periapsis altitude, measurements can be made through the entire declining portion of Solar Cycle 21 (1978 to 1986) and the advancing portion of Solar Cycle 22 (1987 to 1992). This makes possible the study of the effects of the changingi solar input on the properties of the day and night ionospheric and mesospheric structure, as well as the thermal structure of the lower mesosphere. ~

6 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90

(c) Extreme refinement in measurement or delimitation of low order gravity field parameters. Radio science studies of Venus afforded by the Orbiter in its first 2 years were most useful in examining small scale gravity variations for correlation with topography, whereas the frequent maneuvers and low altitude passes with strong atmospheric drag have postponed the opportunity for sensitive evaluation of the gross Venus gravitational profile. The higher altitude (drag-free) periapsides of future orbits, combined with long intervals between reorientation maneu-vers now provide for optimum analyses. The three synodic periods of the Extended Mission will result in a strong array of directional sensitivities within the total data set.

(d) Long term study of Venus' cloud morphology to determine to what extent major cloud structures vary in periods ranging from hundreds of days to several years as suggested by series of ground observations taken in the 1960's and in 1972.

While still limited to the same approximately 80 Earth day intervals in each Venus year, observations from the Orbiter will provide close-up refinements in long term variations, both in short time detail and in local spatial detail, of changes. An example of particular interest is the comparison of the bright polar clouds which are believed to change over very long intervals with an apparent independence between those North and South features.

(e) Direct contributions to other activities, including: (1) Cloud motion data for the Vega.1985 (French/USSR) balloon

(2) Cooperative measurements with 13/14 in 1982, and with future Venera missions through 1991

(3) Precise gravitational data for the flight of the spacecraft, and

(4) Solar wind monitoring for space diversity studies, especially including definition of the Halley Comet's environment near the Sun

(f) Increased statistics on the characteristics and source(s) of gamma ray bursts.

First-ever identification based upon Pioneer Venus and related data from other spacecraft shows the powerful bursts originating from outside the Milky Way Galaxy in the Large Magellanic Cloud. The Pioneer Venus __ Orbiter continues as the only long baseline source for gamma ray data.

(g) Contributions to studies of the solar coronal expansion at low solar latitude as a function of the solar cycle, using Pioneer Venus' S- and X-band signals.

7 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 (h) Participation in studies of X-ray sources in solar flares with ISEE through correlated observations with partial solar .

(i) Contributions to the astronomy community by timing soft gamma bursters that are of sufficiently high energy to permit detection by the OGBD. Soft gamma bursters have been observed by ICE, and 12, and Prognoz 7. The frequencies of the radiation from the bursters are between x~rays and Gamma-rays and cannot normally be detected by the OGBD. However, of 111 events that have been detected, three were at sufficiently high energy to permit timing by the OGBD. The PVO results indicated that the three bursts were from the same source, and further supplied data to permit an accurate determination of the direction to the source. However, the direction is to a populated region of the celestial sphere, and a specific source has not yet been uniquely identified. G) Detection and measurement of disturbances in the solar wind due to upstream passage of the asteroid Oljato or material in the orbit of the asteroid co-orbiting with it.

Disturbances in the solar wind were observed in 1980, 1983 and 1986 when Venus was downstream from the perihelion passage of the asteroid Oljato, which was nearby, but not yet in conjunction with Venus at the time of the observed disturbances. It has been postulated that material in the orbit of Oljato and co-orbiting with the asteroid was contributing mass to the solar wind to create the observed disturbances. PVO in its orbit about ~ Venus has been in a position to observe this portion of Oljato's orbit thirteen , times, but only in the three of these instances was Oljato nearby. No disturbances in the solar wind were detected during the other ten opportunities.

(k) Participation in the observation of effects of disturbances in the solar wind on the aurora of Jupiter.

Instrumentation on board the IUE spacecraft permits observation of the Jovian aurora, but these observations are not made continuously. In mid- 1986 Venus was downstream from Jupiter and the solar wind was monitored, in near real time, for purposes of alerting the IUE team if a major disturbance was detected. The IUE instruments could then be :lirected to the Jovian auroral experiment to await the arrival of the disturbance at Jupiter some 9 to 12 days later. During the course of PVO participation in this experiment a large disturbance was observed and the IUE team was alerted; however, tracking station time was not available to complete the experiment. It is planned to repeat PVO participation in this experiment during the next time interval when Venus passes through a down stream position from Jupiter.

8 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 4. TRAJECTORIES/MISSION PROFILES 4.1 Pioneers 6, 7, 8 and 9 The Pioneer 6 through 9 spacecraftwere launched December 16, 1965, August 17, 1966, December 13, 1967 and November 8, 1968, respec-tively. All four orbit the Sun near Earth's orbit, but slowly cycle through wide variations in relative ecliptic longitude. Table 4.1-1 gives orbital characteristics, and relative longitudinal positions as of January 1, 1990 are shown in Figure 4.1-1.

TABLE 4.1-1. PIONEER 6-9 ORBITAL CHARACTERISTICS Pioneer Q I .8. 2

Aphelion, AU 0.986 1.125 1.089 0.990 Perihelion, AU 0.833 1.01 0.992 0.754

\ Period, days 316.9 403.2 387.6 297.4

Inclination, deg. 0.1840 .077 0.057 0.089 4.2 Pioneers 10 and 11

The Pioneer 10 and 11 spacecraft, launched on March 2, 1972 and April 5, 1973 respectively, are now proceeding toward the solar system boundary in nearly opposite directions. Pioneer 10 is moving outward at about 2.7 AU per year in a direction generally away from the center of our galaxy in the general direction of the constellation and roughly opposite the direction of our basic solar motion with respect to nearby stars; in January, 1990 it was about 48.1 AU from the Sun. (See Table 4.2-1.)

Pioneer 11 is departing from the Solar System at about 2.48 AU per year toward the center of our galaxy in the general direction of the constellation Sagittarius; in January, 1990, it was about 29.8 AU from the Sun. (See Table 4-2.1.)

Figure 4.2-1 shows the trajectories of the two spacecraft, along with and 2, and has annotated on it the velocities (VB), ecliptic latitudes and longitudes of the escape asymptotes. Also shown are the solar apex (direction and speed of solar motion), incoming interstellar wind direction, and direction toward the galactic center. Table 4.2-1 gives heliocentric radii of Pioneers 10 and 11 for 1 January of the years (1989-1999).

9 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(l): 11/30/82 (2): 06/15/90

TABLE 4.2-1. HELIOCENTRIC RADIDS OF PIONEER 10/11, AU (JAN 1.)

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999

Pioneer 10 45.4 48.1 50.7 53.4 56.0 58.6 61.2 63.8 '66.5 69.1 71.7

Pioneer 11 27.3 29.8 32.2 34.8 37.3 39·.8 42.2 44.7 47.2 49.6 52.1

4.3 Pioneer Venus Orbiter (Pioneer 12)

The Pioneer Venus Orbiter was launched in May 1978, and arrived at Venus on December 4, 1978. The 24-hour elliptical orbit about Venus is highly inclined and was originally maneuvered to a minimum periapsis altitude of 142 km.. Prior to July 1980, the tendency of periapsis to rise out of the atmosphere had been counteracted by weekly maneuvers at apoapsis, maintaining pe:riapsis below 253 km. Since then, in Phase II, orbit adjustments. have been abandoned to conserve fuel for . Periapsis rose due to solar gravitation, initially at a rate of 560 km per Earth year. The latitude of periapsis has been decreasing from the . 0riginall1° Nand reached the equator in 1986. The periapsis rise rate slowed and then reversed reaching a maximum altitude of 2309 km on July 4, 1986. The Orbiter wilt re-enter the:atmosphere in 1992 .at approximately 10° S. Thus, the sector sampled from the solar wind interaction volume along the Sun-Venus axis changes to improve definition of both the and tail regions.

Figure 4.3-1 shows the altitudinal variations ofperiapsis through 1992. Figure 4.3:..2 shows how the orbit changes position relative to· the ecliptic with representative orbits from 1980, 19·86, and 1992 shown. Beginning in 1991, opportunity for improved observations of conditions in the southern hemisphere, both of the upper atmosphere and some of the undefined topography, will be available. The final low altitude flight interval is planned as "Phase ill."

10 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 5. SPACECRAFT 5.1 Pioneers 6, 7, 8 and 9

5 .1.1 Systems Description The Pioneer 6 through 9 spacecraft series, designed and built in the early 1960's by STL (now TRW) at Redondo Beach, California, are basically right circular cylinders of approximately 35 in. length and 37.3 in. diameter (see Figure 5.1-1). A linear array communications antenna extends 52 inches from one end, and the Stanford antenna, serving two separate coherent phase-locked receivers, extends 45 in. from the other. Three radial booms, extending about 82.4 in. from the spin axis, house a magnetometer, wobble damper, and orientation nozzle (nitrogen gas jet). The spacecraft range in total weight from 137 lbs (Pioneer 6) to 148.4lbs (Pioneer 9) and the experiments comprise from 34.3 to 41.3 lbs of these totals, with 5 to 7 instruments on each spacecraft (described in Section 6.1).

The communications subsystem consists of one linear array high-gain antenna providing a flat disc-shaped beam in the ecliptic plane, two low-gain antennas, two receivers which provide the transmitter-driver with a phase-coherent signal, a transmitter-driver, two TWT power amplifiers (8 W transmitted power level), and five commandable coaxial switches. Commandable bit rates available are 8, 16, 64, 256 and 512 bps.

The data handling subsystem provides commanded storage of data (15 Kbits maximum) and special data formats.

The electric power subsystem consists of a solar array (cylindrical), a battery (supplying peak demands), bus power converters, sensors, protective devices, and '- power switching and distribution equipment. Average total power levels at launch ranged from about 52 W (Pioneer 6) to 61 W (Pioneer 9).

The thermal control subsystem, required to maintain spacecraft temperatures between 30° and 90°F while solar radius varies between 1.2 and 0.8 AU, consists of passively controlled louvers at the bottom of the spacecraft.

The orientation subsystem, required to maintain the high gain antenna within 2° of the south ecliptic pole, has exhausted its gas propellant and is no longer active (nor needed) on any of the four spin-stabilized spacecraft.

5.1.2 Systems Status

The spacecraft subsystems are still functioning normally on Pioneer 6. The roll eference subsystem on Pioneer 7 is inoperative, so no directional data is obtained, only magnitudes. Also there is insufficient solar array current to operate any science instruments on Pioneer 7 in the vicinity of aphelion. On Pioneer 8, the Sun sensor functions only near perihelion, so roll reference cannot be measured during the rest of the orbit. The battery used to meet peak power demands has been disabled on each spacecraft.

11 Docu01ent No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 The last successful track of Pioneer 9 was on May 18, 1983. ·Subsequent attempts to track the spacecraft indicated there was no signal from the spacecraft detectable by the 64-meter DSN stations. The last attempt to track Pioneer 9 was on March 3, 1987 using SETI equipment at DSS-13 with a very low signal threshold. The spacecraft has been officially declared non-operational.

5.2 Pioneers 10 and 11

5.2.1 Systems Description

The TRW-built Pioneer 10 and 11 spacecraft were launched in 1972 and 1973. Each weighed approximately 550 lbs, including 63 lbs for the 11 scientific instruments (described in Section 6.2.1), 118 lbs for four RTG power sources, and 60 lbs of expendable propellant.

Each structure is 9.5 feet long in the axial direction, including a 14-in. deep hexagonal equipment compartment with 28-in. sides attached side-by-side to a smaller "squashed" hexagonal instrument compartment (s~e Figure 5.2-1). Mounted on the front of the equipment compartment is a 9-ft. diameter parabolic high-gain antenna, and on its rear is a 2.5 ft. low-gain omni antenna. Three radial booms extend from the sides 120° apart: two trusses holding RTG's about 10ft. from the spin axis, and a single-rod boom positioning a magnetometer sensor about 21.5 ft. from the center; all three appendages having been extended after launch. The Pioneer 10 spacecraft is spin stabilized at a nominal 4.5 rpm about its Earth­ directed axis; but Pioneer 11 spins at 8.2 rpm because of an inoperative despin thruster. Both Pioneer 10 and 11 were designed to operate at a nominal5 rpm spin rate.

For communications, there are three antennas, an omni-directional low gain antenna, a medium gain horn, and the large high gain dish. For DSN acquisition, they radiate a non-coherent RF signal, and for Doppler tracking, there is a phase coherent mode with a frequency translation ratio of 240/221. Two transmitters, coupled to two TWT power amplifiers, each produce 8 W of transmitted power at S-band. The beam from the high gain dish, aligned to the spin axis, can be offset 0.8° by movement of the feed and has a 3.2° beamwidth. The medium gain horn is skewed 9.3° from the spin axis for conscan and has an 18° usable beamwidth. The omni has a 120° pattern symmetrical about the spin axis. The bit rate capabilities range from 16 to 2048 bps.

For r:untude control, a sensor () and two Sun ·sensors provide reference, and three pairs of thrusters located near the rim of the antenna dish provide for orientation and roll maneuvers. The magnetometer boom incorpor-ates a hinged viscous dampening mechanism at its attachment point, for passive nutation control. ·

The power subsystem controls and regulates the RTG power output with shunts, supports the spacecraft load, and performs battery load sharing. The .silver cadmium battery is composed of 9 cells of 5 ampere-hours capacity each for sharing peak loads.

The data handling subsystem accepts digital and analog data and formats into PCM/PSK/PM for transmission. There are 11 different science and engineering

12 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(1): 11/30/82 (2): 06/15/90 formats, and the system memory can store 48 Kbits. The data handling system also supplies timing and control signals to the instruments and subsystems. The command system accepts serial data at one bit per second, and can store commands in a stored command programmer, or in the control electronics assembly for certain maneuvers. All thermal control is passive via an aft-mounted louver system, except for off-on control by thermal power dissipation of the various subsytems. 5.2.2 Systems Status At launch the 4 RTG's supplied about 157W on each spacecraft, but due to unequal decay rates the supplied power has decreased to 89.6 Won Pioneer 10 and to 88.1 Won Pioneer 11 as of January, 1990. As a result of this reduction in supplied power the first of a sequence of instrument power sharing plans was started in February, 1985 for Pioneer 11. A power management plan was initiated for Pioneer 10 in September, 1989. Due to Pioneer lO's large distance from the Sun (48.1 AU in January, 1990), the Sun sensor no longer provides a reliable roll reference, and, therefore, the output from the Imaging Photo-Polarimeter (IPP) instrument has been used as a roll reference since May 10, 1986. The IPP instrument output had been pre-viously used as a roll reference from November, 1983 to July 7, 1985. The star Sirius is used as a roll reference by the IPP. 5.3 Pioneer Venus Orbiter (Pioneer 12) 5.3.1 Systems Description

The Pioneer Venus Orbiter, built by and launched in 1978, has a dry weight on orbit of 753 lbs, plus originally 70 lbs of expendable propellant, of which about 4:1 lbs remains as of January, 1990. The science complement weighs about 105 lbs and includes 12 instruments (described in Section 6.3). The spin-stabilized spacecraft (appr. 5 rpm) consists of an 8 ft. diameter circular equipment shelf mounted on the forward end of a thrust tube, and is supported by 12 struts. A cylindrical solar array of 48-in. length encircles the shelf. The magnetometer sensor is located on a 15.5 ft. radial boom; ·a 43-in. diameter mechanically despun SIX band parabolic reflector antenna is mounted forward, along with a backup sleeve dipole high gain antenna, and an omni; another omni is positioned aft on a mast (see Figure 5.3-1).

For communciations in S-band, amplifiers can supply 10 or 20 W to any antenna, while the X-band power is 1 W. Command uplink is received through two S-band ransponders, which provide a phase-coherent carrier for two-way lock or a local auxiliary carrier for open loop tracking. For downlink, an SIX band dual requency radio occultation experiment is provided by the despun parabolic high-gain antenna, steered in azimuth and elevation, with beamwidths of2.2° in X-band and 7.6° inS­ band.

Electrical power is provided by the cylindrical solar array, yielding 312 W near Venus, and two 7.5 A-hr 24-cell Ni-Cad batteries providing 252 W-hours at 60

13 Document No. PC-1001 Original Issue: 20 May 1g81 Revision:(!): 11/30/82 (2): 06/15/go percent discharge when new. A power interface unit provides power switching and fuses for propulsion heaters and science instruments. An under-voltage/ overload switch can disconnect three of the four electrical buses if spacecraft oad current exceeds about 16.5 amperes or battery terminal voltage drops below 27.5 volts.

The command system can either store commands or execute them immedi-ately. It accepts commands at the rate of 5 per minute. The data handling ·subsystem formats data into frames of 64 eight-bit words. The subsystem output is an 8 to 2048 bps· PCM/PSK convolutionally encoded data stream. Data storage for up to 1.048 x 106 bits is available for use during occulted periapse passes or storage during portions of an orbit not covered by ground station racking.

The control subsystem has 3 Sun sensors and two star sensors to provide eference, and an attitude data processor controls sequenced thrusterTirings of he three axial and four radial thrusters (attitude, spin rate, and velocity control).

Fifteen thermal louver modules, attached to the lower surface of the shelf, passively control thermal radiation from the aft cavity.

5.3.2 System Status

Remaining propellant, since control of periapsis altitude was discontinued at the end of Phase I of the PVO mission (see Section 2.3.1), is adequate for control of the spacecraft orientation and spin rate until the spacecraft enters Venus' atmosphere in the latter part of 1gg2. Degradation of the solar panels, since orbit insertion in December, 1g78, by about 50% of the original power-generating capacity has been C the result of solar events and other decay mechanisms. Shadowing of the solar panels by the magnetometer boom during those intervals when the spacecraft was oriented so that the Sun-Look-Angle was less than goo may also have contributed to solar panel degradation. To avoid any further degrading effects of shadowing of the panels, the spacecraft attitude is being maintained to keep the Sun-Look-Angle greater than goo since October, 1986.

Due to the degradation of the solar panels and the need to support remaining science, power sharing of these instruments was initiated in May, 1g85. New · plans, which specify the priority and number .of instruments in use throughout each orbit, are developed and initiated as required by changes in solar array status and orbital parameters. Power Sharing Plan S is currently in operation.

In M~ch, 1g86 one half of the data storage unit ceased operating, limiting the total data storage capacity to 0.524 x 1Q6 bits.

14 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 6. SCIENTIFIC INVESTIGATIONS

A list of active Principal Investigators for Pioneers 10, 11 and 12 is provided in Table 6-1.

6.1 Pioneers 6, 7 and 8

6.1.1 Single-Axis Flux gate Magnetometer CGSFC) (Pioneers 6, 7 and 8)

The Goddard Magnetometer performs measurements of the interplanetary magnetic field which is created by the Sun and modulated by the streams of plasma issuing therefrom. Of particular interest are those measurements which record transients following solar activity.

The instrument design permits sequential measurement of the magnitude of the three orthogonal components of the interplanetary magnetic field, in the range of+ 64 gamma. Since the sensor axis is mounted at an angle of 54°45'to the spin axis and is sampled at three equally spaced intervals during the spacecraft rotation, the experimeter receives three measurements of orthogonal field components, thereby completely defining the magnetic field (assuming constancy during the spacecraft's rotation period of one second).

The sensor of the single-axis fluxgate magnetometer is a saturable inductance driven by a gating magnetic field applied by a winding. The flux induced in the saturable core is modified by the presence of the external magnetic field, whose contribution can be easily separated and quantified. The sensor is mounted on a boom 2.1 m from the spin axis; an explosive-actuated indexing device permits the experimenter to flip the sensor over by 180°, thereby taking into account spacecraft-created magnetic fields. All ordnance has been used, however; no further flips can be accomplished.

Operation of .the experiment has been discontinued on all three spacecraft.

6.1.2 Faraday-Cup Plasma Probe (MIT) (Pioneers 6 and 7)

The scientific measurements of the MIT solar plasma detector are investigating the following characteristics of the interplanetary plasma:

(a) Positive ion flux as a function of energy and direction.

(b) Electron flux as a function of energy and direction.

(c) The temporal and spatial variations of these physical quantities.

(d) Correlation of plasma measurements with magnetic field measurements.

These measurements are made in the following ranges:

Energy/Charge (E/q)- Positive ions 0.1 to 9.5 kV (14 bands) Electrons 0.1 to 1.6 kV ( 4 bands)

15 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90

The Pioneer sensors (Faraday cups) are 6" in diameter with the open side normal to the spacecraft spin axis so that it sweeps out the plane of the ecliptic as the spacecraft spins. At the bottom of the cup, two halves of a split collector intercept those electrons and positive ions that are to pass through a modulator grid. This grid electrically sorts out the plasma particles according to species and energy by applying square waves at different voltage amplitudes to the modulator grid directly in front of the split collector. This collector is split parallel to the spacecraft equatorial plane to provide directional infor-mation about the plasma fluxes in the meridian plane. The Faraday-cup plasma detector has been turned off on both Pioneer 6 and 7.

6.1.3 Solar Plasma Detector (ARC) (Pioneers 6. 7 and 8)

The Ames plasma detector, which is a quadrispherical electrostatic analyzer, measures the energy spectrum, flux and angular distribution of both positive ions and electrons of the interplanetary plasma. It provides more detail than the Faraday­ cup probe by separating the plasma components into different E/q groups and also into much smaller solid angles with better discriminations, although it is correspondingly more complex. Measurements are made in the following ranges:

Energy/Charge (E/q)- Positive ions 0.2 to 10 kV (16 bands) Pioneer 6,7 0.2 to 15 kV (30 bands) Pioneer 8,9

Electrons 0.002 to 0.5 kV (8 bands) Pioneer 6,7 0.014 to 1 kV (15 bands) Pioneer 8,9

Flux Sensitivity - 105 to 109 particles/cm2-sec Pioneer 6,7 5 x 104 to 109 particles/cm2-sec Pioneer 8,9

The curved-surface plasma analyzers work by applying stepped voltages to a pair of _ curved plates; ·positively charged particles are deflected toward one plate, negative particles toward the other. Only those particles within a narrow range of E/q and within a narrow solid angle will reach the particle collector at the end of the curved plates. ·

AlthGugh the basic principle of operation is the same, the Pioneer 6 and 7 instrument is significantly different from that of Pioneer 8, which uses truncated hemisphericaLplates and three current collectors as opposed to the quadrispherical plates and eight current collectors of Pioneer 6 and 7. The differences in range and sensitivity are indicated above.

The instruments are all performing nominally; however, with the loss of the Sun sensor on Pioneer 7, directional data is no longer supplied. On Pioneer 8 the instrument does not operate without the Sun pulse and has been turned off.

The data provides information on solar wind speed and the presence of flares; when several spacecraft (including Pioneer Venus, series, IMP series, Pioneer 11 and the Voyagers) are in heliocentered radial alignment, important data is obtained ~

16 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 on the propagation of solar flares. However, it is necessary to obtain continuous tracking during such periods to gather useful data.

6.1.4 Cosmic Ray Telescope (UC) (Pioneer 6, 7)

The University of Chicago cosmic ray experiment provides measurements of the heliocentric, radial gradient of the proton and alpha particle fluxes in various energy ranges, in conjunction with the intensity, energy spectrum and angular distribution of protons, alphas and electrons. The energy discriminating capabilities of the experiment are:

Protons -6 to 8 MeV and 80 to 190 MeV

Alpha particles - 8 to 80 MeV/nucleon and 80 MeV/nucleon to relativistic energies

Electrons - 1 to 20 MeV and in excess of 160 keV depending on the mode utilized.

The basic instrument is a four-element, solid state, cosmic ray telescope. Three telescope elements are lithium-drifted silicon semiconductor wafers. These three detectors are surrounded by a plastic scintillator which defines the 60° acceptance cone for incident charged particles. A photomultiplier tube monitors the plastic scintillator. The silicon wafers and the photomultiplier tube are all sensitive to sunlight, necessitating a light-tight enclosure. Particle absorbers between the telescope elements define the response of the elements to various particles at various energies. Pulse-height analysis provides energy discrimin-ation as indicated above, while counting rates alone can provide discrimination in different ranges.

The experiment has functioned well since tum-on on Pioneer 6, but has been turned off on Pioneer 7 where it is used only when there is sufficient power. Continued tracking of Pioneer 6 allows monitoring long-term solar cycle modulation and contributes to studies of the long-scale electrodynamical phenomena using Pioneer 10 and 11 in the outer heliosphere, and the Climax neutron monitor at 1 AU.

6.1.5 Electric Field Detector (TRW) (Pioneer 8)

The TRW Systems electric field detector (AC electromet"'r) detects charge differences over small distances in interplanetary space through the electric fields they create along the spacecraft's Stanford antenna. Electric components of low­ frequency radio waves, created by density variations in the solar winds, and other collective efforts in the 100 to 100,000 Hz VLF range of charged particles in collisionless interplanetary space frequencies are detected with the instrument.

The electric field experiment makes use of a short (6.4 in) 423.4 MHz segment of the Stanford antenna as a capacitively coupled sensor with which local plasma waves can be detected. Although relatively insensitive, the sensor is adequate for the measurements being made. The high-frequency channel selected is at 22kHz for Pioneer 8. The low frequency channels are at 400 Hz and 100 to 100,000 Hz (for the broadband survey) on both spacecraft.

17 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90

The experiment continues to operate on Pioneer 8 but can be used only when there is sufficient power. 6.2 Pioneers 10 and 11 6.2.1 Helium Vector Magnetometer (JPL/HVM) Instrument The JPL/HVM measures the interplanetary magnetic field with high accuracy. The scientific purposes include mapping the interplanetary magnetic field beyond 2 AU and locating and investigating the solar/galactic boundary region. Ongoing efforts include: identification and analysis of discontinuities and shocks, the computation of power spectra in the interplanetary field fluctuations at large distances, and the observed properties of Alfven waves at large helio-centric distances. In addition, collaborative studies with energetic particle investigations involve: the acceleration of protons by corotating interplanetary shocks, the effect of corotating interaction regions on cosmic rays, and the relation between interplanetary protons, corotating interaction regions and waves.

The Pioneer 10/11 HVM is an advanced version of the and 5 HVM instruments. The essential elements include a helium lamp, a circular polarizer, a helium absorption cell, Helmholtz coils, a lens, and an IR detector. The presence of an ambient magnetic field causes a sine wave modulation of.the IRradiation passing through the gas cell at the fundamental frequency of the applied circular sweep field; nulling currents applied to cancel this field "signal" are the sensor outputs.

The instrument has the necessary sensitivity over the wide dynamic range needed to ·operate in the very weak interplanetary fields with selectable operating ranges from ± 4.0 gamma to± 1.41 gauss. Fields smaller than 0.01 gamma can be detected.

The HVM has been productive throughout all phases of the Pioneer 11 mission; but the HVM on Pioneer 10 failed one year after Jupiter encounter.

6.2.2 Plasma Analyzer (ARC/PA Instrument)

This experiment investigates the disturbed and quiet time characteristics of interplanetary plasma, providing detailed information about the energy and directional distribution, as well as the spatial and temporal variations of the ion and electr0r. components within the plasma. Present and future studies include: helio­ centric- distance dependence of solar wind parameters; correlation of results with solar activity and results from other spacecraft; identifying and studying a terminal shock (heliospheric boundary); heliocentric distance dependence and dynamics of the solar wind helium component; and velocity· distribution functions of proton plasma data enabling study of the magnitude and occurrence of nonthermal components of the solar wind.

The instrument is an electrostatic energy per unit charge (E/q) spectrometer capable of measuring the flux as a function of E/q and incident direction of positive ions and electrons. The E/q of incoming particles is determined by the voltage across the instrument's quadrispherical analyzer plates. These plates reject all but a narrow band in the incident particle spectrum. ,.,

18 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90

This analyzer system is capable of determining the incidentplasma distribution parameters over the energy range of 100-18,000eV for protons and approxi-mately 1-500 eV for electrons. It covers the dynamic range for charged particle fluxes from approximately 1 x 102 to 3 x 109 cm-2 s-1 and is capable of resolving proton temperatures down to at least the 2 x 10-3°K level. ·

The Pioneer 10 plasma analyzer experiment has operated flawlessly since launch and continues to provide excellent data. On Pioneer 11 the plasma analyzer is currently.operating well; however, the instrument was inoperative between April, 1974 and December, 1977.

6.2.3 Charged Particle (UC/CPI) Instrument

Present and future studies include: radial gradients of galactic cosmic rays (electrons and nucleons); radial and temporal variations of the "anomalous helium component" below about 60 MeV/nucleon; interplanetary corotating phenomena at large radial distances; propagation of solar flare accelerated nuclei and electrons; interplanetary shockphenomena at large radial distances and associated particle accelerations; and acceleration and propagation of low energy protons within corotating interaction regions.

Continuous measurements of the fluxes, energy spectra, and chemical and isotopic composition of energetic charged particles in the interplanetary medium are being obtained. In particular, the instrument separately identifies individual nuclei including protons and helium nuclei through higher mass nuclei up to oxygen and measures the energy and differential flux of these particles over the range from 0.5 to 500 MeV/nucleon. The integral fluxes of nuclei with energies >500 MeV/nucleon from protons through iron are also measured. Electron spectra are measured from 3 to 30 MeV.

The University of Chicago's Charged Particle Instrument consists of four sensor systems: two multi-element telescopes, an electron current detector (ECD) for electrons greater than or equal to 3 MeV, and a fission cell for high-intensity, high­ energy nucleon fluxes. The low-energy telescope (LET) contains a titanium window, a thin (37 micron) silicon detector, and electrically connected annular and flat silicon detectors. The main telescope contains seven detectors and complex logic circuitry, designed primarily for measurements of the inter-planetary cosmic ray composition, flux and spectra.

The instrument continues to operate normally on both spacecraft.

6.2.4 Geiger Tube Telescope (UI/GTT) Instrument

The UI/GTT Charged Particles Experiment is an exploratory survey of the absolute intensities, energy spectra, and angular distributions of energetic electrons and protons, which serves to improve understanding of solar and galactic cosmic radiation beyond 2 AU. Ongoing investigations include the acceleration of ions by interplanetary shock waves and analytical model derivations, the corotating interaction region proton events, and bursts of MeV Jovian protons observed in interplanetary space.

19 DocumentNo. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 The flight instrumentation for the Pioneer 10/11 GTT experiment utilizes seven Geiger-Mueller (GM) tubes as elementary detectors. Three GM tubes are arranged in an array to serve as a multi-function particle telescope. The axes of the three tubes are parallel to each other and to the X-Y plane of the space-craft. The tubes are stack~d one above the other to form a telescope for penetrating particles (Ep > 70 MeV) moving approximately in the +Z or -Z (spacecraft rotational) axis direction. The useful dynamic range extends from 0.2 to 1 x 106 counts per second for individual tubes and from 0.01 to 3 x 104 counts per second for the coincidence conditions. Three other detectors are arranged in a triangular array and fully enclosed in a 7.2 gm/cm2 shield of lead to form a shower detector. Outputs are processed to. compare individual primary events with secondary showers. A final detector is configured as a scatter detector, using a gold scatter target and a thin mica window, affording a 30° full angle view cone; it admits low-energy electrons (Ee > 0.06 MeV) but discriminates against protons (Ep < 20 MeV).

The UI/GTT instrument has operated properly throughout the mission and continues to function on both Pioneer 10 and 11.

6.2.5 Cosmic Ray Telescope CGSFC/CRT) Instmment

The Cosmic Ray Energy Spectra experiment extends investigations into the nature of solar and galactic cosmic radiation to the regions beyond 2 AU. Charged particle spectra and angular distribution are measured over an extended energy interval. The observational objectives of the experiment include: (1) the flow patterns of energetic solar and galactic particles, with selectivity, in the interplanetary field; (2) the energy spectrum, radial gradient, angular distribution, and streaming parameters Q for each nuclear species, over as wide an energy range as possible; (3) the energy spectra and isotopic. composition of galactic and solar cosmic rays, up to 800 MeV/nucleon; (4) time variations of the differential energy spectra of electrons, hydrogen and helium nuclei over the corresponding energy intervals; (5) the energy spectra, time variations and spatial gradients associated with recurrent, non-flare- associated interplanetary proton and helium streams and the particle acceleration processes; and (6) the extent of the solar cavity, the boundary phenomena at the interface and the cosmic ray density in nearby interstellar space.

The flight instrumentation for the Pioneer 10/11 CRT consists of three solid state telescopes. The High Energy Telescope is a 3-element linear array operating in two modes: penetrating and stopping. For penetrating particles, differential energy spectra are obtained for He and H2 from 50-800 MeV/nucleon. The stopping particls mode covers the range from 22-50 MeV. The Low Energy Telescope I is a 3 element linear array, responding to protons and heavier nuclei from 3 to 22 MeV/nucleon, and providing both energy spectra and angular distribution over this range. The Low Energy Telescope II, designed primarily to study solar radiation, is a three element linear array. The top detector will stop electrons in the 50-150 keY range, and protons in the 50 keV-3 MeV range. The second detector will respond to electrons in the interval 150 keV -1 MeV and protons between 3 MeV and 20'MeV. The third element serves as an anticoincidence guard.

The GSFC/CRT instrument has been active through the mission and continues nominal operation on both Pioneers 10 and 11.

20 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 6.2.6 Trapped Radiation Detector CUCSD{IRD) Instrument

The UCSD Trapped Radiation Detector, originally intended to observe energetic corpuscular radiation trapped in the Jovian magnetosphere, has since been demonstrated to be effective for obtaining measurements in the interplanetary medium. Studies are continuing of the cosmic ray gradient above 500 MeV/nucleon, crosscheck of the gradient above 80 MeV /nucleon, and the anisotropies of relativistic particles, including an apparent periodicity in the corotational cosmic ray anisotropy of approximately 59 days.

The Cerenkov counter detector counts galactic cosmic rays in the energy range above 500 MeV per nucleon, higher than the other on-board cosmic ray detec-tors. Also it is directional, measuring anisotropies perpendicular to the spacecraft spin axis. As a result, the radial gradient of the galactic cosmic rays, and its tendency to corotate with the Sun in interplanetary space are being observed. Additionally, another detector with an 80 MeV threshold is providing crosscheck of other instruments.

Of the four detector assemblies in the UCSD instrument, detectors C and M are presently active on both spacecraft. Detector Cis a non-focused Cerenkov counter for energetic electrons, using an alcohol mass enclosed in a plastic can as the radiator, optically coupled to a matched photomultiplier tube. Detector M is an omnidirectional counter for high energy protons and minimum ionizing particles, consisting of a solid state diode embedded in a shield.

6.2.7 Ultraviolet Photometer CUSC/UV) Instmment

The Ultraviolet Photometry Experiment is to determine the interplanetary neutral hydrogen density, measured by photometric observations in the extreme ultraviolet of its interaction with the solar wind over large solar distances, and the radius of the heliosphere from precise measurements of the hydrogen distri-bution.· Continuing measurements will provide: (1) A relatively complete sky survey of UV emissions from B-type or earlier stars, and data on the inter-stellar extinction coefficient; (2) measurements of the density and temperature of the interplanetary H and He gases at large solar distances; and (3) heliosphere boundary data, including observations of UV emissions from neutral H and He, and emissions from the hot plasma at the heliosphere boundary.

The flight instrument for the Pioneer 10/11 UV experiment is a two channel UV photometer operating in the 200-1400 Angstrom range. Selection of wavelength is achieved by the use of a field of view limiter and the use of filters and sensors. An aluminum filter in conjunction with a channeltron sensor is used to provide Hydrogen Lyman-Alpha data at 1216 A. A Lithium fluoride target cathode with a second channeltron sensor provides Helium data at 584 A. The field of view (FWHM) is 1.15° x 9.3°. The photometer optical axis is positioned at an angle of approximately 20° with respect to the spacecraft spin axis; consequently, the field of view swept out by the spin motion is an annular ring 40° in diameter that moves only with the small reorientations of the space-craft's spin axis as it tracks the Earth.

The USC/UV instrument has been active throughout the mission and continues functioning on both Pioneers 10 and 11.

21 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90

6.2.8 Imaging Photopolarimeter CUA/IPP) Instrument

The Imaging Photopolarimetry Experiment has combined three investigations in the visible light range, sharing use of a single flight instrument. mapping is being conducted at intervals throughout the interplanetary flight to assess the quantity and distribution of particulate matter in space and to identify the nature of the particles. Measurements are made of brightness and polarization of light over a wide range of scattering angles. Further work to complete sky mapping of background star-light for use in astronomy data interpretations is being considered.

The flight instrumentation for the Pioneer 10/11 UA/IPP is an imaging photo­ polarimeter, consisting of an optical telescope positioned relative to the spacecraft spin axis by a stepping motor, a beam-splitting optical prism, 2 sets of coupling and filtering optics, 4 channeltron detectors, signal processing, logic, control, interface and power circuitry, all contained in a single housing. The telescope, which protrudes from the side of the spacecraft equipment compartment, has a 1" aperture, 3.4" focal length and provides an image with an instantaneous field of view of 40x40 mrad for Zodiacal light studies. The Wollaston prism splits the image into 2 orthogonally polarized beams which are filtered to 2 color channels: 3900-4900 A · (blue) and 5900-7000 A (red). The imaging photopolarimeter was periodically active throughout most of the mission on both Pioneer 10 and 11. On Pioneer 10 the output from the IPP instrument has been used about once a week as a roll reference ever since May 10, 1986 when the distance from the Sun became so large as to preclude the use of the Sun Sensor for this purpose. The IPP instrument output had been previously used as a roll reference from November, 1983 to July C 7, 1985. ' 6.2.9 Meteoroid Detector CLaRC/MD) Instrument

The Meteoroid Detection Experiment is an in-situ measurement of solid particle population in the 10-8 grams mass range and larger using penetration cells attached to the exterior of the spacecraft. It measures flux levels, distribution and particulate size of too small to detect readily by optical means, and has performed preliminary study of the meteoroid penetration hazard to future spacecraft traversing the . Pioneer 10 has characterized the distribution of particles as small as 10-8 grams to 22 AU, and Pioneer 11 is following with discrimination to l0-7 grams ..

The fl~;ht instrumentation for the Pioneer 10/11 LaRC/MD consists of 12 banks of penetration cells, attached on standoffs to the spacecraft's exterior. Each bank is approximately 8" x 12" in size, constructed like an air mattress, with 18 individual cells in each bank. Each cell contains a pressure-sensitive transducer and is filled with gas prior to sealing. Penetration by a particle causes a gradual pressure loss, .with evacuation time ranging from a few seconds to as long as 30 minutes and longer in duration. The transducer detects this pressure loss as a critical pressure is reached and a plasma discharge takes place across. the cell. These events are counted to indicate meteoroid population. The LaRC/MD instrument has been active on both spacecraft from instrument power tum-on throughout the mission, out to approximately 22 AU. At this point

22 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(l): 11/30/82 (2): 06/15/90 the gas in the detector tubes condenses. Both Pioneer 10 and Pioneer 11 are more than 22 AU from the Sun and have completed their missions.

6.2.10 Radio Science Doppler data from Pioneers 10 and 11 are being searched during the extended mission phase for the conceivable discovery of additional solar planet(s) and for the possible first demonstration of the existence of gravitational waves.

6.2.10.1 Search for Undetected Planets of the Solar System

Residuals in optical measurements of planetary motions suggest to astronomers that at least one more massive "dark" planet remains to be found in the solar system. In fact, a singular planet or other dark matter could diminish all such residuals. An organized search is under way by astronomers, whereby intense metric observations of the positions of and are being analyzed to confirm the existence of, and locate, the suspected planet. The Pioneer 10/11 radio science Principal Investigator notes that his analysis of Pioneer data has distinctly greater sensitivity to dark matter beyond Neptune in a much shorter observation span than does the optical data set. This concept is being pursued, beginning with an analysis ofunmodeled small forces on Pioneer 10 and 11 between 5 and 50 AU.

6.2.10.2 Detection of Gravity Waves

Gravitational waves from cataclysmic cosmic events might be detectable in the Doppler signal between Pioneer 10 and Earth. Pioneer 10 presents the most sensitive capability available to observationally confirm the existence of these waves, predicted by the General Theory of Relativity. Only , among existing or committed spacecraft, might eventually present a comparable capability with coherent two-way Doppler, but not at the very low frequencies available to Pioneer 10.

Doppler data from Pioneers 10 and 11 will be searched whenever one of these spacecraft is near opposition with the Sun relative to Earth. In that circumstance, the solar wind's distortion of the Earth/spacecraft radio path is minimal, and the sequential wave effect upon the spacecraft and the Earth will be most apparent. Data from Pioneer 10 in December 1988 and December 1989 are being analyzed for sinusoidal signals and for bursts of duration up to four hours. Sinusoidal signals with an amplitude of 4 x 10-14 can be detected with 95% confidence.

6.3 Pioneer Venus Orbiter (Pioneer 12)

6.3.1 Radar Mapper (MIT/ORAD) Instrument

The Radar Mapper experiment provides the only direct observations of the surface of Venus to be obtained from the Orbiter. These observations are used to derive surface heights along suborbital tracks as well as radar images of selected regions of the surface.

The Radar Mapper experiment was operated during Phase I and the early part of Phase II during which the periapsis altitude remained low enough to obtain useful radar images. This period of observations ended on March 31, 1981, at which time

23 Document Nci. PC-1001 Originallssue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 the mapper experiment was shut down. During the latter part of Phase ITI, (May to August, 1992) the periapsis altitude will be low enough to continue to produce radar maps of the surface and the instrument may be reactivated if there is sufficient electrical power available for its operation. Periapsis during this period will have shifted toward regions in the southern portion of the planet which were not previously mapped by the radar mapper.

The instrument is a low-power S-band radar system which observes the distances, once each spacecraft rotation, to a series of relatively small adjacent areas lying along the sub-orbital track on the planetary surface below. By subtracting the observed distances from the corresponding spacecraft orbit radius, obtained by routine dynamical fitting to the DSN radio tracking data, the absolute planetary topography may be obtained for those surface regions observed. These measurements were taken for each orbit during Phase I (December 4, 1978 to July 27, 1980) whenever the spacecraft altitude was below 4700 km, subject to constraints set by the antenna pointing limitations and other mission constraints.

6.3.2 Neutral Mass Spectrometer CGSFC/ONMS) Instrument The Neutral Mass Spectrometer measures the number densities of.the neutral particles in the upper atmosphere of Venus in an altitude range from approximately 150 kilometers to 500 kilometers above the surface. The measured parameters will be the absolute values of the number densities of the neutral particles with atomic mass numbers between 1 and 46 AMU. Measurements of the neutral atmosphere below 250 km in the southern hemisphere C will be possible during Phase III. Phase I 'provided data in the northern hemisphere.

The instrument consists ofa quadrupole mass spectrometer with an electron impact ion source and a secondary electron multiplier ion detector. The mass spectrometer can be programmed by ground command to scan continuously from 1 to 46 AMU or to scan any combination of masses within this range.

The ONMS instrument continues to operate and provide valuable measurements.

6.3.3 Retarding Potential Analyzer (Knudsen Research/ORPA) Instrument

The Retarding Potential Analyzer (ORPA) experiment determines the main sources of energy input to the Venusian ionosphere, the dominant .plasma transport processes, and.the solar wind-ionosphere interaction processes. The direct plasma quantiti~s measured are temperatures and concentrations of the most abundant ions, the ion drift velocity, electron concentration and temperature, and energy distribution function of ambient photoelectrons (from about 1 to 40 e V). During Phase II, changing orbital characteristics will allow studies of: 1) source of ion heating in a nightside ionosphere for solar zenith angle (SZA) greater than 150 degrees (higher altitude samples allowing direct obser-vation in the interaction region); 2) development of the mantle region down-stream from the planet; 3) existence of a nightside ionopause; 4) source of night-side ionosphere ionization and suprathermal electrons; 5) source of ion heat-ing between 150 and 170 km in dayside Venus ionosphere; 6) nature of the mantle at the subsolar point; 7) mechanism responsible for acceleration of ions across the terminator; and 8) plasma

24 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 characteristics within flux ropes. Data taken during Phase III will provide determination of the relative roles of solar photons and the solar wind in several phenomena since the relative strengths of these two sources of energy would have changed significantly during the solar cycle.

The instrument is a planar type retarding potential analyzer. It consists of large diameter grids (including entrance grid) and collector with guard ring which provide for a uniform flux radially from the sensor axis. The collector samples the central region of this uniform flux. By varying the magnitude of a potential barrier in staircase fashion, it determines the thermal energy and concentration of electrons and ions. The effective field of view is about pi steradians and makes a half-cone angle of 25° with the spacecraft spin axis.

Utilizing built-in analysis capability, the ORPA senses the optimum location in the spacecraft spin cycle from which to sample the plasma. It then selects for transmission to Earth only the most appropriate values of all the current values sensed in one complete stepping of the retarding potential. All quantities, with the exception of the ion drift velocity, are measured to about 0 5% absolute accuracy within the ionosphere of Venus. An ion drift velocity as small as 10 m/sec is detectable under favorable conditions: The ORPA experiment continues to function productively.

6.3.4 Ion Mass Spectrometer (Rice University/DIMS) Instrument

The Ion Mass Spectrometer experiment performs exploratory in-situ measurements of the distribution and concentration of ionic constituents in the upper atmosphere of Venus with emphasis on altitudes below 5000 km. The 16 ion masses measured by the OIMS are 1, 2, 4, 8, 12, 14, 16, 17, 18, 24, 28, 30, 32, 40, 44 and 56 AMU. The instrument can detect ions above a threshold drift speed of about 500 m/sec and measure volocities up to about 10 km/sec in the spacecraft direction of flight. The ions are sampled about every 1.5 s with a limiting sensitivity of about 3 ions/cm3. For the remainder of Phase IT and Phase Til, two previously unattainable objectives will be pursued: 1) investi-gations of thermal and superthermal ion concentrations and flow characteristics in the Venus wake (upper altitude regions), and 2) structural details of the superthermal ion distributions in the ionopause, ionosheath and bow shock regions.

The instrument is a lightweight model of the Bennett RF ion mass spectrometer. The four stage ion analyzer consists of an aluminum cylinder into which a series of parallel knitted wire mesh grids are placed at positions controlled by insulator spacers of varying dimensions. Both the mass and ambient concentration of individual ion species entering the tube are determined by applying appropriate potentials along the tube axis. Ambient ions enter the instrument orifice, which is parallel to the spacecraft spin axis, are accelerated down the analyzer axis, penetrate a retarding de field and reach the collector assembly at the rear of the sensor tube. Preamplifiers attached to the collector detect the generated ion currents and provide inputs to a series of cascaded post-amplifiers and telemetry output circuits. The ambient concentration and identity of each ionic constituent in the mass range are derived, respectively, from the corresponding amplitudes of the collector current and the accelerating voltage. The OIMS instrument is functioning normally.

25 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 6.3.5 Electron Temperature Probe (GSFC/OETP) Instrument The Electron Temperature Probe experiment provides measurements of the thermal structure of the ionosphere of Venus to contribute to an understanding of how it is heated and cooled. The measured parameters are electron temperature, electron concentration, ion concentration, and spacecraft potential; the mean ion mass is derived from these data. During Phase II, two unique regions are reachable: the ionopause, ionosheath and bowshock in the Venus front stagnation region, and the ionosphere, ionopause and wake region immediately behind Venus. As periapsis altitude decreases between now and 1992, the OETP will investigate: 1) how the subsolar ionosphere deflects the solar wind around the planet; 2) what ionospheric changes occur as a result of solar wind interactions; 3) how and where "ion scavenging" occurs; 4) how far the shocked solar wind plasma penetrates into Venus' wake; 5) why a distinct ionopause is formed on the nightside and what balances the ionospheric pressure at the ionopause; 6) what is the energy source for the high nightside ionospheric temperatures; and 7) what is the source of ionization for the nightside ionosphere itself. Is ion transport from the dayside more important than local production? In Phase III, the same general goals will be pursued except that the southward drift of periapsis will allow different regions to be examined. The OETP experiment status is normal.

6.3.6 Ultraviolet Spectrometer CUC/OUVS) Instmment

The Ultraviolet Spectrometer experiment investigates the composition, temperature and energy balance of the thermosphere as functions of position and time; measures the distribution and escape rate of atomic hydrogen in the thermosphere and exosphere as functions of time; measures the ultraviolet scattering properties of the cloud tops, hazes, and adjacent atmosphere; and investigates the spectral nature, distribution, and movement of the UV features.

Objectives for the extended mission include measurements of physical properties of both Venus and selected comets. The objectives for planet-related science are: (1) to map and monitor the horizontal distribution of atomic oxygen and the horizontal and vertical distribution of carbon monoxide in the dayside thermosphere to help characterize the circulation properties and role of vertical eddy mixing this region; (2) to determine the dependence on solar activity of the day- and night-side thermosphere circulation patterns; (3) to determine the long-term secular behavior of S02 in the cloud tops (timescale of years); and (4) to establish the response of the hydrogen corona to changes in solar activity over the entire solar cycle.

The objectives for comet-related science are: (1) Determine the cometary water evolution rate and its variation; (2) Determine carbon/oxygen/hydrogen ratios and their variation; (3) Search for evidence of rotation of the comet nucleus; and (4) Image the Lyman-Alpha coma.

The instrument measures the day and night air glow spectrum of Venus between 1100A and 3400A; limb profiles of selected air glow emissions, including OI 1304A, 1356A, and 2972A; +CI 1657A; HI 1216A; CO Fourth Positive and cameron bands; C02 doublet bands; the intensity and distribution of the hydrogen Lyman alpha corona; the spectrum of sunlight back scattered from the cloud-top region, between 1900A and 3400A in 512 equal steps of 13A resolution, and disc scans of this scattered light at selected wavelengths. The instrument sensitivity at ,..,

26 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 1980A is 1.5c!kR/32rps, and it achieves a maximum horizontal spatial resolution of 3x0.5 km. The ultraviolet spectrometer optics consist of a 125 mm Ebert-Fastie monochromator and a 125 mm Cassegrain telescope, offset 60° from the spacecraft spin axis. The monochromator entrance slit defines a 1.8° x 0.16° field of view. The instrument is designed to perform both spectrometry and fixed wavelength scans of the planet from a spinning spacecraft. It continues to perform accurate measurements.

6.3.7 Cloud Photopolarimeter CGISS/OCPP) Instrument

The Cloud Photopolarimeter/imaging experiment principal investigations are: (1) measuring cloud and haze properties as a function of location on the planet, and particularly the physical differences between the dark and light regions; (2) determining the vertical and horizontal distribution and temporal variability of cloud and haze particles in and above the visible clouds; and (3) observing the ultraviolet atmospheric markings and circulation patterns and measuring the apparent cloud motions on time scales ranging from about 15 minutes through phases of the solar cycle.

Data from Phase II and Phase III will provide a detailed record of the long-term evolution of significant haze effects, key to understanding the photochemical and aerosol processes involved and the mechanisms of meridional transport. Observations of the buildup and· dissipation over long periods of jet streams at midlatitudes will provide important clues regarding the basic mechanism responsible for the zonal circulation. Long-term data also are required to properly define the climate at cloud levels and the processes which produce the observed cloud structure and general circulation.

The photopolarimetry mode measures the intensity, degree of polarization and direction of vibration for four spectral bands (255-285, 350-380, 545-555, 945- 955 nm) with an instantaneous field-of-view of 7x9 mr and a sample period of about 10.7 msec. The limb-scanning mode measures the intensity for a visual pass band with an instantaneous field-of-view of about 0.25 x 0.25 mr.

The instrument employs a one inch Dall-Kirkham telescope for spin-scan mapping of the planet in different spectral bands; it generates 30 km resolution images in the 365 nm band. Observations are made at selectable fixed look angles, using spacecraft rotation to generate scans across the planet and usinz orbital motion for cross-scan coverage. The optical components of the tele-scope include a 16- position filter/retarder wheel, a Wollaston prism and four photodiode detectors. From the photopolarimetry measurements, as functions of scattering angle and wavelength, particle size, shape and refractive index for local areas in the planet are derived. The vertical distribution of cloud and haze particles as a function of atmospheric pressure down to an optical depth of about unity is defined in observable areas. The instrument status is normal.

6.3.8 Magnetometer CUCLA/OMAG) Instrument

The objectives of the Magnetic Field Fluxgate Magnetometer during Phase II are to obtain new first order information on: 1) the primary (equatorial) solar wind-

27 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 ionosphere interaction; 2) the extent of the atmospheric mass loss phenomena and the mechanisms that control this atmospheric scouring (low latitude passes required); 3) the mechanisms governing energy transfer between the solar wind and ionosphere, and 4) analogs of the comet-solar wind interaction including disconnection events in Venus' wake and tail, and mass-loading in the upstream region. Phase III repeats the geometry of Phase I, however Phase III will occur during a different part of the solar cycle. Further, at the end of Phase III, the Orbiter will pass rapidly through the ionosphere and for a few passes obtain data at altitudes ev~n lower than during Phase I.

The nominal range of the instrument is± 128 nT with a digital window ranging from 1/8 nT for fields less than 16 nT to 1 nT for fields above 64 nT. It can measure fields of over 200 gamma depending on field orientation and operating mode.

The Fluxgate Magnetometer consists of three boom-mounted ring core sensors together with associated electronics mounted on the main body of the spacecraft. Two of the sensors are mounted at the end of the boom; orie perpendicular, and one parallel, to the spin axis.· The third sensor is mounted approximately one-third of the way down the boom and is tilted at 45° to the spin axis, providing redundancy, deduction of the spacecraft field, and simul-taneous three-component field measurement. The ring core sensors consist of a ring around which is wrapped a ribbon of highly permeable u-metal. The cores are then wrapped with a set drive, sense, and feedback coils. External fields along the sense axis of the ring cause the core to enter saturation asymmetrically, producing a signal at the second harmonic ~ of the drive frequency. A feedback signal is applied to the feedback coils to null out \, _ __) the external field. The strength of the feedback signal is then a measure of the component of the external field along the sense axis of the ring core.

On October 16, 1988 the instrument stopped transmitting X and Y axis field strength measurements. It now transmits the Z-axis reading three times at each instrument output cycle. Because the P sensor is oriented at a small angle to the spacecraft spin axis, the PI is attempting to resolve the reading into the X and Y components. However, there is a significant reduction in resolution, and it would take an increase in the spacecraft spin rate to improve the signal to noise ratio. Before a decision is made to increase the spin rate, the PI is working with pre­ failure data to determine how much information can be gleaned from the P sensor alone.

6.3.9 Plasma Analyzer.CARC/OPA) Instrument

The solar wind Plasma Analyzer experiment measures the properties of the solar wind and its interaction with the planet Venus. Bulk velocity, flow direction, flux and temperature are determined from the detailed measurements. During the early portion of Phase II, a better idea of the ionosheath conditions (flow deflection, heating and/or deceleration) near the ionosphere nose was obtained. During Phase II, an improved measure of the bow shock standoff distance at the nose, allowing a better calculation of the fraction of solar wind absorbed by Venus' ionosphere, will be acquired as periapsis rises above the ionosphere and moves equatorward. A marked difference in shock location between and 10 results taken in late 1975 when solar activity was at a minimum, and the initial Pioneer Venus Orbiter ~ 1 results, taken near the peak of the solar cycle, has been.reported. Data taken during • _)

28 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(1): 11/30/82 (2): 06/15/90 Phase II should enable connection of these apparent two extreme states of bow shock location and ionosheath "contraction". It would be hoped that correlative data on Venus' ionosphere could also be obtained. In addition, a monitor of interplanetary "weather" conditions during the declining phase of solar cycle 21 should be provided by the OP A data; solar wind stream development can be studied in conjunction with Pioneers 10 and 11, and the Voyagers, as well as earth-orbiting spacecraft during future inferior conjunctions. Phase III will provide data on the same phenomena as Phase II but during a different portion of the solar cycle.

The instrument is an electrostatic energy per unit charge (E/q) spectrometer capable of measuring the flux as a function of E/q and the incident direction of charged particles (ions and electrons). The E/q of incoming particles is determined by the voltage difference between a pair of quadrispherical analyzer plates (mean radius, 12 em). The voltage on these plates can be varied in equal logarithmic steps through three commandable ranges corresponding to the following range of E/q: 50 to 8000 e V for positive Ions and 3 to 250 e V for electrons and ions. A charged particle entering the acceptance aperture, which views normal to the spacecraft spin axis, is deflected by the electrostatic field between the plates, and, if the E/q of the particle is within the range determined by the plate voltage difference, it exits from between the plates and impinges upon one of five detector targets. The particle's incoming direction determines which of the five targets it will reach after passing the plates. The OPA instrument continues productive operation.

6.3.10 Electric Field Detector CUCLA/OEFD) Instrument

The Electric Field Detector provides information on: the mode of plasma interaction between the solar wind and the exospheric or ionospheric plasma; the variable locations of the Venus bow shock, ionopause and wake cavity boundary; the role of plasma instabilities in modifying the heat flux from the solar wind to the ionosphere; the wave-particle interaction mechanisms that cause thermalization of upstream ions formed when atoms from the Venus exosphere are ionized in the streaming solar wind; the extent of the upstream turbulence region; and the effects of wave-particle interactions within the Venus iono-sphere. Secondary investigations involve a search for whistler mode electromagnetic noise bursts from the atmosphere and analysis of solar wind disturbances at the Venus orbit. Phase II will provide the extended data base needed to assess temporal variations and the effects of the Solar cycle. The plasma-wave instrument uses a short self-contained, balanced electric dipole (effective length, 0.75 m), and the signals are processed with a four-channel spectrum analyzer (30% bandwidth filters with center frequencies at 100Hz, 730Hz, 5.4 kHz, and 30kHz). The V-.jpe electric dipole antenna unit is mounted directly on the electronics box. The threshold levels of the instrument range from about 10-6 to 105 volts/m (Hz) 1/2 depending on frequency.

The electric field detector instrument measures only one component of the vector field of the wave at any instant. Thus, the actual magnitude of the full vector is not determined. However, polarization information in the spin plane is available. In general, the measurements give the wave levels to within a factor of two. The OEFD instrument status is normal.

29 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(1): 11/30/82 (2): 06/15/90 6.3.11 Gamma Ray Burst Detector (LASL/OGBD) Instrument

The Gamma Ray Burst experiment is providing observations of intense, short duration emissions of high energy photons from astronomical sources. By correlating the time of the gamma bursts at widely separated detectors it is possible to derive precise information on source direction. .The spacecraft provides an experiment platform separated from the Earth. Correlations with near-Earth observations provide directional determinations with accuracies less than one arc minute, sufficient for meaningful attempts at optical identification of the sources. The OGBD has been recording gamma-burst events at an average- rate of 18 per year, with only 10-20% sufficiently intense and suf-ficiently well observed by other spacecraft to have yielded high-quality information. Although three gamma-ray burst source locations have been identified, the origin of the bursts thus has yet to be determined; there may even be several types of sources and possibly several gamma-burst classes, based on preliminary evidence. Given the low rate, several more years of high quality observations from the remainder of the mission will be a major contribution to the early stage of this new class of astronomy.

The detector provides a continuous time history of the gamma-ray flux for those events intense enough to be detected. Four-channel pulse height spectra are also obtained during an event. Continuous measurements of the observed counting rate (with much lower time resolution) provide a data base for searching for "slower" transient events, whose rise times are not sufficiently fast to trigger the detection logic.

The experiment consists of two Nai photo-multiplier detector units mounted to ~ i,_ _.-J provide nearly uniform sensitivity over a 4-pi steradian field of view. The detectors are sensitive to photons in the 0.2 to 2.0 MeV energy range and provide coarse spectral information with a four-channel pulse height analysis. To accommodate the very high data rates that occur during an event, the experiment includes a buffer memory of 20 k bits for storing· the event data for later readout. Internal logic continuously monitors the count rate and detects the rapid increase in count rate that signals the beginning of a gamma burst. The angular uncertainty is less than one arc minute under worst conditions and of the order of 10 arc seconds for events of "average" intensity. The detectors are both functioning productively.

6.3.12 Radio Science Investigations (Orbiter Radio System)

6.3.12.1 Pioneer Venus Orbiter Radio Occultation Studies

The Pioneer Venus Orbiter radio occultation investigations provide measurements of: ( 1) the vertical structure of the Venus ionosphere at various solar zenith angles; (2) the vertical structure of the neutral atmosphere at diverse latitudes; (3) small­ scale turbulence and temperature fluctuations in the atmosphere at various altitudes on a global scale; and 4) radio occultation -properties of the solar corona (during superior conjunction).The spinning PV Orbiter is equipped with a despun and steerable parabolic high-gain antenna, through which S-band (2293 MHz) and X band (8407 MHz) signals are transmitted to the DSN. To afford maximum penetration into the Venus atmosphere, the high-gain antenna has been steered to point in the direction of the refracted ray. At the DSN stations, the S- and X-band signals are recorded simultaneously by the Digital Signal Processor (DSP); its programmable open-loop receivers remove the ·excursions caused by orbital motion

30 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 of the spacecraft and Venus' atmosphere refraction, thus enabling the signals to be recorded in relatively narrow bandwidths. These signals are digitally recorded on magnetic tapes. Subsequently a detection sequence is performed, consisting of: a fast Fourier transform spectrum producing a local oscillator function, bandpass filtering and compression, and tracking with a digital phase-locked loop to establish · amplitude and frequency deviation history.

From the frequency residuals the following parameters are derived: electron density structure of the ionosphere; pressure vs. temperature structure in the neutral atmosphere; vertical profile of the atmospheric index of refraction and density; temperature and zonal wind speed fluctuations as functions of altitude and latitude; and vertical absorption coefficient profiles of the Venus clouds. The variability of these quantities with the solar cycle is established by continuing observations throughout Phases II and III of the Pioneer Venus Orbiter mission. Detailed studies of these phenomena are continuing, but further X-band usage is limited by remaining available power.

6.3.12.2 Pioneer Venus Orbiter Dopp1er Radio Tracking

Doppler radio tracking of the Pioneer Venus Orbiter provides gravity measurements over about half of Venus. Feature resolution has been as refined as 300 km at the minimum periapsis altitudes. Many gravity anomalies have been detected and have been correlated with topography from the radar altimetry, indicating internal crustal characteristics. Rising periapsis altitude, and strict minimization of propulsive maneuvers during Phase II provide for the emphasis upon measurement of the shape of Venus' gravity field on a global scale. Higher order harmonics of the gravitational model can be measured, or delimited to extremely fine accuracies using long term Doppler data collections undisturbed by maneuvers or atmospheric drag.

Doppler measurements of the coherently transponded radio link with the Orbiter can be resolved to less than 0.01 Hz (S-band) in 5 second intervals. Thoroughly developed orbit determination software in use at JPL for navigation of planetary orbiters is used to derive orbital parameters whose variations are studied to construct an ever-improving model of the global gravity field. Implications will then be assessed about Venus' internal structure, and perhaps some clues about the planet's evolutionary history.

6.3.12.3 Atmospheric Drag Experiment CLRC/OAD)

The Phase III periapsis altitude profile will result in gooc atmospheric drag measurements on the dayside. The objectives of such measurements are: 1) the determination of long-term changes in the neutral upper atmosphere (Phase III occurs 11 years after the previous measurements during Phase I); 2) measure-ments of the helium-rich regime between 4 AM and 6 AM above 200 km; and 3) measurements of the vertical structure and short-term variability in the lower cryosphere.

6.3.13 Interdiscip1inary Scientists

The Interdisciplinary Scientists, whose investigations are based upon data from combinations of sources, presently number five active on the Pioneer Venus Orbiter

31 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 . m1ss1on. Located at Universities, observatories, and NASA and other agency centers, their studies include: ·

a) Atmosphere: Vertical distribution of the ·ultraviolet absorber; radiative heating rates and development of a circulation model; loss rate of hydrogen to place bounds on the amount of water lost by Venus over its lifetime; correlation of atmospheric motion data from various sources; models for transport and chemistry of H, 0, and CO; and stability of the C02 atmosphere. ·

·(b) Ionosphere: Determination of Venus' ionospheric interaction with the solar wind; and investigations of neutral and ion composition, thermal structure, mass transport, and the role of solar wind and magnetic field in proc~sses responsible for the origin, maintenance and variability of Venus' ionosphere.

(c) Surface: Integration of Pioneer Venus radar imaging and altimetry data with existing earth-based data to produce geologic maps of Venus' surface; synthesis of multi-variate geologic and geophysical data (altimetry, gravity, magnetics); interpretation of Venus topography (processes responsible)' in selected areas; and studies of Venus tectonics.

6.3.14 Guest Investigator Program

Guest Investigators on the Pioneer Venus Program have been supported with NVASA pfu~ds. andiperfor_m data anTahlysiGs activiities i~ coordpination w~thdthe. Piondeer C enus nnc1pa1 nvesugators. e uest nvestlgator rogram 1s es1gne to bring new ideas and activities into the Pioneer Ven:us program to complement and expand the on-going data analysis activities. A broad spectrum of investigators have been supported, including examination of foreshock magnetic fields, modeling of ionospheric mass loss, upper atmospheric circulation and wave dynamics, and various radio science activities. Other activities under the Guest Investigator Program also include some non-Venus science such as examination of solar flares,· interplanetary Lyman-Alpha and disturbances in the int~rplanetary magnetic field. Such interplanetary activities typically involve data from other spacecraft.

The Guest Investigator Program has been supported during fiscal years 1981 and '1984 through 1989, inclusive. A complete list of all guest investigators, the institution with which they are associated, and the title of their research activity is provi~~d in Appendix A. The ·list is organized on the basis of fiscal year of participation and is followed by a tabulated summary indicating the number of investigators from each of five different categories of institutions for each fiscal year the program has been in existence.

Continuation of the Guest Investigator program depends upon year-to-year availability of funds for this supplemental scientific effo:r:t.

32 Document No. PC-1001 Originallssue: 20 May 1981 Revision:(!): 1 l/30/82 (2): 06/15/90 TABLE 6-1. ACTIVE PRINCIPAL INVESTIGATORS

Pioneers 10 and 11

Instrument Principal Investigator

1. Helium Vector Magnetometer E. J. Smith- JPL 2. Plasma Analyzer A. Barnes - ARC 3. Charged Particle Instrument J. A. Simpson - U. Chicago 4. Geiger Tube Telescope J. A. Van Allen - U. Iowa 5. Cosmic Ray Telescope F. B. McDonald- U. Maryland 6. Trapped Radiation Detector R. W. Fillius - UCSD 7. Ultraviolet Photometer D. L. Judge - USC 8. Imaging Photopolarimeter T. Gehrels- U. Arizona J. L. Weinberg - U. 9. Radio Science J.D. Anderson- JPL

Pioneer Venus Orbiter (Pioneer 12)

Instrument Principal Investigator

1. Radar Mapper G. H. Pettengill- MIT 2. Retarding Potential Analyzer W. C. Knudsen- KGR 3. Ion Mass Spectrometer P. A. Cloutier- Rice 4. Neutral Mass Spectrometer H. B. Niemann- GSFC 5. Electron Temperature Probe L. H. Brace - GSFC 6. - Ultraviolet Spectrometer A. I. F. Stewart- U. Colo. 7 . Cloud Photopolarimeter L. D. Travis - GISS 8 . Magnetometer Instrument C. T. Russell- UCLA 9. Plasma Analyzer A. Barnes - ARC 10. Electric Field Detector R. J. Strangeway - UCLA 11. Gamma Ray Burst Detector R. W. Klebesadel - LASL 12. Radio Science A. J. Kliore- JPL

Interdisciplinary Scientists

1. S. J. Bauer- U. Graz, Austria 2. T. M. Donahue- U. Mich. 3. D. M. Hunten- U. Arizona 4. H. Masursky- USGS 5. A. F. Nagy- U. Mich. 6. J. B. Pollack - ARC 7. N. Spencer- U. Maryland

Pioneers 6, 7, 8 and 9

Instrument Spacecraft Investigator

1. Solar Plasma Analyzer 6,7, & 8 J. Mihalov - ARC 2. Cosmic Ray Detector 6,7 J. Simpson- U. Chicago

33 Document No •. PC-1001 Original. Issue : 20 May 1981 Revisiom(l)i 11/30/82 (2)• 06/15/90 7 .. OPERATIONS

A narrative 0utline of the operations of the Pioneers' extended missions is provided he11e to show h0w the elements identified in othe11·sections inter.act.

7.1 Guidelines.

Guidelines. for. the Pioneer Missions Operations are based mainly upon scientifiC ad;visoiiies.. Scheduling requirements for tracking and data 'acquisition are summarized in Section. 9.

7.1.1 Pioneers.6-8.

Individual, interests ha:ve been expressed. by the· University of Chicago (Cosmic· Ray Detector.); ARC (Plasma Analyzer); MIT< (Plasma Probe), and NOAA (composite data) for data from Pioneers 6-8 at selected times, such as when alignments of· spacecr.aft occur, and for selected' studies o£ the Sun~s comnal expansion. Some configuration instructi0ns are received for the Plasma Analyzer; otherwise, the scientific instruments.are operating in. a. standard' format.

7.1.2 Pioneers.lO' and 1:1

Pieneer l'C)' and 1' 1 data• flow requires only occasional· guidance from the science group, as the active instruments can all be accommodated in. the nominally used fmmat. Individual experimenters. provide the Pieneer Missions OffiCe with' their specific needs. for cenfiguration changes. and: calibration' tests~ etc., orr their ~ instruments~

7 .. 1:.3 Pioneer, Venus Orbiter (:2):

Science Steering Group: (SSG). meetings for Pioneer Venus are held semi-annually., and: the Orbital Missi0n Opemtions Planning (OMOP} committee meetings are . generally· heltt conculifently with:, the SSG meetings Gand. by teleconference when needed). These groups recommendr allocation of the limited telemetry data link among the v:arious scientific interests as functions. of the· Sun/Venus/orbitat-plane ·alignment~ the available tracking time, and other limitations. The SSG meetings pmvide the general' exchange of scientific progress by which means arty concerted publicu.cions efforts are planned, and any speeial interdisciplinary investigations are encouraged~ The OMOP·committee is auth0rized\to res0lv:e problems that are more. fr.equent· and immediate than the issues. addressed by the SSG. Individual investigators provide regular and< frequent instructions. as to the configurations to. be commanded for their instruments.

Since· the· prospects for. survival to atmospheric re-entry have increased, planning for the use of remaining fuel and optimizing. scientific data return wiH' receive special attention. at all· future SSG. meetings. At the meeting of the Pioneer Venus Science Steering Group (SSG} in the spring of 1989, an Operations Plan Task Force (OP'TIF) was chartered: to describe the sdentific rationale for. Phase Hit of the mission and to define requirements for experiment operations, science sequences, formats, data storage, bit rates, quick look data and post- entry data. analysis ~

34 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(1): 11/30/82 (2): 06/15/90 needed to achieve the science goals. The OPTF, a subcommittee of the Entry Planning Committee (EPC), is to submit its plan at the 1990 spring meeting of the SSG. Many of the details of the plan can be defined only after decisions are made by the SSG on priorities for competing scientific goals and instrument operations during the entry period. Issues such as the collection of additional radar altimeter measurements, the relative priority of low altitude in-situ measurements versus remote measurements, the importance of drag measure-ments, and questions of spin rate and spin axis orientation are crucial to the definition of OSEQs, instrument modes, and intervals between periapsis restoration adjustments. Until these q~estions of priority are resolved, the OPTF will base the plan on the experimenter inputs provided to the Entry Planning Committee at recent SSG meetings; particularly those presented at the 1988 spring meeting in Annapolis and later distributed ,to the SSG membership. These inputs are the most complete assembled to date, and are probably adequate to define the long lead-time items needed to support the plan, such as q:uick look data requirements, spacecraft spin rate, spacecraft orientation and changes to instrument data processing software that may be required by proposed changes in data formats.

7.2 Planning and Development

General planning and procedure preparation is performed by the staff of the ARC Pioneer Missions Office under the coordination of the Flight Director. The support service contractor at ARC translates the general plans to detailed schedules for cormnand transmissions and real time data communications and processing.

Scheduling of DSN resources is accomplished through the Pioneer Missions representative of the JPL staff. He maintains close liaison with the Pioneer Missions Office so that plans can be adjusted to tracking

The DSN produces both long term and near term (weekly) schedules for project support. ARC's support service contractor produces a detailed weekly computer schedule for telemetry and command activities.

The Pioneer Missions Office and support contractor at ARC also jointly maintain lists of software and hardware problems to be resolved fJr continuing and improving operations. Most of the modest developmental effort is dedicated to solving relatively short term problems that arise as circumstances change, or as long-standing complaints can be worked off. Long term larger projects also are worked to maintain compatibility with DSN computer interfaces (e.g., for commands) and with NASCOM (e.g., for bit error corrections and longer data blocks). Maintenance of very long term competence in the data processing software is an important objective in scheduling of these efforts.

7.3 Flight Operations

Flight Operations are routinely conducted in the Pioneer Mission Operations Center at ARC by support services contractor personnel. Computers have been kept on,

35 Document No. PC-1001 Original Issue: 20 May 1981 R~vision:(1): 11/30/82 (2): 06/15/90 and the facility has been manned, 24 hours per day, 365 days per year since the · summer of mid-1965 except for one shift on each of the last three Christmas holidays. Console operators are in constant voice communications with the DSN operations center at JPL. All of the immediate detailed coordination of tracking operations, command transmissions, and telemetry data flow are handled by these operators. At least one flight operator and a computer operator are nominally on duty at all times at ARC for the extended Pioneer Missions.

Daily operations nominally include three DSN station passes for the Pioneer Venus Orbiter, two passes for Pioneer 10, one or two passes for Pioneer 11, and an occasional (2 or 3 per year) pass for ohe of the Pioneer 6-8 series. Each pass is typically 6 to.11 hours in duration. Exceptions are imposed by DSN operating schedules, and by occasional special competing circumstances.

Operations procedures are defined and documented by the ARC engineering staff. PC-488, "Pioneer Venus Orbiter In-Orbit Operations," specifies operations for the Pioneer Venus Orbiter. PC-250, "Pioneer FIG Standard Procedures for Flight Operations," specifies operations for Pioneers 10 and 11. PC-053, "Pioneer A Flight Operations - Standard Procedures," defines the operating procedures for Pioneer 6, and is applicable for Pioneers 7 and 8. However, the DSN's Network Operations Plan 616-55 is a more current reference for Pioneers 6-8.

Special operations, such as maneuvers or unusual spacecraft or instrument tests, are additionally attended by specialists from the ARC (or the contractor's) staff.. Maneuvers to change Pioneer Venus Orbiter's orientation or spin rate, for example, are directed by an ARC engineer. The more routine reorientations of the Pioneer ~ 10/11 _spin axis adjustments are directed by a specially qualified contractor ·, __ . representative, who regularly reviews plans and procedures with ARC engineers.

The duty personnel have lists of home telephone numbers of cognizant ARC engineers to call when problems arise that cannot be resolved by prescribed procedures. If the telephone communication does not suffice, engineers usually can be in the ceriter within about 30 minutes when the situation requires. The worst of these types of problems appear to have diminished to an average of several months between occurrences with experience accumulated to date. In addition to the regular Pioneer staff engineers, former members of the Pioneer team at ARC experienced in the development of the spacecraft are called upon when their advice is needed.

Maintenance of the computers used in Pioneer operations is contracted to companies speciP~:zing in such service. The facility has sufficient depth to operate with any two spacecraft while any one computer string is disabled, so off-hour premium maintenance expense is minimized. A Pioneer Missions Office staff engineer monitors and directs the maintenance contract support .

. Metric tracking data are analyzed and processed by the Navigation Team at JPL. Trajectory predictions are provided by the Navigation Team to the DSN for computations of pointing angles and Doppler shifts to be used in DSN operations with all Pioneer spacecraft. They provide daily predictions of the exact epoch of periapsis of the Pioneer Venus Orbiter so that the detailed command sequence schedule prepared at ARC can be keyed to it. The Navigation Team also provides periodic predictions of orbital parameters for use in ARC computers, to relate commands to conditions such as eclipses and occultations. ~

36 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(1): 11/30/82 (2): 06/15/90

Logs of engineering data, command transmissions, and operational factors are maintained by the PMOC staff. ·

7.4 Data Processing and Distribution About 5,000 computer tapes are sent to experimenters annually. In addition, packages of "quick look" printed data are sent to some investigators to maintain checks of configuration and performance prior to the total processing sequence. Also, raw and processed trajectory and signal strength data are sent directly to radio science investigators by the Navigation Team at JPL.

7 .4.1 Pioneers 6-8

Data from Pioneers 6-8 are produced in the form of printed tabulations only.

7.4.2 Pioneers 10 and 11

Data from Pioneers 10 and 11 are processed on ·a Xerox Sigma 5 computer in the Pioneer Mission Computer Center (PMCC) to produce Experimenter Data Records (EDRs). This processing is accomplished by the regular shift crew in the computer center. EDRs for Pioneers 10 and 11 are normally processed 12 to 24 days after origination. Trajectory (TRAJ) tapes, which provide orbital information, are produced annually.

7 .4. 3 Pioneer Venus Orbiter (Pioneer 12)

Data from the Pioneer Venus Orbiter are normally processed within 12 to 24 days after origination. Intermediate data records are shipped from JPL, and command and orientation data are prepared at ARC. These data sources are then used as input to the processes which produce Experiment Data Records (EDRs) and Supplemental EDRs (SEDRs) which provide orbital information, attitude data, and command files. The individually designed EDRs and SEDRs are shipped to the Investigators' laboratories where they can be read directly on their computer systems. The data processing for the Pioneer Venus Orbiter is performed on a Xerox Sigma 9 computer in the PMCC by the regular shift crew.

7.5 Scientific Data Analyses and Reporting

7.5.1 Data Analysis Activities

Analyses of scientific data, modeling of the Venusian or interplanetary space environment, and reporting to the scientific community are conducted by the Principal Investigators, Interdisciplinary Scientists, and participants in the Guest Investigator Program. The Project Scientists at ARC monitor publication activities related to the Pioneer Missions. They lead, or assist in the coordination of, scientific meetings dedicated to the Pioneer areas of investigation. The Project Scientists for both Pioneer Venus and Pioneers 10 and 11 actively participate in the review of the yearly proposals for continued research, funded as parts of the Pioneer Missions, advise on their merits and recommend priorities for the proposed investigations.

37 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 Publication of results from Pioneer Missions data is required of all investigators, as are submission of reduced data and related information to the National Space Science Data Center (NSSDC). 7 .5.2 Data Archiving

Pioneer Venus data, in reduced fonrt; is routinely submitted to the National Space Science Data Center which serves as a central base for archiving these data. In addition to these submissions of data to NSSDC, NASA's Planetary Data Systems (PbS) Committee is urging development of a high resolution archive of Pioneer data. the NSSDC and PDS Committee will decide which data will reside at each institution.

38 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 8. MANAGEMENT · Management of the Pioneer Missions at Ames Research Center is described below in terms of organization and responsibilities.

8.1 General

General managment responsibility for the Pioneer Missions is assigned to the Pioneer Missions Office (Code SEP), which is part of the Space Exploration Projects Office (Code SE) of the Directorate (Code S), at Ames. Science policy guidance for Pioneer Missions is provided from the Space Science Division of the Space Research Directorate. ARC's top management holds a semi­ annual review of the Pioneer Missions work at ARC, and annual meetings are scheduled with NASA Head-quarters to maintain visibility of objectives and progress for program officials.

General management at the Branch level and above consists of policy review and provisions for local resources and administrative support. Except for scientific oversight and occasional specialized engineering assistance, ARC personnel directly supporting Pioneer Missions are members of the Pioneer Operations Office. The Pioneer Project Manager and Pioneer Missions Office Chief is R. 0. Fimmel.

8.2 Scientific Policy

Scientific policies of the Pioneer Venus Mission are developed by the Science Steerj.ng Group (SSG) under the leadership of its chairman. Interfacing with the Mission management is the responsibility of the Project Scientist, L. Colin. The Pioneer 10/11 Project Science Group (PSG) advises the Mission management via the Pioneer 10/11 Project Scientist, P. Dyal, also the Assistant Director for Projects, Space Research Directorate. Scientific guidance for Pioneers 6-8 is accepted directly from users of the data.

8.3 Missions Management

Manager of the Pioneer Missions is R. 0. Fimmel, Chief of the Pioneer Missions Office. He is responsible for budgeting and for overall direction of the Pioneer Missions execution. As ongoing flight operations, these missions have priority claim on the resources of the office as necessary to maintain optimum operations.

Other key assignments include:

Director of Flight Operations, D. W. Lozier- responsible for procedures and for operating interfaces with JPL.

Science Chief, L. E. Lasher - responsible for responsiveness of operations to specific requirements of scientific investigators.

Computers and Facilities Engineer, M. N. Wirth - responsible for performance and updating of data communications, computational, and display facilities.

39 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11!30/82 (2): 06/15/90 Technical Monitor for Support Services Contractor, M. N. Wirth and R. 0. Fimmel - responsible for directing the contracted support services for operations, data processing, and software.

Data Processing, L. E. Lasher - responsible for post-processing and delivery of data for scientific analyses.

Administration and Budgeting, C. L. Jackson - responsible for accounting for funds required, available, committed, and obligated.

Support of the Pioneer Missions for operations, data processing, and software maintenance and updating is contracted to a services contractor - presently the Bendix Field Engineering Corporation. The contractor is responsible for on line operations 24 hours per day in accordance with procedures provided, or approved, by the SEP respresentative. The contractor is similarly responsible for timely processing of data, and for shipping it to scientific investigators. Software in use, both on-line and off-line, have been adapted to operational use under this same contract; and necessary modifications and advances in software design are accomplished by the contractor subject to the direction of the SEP representative.

Support by JPL for Deep Space Network operations and for navigation are provided for as stated in Section 9.

In addition to the senior engineering assignments listed above, several engineers have joined the SEP since its establishment late in 1979. These newer personnel are assuming ever increasing responsibilities for the direction of Pioneer mission ~- activities in anticipation of the continuing operational mission for 5 more years. Figure 8. 3-1 shows the Pioneer functional organization in bloclc form.

8.4 Project Control

Budgetary requirements are established in the annual NASA Program Operating Plan (POP) cycle by the Pioneer Missions Manager with the assistance of the key personnel designated above. The budget, and· the process of adjusting to guidelines, are actively reviewed by the SEP Office management. Final submittals to Headquarters are reviewed by the Space Projects Division management.

. Nearly all expenditures fall into four major areas: science and data analysis, operational support services, navigation and tracking support, and computer main~;;11ance and related expense. All scientific investigations are controlled )Jy a formal process of proposal review and are activated by contracts, grants, or letters ofagreement. Support for navigation and DSN coordination is provided under a letter of agreement with JPL, and budget requirements are negotiated annually. Operational support services are contracted under a single performance incentive contract monitored by means of NASA Form 533 financial reports, monthly progress reports, and daily interactions with the SEP staff. Computer maintenance services are contracted competitively at fixed price.

Other expenditures, mostly for updated computer subsystems and for supplies, are made for GSA stock itenis or by standard procurement processes. The Ames management information system is used to track the status of commitments and

40 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(l): 11/30/82 (2): 06/15/90 obligations and costs. The Project Control Office (SE) maintains an overview of the Pioneer Missions fiscal status.

Technical status and problems of mission operations are reviewed weekly by the Pioneer Missions Manager in a joint meeting of supporting SEP personnel and the several key support services contract personnel. Monthly DSN support coordination meetings at JPL are attended by a Pioneer Missions Office representative. Monthly reports are made to the Headquarters Program Manager. Biannual meetings are held with the Science Steering Group for Pioneer Venus, and an annual meeting with the Pioneer 10/11 Project Science Group.

41 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(l): 11/30/82 (2): 06/15/90 9. RESOURCES 9.1 Tracking and Data Acquisition

The "Tracking and Data Systems Support Agreement," which documents the agreement between OSSA and OSTDS for continued support by the DSN of the Pioneer Missions, has been negotiated with JPL. The agreement specifies continuation of the DSN interface with the Project Control Center operations at Ames Research Center. The agreement includes the following requirements:

Pioneer 6-8 - One four-hour track per month per spacecraft as time is available; daily tracks when special spacecraft alignments occur.

Pioneer 10-11 - Two tracks per day per spacecraft are required. Pioneer 10 and 11 must have 70-meter antenna coverage due to extreme distance.

Pioneer 12 (Venus)- Two and one-half tracks per day are required, using a mix of 34- and 70-meter coverage. (The typical "track" interval is eight hours.)

A detailed definition of the Pioneer Mission tracking requirements and science objectives upon which the "Tracking and Data Systems Support Agreement" is based is provided in Appendix B. This description of requirements and objectives is divided into two parts. The first part is a definition of the Pioneer Project guidelines for spacecraft survival tracking for Pioneer 10, 11 and 12. The. second part deals with Pioneer 12 tracking requirements, scientific objectives· and the impact upon achieving the stated objectives incurred by a reduc.tion of tracking to ~

levels below the basic tracking requirements. ' _¥

Practical limitations of scheduling are recognized. During certain periods, such as Voyager planetary encounters or scheduled DSN station downtimes for upgrading antennas from 64 to 70 meters, or other purposes, only minimum tracking support for Pioneer spacecraft was available. "Minimum" tracking includes: daily contacts with Pioneers 10, 11, and 12 to maintain their radio system configuration and allow for minimal health monitoring; periodic reorientations of Pioneer 10 and 11 spin axes to maintain Earth communication; commandingPioneer 12 battery charge . control during long eclipse seasons; continuous (if practical) tracking during spacecraft hazardous flight conditions which might threaten to curtail their continued productivity.

Finall:;, the Agreement provides that, as Pioneer 10 and 11 approach the ultimate limit of DSN's ability to acquire data from the extreme range, DSN's then-available special augmentation techniques (such as arraying or improved receivers) will be applied to maintain communications.

9.2 Ground Data System

Telemetry data from, and command inputs to, the six operating Pioneer spacecraft are processed at ARC using the facilities described below. Monitoring of spacecraft and instrument health, distribution of telemetry data, and interfacing with DSN are all accomplished at these facilities, which are located on two floors of the Space Projects Facility Building (Building N-244), and staffed by a support services contractor. The system is diagrammed in Figure 9.2-1. ~

42 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90

9.2.1 NASCOM The Pioneer mission operations staff rely on the NASCOM communications network to monitor and control all Pioneer spacecraft. Six alternate voice/data circuits between ARC and the West Coast Switching Center at JPL exist, with the capability to terminate up to four high speed data sets simultaneously at ARC, at 9600 BAUD each. Two-way voice communications are provided to JPL, GSFC, . and DSN tracking stations. Patch panels and switching consoles are employed to switch among the four data sets and the different voice stations.

9.2.2 Pioneer Mission Computer Center CPMCC) The PMCC contains four DEC PDP-11/44 computers, one Xerox Sigma 5 computer, and one Xerox Sigma 9 computer. Each of the PDP-11/44 computers is connected to four NASCOM data sets. The Xerox computers are stand-alone processors for Experimenter Data Records (EDR) production. Figure 9.2.2-1 shows the computer configuration diagram of the PMCC.

Three of the four PDP-11/44 computers are dedicated for real-time commnand and telemetry processing. Each of these on-line computers can process the telemetry data for any two Pioneer spacecraft simultaneously, or can be used to command any two Pioneer spacecraft simultaneously. The fourth PDP-11/44 computer serves as back-up to the on-line systems, as an engineering data base processor, or as a software development system. All PDP-11/44 computers are connected to Video Display Terminals (VDT's) and Low Speed Printers (LSP's) via 16-port multiplexers.

The Sigma 5 computer is used off-line to process Pioneer 10/11 Experimenter Data Records for the Principal Investigators.

The Sigma 9 computer is used off-line to process Pioneer Venus Experimenter Data Records for the Principal Investigators.

9.2.3 Pioneer Mission Operations Center CPMOC)

The PMOC consists of two large control consoles containing video display terminals, voice communication stations, and high speed data control and display equipment. In addition, several low speed line printers are available for monitoring the spacecraft and instrument status and health. Processin: performed by the PMCC computers is controlled by the mission controllers in the PMOC using display terminals, both in command and data reduction modes. In addition, the controllers can monitor tracking station performance and coordinate tracking station operation with the DSN; they continuously monitor health of engineering subsystems and science instruments on all the Pioneers, and control instrument operating parameters; and they perform trajectory modification and attitude control maneuvers from the PMOC.

9.2.4 Navigation Data System

Navigation data used for precise orbit determination of all Pioneer spacecraft are (';.....__, obtained from the tracking Intermediate Data Records (IDR) recorded at JPL.

43 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 Doppler and Doppler rate data sent from the DSN stations are recorded by the JPL Central Communication facility in the IDR format.

The IDR tapes are used by the Pioneer Navigation Team at JPL to produce the best trajectory prediction for each of the Pioneer spacecraft. The IDR tape is processed on JPL's Univac 1108/81 computer to edit the raw data and eliminate errors. The output from this process is then processed by the Orbit Deter-mination Program (ODP) to produce the spacecraft state vector.

.The state vector produced by the ODP is used ·to generate a predicted trajectory ephemeris which is sent, in the form of a 'SAVE Tape', to the Pioneer Project Office at ARC. Here the trajectory is merged with other data to produce Supplementary Experimenter Data Records (SEDR's) for distribution to the individual experimenters in formats compatible with their data systems.

9.2.5 Unified Abstract Data System CUADS)

This capability was terminated on January 31, 1982.

9.3 Manpower The sections that follow enumerate the personnel assigned to various tasks supporting all the Pioneer missions, both at ARC and elsewhere. Personnel levels at ARC, both civil service and contractor, are shown in Table 9.3-1.

9.3.1 Management and Technical Direction

NASA/ARC civil servants tasked with the management and coordination of all Pioneer mission activities consist of approximately eleven full time equivalent personnel.

9.3.2 Flight Operations and Data Processing and Distribution

Flight operations and data processing and distribution activities are contracted as support services, employing 42 personnel at ARC.

9.3.3 Support

The Pioneer missions are directly supported by personnel at JPL charged to the Piow~:.r Project, as described in the following sections.

9.3.3:1 DSN Scheduling and Coordination

Two JPL employees are assigned to Pioneer missions for DSN scheduling and coordination.

Navigation Support

The JPL navigation support team for Pioneer missions, occupies 5 personnel and employs the computer facilities at JPL.

44 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 9.3.4 Scientific Investigators Approximate manpower commitments to scientific investigations of the Pioneer missions in 1987 are outlined below. Budgetary constraints have severely reduced the numbers and intensities of individual involvements beginning in 1982.

9.3.4.1 Pioneers 6, 7 and 8 Scientific investigations of Pioneer 6-8 data do not account for any specifically identifiable (nor chargeable) manpower, but are treated as part-time adjuncts to the efforts of about a dozen scientists at ARC and other agencies.

9.3.4.2 Pioneers 10 and 11 Scientific investigators who are active on the Pioneer 10 and 11 programs include 8 Principal Investigators and 35 Co-investigators at various NASA centers, other agencies, and universities.

9.3.4.3 Pioneer Venus Orbiter (Pioneer 12)

\ Scientific investigators who are active on Pioneer Venus Orbiter comprise 9 Principal Investigators, 42 Co-investigators, 11 Guest Investigators, and 5 interdisciplinary scientists at NASA centers, other agencies, and universities (see Table 6-1).

9.4 Funding

Funding for the Pioneer Missions is authorized under UPN 889-50 for Pioneer Venus, and under UPN 889-51 for Pioneers 6 through 11. Projections beyond the primary missions were initiated in POP 80-1, and have been sustained through POP 89-1. The scientific potential and spacecraft health of Pioneer Venus currently suggest projection through 1992, as periapsis migrates into Venus' southern hemisphere with data analysis continuing through FY 1994.

The corresponding projection is also made for Pioneers 6-11. Pioneer 10 appears o have the longest life potential, continuing beyond 60 AU from the Sun in 1995. Both electrical power and communications limits (based on currently existing technology) are likely to be reached by mid-1990's. Pioneer 11's power supply is decaying somewhat faster and probably will not continue beyond approximately 40 AU reached in early 1995. Pioneers 6-8 should continue to br productive also for several more years, but their budgetary impact is very small.

The DSN is in the process of developing a very sensitive receiver with loop bandwidths of 0.1 to 0.3 hertz, which are expected to improve performance by 3 dB. This could extend the communications capability for both Pioneer 10 and 11 beyond the year 2000.

Dispositions of funds are currently as projected in the POP's. More than half is allocated to scientific investigators. Of the balance, about one third is for the operational support services contract; somewhat less is for JPL's navigation and DSN coordination support; and the remainder is for computer maintenance, equipment purchases, computer leasing, magnetic tapes, etc.

45 DocumentNo. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90

Budget constraints compared with investigators' proposals have been resolved hrough negotiations based upon the advice of the Project Scientists and the comparative analyses of costs for described activities. Staffing within the support services contract has been reduced since the primary mission to conform with the more stable operating environment. JPL has similarly reduced staff and prime-time computer usage for navigation support.

TABLE 9.3-1. MANPOwER, AMES RESEARCH CENTER

FISCAL YEAR (Note 2) 1989 1990 1991 1992

CIVIL SERVICE (Note 1)

Project Management, 11 11 11 11 Technical Direction

CONTRACTOR

Mission Operations 42 ' 42 42 42 Support

(1) Equivalent full time positions

(2) POP89-1 projections for operations through 1992. Later POP's will be extended.

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MEAN ORBITAL DISTANCE FROM SUN \ *BASIC SOLAR MOTION IS 39.4AU DEFINED WRT LOCAL ...... ::.. 1\) SYSTEM OF REST FOR ...... I STARS IN ·SOLAR Voo :: ~ AU/yr 0 "T1 NEIGHBORHOOD• fj :: ECLIPTIC LATITUDE, deg A ::. ECLIPTIC LONGITUDE, deg :IIm ""0 ~ cCJ Lm~ All ITUDE PUASE U7' NOR HI> RE-ENTRY (lOa SOUTH) 0m CJ 11 1979-1930 1992 ~ s:::

:Dm < z ""(J . ECLIPSES 9 m-e ~ :D­ SUPERIOR CONJUNCTION 1\) :l>z-o -em 0 ~m CfJ:o )>

SUPERIOR CONJUNCTIONS 1\ 1\ 1\ 1\ 1\

ORBIT NUMBER (DAYS) 1000 2000 3000 4000

0 1 CELESTIAL ----NORTH ECLIPTIC PLANE

19920RBIT

19860RBIT ~----.,.

REPRODUCED FROM TITLE PIONEER PROGRAM NASA ORBITAL DYNAMICS OF AMES RESEARCH CENTER PIONEER VENUS ORBITER: . MOFFETT FIELD, CALIFORNIA 1980-1992 DOC. NO. PC-1001 FIG. 4.3-2 REV. NO. 2 DATE 6/15/90 SHEET 1 OF 1 z 9 J 1\) 87.20. / M~GNETOMETER. iX.PERIMEt.jf . r·" SUN.... ,_. ·.· SENSORS..• , ...

-- -..,., .,.__,.~ ~ .... WOB~~~ ()AMP~R

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QRIENT~TI9~ N()Z~l.E

EQUIPMENT PLATFORM ., . - '• ' . . .. •:~ . ' . . . ~ - : :·· -

0 IMAGING PHOTOPOLARIMETER

GEIGER TUBE TELESCOPE

·METEOROID DETECTO~ SENSOR PANEL ~/ ASTEROID - METEOROID DETECTOR SENSOR HELIUM VECTOR MAGNETOMETER

ttr,....--....~;;,;;;;I....--TRAPPED RADiATION ~~~'),~~ DETECTOR

FLUX GATE MAGNETOMETER INFRARED RADIOMETER CHARGED PARTICLE INSTRUMENT

REPRODUCED FROM TITLE PIONEER PROGRAM NASA AMES RESEARCH CENTER PIONEER 10 AND 11 SPACECRAFT MOFFETI FIELD, CALIFORNIA DOC. NO. PC-1001 FIG. 5.2-1 REV. NO. 2 DATE 6/15/9~0 SHEET 1 OF 1 MAGNETOMETER OMNIANTENNA BOOM

BACKUP HIGH GAIN ANTENNA

MECHANICALLY DESPUN ANTENNA ASSEMBLY

HIGH GAIN ANTENNA FORWARD AXIAL THRUSTER

SUN SENSOR ~. --' STAR SENSOR

SOLAR ARRAY DESPIN BEARING RADIAL THRUSTER EQUIPMENT SHELF ORBIT INSERTION MOTOR AFT OMNI ANTENNA

REPRODUCED FROM TITLE PIONEER PROGRAM NASA. AMES RESEARCH CENTER PIONEER VENUS ORBITER SPACECRAFT MOf=FETT FIELD, CALIFORNIA DOC. NO. PC-1001 FIG. 5.3-1 REV. NO. 2 DATE 6/15/90 ·SHEET 1 OF 1 (} (} (}

JJ m "'tl e3 0 FISCAL c SUPPORT 0 m PIONEER MISSIONS 0 SSG-PV PROJECT "TI OFFICE C. JACKSON JJ SCIENTIST s::0 T.DONAHUE r- - D.HUNTEN L.COLIN : PIONEER VENUS PROJECT R. FIMMEL SCIENTIST MANAGER --1 I P. DYAL JJ =i m r M.WIRlH PIONEER 10/11 :< m z OMOP-PV DEPUTY MANAGER 9 c"'T1 z H.MASURSKY 0 D.HUNTEN PROJECT 1\) _, SCIENCE CHIEF 0 z J. MIHALOV ~:-u ,..- ro PIONEER 6-9 0 oz :nm ~ Ci)m I I l I ~:II FLIGHT SIC ANALYSIS ..._0) z SCIENCE DATA COMPUTERS & NAVIGATION _. INTERFACE PROCESSING COMMUNICATIONS OPERATIONS & MANEUVERS R.JACKSON U1 ~ ..._ _, D. LOZIER M.SMITH (0 L. LASHER L. LASHER M.WIRTH J. PHILLIPS 0 J. PHILLIPS 0 z I

PRINCIPAL · . JPLDSN en ::!! 0 "tJ INVESTIGATORS OPERATIONS ::c 0 m p p ~:t> 0- PIONEER 10/11112 !!! z =H~ z 9 ~en m _. JJ m ::!!rnz:u (X) ""C )> "tJ (.,J 0 p:! g;! BENDIX FIELD ENGINEERING 0 I OJJCJ) "TI _.I _. ·o :D CORPORATION 0 ~::c>o _.0 cfri G) T. YOUNG, MANAGER _. "TI z :D ~ill )> ~ JJ s: :n m "'U ~ c0 m0 0 "'T1 ~ NETWORK PIONEER MISSION OPERATIONS s::: DEEP SPACE STATION (DSS) I CONTROL SYSTEM (NCS) I CONTROL CENTER (PMOCC) I I

I PDP-11 :n -I CMD PIONEER m ;3 COMMAND .._MISSION CONTROL :< m TELEMETRY PROCESSOR z ""'0 5 ITLM) HSDL 9 z m COMMAND m (CMDI PDP-11 JJ G> PIONEER JJ MISSION CONTROL 0 c NETWORK 0 z CONTROL 0 SYSTEM ~ 0 m )> TRACKING O'l ~ (RMD) ...... -01 ~ (/) co -; -0 m s: -_I

DSN OPERATIONS CONTROL --....1 (/) "'T1 0 "tt I p 0 s:::)> - m () ~s::: 0 "'Tlm z ~ z men m 9 ~~ m ...... co ""'0 :!!cnz:tl 1\) () I I !Il~l>"tt ...... _o~cn::u 0 0 0 "TI ...... §;:x::>o -mrO G') ...... (Jz :tl ::Drrl ZJJ :r>. )> 3: () (} ()

DATA SET 1 DATA SET 2 DATA SET 3 DATA SET 4 T I I I ' PATCH PANEL ::0 m -1 ~ ~m z -uO I I 0 -0 I I 0:;: Z-u BED 1 BED 2 BED 3 BED 4 BED • li.OCK ENCODER/D£CODER me m-i :om -os::::D I I I I 1-- cno 0 o,~z )> z- BMXR 1 BMXR 2 BMXR 3 BMXR 4 -Im o~ "'U:IJ m::x> ::0--i::x>­ ~ ~ ~ -~ --10 ~ 11 n a ~ 11 n a ~ 11 n a aoo 11 n a o,-z ' ~ ~ ~ ~ ' ~ ~ zo ' ' ~ ~ cn::o

I PDP A I I PDP B I I PDP c I [::1 PDP D~~ en 11 o "'tt I 0 0 I BACKUP/ m o ~~ 0 I'------COMMAND AND TELEMETRY PROCESSING----"- OFTWARE 11m ·Z DEVELOPMENT ~ z m U> m DATA BASE 9 ~::o m EXPERIMENTER ~ ...... c.o ,rnz:c EXP£RIUENTER -u iii m- DATA RECORDS SIGMA 9 DATA RECORDS ~ N 0 r)>-"'tt PRODUCTION - , o ::o en (PIONEER VENUS) PRODUcnOH 0 I}';::;-() :c (PIONEER 10/1 t) , ...... o ~ :::r:l>o ...... r () - - m u1 ~~ :c :Om )> ~::0 s: Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90

APPENDIX A

PIONEER VENUS ORBITER GUEST INVESTIGATORS

INVESTIGATOR INSTITUTION TITLE

FY1981

C. Bowin Woods Hole "Gravity, Topography and Crustal Oceanographic Evolution of Venus" Institute

M. Dryer National Oceanic "Viscous Interaction of the Shocked and Atmospheric Solar Wind with the Ionosphere of Administration Venus"

J. Fox University of "Studies of the Role of Meta Stables Illinois and Doubly Ionized Species in the Chemical and Thermal Structure of the Venusian and Martian "

J. Gerard Institut "Chemistry and Transport of Thermo- D'Astrophysique spheric Odd Nitrogen on Venus"

S. Kumar University of "Determination of Global H2 Distri- Southern bution from the OIMS Measurements California

S. Limaye University of "Morphology and Movements of Polar- Wisconsin ization Features"

P. Rodriguez Corp. "Plasma Waves in the Venus Ionosheath"

R. Wolff JPL "A Study of the Dynamics of the Venus Ionosphere"

A. Young California State Proposal to Investigate the Clouds University, San and Atmosphere of Venus" Diego

FY1984

A. Ajello - JPL "Pioneer Venus Observations of Inter- planetary Lyman-Emissions: Inter-action of the Solar Wind and Solar Lyman with Interplanetary Gas"

A-I Document No. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90

APPENDIX A

PIONEER VENUS ORBITER GUEST INVESTIGATORS (CONTD)

INVESTIGATOR INSTITUTION TITLE

J. Appleby JPL "Local Variability in the Stratospheric Thermal Structure of Venus"

G. Balmino Bureau "Venus Gravity Field- Improvement of Gravimetrique a Global Model as a First Step Towards a International PVO-VRM Future Combined Solution"

R. Daniell Beers Associates "Turbulent Flow in the Venus Ionosphere"

E. Greenstadt TRW "Initial Study of Venus Foreshock"

S. Kumar University of "Venus Ionosphere: An Investigation of Arizona Some Problems Regarding Composition and Structure"

S. Limaye University of "Dynamical Behavior of the Haze Layer Wisconsin on Venus from Pioneer Venus Orbiter Cloud Photopolarirneter Data"

M. McElroy Harvard "Photochemical Modeling of Venus' Clouds Using PV Data"

R. Meier Naval Research "An Improved Model to Obtain Hydrogen Laboratory Densities from an Analysis of the Lyman­ Alpha Airglow on Venus"

P. Mouginis-Mark University of "Terrain Analysis of Pioneer Venus Hawaii Altimetry Data"

H. Revercomb University of "Diagnostic Modeling of Meridional Wisconsin Circulation of Venus"

J. Rodriguez Atmospheric and "The Variability of Exospheric Hot Environmental Hydrogen Concentration andEscape of Research, Inc. Hydrogen in Venus"

B. Schizgal University of "Data Analysis of the Pioneer Venus British Columbia Mission of the Upper Atmosphere and Exosphere of Venus: A Test of Theoretical Models"

J. Slavin JPL ·"A Study of the Venus Magnetotail"

A-2 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90

APPENDIX A

PIONEER VENUS ORBITER GUEST INVESTIGATORS (CONTD)

INVESTIGATOR INSTITUTION TITLE

D. Smith Berkeley Research "Three-dimensional Simulation-Data Association Interaction for the Plasma Environment of Venus"

Y. Yung California "Photochemical Production of H2S04 Institute of Aerosols on Venus" Technology

FY1985

J. Ajello JPL "Pioneer Venus Observations of Inter­ planetary Lyman-Emissions: Interaction of the Solar Wind and Solar Lyman with Interplanetary Gas"

J. Anderson · JPL "Analysis of Pioneer Venus Radio Science Data: Improvement of Venus Science"

J. Appleby JPL "Local Variability in the Stratospheric Thermal Structure of Venus"

E. Greenstadt TRW "Initial Study of Venus Foreshock"

J. Fox State University "Studies of the Aurorally Induced UV of New York Emissions of the Nightside of Venus"

S. Kumar University of Venus Ionosphere: An Investigation Arizona of Some Problems Regarding Composition and Structure

S. Limaye University of "Dynamical Behavior of the Haze Layer Wisconsin on Venus from Pioneer V .:nus Orbiter Cloud Photopolarimeter Data"

P. Morgan Purdue University "Investigation of the Mode of Compen­ sation of Venus Topography"

P. Mouginis-Mark University of "Terrain Analysis of Pioneer Venus Hawaii Altimetry Data"

L. Paxton Naval Research "Photoelectrons in the Venus Thermo­ Laboratory sphere: An Intercomparison of PVORP A and PVOUVS Measurements and Model Calculations"

A-3 Document No. PC~ 1001 Originallssue: 20 May 1981 Revision:(!): 11!30/82 (2): 06/15/90

APPENDIX A

PIONEER VENUS ORBITER GUEST INVESTIGATORS (CONTD)

INVESTIGATOR INSTITUTION TITLE

H. Revercomb University of "Diagnostic Modeling of Meridional Wisconsin Circulation of Venus" ·

J. Rodriguez Atmospheric and "The Variability of Exospheric Hot Environmental Hydrogen Concentration and Escape of Research, Inc. Hydrogen in Venus"

B. Schizgal University of "Data Analysis of the Pioneer Venus British Columbia Mission of the Upper Atmosphere and Exosphere of Venus: A Test of Theoretical Models"

N. Sheeley Naval Research "Coronal Mass Ejections and Shocks at Laboratory Venus"

J. Slavin JPL "A Study of the Venus Magnetotail"

D. Smith Berkeley Research "Three-dimensional Simulation-Data Association Interaction for the Plasma Environment of Venus"

Y. Yung California "Photochemical Production of H2S04 Institute of Aerosols on Venus" Technology

FY1986

A. Ajello JPL "Pioneer Venus Observations of Inter­ planetary Lyman-alpha Emissions: Interaction of Solar Wind and Solar Lyman-'alpha with Interplanetary Gas"

K. Anderson University of "Measurements of the Spatial Structure California and Directivity of> 100 kev Photon Berkeley Sources in Solar Flares Using PVO and ISEE-3 Spacecraft"

J. Appleby JPL "Analysis of PV-OIR Observations at 2 microns"

P. Clark JPL. "Comparison of Earth-Based s:.. and X-Band Radar Observations with Orbital Radar Observations"

A-4 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90

APPENDIX A

PIONEER VENUS ORBITER GUEST INVESTIGATORS (CONTD)

INVESTIGATOR INSTITUTION TITLE

L. Elson JPL "Venus Atmospheric Wave Dynamics"

J. Fox State University "Continuation of Study of the Aurorally of New York Induced UV Emission of the Nightside of Venus"

E. Greenstadt TRW "The Upstream Magnetic Environment of Venus"·

M. Harel JPL "An Investigation of the Venus Ionosheath:- Mass Loading and Depletion Layer Formation"

W. Hoegy Goddard Space "Pioneer Venus Data Analysis of ONMS Flight Center and OETP Data for Evidence of Thermo­ spheric Internal Gravity Waves, Plasma Waves, and Neutral Density Structure"

S. Limaye University of "Dynamic Behavior of the Haze Layer on Wisconsin Venus from the OCCP and the OUVS Observations"

L. Paxton Naval Research "Analysis of the Orbiter Ultraviolet Laboratory Spectrometer OI 1304 Limb and Disk Data"

H. Revercomb University of "Radiative Drive for the Circulation of Wisconsin Venus"

J. Rodriguez Atmospheric and "The Aeronomy of Atomic Hydrogen on Environment the Day- and Nightsides of Venus" Research, Inc.

P. Rodriguez Naval Research "Venus Magnetosheath: f ~asma Wave Laboratory Turbulence"

D. Winske Los Alamos "Structure of the Venusian Bow Shock" Research Laboratory

R. Wolff JPL "Plasma Streamers, Rays, and Clouds in the Venus Ionosheath"

A-5 Document No. PC-1001 Original Issue: 20 May 1981 Revisiori:(1): 11/30/82 (2): 06/15/90

. APPENDIX A-

PIONEER VENUS ORBITER GUEST INVESTIGATORS (CONTD)

INVESTIGATOR INSTITUTION TITLE

R. Woo JPL "Pioneer Venus Radio Observations of Interplanetary Disturbances within 0.3 AU" FY1987

J. Ajello JPL "Pioneer Venus Observation of Inter­ planetary Lyman-alpha Emissions: Interactions of the Solar Wind and Solar Lyman-alpha with Interplanetary Gas"

K. Anderson University of "Measurements of the Spatial Structure California, and Directivity of> 100 keV Photo Sources Berkeley in Solar Flares Using PVO and ISEE-3 Spacecraft"

P. Clark JPL "Utilization of S-and X-Band Ground­ Based and Pioneer Venus Orbiter Radar Observations to Characterize Surface and · Lower Atmosphere of Venus"

L. Elson JPL "Venus Polar Atmospheric Dynamics"

J. Fox State University "Studies of the Aurorally Induced ofNewYork Ultraviolet Emissions on the Nightside of . Venus"

E. Greenstadt TRW "An Investigation and Characterization of the Venus Foreshock and Upstream Wave Environment"

M. Harel J'PL "An Investigation of the Venus Ionosheath: Mass Loading and Depletion Layer Formation"

S. Limaye University of "Dynamic Behavior of the Haze Layer on . Wisconsin Venus from the Pioneer Venus Orbiter Cloud Photopolarimeter (OCPP) and Ultraviolet Spectrometer (OUVS) Observations"

P. Morgan Northern Arizona "A Combined Analysis of Venusian University Gravity and Surface Morphology"

A-6 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(l): 11/30/82 (2): 06/15/90

APPENDIX A

PIONEER VENUS ORBITER GUEST INVESTIGATORS (CONTD)

INVESTIGATOR INSTITUTION TITLE

J. Rodriguez Atmospheric and "The Aeronomy of Atomic Hydrogen on Environment Day- and Nightside of Venus" Research, Inc.

R. Woo JPL "Pioneer Venus Radio Observations of Interplanetary Disturbances within 0.3 AU"

FY1988

K. Anderson University of "Measurements of the Spatial Structure California at and Directivity of> 100 keV Photo Sources Berkeley in Solar Flares Using PVO and ISEE-3 Spacecraft"

W. J. Borucki NASNAmes "Optical Search of Venus Nightside"

S. W. Bougher University of Arizona "Ionosphere-Thermosphere Solar Variation"

S. H. Brecht Berkeley Research "Venus/Solar Wind Interaction Model" Associates

D. L. Carpenter Stanford University · "Plasma Waves and the Lightning Question"

R. T. Clancy University of Colorado "Microwave/ORO Atmosphere Temperature Correlations"

E. G. Fontheim University of Michigan "Bowshock Precursors"

J. L. Fox State University of "Nightside Ionosphere Chvmistry" New York

M. Harel Jet Propulsion "Ionosheath: Mass Loading" Laboratory

C. W. Smith Bartol Research "Solar Wind- Turbulence" Institute ·

P. G. Steffes Georgia Institute of "H2S04 Abundance from ORO Profiles" Technology

D. L. Turcotte Cornell University "Volcanism and Tectonics"

A-7 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(1): 11!30/82 (2): 06/15/90

APPENDIX A

PIONEER VENUS ORBITER GUEST INVESTIGATORS

INVESTIGATOR INSTITUTION TITLE

W. T. Vestrand University of New "Stereo Solar Flare Observations Hampshire (PVO and SMM)"

D. R. Williams Arizona State "Geophysics of Tell us Regio" R. Greeley University

FY1989

W. J. Borucki NASNAmes "Optical Search of Venus Nightside"

S. W. Bougher University of Arizona "Ionosphere:-Thermosphere Solar Variation"

S. H. Brecht Berkeley Research "Venus/Solar Wind Interaction Moder' Associates

D. L. Carpenter Stanford University · "Plasma Waves and the Lightning Question"

R. T. Clancy University of Colorado "Microwave/ORO Atmosphere Temperature Correlations"

E. G. Fontheim University of Michigan "Bowshock Precursors"

J. L. Fox State University of "Nightside Ionosphere Chemistry" New York

C. W. Smith Bartol Research "Solar Wind- Turbulence" Institute

P. G. Steffes IJeorgia Institute of "H2S04 Abundance from ORO Profiles" Technology

D. L. Turcotte Cornell University "Volcanism and Tectonics"

W. T. Vestrand University of New "Stereo Solar Flare Observations Hampshire (PVO and·SMM)"

D. R. Williams Arizona State "Geophysics of Tell us Regio" R. Greeley. University

A-8 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(1): 11/30/82 (2): 06/15/90

PIONEER VENUS GUEST INVESTIGATOR PARTICIPATION

BY

FISCAL YEAR AND INSTITUTION CATEGORY

Fiscal Other Fed Year University Indus tty NASA JPL Agency Foreign Total

FY81 5 1 0 1 1 1 9 FY84 6 4 0 3 1 2 16 FY85 7 3 0 4 2 1 17 FY86 4 2 1 7 3 0 17 FY87. 4 2 0 5 0 0 11 FY88 10 2 1 1 0 0 14 FY89 9 2 1 0 0 0 12

Total 45 16 3 21 7 4 96

A-9 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 APPENDIXB

PIONEER MISSIONS TRACKING REQUIREMENTS AND SCIENCE OBJECTIVES

In accordance with the Pioneer Mission SIRD, paragraph 2, this appendix details the correspondence of tracking requirements with science objectives and spacecraft operational needs.

Spacecraft Survival Tracking Requirements

In general, the following guidelines are followed for determining survival tracking coverage for all the Pioneer spacecraft:

1. Maintain the spacecraft in their normal operating modes.

2. No instruments or spacecraft· components powered off, except as needed for power management.

3. Minimum tracking durations determined with no margins for problems at the stations, ground transmission network, or Ames facilities.

4. No allowances for real-time decisions; response to status changes will be during subsequent tracks.

Specific guidelines for survival tracking for each spacecraft are contained in Enclosure 1.

Pioneer 10/11 Mission Tracking Requirements

1. Pioneer 10/11 tracking requirements are determined by the scientific and engineering properties of the spacecraft. As a general rule, one may associate the following scientific phenomena with a characteristic time:

Sunspot cycle ...... 11 years

Solar rotation ...... 27 days

Solar flares ...... 4 to 10 days

Cosmic ray and solar wind ...... 10 days

Radial gradients (assumes spacecraft velocity is 3 AU/yr) Heliospheric current sheet geometry ...... 3 days

Cororating interaction regions ...... 3 days

Jovian electron modulatation ...... 10 hours

Shock waves ...... 3 hours

Forbush decreases ...... 3 hours 6 times per year

B-1 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(l): 11!30/82 (2): 06/15/90 2. The search for gravity waves requires tracking the. two spacecraft continuously for a two week period at one doppler sample per second during opposition which occurs once per year.

3. The search for a trans-Neptunian planet requires tracking the two spacecraft continuously with a two-way downlink for ten hours at one doppler sample per minute ·

4. The search for the heliospheric boundary requires tracking the spacecraft at a minimum of three times per year for a period of 27 days. This event may only occur once during the entire mission.

5. A reduction from the nominal tracking requirements of 2 tracks per day would result in the following loss of capability. ·

a. Less than one track per day would eliminate the particle and fields study of:

1. Interplanetary stream structure ·2. Shock acceleration and propagation 3. .Heliospheric current sheet crossings 4. Corotating interaction regions 5. Cosmic ray Forbush decreases

b. Less than one track per week would eliminate the particle and fields study of:

1. Large scale statistical studies of the solar wind density, velocity, and temperature 2. Radial and latitudinal gradients in the magnetic field 3. Large scale.structure of the heliospheric current sheet 4. Most solar flare events 5. Anomalous helium flux spatial vs time variations

c. Less than one track per thre~ months would eliminate the particle and fields study · of:

1. Detection of the heliopause boundary 2. Cosmic ray radial and latitudinal gradients .3. Solar rotation modulation of cosmic ray intensity 4. Jovian ten hour modulated electrons . 5. Search for galactic electrons

Pioneer Venus Orbiter Mission Tracking Requirements

The Pioneer Venus Science objectives and tracking requirements are detailed in Enclosure 2. The tracking requirements are summarized in the "Pioneer Missions Support Instru-mentation Requirements Document". Enclosure 2 indicates that approximately 70% of the science objectives require tracking about the periapsis portion of each orbit. Only about 10% require tracking about Apoapsis. The remaining objectives concern special alignments, such as superior conjunctions, eclipses and occultations.

B-2 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(1): 11!30/82 (2): 06/15/90

Enclosures: 1. Pioneer Project Guidelines for Spacecraft Survival Tracking 2. Pioneer Venus Mission Tracking Requirements, Scientific Objectives, and Impact of Tracking Reductions

B-3 Document No. PC-1001 Originallssue : 20 May 1981 · Revision:(!): 11!30/82 (2): 06/15/90

PIONEER PROJECT GUIDELINES

FOR SPACECRAFT SURVNAL TRACKING

NASA/Ames Research Center Moffett Field, California 94035

Enclosure 1

B-4 DocumentNo. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 PIONEER 10 SURVIVAL TRACKING DURATIONS

1. For spacecraft and science health monitoring (daily):

3 hr 35 min continuous track is sufficient for spacecraft and most of science at 16 bps.

5 hr 35 min continuous track is needed for complete status monitoring at 16 bps.

2. For navigation (quarterly):

4 hrs of coherent data viewed an RTLT later (for 4 hrs)

3. For roll rate measurements using a star such as SIRIUS (weekly):

two tracks separated by a RTLT, each track with a duration of 2 hr 45 min. (total of 5 hr30 min)

4. For precession maneuvers (-3/yr, not evenly spaced):

Command: 1 hr on either 34m or 70m DSS Data: 1 hr on 10m DSS an RTLT after commanding starts to view execution of commands

5. For attitude determination (CONSCAN): (-6/yr, timed rel to maneuvers)

Command: 2 hrs on 70m DSS Data: 2 hrs on 70m DSS an RTLT after commanding starts to view execution of commands. Downlink will be at reduced signal strength (-3dB); due to antenna feed offset, so track should be when s/c is at high elevation

·-> -> Attitude determinations must be done about 3 days after each precession maneuver, and are also usually done a week or two before each precession maneuver

6. Daily average tracking:

One combined navigation and roll rate track each week

RTLT + 5 hr 30 min= RTLT + 5.50 hr

Six minimum monitoring tracks each week

3 hr 35 min = 3.58 hr

B-5 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(1): 11!30/82 (2): 06/15/90 RTLT Daily average= (6x3.58 + RTLT + 5.50) 17

1/1!90 13.09 hr 5.72 hr 1/1/91 13.82 5.83 1/1/92 14.55 5.93

1/1!93 15.28 6.04 1/1/94 16.01 ' 6.14 1/1/95 16.74 6.24

1/1/96 17.47 6.35 1/1/97 18.20 6.45 1/1/98 18.93 6,56

1/1!99 19.66 6.66 1/1/00 20.39. 6.77

Pioneer 10 Minimum Track for Monitoring Health

The minimum track for monitoring the spacecraft is determined using 16 bps which is the prevailing DSN maximum capability. At this bit rate, the longest time required (when aD format is active) for a complete cycle of the Engineering Subcom is 51.2 minutes (25.6 min without D Fmt · active). The longest time for a complete cycle of the Plasma Analyzer (the instrument with the longest cycle time) data is 2 hr 23 min.

1. Minimum track duration with monitoring of spacecraft health and most of the instrument health data. No navigation data is included. ·

20min uplink sweep and command mod on 2 hr 40 min 3 complete cycles of eng'g data (w/ D Fmt) 05min DSS turns cmnd mod off 5 min before trk end 30min Reaction time for corrective commanding 3 hr35 min Total is 2 hr 15 min when D Fmt is not active

2. Minimum track duration with monitoring of spacecraft health and complete instrument health. No navigation data is included.

20min uplink sweep and command mod on 4!:-... 46min 2 complete Plasma Analyzer data cycles 30min Reaction time for corrective commanding 05min DSS turns cmnd mod.off 5 min before trk end 5 hr41 min

PIONEER 11 SURVIVAL TRACKING DURATIONS

1. . For spacecraft and science health monitoring (daily):

1 hr 14 min continuous track is sufficient for spacecraft and most of the science at 64 bps.

B-6 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 1 hr 33 min continuous track is sufficient for spacecraft and most of the science at 32 bps. The above requirements are stated for nominal bitrates of 64 bps a~d 32 bps which starts in mid-1991.

1 hr 17 min continuous track is needed for complete status monitoring at 64 bps.

1 hr 39 min continuous track is needed for complete status monitoring at 32 bps.

2. For navigation (quarterly)

4 hrs of coherent data viewed an RTLT later (for 4 hrs).

3. For precession maneuvers (-6/yr, not evenly spaced):

Command: 1 hr 30 min on either 34m or 70m DSS Data: 1 hr 30 min on 70m DSS an RTLT after commanding starts to view execuclon of commands

4. For Attitude determination (CONSCAN): (-6/yr, timed rel to maneuvers):

Command: 2 hrs on 70m DSS Data: 2 hrs on 70m DSS an RTLT after commanding starts to view execution of commands. Downlink will be at reduced signal strength (-3dB); due to antenna feed offset, so track should be when s/c is at high elevation

-> -> Attitude determinations must be done about 3 days after each precession maneuver, and are also usually done a week or two before each precession maneuver.

5. Daily average tracking:

One navigation track each quarter RTLT+4hr

Six minimum monitoring tracks each week

1 hr 14 min at 64 bps

1 hr 33 min at 32 bps

B-7 Document No. PC-1001 Originallssue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 Date RTLT Daily average= ((6x1.23)+(RTLT+4)/13)/7 ~

1/1/90 8.52 hr 1.19 hr 1/1/91 9.22 1.20 1/1/92 9.91 1.21

1/1/93 10.60 1.21 1/1/94 11.29 1.22 1!1!95 11.97 1.23

1/1/96 12.66 1.24 1/1/97 13.35 1.24 1/1/98 14.04 1.25

1/1/99 14.73 1.26 1/1/00 15.42 1.27

The average daily tracking in the preceding table is for a data rate of 64 bps. When operating at 32 bps the daily averages in this table are increased by 0.32 hours.

Pioneer 11 Minimum Track for Monitoring Health

I. At 64 bps

The minimum track for monitoring the spacecraft is determined using 64 bps, which is the ~ prevailing DSN maximum capability. At this bit rate, the longest time required (when \__ _) using an A format)· for a complete cycle of the Engineering Subcom is 6.4 minutes. The longest time for a complete cycle of the Plasma Analyzer (the instrument with the longest cycle time) data is 11 minutes. ·

1. The minimum track duration with monitoring of spacecraft health and most of the instrument health data. No navigation data is included.

20min uplink sweep and command mod on 19min 3 complete cycles of eng'g data (w/ A Fmt) 05min DSS turns cmd mod off 5 min before trk end 30min Reaction time for corrective commanding 1 hr 14 min

2. The r;..inimum track duration with monitoring of spacecraft health and complete instrument health. No navigation data is included.

20min uplink sweep and command mod on 22min 2 complete Plasma Analyzer data cycles 30min Reaction time for corrective commanding 05min DSS turned cmd mod off 5 min before trk end lhr17min

II. At 32 bps

Tracking requirements are also included for operations at 32 bps. This data is included because the spacecraft sometimes operates at this data rate (such as during CONSCANs)

B-8 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(1): 11/30/82 (2): 06/15/90 and because it is expected that the bit rate may need to be lowered to 32 bps before the end of the mission. At this bit rate, the longest time required (w/ A Fmt) for a complete cycle of the Engineering Subcom is 12.8 minutes. The longest tiine for a complete cycle of the Plasma Analyzer is 22 minutes. 1. The minimum track duration with monitoring of spacecraft health and most of the instrument health data. No navigation data is included.

20min uplink sweep and command mod on 38min 3 complete cycles of eng'g data (w/ A Fmt) 05min DSS turns cmd mod off 5 min before end trk 30min Reaction time for corrective commanding 1 hr33 min

2. The minimum track duration with monitoring of spacecraft health and complete instrument health. No navigation data is included.

20min uplink sweep and command mod on 44min 2 complete Plasma Analy:z;er data cycles 30min Reaction time for corrective commanding 05min DSS turned cmd mod off 5 min before trk end 1 hr39 min

PIONEER VENUS ORBITER SURVIVAL TRACKING DURATIONS

1. For spacecraft and science health monitoring; no navigation (daily):

1 hr 16 min, AOS to LOS

2. For spacecraft and science health monitoring, plus low level science data acquisition; no navigation (daily):

3. Precession maneuver tracking (monthly): 3 hr 5 min, AOS to LOS

4. Navigation (weekly):

RTLT + 4 hr, AOS to LOS. (maximum time is 4 hr 30 min)

5. The minimum track for spacecraft operations at minimum level with no science was determined using the following assumptions:

Operate spacecraft at real time data rate. No stored commands. No stored data. Minimum spacecraft operations of status checks, attitude measurements, antenna elevation adjustments.

B-9 Document No. }>C-1001 Original Issue : 20 May 1981 Revision:(1): 11/30/82 (2): 06/15/90

Spacecraft timeline is:

0 min 30 sec SCL Read Out (bit flip check) 10min Attitude measurement (ACS format) 6min HGA elevation adjustment 10min Verify commands after RTLT 26 min 30 sec

Pass duration is:

20min uplink sweep and command mod_e on 26 min 30 sec spacecraft activities 30min RTLT 1 hr 16 min 30 sec

Pioneer Venus Orbiter Minimum Tracking for Maneuvers

Precession maneuve:r:s are normally required at a frequency which ranges from once every 2 weeks to once every 10 weeks (depending on the High Gain Antenna orientation with respect to the Sun, which varies throughout the year). Over an extended period, maneuvers are required an average of once each 4 weeks. Each maneuver requires a track with a duration of 1 hr 15 min +3 RTLT, for commanding and confirming the spacecraft status. ·

Pass duration is:

20min uplink sweep and command mod on 1 hr 15 min commanding and verificatiqn 1 hr 30 min 3RTLT 3 hr 5 min

B-10 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90

PIONEER VENUS MISSION TRACKING REQUIREMENTS, SCIENTIFIC OBJECTIVES, AND IMPACT OF TRACKING REDUCTIONS

NASA/Ames Research Center Moffett Field, California 94035

Enclosure 2

B-11 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 A. RETARDING POTENTIAL ANALYZER EXPERIMENT (LMSC/ORPA) 1. OBJECTIVES FOR THE ORP A EXPERIMENT 0987) a. Define the solar cycle changes in the morphology of the Venus ionotail. b. Define the morphology and the plasma properties of the interaction region between the ionosphere and the magnetosheath. c. Define the median magnetosheath (ionosheath) electron density and temperature fields in the near-planet region.

d. Define the i) near-planet and ii) distant wake plasma properties of the magnetotail and plasma sheet. e. Define the bulk velocity field of the dusk and nightside ionosphere with improved precision.

f. Determine the nature and extent of the precursor phenomenon and its relation, if any, to the bow shock. 2. TRACKING REQUIREMENTS FOR THE ORPA OBJECTIVES Objective Time interval Periapsis hour angle location

a p ± 1.5h 1800-0600 ~ b p ± 0.5h 2400-0000 c p ± 1.5h 2400-0000 di p ± 1.5h 1800-0600 d ii) p + 7h- p + 17h 0900- 1500 e p ± 0.5h 1500-0900 f P ± l.Oh 0300-2100 Notes: Periapsis hour angle is the solar hour angle of the meridian passing through periapsis. The subsolar meridian is 1200, the dusk terminator is 1800, midnight is 0000 (2400), and the terminator is 0600.

B-12 Document No. PC-1001 Original Issue : 20 May 1981 . . .' . - · Revision:(!): 11/30/82 (2): 06/15/90 3. ORBIT INTERVALS FOR THE OBJECTIVES

a, d i) b, c d ii) e f

4089 - 4202 3105 - 5085 4202-4258 4258-4426 4145- 4314 4511-4624 4427- 4483 4483- 4651 4370- 4539 4736-4849 4652- 4708 4708 - 4876 4595 - 4764 4961-5074 4877- 4933 4933- 5101 '4820- 4989 5186-5299 5102- 5158 5158- 5326 5045- 5214

B-13 DocumentNo. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 B. ION MASS SPECTROMETER EXPERIMENT (GSFC/OIMS).

1. OBJECTIVES FOR THE OIMS EXPERIMENT a. Study and define the interaction of the solar wind and solar radiation with the various regions of the Venus dayside ionosphere. b. Identify the response of the upper ionosphere to short term solar perturbations, including solar flares and associated shock fronts and interplanetary magnetic field sector passages.

c. Examine the upper ionosphere for response to long term solar variations, in particular the extremes in EUV (Extreme Ultraviolet) radiation.

d. Investigate the ion composition in the wake region for:

(1) The behavior of the light and heavy ions in the depletion regions seen frequently at night and

(2) Search for evidence of organized morphologies of superthermal ion flows that would aid in understanding the dynamics of the tail region. e. Study and define the relationships between ion and neutral variations observed in the predawn bulge during the first 3 revolutions of Venus abOut the sun. 2. TRACKING REQUIREMENTS FOR THE OIMS EXPERIMENT

Objective a.

Requires at least 3 perhipsis ·passes (P ± 1 hour) per week. The 3 tracks should be · spaced every other day rather than successive days.

Reduction to 1 periapsis track per week would leave uncertainty relative to EUV and would eliminate the ability to determine low level EUV changes. This is a loss of resolution and only gross changes in EUV could be detected.

Reduction to less than 1 periapsis track per fo11Ilight would eliminate objective a.

Objective b.

. ' Shock fronts have a time scale of 1 to 2 days and require 1 periapsis track per day (P ± 1 hour) to. detect and define. A reduction to 1 track per week would eliminate the ability to detect shock fronts. ·

The interplanetary magnetic field sector passages have a time scale of 4 to 6 days and require 3 periapsis passes per week (P ± 1 hour) to detect. Reduction to less than 1 track in 10 days eliminates the ability to detect sector passages.

B-14 DocumentNo. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 Objective c.

The long term solar variations have time scales of several solar rotations of 27 to 28 days each as well as extremes in the solar cycle which involve time scales of several years.

The solar rotation related effects require at least 2 periapsis passes (P ± 1 hour) per week spaced uniformly. Reduction to 1 track per fortnight yields a marginal ability to detect the more complex variations and the more subtle differences. Further reduction to 1 track per month eliminates the ability to achieve the solar rotation related effects of objective c.

The solar cycle related effects require 1 periapsis track (P ± 1 hour) per 27 days. Reduction to less than 1 track per 2 months eliminates the ability to detect the longer scale solar cycle related effects. ·

Obiective d.

The ability to characterize the behavior of the light and heavy ions in the depletion region requires 1 periapsis track (P ± 1 hour) per week. Reduction in tracking gradually deteriorates this ability and at less than 1 track per month it is eliminated.

Objective e.

The data for objective e are in hand and there is no tracking requirement.

B-15 D0eumen:t No~. PC~l!(r)€)\1 Origin.al' Issae : 2@ May 198\l! Revisi0n:(li)t.· r li/t30182 (2)~: @'6/E5/901 ELE'C1!RON 'FEMFEAA'JURE PROilE.EXIPERIMEN1fS: €GSFC/OE1'P);.

:t. OBJECTIVES: FOR OETP EXPERIMEN1'

a. Resolve the nigntside· ienosphere and magneto tail interacti0n.

fu.. Defme the shape of the nightside ionopanse.

c·. S'tt:idy dayside bowshock near. the stagnation: region.

2·. TRACKING REQUIREMENTS FOR THE OE'FP' EXPERIMENT

Objective a.

RequiFes daily periapsis data fOF P + 1 hour. The OFbit intervals of prime importance are orbits. 4289' thru 4399·, 4515- thru 46Q:5, 4739· thru 4849 and 4965 thru 5075·.

The nightside ionosphere and magnetotait interaction is so dynamic that good resolution can only be obtained from daily data acquisition.

Reduction to less than 1 track per day reduces the abiLity to resolve the nightside ionosphere and magnetotaili interaction (objective a}.

Reduction to I track per week eliminates objective a entirely.

Objective b.

Requires daily periapsis data for P ± 1 hour for 3 weeks centered on orbits 4344, 4570, 4794 and 5020.

When periapsis is at or after 2 hours (0200) past midnight on Venus, 2 periapsis ~ata acquisitions per week for P ± 1 hour will give useful data on the shape of the 1onopause.

Reduction to less than i trackper day degrades the ability to define the shape of the night side ionopause (objective b)~

Reduction to 1 track per week eliminates objective b.

Objective c.

Requires daily periapsis data for P ± 1 hour for 2 weeks centered on orbits 4230, 4455, 4680, and 4905.

Reduction to less than 1 track per day degrades the study of the dayside bowshock (objective c) needed to determine how the solar wind gets diverted around the planet, at what altitude it begins to tum, and what density build-ups cause the solar wind to divert around Venus.

Reduction to 1 track per week eliminates objective c.

B-16 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 D. ULTRAVIOLET SPECTROMETER EXPERIMENT (COLO/OUVS) 1. OBJECTIVES FOR THE OUVS EXPERIMENT

In descending order of priority: a. Observe the relationship between aerosols, sulfur dioxide, albedo, and contrast in the cloud-top region. Monitor changes in long-term trends in the relationship, and look for large, transient changes in the sulfur dioxide content that might indicate volcanic or violent atmospheric activ-ity.

b. Monitor the UV signature of the Venusian aurora, and establish its response to changes in solar activity and solar wind characteristics. c. Investigate the character and measure the quantifiable properties of the circulation in the day and night .thermospheres, including its response to short- and long-term changes in solar activity.

d. Establish the distribution of neutral UV -active species (H,O,CO) in the dayside exosphere and thermosphere and measure exospheric temper-ature. Monitor responses to short- and long-term changes in solar activity. e. (Non-Venus objectives) Monitor the interplanetary hydrogen distribution and its changes with solar cycle. Observe '1comets of opportunity." Also, monitor OUVS calibration by observing UV stars.·

2. TRACKING REQUIREMENTS FOR OUVS

General

All of the OUVS objectives require continuous local time coverage, although some require dayside viewing and some nightside.

The search for transients calls for frequent (more than one orbit per week) observations; loss of frequent observations will degrade the observations through missed events and poorer time resolution.

Observations of Venus near periapsis normally require tracking (or DSU storage) from P-30 min to P+30 min; minimum coverage is P-20 toP ~-10. Observations inbound from apoapsis require tracking for several hours; the exact timing depends on the spin-axis orientation. Current limits are: earliest start P-7 hours, latest finish P-1 1/2 hours, typical duration 2 1/2 hours. The limits move to earlier times as the orbit precesses. ·

Useful formats for Venus observations are PER A, B, and C. For observations of interplanetary hydl-ogen and UV stars, APO B is required when Venus is not in OUVS view (P + 1/2 hours- P-7 hours). Comets require PER, A, B, or C.

B-17 Document No~ PC-100:1' Original Issue : 2Cil May, 198:1 Revision:( 1): 11f30t82 (2): 06/15/90 Objective a

S02 and Volcanoes (SV): Requires dayside observations; 3-color images (3C). from apoapsis, F-spectra from periapsis. Up to 3 orbits/week.

Objective b

Aurora (A): Requires nightside measurements (0 (130) and 0 (136) nm) up to 4 orbits/week.

Objective c

Thermospheric winds {W): Requires dayside (0) and nightside (NO) observations, up to 2 orbits/we~k.

Objective d

Composition (C) and limb exospheric temperatures (TL): Requires dayside (H, CO, 0) and nightside (H) measurements·, up to 2 orbits/week. Also can use 0 measurements made for objective (c}.

Objective e

Non-Venus: Interplanetary hydrogen and comets are ·"objectives of opportunity": observations are made when tracking is avail-able. UV star observations require not less than 30 apoapsis sessions (averaging 6 hours) every Venus year. a 3. IMPLEMENTATION AND PRIORIDES

Table 1 shows the assignment of a week's worth of orbits to the various OUVS objectives (Venus only, objectives (a)-(d)}. The assignments are shown for two ranges. of orbit orientation, i.e., dayside apoapsislnightside periapsis, and nightside apoapsis/dayside periapsis. Within each section of the diagram, assignments· are arranged in descending order of priority.

The nature of the impact of any reduction in PV tracking depends on the nature of the reduction. lf fewer than 7 orbits/week are available, but full local time coverage is maintained, then successive reductions will result in loss· of time resulution and ultimately in loss of objectives. Specifically:

7 orbit/week All objectives attained

6 orbit/week Loss of dayside H measurements (d)

Loss of time resolution in aurora (b) measure­ ments

5 orbit/week Loss of time resolution in cloud top (a) and aurora (b) measurements

4 orbit/week Loss.of composition objective (d), except for exospheric 0.

B-18. Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90

3 orbit/week Loss of time resolution in winds (c)

2 orbit/week Loss of time resolution in cloudtops (a)

1 orbit/week Loss of winds objective (c) and remainder of composition objective (d)

B-19 DocumentNo. PC-1001 Originalissue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 .

TABLE I

APOAPSIS _ PERIAPSIS (P-7 TO P-1 1/2) (P- 1/2 TO P+ 1/2)

DAY NIGHT (a) sv 3C (b) A 0 (130) (c) w 0(130) (c) w N0(198) (a) sv 3C (b) A 0 (136) (c) w 0(130) (c) w N0(198) (d) c C0(160) (d) c H (122) (a) ·SV 3C (b) A 0 (136) (d) c H(122) (b) A 0 (136)

NIGHT DAY (b) A 0 (130) (a) sv F Spectra (c) w NO(l98) (c) w 0 (130) * (b) A 0 (136) (a) sv F Spectra (c) w N0(198) (c) w 0 (130)** (d) c H (122) (d) c C0(139) c (b) A 0 (130) (a) sv F Spectra (b) A 0 (136) (d) c . H (122)

* to be replaced (1990) by (d) TL C0(216) **to be replaced (1990) by (d) TL 0(130) Observation symbols: F Spectra: Spectra, 190-330 nm H(122): atomic hydrogen, 122 nm 0(130): atomic oxygen, 130 nm 0(136): atomic oxygen, 136 nm C0(139): carbon monoxide, 139 nm C0(160): carbon mo11r-xide, ·160 nm . N0(198): carbon monoxide, 198 nm 3C: 3-color (107, 237, 318 nm) cloud-top images

B-20 DocumentNo. PC-1001 Original Issue: 20 May 1981 Revision:(l): 11/30/82 (2): 06/15/90 If tracking is lost for extended periods, the impact is simply loss of continuous coverage. In this event, OUVS objectives are best maintained if the gaps occur when the orbit is over or near the terminator, since the best OUVS images and measurements are obtained from near noon or midnight. Table II gives the preferred orbits, from the present until1992, assuming 50% loss of tracking.

TABLE IT

Noon Apoapsis/ Midnight Apoapsis/ Midnight Periapsis Noon Periapsis

4311-4367. 4199-4255 4536-4592 4424-4480 4761-4817 4649-4705 4986-5042 4874-4930 521,1-5267 5099-5155 5324-5380

B-21 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(l): 11/30/82 (2): 06/15/90 E. NEUTRAL MASS SPECfROMETER EXPERIMENT (GSFC/ONMS)

1. · OBJECTIVES FOR THE ONMS EXPERIMENT

a. Determine vertical, longitudinal and temporal variations of the neutral gas composition and its kinetic temperature.

b. Measure ion composition for the diurnal and temporal behavior of the various ion species. ·

c. Measure energetic ions with energies above 40 electron volts. The ONMS is the only instrument on the Pioneer Venus Orbiter spacecraft capable of measuring ions of greater than 40 electron volts.

2. TRACKING REQUIREMENTS FOR THE ONMS EXPERIMENT

Objective a.

The neutral atmosphere data for the Pioneer Venus Orbiter Extended Mission IT are in hand.

Objective b.

The supplemental ion composition measurements are not a prime objective for this experiment and hence there are no specific tracking requirements. Nevertheless, the ~ value of the continuing measurements is almost directly related to the frequency of \. __) periapsis tracking. ·

Objective c.

Measurement of the energetic ions requiring 1 track (P + 1 hour) per day. Reductions in tracking to less than 1 track per day would result in proportional reductions in the degree of definition achieved.

B-22 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11!30/82 . (2): 06/15/90 F. CLOUD PHOTOPOLARIMETER EXPERIMENT (GISS/OCPP)

1. OBJECTIVES FOR THE OCPP EXPERIMENT

a. To obtain high resolution images of Venus in the near ultraviolet and low resolution multicolor images. Analyze the images to character-ize the zonal and meridional circulation of the atmosphere in the region of the cloud tops by means of tracking small scale cloud features, to monitor the intermediate and long term evolution of the circulation, and to establish the relationship between the basic circulation and the general appearance of planetary scale cloud patterns.

b. · To determine the spatial and temporal variation of the cloud and haze particle microstructure.

c. To determine the distribution of cloud and haze particles at visible levels of the Venus atmosphere, as well as temporal variation in the polar submicron haze and its role in polar brightening.

2. .TRACKING REQUIREMENTS FOR THE OCPP EXPERIMENT

Objective a.

The cloud tracked wind and circulation analysis requires 18 hr per day tracking at apoapsis for at least 15-20 consecutive days during each 2 1!2 month period when apoapsis is over the sunlit hemisphere of Venus, during orbits 4302-4378, 4527- 4603, 4752-4828 and 4976-5052.

Tracking reduction to 10 hours per day could be tolerated but wind determinations would be marginal because of large uncertainties. Tracking reduction to less than 10 hours each day would prevent any cloud tracked wind analysis.

Tracking is required for 15-20 days to span the period of 4 to 5 rotations of Venus cloud top region to determine eddy components of the wind to an accuracy of 5 m/sec. Tracking for shorter time periods would decrease statistics and thus would increase the uncertainty of wind determinations to the point that determination of eddy components, which are expected to be about 10m/sec will be difficult if not impossible.

For cloud morphology studies, tracking is required for at least 1 hours at apoapsis on five consecutive days during 2 periods during the 2 1/2 month period when apoapsis is over the sunlit hemisphere of Venus. Tracking for fewer hours each day would not provide enough time to acquire a complete image of Venus. Tracking for fewer than 5 consecutive days would prevent observing a complete rotation of Venus' atmosphere. Any characterization based on less thart one such rotation of the cloud top region would in general be unrepresentative.

B-23 Document No. PC-1001 Original Issue: 20May 1981 Revision:(l): 11/30/82 (2): 06/15/90 Objectives b and c.

Requires 5 hours of continuous tracking at apoapsis once every three days during a 110 day period when apoapsis is over Venus' dayside hemisphere; plus two orbits with 21 hours of tracking near the time of maximum illumination of Venus. .

Less than 5 hours of tracking at apoapsis will not allow enough time to observe the polarization over the complete Venus disc. Tracking less frequently than once every three days will not allow analysis with a sufficient resolution in phase angle and a data set independent of the phase of the four days rotation.

The two ~rbits with 21 hours of tracking are needed to me'asure the small scale temporal variation of the cloud and haze structure and the cloud particle microstructure. At least two orbits of data are needed to detect any atypical condition. ·If only one orbit of data is available, the measurements may not be reliable.

B-24 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(1): 11/30/82 (2): 06/15/90 G. INFRARED RADIOMETER EXPERIMENT (JPL/OIR) Not applicable. Instrument failed.

B-25 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 H. MAGNETOMETER EXPERIMENT (UCLNOMAG)

1. OBJECTIVES OF THE OMAG EXPERIMENT

a. Determine Venus' intrinsic magnetic field.

b. Search for and examine upstream waves.

c. Study Venus' bow shock

d. Study Venus' ionopause.

e. Study flux ropes.

f. Study dayside ionospheric fields.

g. Study nightside fields.

h. Study the distant wake.

i. ·Survey the planet for lightning sources.

j. Interaction of solar wind with interplanetary dust.

2. TRACKING REQUIRED FOR THE OMAG EXPERIMENT*

Objective a.

Any data beyond orbit 4970 will be useful.

Objective b.

A minimum of 6 tracks (P ± 1 hour) uniformly spaced during the 4 week period centered on when periapsis crosses the terminator are required to monitor the effects of the 11 year solar cycle.

Objective c.

Tracking is required at periapsis the 2 month period centered on when periapsis eros~:.., the subsolar point for 15 orbits uniformly spaced. To monitor the change in mass loading in magnetosheath we need to monitor ± 1 hour around periapsis on orbits 4296-4396,4521-4621,4746-4846 and4971 and above.

Objective d.

This objective will use data from the same orbits as objectives band c above

Objective e.

All orbits beyond 4900.

Objective f.

B-26 Document No. PC-1001 Original Issue : 20 May 1981 Revision:(l): 11!30/82 (2): 06/15/90

All orbits beyond 4900.

Objective g.

Tracking is required at periapsis during the 2 month period around the anti-solar pointJor 15 orbits uniformly spaced. Periapsis data beyond orbit 4970 is very important to this objective.

Objective h.

Tracking is required on every orbit at apoapsis during 2 week period centered on the long eclipse season.

Objective i.

All nightside periapsis data is important to this objective.

Objective j.

Data should be obtained continuously for all orbits during the solar wind portion of the orbits whenever possible. Extra effort should be expended to ensure coverage during the following periods: 10/20/90-11/4/90, 6/1/91-6/15/91, 1/12/92-1/26/92, and 8/24/92-9n/92.

* These tracking requirements were formulated before the instrument stopped transmitting X andY components on October 16, 1988.

B-27 DocumentNo. PC-1001 Original Issue : 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 I. PLASMA ANALYZER EXPERIMENT (ARC/OPA) 1. OBJECTIVES FOR OPA EXPERIMENT

a. Investigate the plasma environment in the solar-wind wake of Venus and determine the formation and character of the extended wake (tail) behind the - planet. b. Study the ion pickup by the solar wind near Venus and determine constraints on the pickup mechanism. c. Study low-energy ion flows.

d. Study the night-side electrons and search for evidence of the source of electrons.

e. Monitor the magnetosheath and solar wind (planetary context) and study the flow field about the planet.

f. Monitor the solar wind (interplanetary context) to investigate the evolution of shocks from solar flares and the evolution of solar wind streams. 2. TRACKING REQUIREMENTS FOR THE OPA EXPERIMENT

Objective a. The time scale for solar wind streams is 1 to 3 days. The characterizations of the environment in the solar-wind wake of Venus requires continuous tracking (P ± 12 hours) for 20 orbits per Venus year centered on orbits 4237, 4462, 4687 and 4912. Reduction to 1 track per day for P + 8 hours or alternate day 24 hour tracks seriously degrades th~ ability to achieve objective a.

Reduction to less than every other day 24 hour tracks eliminates objective a. Objective b. To adequately study the ion pickup by the solar wind (objective b), requires 1 track (P ± 1 hour) per day for 44 orbits centered on periapsis at the moving terminator (orbit~: 1395, 4620, 4844, and 5096) and for 44 orbits centered on periapsis at the evening terminator (orbits 4283, 4507, 4732 and4956). -

Reduction in tracking will result in a proportional degradation in the ability to achieve objective b down to 1 track in 3 days. Less than 1 track in 3 days eliminates objective b.

B-28 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(l): 11!30/82 (2): 06/15/90 Objective c. To obtain sufficient data to study low energy ion flows requires 1 track (P ± 1 hour) per day.

Reductions in tracking will result in a gradual degradation of the ability to. achieve objective c down to 1 track in 3 days. Less than 1 track in 3 days eliminates objective c.

Objective d.

The study of the night side electrons and search for evidence of their source requires 1 track (P ± 1 hour) per day for all orbits where periapsis occurs at night (Venus local time 6pm to 6am). These orbits are 4283-4395, 4507-4619, 4732- 4844 and 4956-5068.

Reduction in tracking will result in a gradual degradation of the ability to achieve objective c down to 1 track in 3 days. Less than 1 track in 3 days eliminates objective d.

Objective e.

Adequate monitoring of the magnetosheath and solar wind (planetary context) and to study the flowfield about Venus requires 1 track (P ± 8 hours) per day for all orbits.

Reductions in tracking will result in a proportional degradation of the ability to achieve objective e.

Objective f.

Adequate tracking to monitor the solar wind (interplanetary context) to investigate the evolutions of shocks from solar flares and the evolution of solar wind streams requires 1 track (Apoapsis +/- 8 hr) per day.

Reductions in tracking will result in a proportional degradation of the ability to achieve objective f.

B-29 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 J. RADAR MAPPER EXPERIMENT (ARC/ORAD) Not applicable. Instrument powered off until periapsis altitude comes back down in 1991. then the requirement will be P ± 32 minutes every orbit. Document No. PC-1 001 Original Issue : 20 May 1981 Revision:(1): 11/30/82 (2): 06/15/90 K. ELECTRIC FIELD DETECTOR EXPERIMENT (TRW/OEFD)

1. OBJECTIVES FOR THE OEFD EXPERIMENT

a. Analyze Venusian lighting.

b. · Analyze wave-particle interactions in the Venus, wake, and tail regions.

c. Analyze the physics of the Venus bow shock, foreshock and ionopause.

2. TRACKING REQUIREMENTS FOR THE OEFD EXPERIMENT

Objective a.

To study the source of Venus lightning, tracking is required on every periapsis which is over the dark side. Since the periapsis latitude is changing, each combination of periapsis latitude and longitude will never be repeated, so any lost periapsis will leave an unmonitored hole in the data.

The required tracking interval is P ± 1 hour for orbits 4283-4395, 4507-4620, 4732-4844 and 4956-5069.

Objective b.

To study Venus wake and tail, tracking is required during the 5 hours of tail crossing each day during the 2 week period which includes the tail crossing. As few as two orbits per week can be used for this objective.

The required tracking interval is from P - 10 hours to P - 5 hours during orbits: 4227-4241, 4452-4466, 4677-4691 and 4902-4916.

The ionosphere and ionosheath portion of Objective b, requirement b can be met with data collected during the P ± 1 hour portion of all orbits.

Objective c.

The Venus foreshock, bowshock and ionopause physics can be analyzed from the P ± 1 hour data. The tracking requirement is for all orbits and the ability to achieve this objective degrades proportionally as tracking is reduced.

B-31 Document No. PC-10()1 Original Issue: 20 May 1981 Revision:(l): 11/30/82 (2): ·96/15/90 L. GAMMA BURST DETECTOR (LASUOGBD) l .. OBJECTIVES-FOR THE OGBD EXPERIMENT a. Detect Ga~a-ray in order to: (1) contribute toward location of burst sources by time-of-flight analysis,

(2) characterize temporal characteristics of bursts, and

(3) characterize the distribution of the gross spectral distribution of bursts.

b. Similar measurements from solar flares are used in a continuing study of directivity and spatial distribution of flare emissions.

2. TRACKING REQUIREMENTS FOR THE OGBD EXPERIMENT

Tracking requirement for both objectives are met by a read out of the Gamma Burst Detector instrument memory whenever tracking allows but not more often than once per day.

B-32 DocumentNo. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 M. RADIO OCCULATION EXPERIMENT (JPI.IMORK) 1. OBJECITVES OF RADIO OCCULTATION EXPERIMENTS a. Acquire dayside and nightside ionosphere measurements to study the behavior of the ionosphere during the solar cycle. b. Analyze occultation measurements to determine the atmosphere temperature structure and study the behavior of the structure with latitude and time, which in turn determine changes in the global circulation pattern.

2. TRACKING REQUIREMENTS FOR THE RADIO OCCULTATION EXPERIMENT

Objective a. Dayside ionosphere measurements require occultation coverage by a 34m or 64m station capable of receiving S- and X-band doppler data. Approximately 40 occultations are required during each occultation season to span the complete range of solar zenith angles. Tracking can be reduced to cover fewer occultations with a corresponding reduction in the knowledge of the solar zenith angle effects. Less than 10 occultations per season, however, will prevent this scientific objective from being achieved. Objective b.

Atmosphere structure measurements require occultation coverage by a 64m station equipped with DSP equipment for recording of S- and X-band open loop data. Approximately 20 equally spaced occultations are required during each occultation seaso-n to provide complete latitude coverage. Tracking can be reduced to cover fewer occultations with a corresponding reduction in the knowledge of latitude effects. Any number of occultations will provide useful information.

B-33 DocumentNo. PC-1001 Originallssue : 20 May 1981 Revision:( 1): 11/30/82 (2): 06/15/90 N. RADIO SCINTILATION EXPERIMENT (IPL/MORW)

1. OBJECTIVES OF THE RADIO SCINTILATION EXPERIMENT

a. Obtain measurements of turbulence in Venus' atmosphere and define the turbulence variations with latitude and solar zenith angle.

b. Probe and study the solar wind including velocity fluctuations, and investigate coronal transients and their evolution outward from the Sun.

2. TRACKING REQUIREMENTS FOR THE RADIO. SCINTILATION EXPERIMENT

Objective a.

Occultation coverage by a 64m station (with ODA) is required for approximately 45 occultations to collect data for all Venus latitudes and Solar Zenith Angles.

Objective b .

.Solar wind and coronal transients require tracking during the 8_ week period which includes Venus superior conjunction with the Sun. Tracks are required from 64m stations with at least 1 hour duration.

Solar wind and coronal events occur randomly in time with a frequency between once per week and once per day, so approximately one week of tracking is required U during superior conjunction to observe at least one event.

B-34 Document No. PC-1001 Original Issue: 20 May 1981 Revision:(1): 11/30/82 (2): 06/15/90 0. GRADIENT AND RADIO PROPAGATION EXPERIMENT (STAN/OGPE)

1. OBJECTIVES FOR THE OGPE EXPERIMENT a. Detect and analyze horizontal atmosphere density gradients from grazing occultations.

b. - Detect and analyze horizont~ atmosphere and ionosphere gradients from groups of consecutive conventional occultations.

c. Detect and analyze atmosphere and ionosphere layers which produce frequency excursions in the downlink.

d. Search for and analyze ground reflections of the radio downlink.

e. Analyze solar conjunction data to study the solar corona.

2, TRACKING REQillREMENTS FOR THE OGPE EXPERIMENT

Objective a.

Tracking is required for P ± 10 minutes during the three grazing occultations at each end of each short occultation season. The data return is directly proportional to the number of grazing occultations. As few as one grazing occultation is useful. (64m or 34m stations are acceptable).

The orbits with grazing occultations for 1990 through 1992 requiring one track (P ± 10 minutes) per day are orbits 4381-4383, 4660-4662, and 4799-4801.

Objective b.

No special tracking is requested for this objective. Whenever the scheduled tracking is satisfactory, the data will be analyzed.

Objective c.

No special tracking is required for this objective. Whenever occultation data is collected, it will be analyzed for layers.

Objective d.

No special tracking is required for this objective. Whenever occultation data is collected, it will be analyzed for ground reflections.

Objective e.

No special tracking is required for this objective. Whenever tracking is scheduled during solar conjunction, the data will be studied.

B-35 Documefit No. PC- 10tH btigirtal Issue: 2() May 1981 Revision:(l): 1i/30/82 (2): 06/15/90 . P. CEtESTiAL MECHANICS EXPERIMENT (Mit/OCM) 1. OBJECTIVES FOR THE ocM EXPERiMENT. a. Detemrille the gravity field of Venus. b. Investigate the near surface geophysics artd the internal mass distribution of Venus.

c. Study the structure and heat transport irt the upper atmosphere of Venus.

d. !rtvestigate the current artd past rotations of Venus. ·2. TRAC:kiNG REQUIREMENTS FOR THE dCM EXPERIMENT

Objective a.

Sufficient data to detetlilirte the low resolution global model of Venus' graVity field has been collected during previous orbits and no additional tracking is reqtilied.

· Objectives b. c. artd.d.

No tracking is required. Document No. PC-1001 Original Issue: 20 May 1981 Revision:(!): 11/30/82 (2): 06/15/90 Q. INTERNAL DENSITY DISTRIBUTION EXPERIMENT (JPL/OID) 1. OBJECTIVES FOR THE OlD EXPERIENCE

a. Determine the lOth degree and order global gravity field of Venus.

b. Use the spherical harmonic coefficients of the gravity field to study Venus' geophysical parameters.

c. Study local gravity anomalies.

2. TRACKING REQUIREMENTS FOR THE OlD EXPERIMENT

a. Objectives a, b, and c.

Tracking is required during ± 4 hours from periapsis every day plus 24 hours of tracking once per week and 24 hours of tracking, immediately after a spacecraft maneuver. Tracking could be reduced to one periapsis every other day if station or ground system problems did not occur. Tracking losses which exceed one day will degrade the accuracy of the global model and will severely degrade or eliminate the ability to study local anomalies in the area with lost tracking. Tracking of less than one complete orbit per week will provide insufficient data for any useful gravity models.

B-37