' Telecommu,Nications ,And I Data . ' Acquisition. Systems Support for , the Viking 19-75 Mission to Mars

' Telecommu,nications ,and-.\ I Data .'

.. Acquisition. Systems Support for , . ' \ ' , the Viking 19-75 Mission to Mars,-

The Viking Lander Monitor- Mission. '

May 19801,983March to I

D. J. Mudgway I ,-

runsn , National Aeronautics and Space Administration

Jet Propulsion Laboratory ' , California Institute of Techno,logy -.Pasadena] California ' L. Telecommunications and Data Acquisition .Systems Support for the Viking 1975 Mission to Mars A recent panorama taken by the cameras of Viking Lander 1 on the surface of Mars. The picture is a mosaic of six images taken on separate occasions over the period June through August 1982. JPL PUBLICATION 82-1 07

Telecommunications and Data Acquisition Systems Support for the Viking 1975 Mission to Mars The Viking Lander Monitor Mission May 1980 to March 1983

D. J. Mudgway

May 15, 1983

National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California The research described in this publication was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. PREFACE

In late 1976 therewere two Viking Landers and two Viking Orbiters in full operationon the surface and in orbitaround the planet Mars. Of thesefour spacecraft,only the Viking Lander 1 was activeinto October of 1982. As the Thomas A. MutchMemorial Station, this spacecraft represented the United States' presenceon Mars. As theViking Lander Monitor Mission (VLMM), it gatheredand regularly transmitted to Earth imaging and meteorology data relative to its local Martianenvironment.

This report continues the description of the tracking anddata acquisition support for the Viking Mission to Mars published in five previous volumes,which are listed in thereferences.

The first volumedescribes organization, planning, implementation, and test activity from inception of the Project in 1969 tolaunch operations in 1975. Cruise activity from the launch of twospacecraft to the landing of Viking 1 in July 1976 is described in Volume 11. The third volumecovers the landing of the secondViking Lander and Mars planetary operations for two Orbiters and two Landersthrough the end of the prime mission in November 1976. VikingExtended Mission support activity from November 1976 through May 1978 is described in Volume IV. FromJune 1978 through April 1980, VikingMission Operations were conductedunder various names related to the condition of the remaining spacecraft andthe funding available to support mission operations. This period is described in JPL Publication 82-18.

The Deep Space Networkcontinued to supportViking from May 1980 to the present(March 1983). This phase of the continuing lifeof the Viking Project was termed,theViking Lander Monitor Mission, and was expectedto continue through the year1994. However, the spacecraft failed in November 1982,and in March1983, the mission was considered to have ended.

In this document, thetracking anddata acquisition support for the Viking Lander Monitor Mission from May 1980 to March1983 is described together with an overviewof :'the science results. The eventsleading to the failure and theNet- work'sefforts to recover the Lander signal are also included.

/ &&0 N. A. Renzetti

V ABSTRACT

From May 1980 until theViking Lander Spacecraft failed to transmit a downlink to Earth in November 1982, the Deep Space Networkprovided tracking and data acquisition support to the Viking Lander Monitor Mission (VLMM).

Thisreport gives the background for the VLMM anddiscusses the technical and operationalaspects of the tracking and dataacquisition support that the Network was calledupon to provide. An overviewof the science results obtained from the imaging,meteorological, and radio science data isalso given.

The reportconcludes with a description of the intensive efforts that were made torecover the mission from November 1982 until the effort was discontinued in March 1983.

vi CONTENTS

I. INTRODUCTION ...... 1-1

I1 . BACKGROUND ...... 2-1

I11. DSNSUPPORT ...... 3-1 A . OPERATIONS ...... 3-1

B . CONFIGURATIONS ...... 3-5

C . REAL-TIME LINK TOTHE UNIVERSITY OFWASHINGTON ...... 3-5

D . AUTOMATICS-BAND DOWNLINK ...... 3-10

E . THE VL-1 RECOVERYEFFORT ...... 3-12

IV. VLMM SCIENCE RETURN ...... 4-1

A . RADIOSCIENCE ...... 4-1

B . METEOROLOGY ...... 4-2

C . IMAGING EXPERIMENT ...... 4-6

V . CONCLUSION ...... 5-1

DEFINITION OF ABBREVIATIONS ...... 6-1

ACKNOWLEDGMENT ...... 7-1

REFERENCES ...... 8-1

APPENDIXES

A . SAMPLENEWS RELEASE ...... A-1

B . VIKING LANDER MISSION SUPPORT EXTENSION REQUEST ...... B-1

C . VIKING LANDERMONITOR MISSIONDIRECT-LINK REQUEST SUMMARY ... C-1 D . VIKING LANDERMONITOR MISSIONDIRECT-LINK REQUEST DETAIL ... D-1

E . AN EXAMPLE OF VIKING LANDERSEQUENCE OFEVENTS ...... E-1

F . RECOVERYSTRATEGY LOG FOR VIKING LANDER 1 ...... F-1

G . ANNOTATED BIBLIOGRAPHY ...... G-1

H . VIKING FACTS ...... H-1

vii Figures

2.1 . VikingLander ...... 2-3

2.2 . VikingLander 1 Radio System. FunctionalBlock Diagram .... 2-5

3.1 . TypicalLander Pass ...... 3-2

3.2 . VikingLander Uplink Acquisition Sequence ...... 3-4

3.3 . PredictedDownlink Signal Level From Vikins Lander 1 ..... 3-4

3.4 . VikingLander Telemetry Configuration .DSS 14 ...... 3-6

3.5 . VikingLander Tracking Configuration .DSS 14 ...... 3-7

3.6 . VikingLander Command Configuration .DSS 14 ...... 3-8

3.7 . Viking Lander Monitor and Operations Control Configuration . DSS14 ...... 3-9

3.8 . Real-TimeData Transfer to University of Washington ...... 3-11

4.1 . TypicalViking Lander 1 PressureRecord ...... 4-3

4.2 . TypicalViking Lander 1 LocalAmbient Temperature Record ... 4-4

4.3 . Yiking Landers 1 and 2 Local AmbientPressure for 3 Martian Years ...... 4-5

4.4 . VikingLander 1 ComparativeMars Images ...... 4-7

4.5 . VikingLander 1 Seven-Picture Sequence ...... 4-7

Tables

2.1 . VikingOrbiter 1 SurveyMission. 1980 ...... 2-2

2.2 . GeneralViking Orbiter Statistics ...... 2-3

2.3 . VikingLander 1 SpacecraftTelecommunication Parameters .... 2-6

3.1 . Comparative Success Rates for VikingLander Data Acquisition . . 3-2

viii I. INTRODUCTION

In late 1976 therewere two Viking Landers and two Viking Orbiters in full operationon and around the planet Mars. Of thesefour spacecraft, Viking Lander 1 hadthe longest life; it was still active in October1982. As the Thomas A. Mutch MemorialStation, Viking Lander 1 representedthe United States' presence on Mars. As theViking Lander Monitor Mission (VLMM), is continuedto'gather and regularly transmit to Earth imaging and meteorology data relative to its local Martian environment.However, late in 1982, thelander failed to respond to uplink commands for a downlinktransmission. Repeated attempts over a periodof four months failedto recover the lander signal. Finally, in March1983, the Viking I Lander Monitor Mission was terminated.

Previoustracking and datasystems support for the Viking Mission to Mars aredescribed in Refs. 1-1 through 1-5.

1-1 11. BACKGROUND

In July 1980, a pressrelease (Appendix A) announced theimminent conclusion ofthe Viking Orbiter 1 (VO-1) Mission and thebeginning of the VLMM. This an- nouncementmarked the end of the major Viking operations activity, and thebeginning of a new era of low-level support of anautomatic lander mission on an "op- portunity"basis. The requestfor telecommunications and data acquisition support fromthe Deep Space Network (DSN) for the VLMM through1990 is reproduced in Appendix B.

A comprehensiveand informative account of the last year of the Viking Mis- sion is given in Reference 2-1 from the point of view of one of the scientists most closelyinvolved with theproject from its inception in 1969.Table 2-1 is takenfrom Reference 2-1 to show the principal mission events of the final months of Viking Orbiter 1.

On August 7, 1980, at 2015 GMT, the Deep Space Station (DSS) 61 in Spain sent a command to VO-1 to turn off its S- and X-band transmitters. To satisfy international agreementsregarding uncontrolled radio transmissions from mace- craft, the s- and X-band transmitters wereturned off before ground control was lost. Subsequent RF searches atthe VO-1 frequenciesverified that both trans- mittersremained off. These searcheswere repeated several times over subsequent weeks, but no carrierswere detected.

Thus ended the Viking Orbiter 1 Mission to Mars after five years of continuous operationalsupport by the Network. Throughout this period, the Network pro- videdcontinuous mission support and was effective in developingoperational techniquesto overcomeproblems caused by highly reduced staffing levels, obsolete hardwareand software, and the steady attrition of experienced Viking.operations staff.

The VikingProject Scientist compiled the statistics of general interest given in Table 2-2 regardingthe two Viking Orbiters and the Deep Space Network support.

VikingLander 1 (Figure 2-1) is located in ChrysePlanetia at 22"N,48" and was in anautomatic operational mode sinceMarch 1979, transmitting stored imaging andmeteorology data on activation from one ofthe deepspace stations.This activity became identified asthe Viking Lander Monitor Mission (VLHM) on Novem- ber 6,1979, and continued toprovide regular transmissions of stored engineering, imaging,and meteorological data through October 1982.

The VikingLander 1 (VL-1) spacecraftradio system had one activereceiver (oftwo) and two active transmitters. A storedprogram in thelander turned a transmitter on at a specifiedtime corresponding to eachEarth view period, and a long-termstored program maintained the antenna's Earth-pointing direction. The Earth-pointingantenna program was writtento be valid through 1994. In the periodbetween Network communication passes, imaging and meteorological data were accumulatedon the tape recorders for readout during each Network pass.

2- 1 Table 2-1. VikingOrbiter 1. SurveyMission, 1980

Date Event

April 23 Orbit trimbegin to survey mission

May 17 Last Sun occultation

June 15 Lastinfrared ‘observation of planetthe

July 12 occultationEarthLast

July 14 Finalimaging sequencesurvey of

July 15 First engine burn in propulsionsystem test

July 17 Second engine burn in propulsionsystem test

July 18 Thirdengine burn in propulsion system test fails to exhaustpropellant as intended

JulyTwo 26 imaging sequences: globalsurvey from apoapsis, andground-track strip near periapsis

July 28 Ground-track stripperiapsisnear

July 30 Finalimaging sequence:ground-track nearperiapsis

July 31 Fourthengine burn in propulsion system test exhausts propellant, Rev. 1485

August 5 Playback of lastorbiter picture, Rev. 1488

August 7- Orbiter power turnedoffbyground command, Rev. 1489

2-2 Table 2-2. GeneralViking Orbiter Statistics

Parameter vo-1 vo- 2

Number of daysfrom launch endto of mission 1813.981049.52

Numberof of orbits Mars 706.1 1488.0

Number of picturesrecorded in orbit 16,04136,622

Number of data bits played back from the two 9 9 taperecorders (including lander relay data) 357.7 x 10 161.3 x 10

Tape recorderacrosstravelheads, km 13972955

Number of commands sent byNetwork the 269,500

Number of trackingpasses supported by theNetwork 7,380

Amount oftracking time provided by theNetwork, h 56,500

nS-BAND HIGH GAIN ANTENNA (DIRECT)

MAGNIFYING MIRROR i".. 1 RADAR ALTIMETER ELECTRONICS 2

METEOROLOGY (RELAY) SENSORS UHF ANTENNA (RELAY)

METEOROLOGY BOOM ASSEMBLY (INSIDE COVER)

RTG WIND COVER (2 EA) LANDING SHOCK ABSORBER

ET CLEANING

ROLL ENGINE (4 E LEG 2

TERMINAL DESCENT PROPELLANT TANK (2 EA)

RADAR ALTIMETER ANTENNA AND TERMINAL DESCENT LANDING RADAR (UNDERSIDE OF LANDERSTRUCTURE) SURFACE SAMPLER BOOM

TERMINAL DESCENT ENGINE (3 EA) 18 NOZZLECONFIGURATION MAGNETS COLLECTOR HEAD

Figure 2-1. Viking Lander

2- 3 A functional block diagram of the VL-1 radiosystem is shown in Fig. 2-2. Receiver 1 on that diagram failed prior to the end of VLMM, although its associated command detector and modulator-excitercontinued to work satisfactorily, as did all other elements of theradio system.Loss ofreceiver 1 forcedaccess to either command decoderthrough receiver 2, which is permanentlyconnected to the high-gainantenna. Thus, bothuplink and downlinkcommunication with the spacecraft was dependentupon the high-gain antenna automatic pointing program.

Spacecrafttelecommunication characteristics are given in Table 2-3.

By Januaryof 1982, threeof the four 8-A.h, nickel-cadmiumbatteries on- boardViking Lander 1 showed signs of significant loss ofenergy-storage capacity. An intensive program of deep-discharge battery conditioning was begun in January 1982 in an attempt to return the batteries to levels of capacityapproaching early mission levels.

The reconditioning was relatively successful, but the ability of the batter- iesto retain their energy-storage capacity was poor. In one case, 80% of the gainedcapacity was again lost only four months after the last reconditioning cycle.

In an attempt to extend the life of the batteries as long as possible,the battery.performance and the method of reconditioning the batteries was reviewed in detailby several experts in thisfield. This review, held in August 1982, ledto the adoption of a new batteryconditioning and operatingstrategy. Reauc- tion in thefrequency of battery charging, deeper discharging during reconditioning, and shorterduration of recharging were considered key items in prolonging theViking Lander battery life. These strategieswere incorporated in theViking Lander sequences,and the effects on batteryperformance were carefully observed.

Following one of the uplink sequences,however, thenetwork was unable to detectthe presence of a downlinksignal. Subsequent efforts to command the downlink "on," rechargethe batteries, and pointthe lander antenna were unsuccessful in producing a downlinktransmission. After four months of unsuccessful recovery efforts, the VLMM was terminated in March 1983.

2-4 ccu------I r ‘ r- I COMMAND MOD- LGA 4 DECODER EXCITER PORT I NO. 1 NO. 1 NO. 1 I TWTA - I NO. 1 I, - b TRS 4-PORT 4 I I HYBRID I I I TWTA TRANSPONDER NO. 2 NO. 2 I ” - 1I 1

COMMAND COMMAND MOD- 1 DECODER .C- DETECTOR EXCITER - I NO. 2 NO. 2 NO. 2 I I . 1- I DIPLEXER ASSEMBLY 1 I L“?” J 7 SINE COSINE TO HGA HGA DRlM PORT *-TRAl N Figure 2-2. Viking Lander 1 Radio System, Functional Block Diagram Table 2-3. VikingLander 1 SpacecraftTelecommunication Parameters I Parameter Value I Transmitfrequency, MHz 2294.629630(channel 13a) Tra nsm itter power,Transmitter dBm 42.6

I antenna,High-gain dB 22.3, transmit; 21.3, receive Low-gainantenna, dB 4.5, receiveonly

Receivernoise figure, dB 7.8

System noisetemperature, K 1549, highgain; 1150, lowgain

Receivefrequency, MHz 2112.971451(channel 13b>

Science bit rate, bitsls 1000, 500, and250 ,

Coding Biorthogonalblock coding (32:6)

Engineering bit rate, bitsls 8-113, uncoded

Subcarrierfrequency, kHz 12,engineering; 72, science

Command bit rate,bits/s 4

2-6 111. DSN SUPPORT

The history of tracking and data acquisition support for the Viking Project from its inception through mid-1980 is given in Refs. 1-1 through.1-5.

A. 0PERAT:IONS A.

A comptehensivereport on all the direct DSN to VL-1 downlipk opportunities from the beginning of the Viking Lander Monitor Mission in August1980 to October 1982 is given in Appendixes C and D. Over this 2-yr period,the success rate for theentire Network was 90% for telemetry (TLM) and 80% forradio metric (Tracking System (TRK)) data.Success rate is the ratio of goodpasses to total passes scheduledfor the Network. Passes are judged "good" or "nogood" onthe basis of the amount and quality ofthe data return. A comparison of thedata acquisition successrate for 1980, 1981, and 1982 is given in Table 3-1. Success ratesfor allstations over the 3-yr period are in theregion of 80% to 90%. A summary of the direct-link requests is given in Appendix C, with the details of each pass given in Appendix D. These dataafford a good insight into the overall performance of theNetwork in supporting these rather random VikingLander passes over an entire 3-yr period. I

The VLMM did not enjoy a high priority in theassignments of tracking time. Frequently an available view period was lost becauseantenna time was not available, or a passscheduled for Viking was preempted for another flight project. Examples of this are given in Appendix D.

The VLMM created some operational difficulties for the Network operations teams. Duringthe Viking prime mission, command sequepcesdeveloped by theflight teams wereloaded into IBM 360-75 computerslocated in the JPL Mission Control Center.From there, all interactions with the Deep Space Station Command System - includingverification, transmission, and confirmation - wereautomatic. With thedecommissioning ofthese three computers at the end of the prime mission, the Network accepted responsibility for sending all VL-1 commands manually,although the small VLMM operations staff remaining with the project actually designed the desired command sequences. The command sequence desiredfor the pass was transmitted by theNetwork Operations Project Engineer (NOPE) to the station by teletype (TWX). An example of a VikingLander sequence of events is given in Appendix E. At the DSS, the TWX command sequence was loabedmanually into the command buffer, recalled by the NOPE, and verified for accuracy.

A typicallander pass is illustrated in Fig. 3-1. Duringthe first 60 min ofthe pretrack preparation (PTP), thestation counted down thetelemetry, command, monitor,and radio metric data systems. During the last 30 min of the PTP, the station turned over the command systemto Network Analysis Team(NAT) command for a command-system validation.After NATcommand validatedthe command system, the DSS enteredthe commands requiredfor the pass; these commands werereceived by TWX message fromthe NOPE into the manualbuffer. NATcommand thenrecalled the manual buffer andvalidated the command bit pattern.Following verification by NATcom- mand, the DSS thentransferred the contents of the manual buffer to Module 1 of the DSS Command System.

3-1 Table 371. C,omparativeSuccess Rates forViking Lander Data Acquisition

Passes

Ye ar Station Year Good Bad Rate, Success %

TLM TRK TLM TRK TLM TRK TLM TLM TRJK

1980 Goldstone 2 2 1 67 1 67 Australia 3 2 0 1 100 67

Spain 3 3 0 0 100 100

1981 Goldstone 4 3 1 2 80 60 Australia 9 9 2 82 2 82

Spain 11 11 2 35 2 85

1982 Goldstone 8 7 1 78 2 89 Australia 13 10 0 3 100 77 Spain 12 11 0 1 100 92

1980 All stations 8 7 1 2 89 73 1981 All stations23 24 5 79 6 83 1982 All stations28 33 1 82 6 97

COMMAND UPLINK

SWEEP START MATURN ON

DOWNLINK START DOWNLINK STOP PROGRAM START SWEEP ACQUISITION DOWNLINK AND SPACECRAFT TIME COMMAND II \ \ SYSTEM \ \ DETECTORLOCK \ \ \ \ COMMAND DATA VALIDATION \ '\ \\'\ \ DSS \ \ \\ DSS POST \\, \\CALIBRATION\

a 90 rnin

a 2H) rnin MAXIMUM

Figure 3-1. Typical Lander Pass

3- 2 Followingthe start of track, approximately 15 min wererequired for the uplink acquisition sweep; there was a padof 12 min in which to turn on command modulationbefore the command windowopened. The command window was usually of 15 min duration.

The actual downlink lasted 60 min when thespacecraft was configuredon TWTA1. Allowing a 30-minutepostcalibration on the ranging system and the maximum one-way light time expected during the mission, the maximum VLMM track was 270 min.

Because ofthe temperature-sensitive nature of the oscillators onboard the VikingLander and the large temperature excursion on the planet's surface, a non- conventionalacquisition sweep procedure was devised to insure reliable two-way tracking.Figure 3-2 illustratesthis procedure.

Because thelander transmitter was programmed "offr'after each successful direct-link pass,the lander uplink was alwaysacquired in theblind. Unlike normalacquisition sweeps, the initial transmit XA was alwaysabove that shown on thepredicts, andthe first ramp was always in thenegative direction. Under nor- malconditions, the spacecraft receiver was captured during this portion of the sweep.. The next portion of the sweep was at a slowerrate and in thepositive directionover the same range. The final downwardramp tookthe spacecraft receiver to a nominalcenter frequency, which was designatedthe track synthesizer frequency (TSF) forthe pass.

Thisprocess was time-consumingand cumbersome, and verysusceptible to-human error,particularly if a long command sequence was calledfor. It is a tribute to the NetworkOperations Team thatmistakes seldom occurred; this fine record has beenrecognized by the Project Manager in a memo of commendation. In contrastto command'ing, thetelemetry operational procedures became much simpler.There was noreal-time processing of telemetry engineering or science data at JPL. Instead, a real-time record of the telemetry stream wasmade by thedata records generator in theNetwork Operations Control Center (NOCC). From this, and usingrecalls if necessary,an Intermediate Data Record (IDR) wasmade andshipped immediately to theUniversity of Washington where the telemetry processing was carriedout. The VLMM spacecraftengineer accessed this source for spacecraft engineering data and the imaging and meteorological investigators also obtained their data from this source.

Signallevels on the up and down telecommuncationlinks between the DSN and VL-1 were quite high andgenerally allowed the DSN the option of supporting the VL-1 passeson a 64-m or 34-m antenna. A plotof downlink signal level andEarth- Marsrange through 1988 is shown in Fig. 3-3. Typical S-band downlinktelecom- municationsparameters in October1982 were:

Downlinkreceived carrier power, dBm -148.2 DSS receivermargin, dB 26.9 Telemetry SNR at, 8-113 bitsls, dB 20.9 Telemetry SNR at 1000 bits/s, dB 6.1 Uplinkreceived carrier power, dBm -119.1 VL-1 command receivermargin, dB 26.2

Forelevations other than 90deg, the above datamust be reduced accordingly; the maximum correction at 10-deg elevation was 2.00 dB.

3-3 XA + 35,000 HZ

XA + 10,000 Hz

FREQUENCIES ARE S-BAND. RATES ARE FROM THE PROGRAMMABLE OXILIATOR CONTROL ASWBLY.

Figure 3-2. VikingLander Uplink Acquisition Sequence

450 I I I I I

, - -152

YEAR

Figure 3-3. PredictedDownlink Signal Level From Viking Lander 1

3-4 Over theyears of the primary mission, the operational complexities of the Networkranging system frequently resulted in the loss or degradation of the rangingdata. This situation improved in lateryears, and theNetwork provided excellent radio metric data return and high-qualityranging data, as seen from theranging performance statistics given in Appendixes C and D. The substantial contributionto the radio-science investigations resulting from the improvement in ranging data quality is reflected in theradio-science discussion in Sub- section II-A.

B. CONFIGURATIONS

The basicNetwork capabilities required to support the VLMM follow:

(1) Telemetry:process two telemetry subcarriers simultaneously at data rates of 8.333 bits/s uncodedand up to 1000 bits/s block coded.

(2) Command:command a singlespacecraft at a bit rateof 4 bits/s.

(3) Tracking:generate S-band dopplerranging and differenced range versus integrateddoppler (DRVID) radiometric data.

(4) Monitor:output the standard Network status and configuration blocks.

The ways in whichthese requirements were translated into a typical station configuration (DSS 14 atGoldstone) are shown in Figs. 3-4 through 3-7.

The standard 64-mDSS configurationfor telemetry is shown in Fig. 3-4. It is obviousthat the Block Decoder Assemblies (BDA) requiredfor the higher 16- kbits/sblock-coded data rates of the Viking Orbiters were deleted. In other respects, a standardstation configuration was used.

The tracking configuration required to generate radio metric data is shown in Fig. 3-5.

Provision for manual commanding throughthe terminet connected to both command processorassemblies (CPA) is apparent in the command configuration of Fig. 3-6.

Monitor and operationscontrol provided by the configuration in Fig. 3-7 afforded the high degree of interactive control between the NOCC and the DSS requiredfor the short passes, complex acquisition procedures, and manual commanding proceduresthat resulted from the reduced scope of Viking operations in this period.

C. REAL-TIME LINK TO THE UNIVERSITY OF WASHINGTON

Early in 1982, Dr. James Tillmanof the University of Washington proposed a real-time da,ta link between JPL andthe University of Washington (UW) to transfer the VLMM telemetry data directly to UW forprocessing and display. It was envisaged thatthese and other supplementary data would eventually be transmitted from UW to theSmithsonian Air andSpace Museum in Washington, D.C., for display to the general public.

3-5 64-m MDA PPR ANTENNA 4 4 1 1 1 uwv 20-kw BLOCK IV TXR - -EXCITER ------4 DOPPLER * MDA I EXTRACTOR - t II SPD RCVR SPD SDA 3 SSA Y TWM 3 - TPA 1

4 SDA 4 SSA 2 "---) sscs PPR

EXC N'" ANGLES

CMF, CPA, MDA, t TPA CONTROL DOPPLER EXTRACTOR

Figure 3-4. VikingLander Telemet-ry Configuration - DSS 14

3-6 DSS/GCF INTERFACE I I I I I

RCVR 1 4-LU DOPPLER DOPPLER EXTRACTOR C COUNTER /8 n?ELK 111 1 7 RCVR 2 BLOCK Ill COUNTER TERMINET

S W I T C MDA ssc I H - 1/2 M A T T R I X ANGLE -C DATA ODA ASSY L L I // U T EXC 1 I18.2 p-lI PRDX I

I ODA & DATA WEATHER DATA STRIP CHART

ANTENNA ANTENNA SERVO IONOSPHERIC MECHANICAL DATA

Figure 3-5. VikingLander Tracking Configuration - DSS 14 DSS/GCF INTERFACE 1 I

TERMINET w I m -1 I

A BLOCK 111 EXCITER USED DURING I BACKUP MODES ONLY

Figure 3-6. Viking Lander Command Configuration - DSS 14 DSS INTERNAL r""""""""""" INTERFACES D MC 1

I _""HOST

TLM

MCD I

CMD CMA

C M D CMA CMD t .) SMC 28 DOPPLER * piZZl W XD S -1 I 920 ul t * + A 1 PAPER-TAPE PAPER-TAPE TERMINET PUNCH READER

DIS II v ANALOG I DIGITAL SIGNAL COUPLER INTERFACE w

L______J

Figure 3-7. Viking LanderMonitor and Operations Control Configuration - DSS 14 The plannedconfiguration is shown in Fig. 3-8. In thecentral communications terminal (CCT) at JPL, theincoming Viking Lander engineering data (8-1/3 bits/s) andscience data (1 kbits/s) was fed to a dataset with FTS dial-up capability to a correspondingdata set at UW. The datastream was buffered at this point prior toentry into the UW dataprocessor. In additionto the real-time link described above, theData Records Generator in the CCT at JPL continuedto record the incom- ing data to make the IDR for nonreal-time delivery to UW.

By May 1982, thereal-time system had been set up, and on May 14 real-time VikingLander data was transmittedto UW from JPL. The purposeof the transmission was totest the 4.8-kbitsIs data-link modifications at JPL, and to test the capabilityof receiving anddecoding the data at UW. This was accomplishedsuccess- fully oninterim data processing equipment then available at UW. ByOctober 1982, uw.regular Viking transmissionswere taking place using a permanent installation at

Implementationof the link to the Smithsonian was well advanced by October 1982,and planswere being made to openthe display in the Air and Space Museum to the general public by theend of theyear.

D . AUTOMATICD. S-BAND DOWNLINK

Duringthe Viking extended missions, one of the two VL-1 command receivers failed,leaving only Command Receiver 2 (CR2) in service for the Viking Lande? MonitorMission. CR2 had a temperatureproblem that caused it todrop lock when its casetemperature exceeded 25OC. As a result,downlink transmission periods that required activation of the spacecraft transmitters were limited to onehour toavoid the temperature-sensitive operating condition.

In November 1981, A. Britting, Jr., proposedthat an automatic sequence be designedfor VL-1, one thatwould activate the downlipk transmission in theevent of failureof the one remaining command receiver. Thesequence would include a timerinitiated at the end of eachsuccessful downlink transmission. If thetime sincethe last transmission exceeded a preselectedvalue (e.g., 2 mo), thenext downlink would be initiated automatically and repeated at regular intervals through December 5, 1994, at which time the existing high-gain antenna Earth- pointing program would expire.

Such a scheme was consideredan expedierlt to ensure a continuumof regular V&-1 data in theevent of a potential loss of uplink capability.

Approvalfor a waiverto the National and NASA Directive (NMI 2570.3) requiring on/off telecommand capability for NASA spacecraft was soughton the groundsthat the VL-1 wouldcontinue to use its approved transmission Channel 13, and thetransmitter would be programmed toshut down in 1996. Additionally,should the programmer fail, it was consideredthat the RTG performancewould have de- graded by 1996 to the point wherethe RTG poweroutput could not support further VL-1 transmissions. The waiver was approved on January 20, 1982(Refs. 3-1 and 3-2). The automaticprogram was transmittedto VL-1 on January 27, 1982.

3-10 [- VIKING SUPPORT DSS's \ -TRANSMISSION- \< JPL - PASADENA, CALIFORNIA \ IDSSC's (GOLDSTONEIMADRIDICANBERRA) 1 ;CF 20 - WCSC CENTRAL COW TERMINAL (BLDG BO) ' MISSION CONTROLCENTER UEL (213) ?54-5801/5802/58m) ,

(NED) + ENCODER/ DECODER - /1"" \ VIKING (8 ID/ 1K) TLM I ' I - ! DATARECORDS TO UNlV ! FTS (2) WIRE DIAL OF WASH VIAAIRMAIL I HSD (4.8 KB/S) J SYNCHRONOUS L" TX MODE g-" "" I VK TLM + FILLER DATA DSN 1200/22 BIT BLOCKS I w SMITHSONIAN INSTITUTE - WASHINGTON. LC. I UNIVERSITY OF WASHINGTON (SEATTLE WASH.) - =INATIONAL AIR AND SPACE MUSEUM I FTS-VOICE (206)543-0500. HARRY EDMOND "VKLGRJ DIAL-UP I DATADISPLAY I *ED 512 I COLORIMAGE I FTS-DATA PROCESSING VIKING I I INTEL TERMINAL I SYSTEM MICRO PRIME 4W PROCESSOR -I COMPUTER

COMPUTER 1 DIAL-UP

I I NOTES: A RANNED VIKING LANDER SUPPORT I-PASS/ WK WITH MAX OF I HR TLM DATA L SET A DIAL-UP DATACONNECTION CKT AND PARALLEL w DATA STREAM SWITCHING TO BE ESTABLISHED BY OCT 82 IS PLWNED DATE FOR VIKING REAL TIME DATA NO ATRS OR POSTPASS REPLAY DATA TO BE ROUTED TO UNIVOF WASHINGTON GcF 2occTON REAL-TIME REaUEST NOC(BASED A A SWITCHINGUNlV TO OF WASH RECALL DATA TO BE PROVIDED ON IDR ONLY ONTIME IDENTIFIED IN VIKING PASS MSG WE) COMMANDWINDOW JPL6CS (CCT) CWWTER WILL BE CONFIGURED/VIILIZED ECSA ALL FOR SWITCHINGUNlV TO OF WASH, DSS TO ADDRESSALL VKG LDR TLM , A VK LDR IDR To BE PROV,DE UNIV TO SWITCH VK LDR TLM DATA IN REAL TIME TO UNlV OF DATA TO DESTINATION CODE MI-- - - ECS OPERATOR TO REROUTE DATA WITH WASHINGTON VIA FTS DIAL UPCKT INTERFACE ANY UNUSED AMES ALT ROUTE DESTINATION CODE (An THROUGH AD) UTILIZING PORT 10 ATTHE HIGH SPEED LINE SWITCH (HLS)

Figure 3-8. Real-TimeData Transfer to University of Washington As of that date, the automatic S-band downlinktransmission was activated after eight consecutive downlink intervals elapsed without an uplink reception. Because of the difference in thelengths of Marsand Earthdays, the interval betweendownlink transmissions varied from 7 to 8 Earthdays. Thus, anauto- maticdownlink was initiated between 56 and 64 days after the previous downlink hadbeen completed, unless a scheduleduplink had been successfully completed.

The program was interrupted andthe counter reset to zeroat any time in the event that the absence of an uplink wasd.ue to the unavailability of antenna time,rather than a VL-1 receiver failure.

E. THE VL-1 RECOVERYEFFORT

Althoughthe Viking Lander Monitor Missi.oncontinued successfully for several years,signs of a seriousbattery problem began to show in late 1981. The advice of experts in this field from all over the country suggested a change to the battery-chargingstrategy described in Section 11; thisstrategy involved discharging the batteries to a known voltagerather than for a fixedtime. A command sequence intended to make these changes to the battery-charging sequence was uplinked by DSS 43 on November 19, 1982,and an acquisition sequence forthe expected downlink was carried ou$

However, theexpected downlink did not appear, and theProject declared a spacecraft emergency on November 20, 1982.

It was assumed thatthe battery under-voltage (UV) switch,andtripped, and the Project directed its strategy for subsequentpasses to closing the UV switch and increasing the battery-charging cycles.

However, shortlythereafter, it was recognizedthat the new battery-charging sequence hadbeen written into spacecraft memory locationsoccupied by the lander high-gainantenna pointing parameters. It followed,,therefore, that the VL-1 antenna was nolonger pointing to Earth. Using the old, Lander simulation program, a new set of antennapointing angles was developedbased on the erroneous batteryparameters then residing in thelander computer memory. The landerantenna thencontinued to execute regular antenna pointing sequences, but these did not crossthe Earth-Mars line exceptfortuitously on specific daysand times.

Most ofthe following recovery strategy was basedon this assumption. As shown in thechronology of events in Appendix F, many attemptswere made to transmit commands tothe spacecraft, close the UV switch, andundo the erroneous pointingparameters in thecomputer.

This involved a great deal of manual commanding at the DSSs usually in much longer sequences thanhad previously been used on theViking extended missions. Some mistakesresulted in lost passes,but these were quickly rectified, and after the first week or two, Networksupport for the long manual command sequencesand the high-power transmitter running at 80 kW was very good.

3-12 A telecommunicationsuplink analysis showed that, at a transmitter power of 100 kW nominal(actual power of 80 kW), there was a 10- to 14-dB margin for command with thepointing angle passing through the side lobes of the VL-1 antenna polardiagram. There was noconcern for limitations in theuplink margin on this basis.Nevertheless, because of.uncertainty in thepolarization effects at angles well off the main beam ofthe VL-1 antenna,sometransmissionswere made in the left circular and linear modes, as well as the normal right circular polarization.

By the end of December 1982, thespacecraft had not responded to these repeated efforts to initiate a downlink, and furthes efforts weresuspended pending an in-depth investigation by Martin Company engineers.

Although all options for improving the uplink margin had been tried, it was decidedthat the uplink margin was adequateeven with theantenna off point. It was thoughtthat the VL-1 antennamight not be pointing in the direction indicated by the simulation program,and that the VL-1 computerhad also been switched off bythe UV switch.Other failure modes were alsoproposed. The outcome ofthe Martin-JPL investigation was a strategy involving reconditioning the batteries, reinitializing the lander computer,closing the UV switch,and various other lander housekeeping activities.

Thisstrategy would require much longerNetwork command sequences, repeated many timesduring the limited view periods. It became obviousthat this was be- yond the capability of the existing manual command system,and some form of auto- mating the command sequences wouldbe necessary.

Over thepreceding several years, a manual command procedurehad been used in which a maximum of 24commands could be sentmanually from thestation. The sta- tionrequired 2 minutesper command toload and verify. Once theloaded set of commandswas transmitted,the process had to be repeated for any further command sequences.

Sincethe new VL-1 strategy called for command seauences of at least 30 commands in length to be transmitted every 20 minutes, it was apparentthat such a strategy was tootime consuming and too prone to errors for use in thethen-current command procedures.

Therefore, new software was developed to permit the MCCC multimission' command system to convert 360-75 card-based command sequences into files thatcould beaccepted by the CPA at each DSS. A spacecraft ID previouslyused for HELIOS simulationenabled the NOCC to overlayViking "standards and limits" tables on the unused HELIOS tables,and cause the CPA to respond to continuoustransmission ofViking command files fromthe MCCC. Thiscapability was first tested with CTA 21 andworked satisfactorily in all respects.

This new capability was used operationally for the first time on February 1, 1983, to transmit 30commands every 20 minutesfor the total duration of the DSS 43-viewperiod. The first command loadrestarted the VL-1 computerand initial- izedthe battery-charging sequences. The second command closedthe UV switch and parked.theantenna. The first part of this load was transmittedover DSS 43 and the second partover DSS 63 onFebruary 10. The thirdload on February 11

3-13 turnedon the downlink, and the station carried out the appropriate downlink search. All this was accomplishedby February 11, 1983, without anyappearance of a downlink. Two furtherstrategies wereproposed. The first of these was to change tothe spare TWTA-modulator/exciter string, even though there was noevi- dence to suggestthat the original string had failed. These commands weresent onFebruary 16, but nodownlink could be found.

The second strategypresupposed that the antennapositi-on and thecomputer instructions wereout of alignment,possibly because the antenna stuck or slowed duringearlier repositioning sequences. The antenna was driven to its limits to realign the computerand antenna at a common reference point, andthen moved to anEarth-point position. A downlink was thenactivated on February 25.

The correct uplink commands weresent on February 18 to reposition the antenna,and the downlink "flag" was senton February 25; this was followed by a, downlinksearch over Goldstone. No downlinkcould be found.

Next, a highly sensitive wide-bandwidth spectrum analyzer used for RFI detection purposes at Goldstone was alsoused for the search. The thresholddetection sensitivityof this instrument was -186 -,dBm, but subsequentanalysis of the resulting integrated spectra revealed nothing.

At this point the Project announced that no further action was warranted and it was presumed that the lander was unable to communicate with Earth.

3 -14 IV. VLMM SCIENCERETURN

A. RADIO SCIENCE

Duringthe course of theViking Mission, a substantial contribution to the field of radio science wasmade by investigators using the orbiters or landers or both.

Specific areas in whichpapers have been published are:

(1) Rangingvalidation.

(2) Relativityinvestigation.

(3) Dynamicalconstraints of Mars.

(4) Solar-windscintillation.

(5) Shape of Mars.

(6) Marsgravity.

(7) Radiobeacon for deepspace navigation.

(8) Gravity waves.

(9) Solargravity.

(10) Solar-windelectron density.

(11) Ephemerisrefinement.

Some of this workcarried over into the VLMM, particularly in theareas of gravitational theory andephemeris development.

VLMM radioscience data generated by theNetwork was gatheredover a period of tensuccessful VL-1 rangingpasses and delivered as a package to the investigators I.Shapiro and R. Reasenberg atthe Massachusetts Institute of Technology and to W. Michaelat the Lewis Research Center. Each package delivered contained thefollowing items:

(1) A tapecontaining a MasterTracking Data File of doppler and ranging datafrom ten successful passes.

(2) A rangingcalibration summary and a set of punchedcards containing the summary data.

(3) A current set of Range "Z" corr.ectionsto adjust the measuredrange to thestation reference location.

(4) A COPY ofthe pass folder containing a logof station events during each pass.

4-1 (5) A copy of the latest status report onthe VLMM written by the Project Engineer.

(6) A commentary summarizingthe quality of the data return and noting significant events for each pass during the period covered by the package.

This substantial package of data was assembled by one of theengineers supporting the VLMM on a part-timebasis. Much of the.data was handwritten to save costs. Seven packages containingthe data described abovewere transmitted to the investi- gatorsduring the period 1980 to 1982.

Two recent papers describing the Viking Relativity Experiment are given in Refs. 4-1 and 4-2. Analysis of rangingdata from the Viking spacecraft, including the landers, verified a prediction of the General Theory of Relativity relating to the influence of solar gravity on the round-trip light time of signals passing between Earth andMars.

The estimatedaccuracy of these results was 0.1%based on observations over a periodof about one year.Further reduction in theuncertainty of this test of general relativity was dependenton the coll.ection and refinement of additional data.

More recently,the VLMM radiometric data was usedby Shapiro, et al., to evaluate evidence for the time variation of the gravitational constant as a func- tion o'fatomic time.

In investigating these long-term effects, precise measurements of the orbital periods of Earth andMars (representing a gravitational clock) are made with hy- drogen-maser timestandards (representing atomic time). In an effortto reduce theresiduals between predictions andmodels, the quality of the radio metric data,the computer programs, and the modelsthemselves are being investigated, as well as perturbations of the Earth and Mars orbits by.the gravitational effects of several asteroids and planets.

B . METEOROLOGY

Two meteorologyexperiment sensors on VL-1 were the Local AmbientPressure Sensorand theLocal AmbientTemperature Sensor. Under theleadership of Dr. James Tillman of theUniversity of Washington, thelong periods of continuousViking observations from these two instrumentshave provided major insight into many Martianatmospheric processes, such as frontal systems, annual climate measurements, interannualclimate variations, and duststorms.

Typical daily records of pressure and temperaturefrom VL-1, whichhave been processed at UW asdescribed in Subsection C, are shown in Figs.4-1 and 4-2.

Similardata covering a span of 3 Martianyears is shown in Fig. 4-3. In this diagram, 669.0 sols equal 687 Earth days. This is typical of theanalytical datadeveloped by Tillman, and revealsthe presence of duststorms in wide

4-2 9 .Ooo I I I I (a)

8 .Ooo

7 .OM 2200 .o 2202 .o 2204.0 2206 .o 2208 .o 9 .om I I I I I I I (b)

8 .ooo VL-1

2208.0 2210.0 2212.0 2214.0 2212.0 2210.0 2208.0 2216.0

TIME NORMALIZED TO LOCAL MIDNIGHT, VL-1 sols

Figure 4-1. TypicalViking Lander 1 PressureRecord: (a) Wednesday, October 6, 1982,16:04:58; (b) Wednesday, October 13, 1982, 03:38:44 (Courtesy of theUniversity of Washington Department of AtmosphericSciences) I I I

260 .O

VL-I

240 .o

220 .o

Y J W OL 2 4, W 0

c 0 260.00 I I I P

I-

) I I I I 2208 .o 2210.0 2212 .o 2214.0 2216 .O TIME NORMALIZED TO LOCAL MIDNIGHT, VL-I sols

Figure 4-2. TypicalViking Lander 1 Local AmbientTemperature Record: '(a) Wednesday, October 6, 1982, 16:07:21; (b) Wednesday, October 13, 1982, 03:39:14 (Courtesy of theUniversity of WashingtonDepartment of AtmosphericSciences) VL-I

I YEAR 1 YEAR 2 L1 I I I YEAR2007 3 .O 0 .o 33b .5 669 .O 1003.5 1338 .O 1672.5 7 TIME NORMALIZED TO LOCAL MIDNIGHT, VL-1 sols

Figure 4-3. VikingLanders 1 and- 2 LocalAmbient Pressure for 3 Martian years.Lower Plot: Daily Average. Upper Plot: Standard Deviationsof Pressure Around Daily Mean at Viking Lander 1, Which is anIndicator of Atmospheric Dust for Values of Sigma 2 0.1 andLongitude (Season) (L,) Between 180 and 300; After 300, Synoptic Systems GenerateLarge Variations Within a sol atThis Tropical Site (Courtesy of the University of WashingtonDepartment ofAtmospheric Sciences)

4-5 perturbations of the daily pressure patterns due to solar heating of atmospheric dusts,at, for example,1977a and 1977b. Features ofinterest identified by Tillman are shown bythe small pressure spikes labeled "C" occurring at approxi- mately1-Martian-year intervals.. These spikes seem tobe associated with the passage oflarge-scale dust storms andappear at almostthe same Martian season eachyear. Because thesedisturbances were being sought in the 1982 data,the Networkreceived requests for as much continuoustracking data as possible to maximizethe chance ofrecording these data for further study and analysis.

C. IMAGINGEXPERIMENT*

VikingLander 2 ceased operation in February1980 because of onboard battery failure. At thattime both cameras were fully active after 3-1/2 yearsof Mars operations,during which they had performed 2156 camera events(imaging sequences). Fortunately,both cameras on VL-1 alsoremained operational, and continued to perform programmedcamera eventsthroughout the VLMM. Duringthe VLMM, .therewere 164 possibleimaging opportunities, of which 88 resulted in images received and deliveredto the investigators. The difference is due mainlyto the lack of available antenna time in theearly years because of higher priority Voyager Jupiter andSaturn support.

The VL-1 cameraswere activated by a storedprogram that set all the camera parametersincluding pointing, so that the same scene was viewedonce each Mar- tianyear. Comparison of successiveannual i.mages was used to check fordust or condensatedeposition or erosionover the interval of time. A recent example ofcomparative imaging is shown in Fig. 4-4, where thetime interval between the two photosextended from February 1979 (left)to July 1981 (right). The subject was a 5-cm pile of soil placed beside and partly atop an ll-cm rock by VL-1's soil-sampling arm.Comparison of the twophotos shows that some of the soil had beenremoved byMartian winds to reexpose the rocks. The small change is impor- tant,scientists say,because it shows thatd.eposition and removal of fine-hate- rial.is a continuingcycle on Mars,as it is onEarth.

The IDRs made bythe DSN in the NOCC contained the l-kbit/s imaging and 8-1/3 bitslsengineering data; they were deliveredto the Image ProcessingLab (IPL) at JPL for processing. The IDRs wereprocessed intoprints and digital tapes,and 10 copiesof each were distributed by the VLMN Project to the sevenregional planetaryimaging facilities throughout the U.S.A. The otherswere archived. Investigators in variousareas had access to the continuing flow of Mars imaging products from theseregional facilities.

A recentLander 1 picture sequence showing a uniqueMars event, a duststorm, is shown in Fig. 4-5. The seven-picture sequence was acquiredover a period of 16 mo fromindividual Viking' Lander imaging sequences. Such images allow re- searchersto observe the year-to-year surface changes aroundthe lander - changes thathelp quantify the magnitudes of the geological processes acting to shape the surfaceof Mars. The predominanttype of surface changes are due todust - both erosional and depositional. In thesixth frame(June 14, 1901), theentire scene was darkenedby the passage of what apparently was a localized dust storm. Prior to and afterthis image, thesky and surfacewere brighter. The change in

*A listing of NASA publications relating to the Viking Orbiter and Landerimaging experiments is given in Appendix G.

4-6 Figure 4-4. VikingLander 1 Comparative MarsImages

Figure 4-5. VikingLander 1 Seven-Picture Sequence

4- 7 apparent brightness of the large boulder named "Big Joe" early in the mission was due toseasonal changes in theSun's angle. .After one complete Mars year, the Sun returns to the same position in the sky,and images can be compared by computer to search for differences.

The Marsimaging program was tocontinue throughout the VLMM, systemati- cally returning images of the same Marsscene, each Mars year, until End of Mission (1994).

4-8 V. CONCLUSION

The Networkhas been involved with the Viking Project through its various phasessince itsinception in 1968 tothe present time, 1983." Throughoutthe prelaunchplanning and the prime mission, the Network responded to the project's requirements for support with total commitmentand an extremely high standard of performance.This was achievedunder the difficult- conditions of limited staff, obsoletehardware and software, and sparse documentation.

Followingthe prime mission, the "extended" and "continuation"missions re- ! ceivedthe same leveloftechnical support, although competition for antenna time by flight projects of higher priority resulted in reducedtracking time for the VLMM. As NASA interest in theremaining operational Viking spacecraft declined, it became more difficultto schedule all the requested antenna time, even though scientificinterest in thereduced data return quickened. This placed much moreemphasis on achieving "goodpasses'' to reap maximum return from the limited opportunitiesavailable.

During the final phase of the VLMM, theNetwork was calledupon to develop and carryout many innovativetechnical and operationalstrategies to support the effort to recover the VL-1 spacecraft.

*Facts relative to the Viking missions are given in Appendix H.

5-1 DEFINITION OF ABBREVIATIONS

ANT antenna

AP S Antenna Pointing Subsystem

CB circuit breaker

CCT Central Communications Terminal

ccu command control unit

CMA Command Modulation Assembly

CMD Command System

CMF Communications Monitor and Formatter Assembly

CO" communications

COORD coordination

CPA Command Processor Assembly

CRT cathode-raytube

C SA Command Switch Assembly

DCO digitally controlled oscillator

DEC declination

DIS Digital Instrumentation Assembly

DODR Digital Original Data Record

DRA Digital Recorder Assembly

DRG Data RecorderGenerator.

D/S data set ,-. DST Data System Terminal Assembly

ECS error correcting and switching

ESA Exciter Switch Assembly

EXC Exciter Assembly

EXT external

6- 1 FDX full duplex (two-way)

FMTR formatter

FTS FederalTelecoqunications System

GCF Ground Communications Facility

GDSCC Goldstone DeepSpace Communications Complex

HGA high-gain antenna

HOST HOST softwareprogram

HSD high-speeddata

HSDL high-speeddata line

IF intermediatefrequency

I/O input/output

JPL Jet Propulsion Laboratory

KB keyboard

LGA low-gainantenna

MAG magnetic

MCA Microwave Control Assembly

MDA Metric Data Assembly

MET meteorological

MMR Multimission Open-Loop Receiver Assembly

MON Monitor and Control System

NB narrow band

NOC NetworkOperations Chief

ODA Occultation Data Assembly

OLR Open-Loop Receiver Assembly I OP s operations

PPR Pre- and PostdetectionRecording Subsystem

PRA Planetary Ranging Assembly

6-2 PRDX predicts

RA rightascension

RCVR receiver

RDA Ranging Demodulator Assembly

SIC spacecraft

SDA Subcarrier Demodulator Assembly

S IA star switch interface adapter

SMC Station Monitor and Control Subsystem

SPD S-Band Polarization Diversity

S SA Symbol Synchronizer Assembly

ssc Star Switch Controller

SSI SpectralSignal Indicator

STA Stimulus Assembly

S/W IiD software block decoder

SYNC synchronization

TODR temporary original data record

TPA Telemetry Processor Assembly

TRS transmit/receive selector

TWTA traveling-wavetube amplifier

TX transmitter

TXR Transmitter Subsystem

uwv Antennallicrowave Subsystem

VOCA Voice CommunicationsAssembly

VK LDR Viking Lander

WB wideband

WBDL widebanddata line

6-3 ACKNOWLEDGMENT

The Viking Lander Monitor Mission depended for its successful data return upon the individual efforts of a small number of people in and associated with, theNetwork. Some of thesepersons made substantialcontributions to thisreport by furnishingdata, reports, or opinionsto the author. In thisregard, the contributions of P. Eshe, S. LaVoie, A. Britting, Jr., J.C. Nash, and J.P. Brenkle are gratefully acknowledged.

7-1 REFERENCES

1-1. Mudgway, D.J., and M.R. Traxler,Tracking and Data SystemsSupport for the Viking 1975 Missionto Mars: Volume I. PrelaunchPlanning, Implementation, andTesting, Technical Memorandum 33-783. JetPropulsion Laboratory, Pasadena, Calif., Jan.15, 1977.

1-2. Mudgway, D.J., and M.R. Traxler,Tracking and Data SystemsSupport for the Viking 1975 Missionto Mars: Volume 11. LaunchThrough Landing of Viking 1, Technical Memorandum 33-783. JetPropulsion Laboratory, Pasadena, Calif., March 15, 1977.

1-3. Mudgway, D.J., Trackingand Data Systems Support for the Viking 1975 Mission to Mars:Volume 111. PlanetaryOperations, Technical Memorandum 33-783. JetPropulsion Laboratory, Pasadena, Calif.,Sept. 1, 1977.

1-4. Mudgway, D.J., Trackingand Data Systems Support for the Viking 1975 Mission to Mars: Volume IV. ExtendedMission Operations, Technical Memorandum 33- 783. JetPropulsion Laboratory, Pasadena, Calif., Dec. 15,1978.

1-5 Larkin, W.E., Telecommunicationsand Data Acquisition Systems Support for the Viking 1975 Mission to Mars, 1 June1978 to 30 April 1980, JPL Publica- tion 82-18. JetPropulsion Laboratory, Pasadena, Calif.,April 15, 1982.

2-1 a Snyder, C.W., and N. Evans, "The Final Phases of the Viking Mission to Mars," Icarus, Vol. 45, pp. 2-24, 1981.

3-1. Manager,Frequency Management Programs, OSTDS, Wa'shington, D.C., "Waiver of National and NASA Directives Requiring On/Off Telecommand Capability for Remaining Viking Lander," Letter to Director, SpectrumPlans and PolPcy, NationalTelecommunications and Information Administration, Washington, D.C., Jan. 20, 1982.

3-2. Director,Spectrum Plans and POlicy,National Telecommunications and Infor- mationAdministration, Washington, D.C., "Concurrence With Request for Waiver," Letter to P. Struba, Code TN-OSTDS, Jan. 20, 1982.

4-1. Reasenberg, R.D., 1.1. Shapiro, P.E. MacNeil,and R.B. Goldstein (MIT),and J.C. Breidenthal, J.P. Brenkle, D.I. Gain, T.M. Kaufman, T.A. Komarek, and A.I.Zygielbaum (JPL), "Viking Relativity Experiment: Verification of SignalRetardation by Solar Gravity," Astro. J., Vol. 234, Nos. L219 - L221, Dec. 15, 1979.

4-2. Shapiro, I.I.,R.D. Reasenberg, P.E. MacNeil,and R.B. Goldstein(MIT), and J.P. Brenkle,D.L. Gain, T. Komarek,,andA.I. Zygielbaum (JPL), and W.F. Cuddihy and W.H. Michael, Jr., (LRC), "The VikingRelativity Experiment," J. Geo. Res.. Vol. 82, No. 28, Sept. 30, 1977.

8-1 APPENDIX A

SAMPLE NEWS RELEASE

A- 1 OFFICE OF PUBLIC INFORMATION JET PROPULSIONLABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. PHONE (213) 354-5011

FOR IMMEDIATE RELEASE

After more thanfour years exploring Mars, NASA's

VikingOrbiter 1 hasalmost reached the end of its mission.

The orbiter hasused almost all its attitude-control gas, that keeps itssolar panels pointed to the Sun and the antenna aimed atEarth. When thegas is exhausted -- probablyabout July 23 -- controllersat Jet Propulsion Laboratory will send commands to turn off VikingOrbiter 1 to end its long and productive mission.

Meanwhile,Viking Lander 1 is programmed tooperate un- attendedon Mars into 1990, perhaps to beextended into 1994.

Duringthe most recent phase of Viking'smission the orbiter hastaken about 30 pictures a day of a regionsouthwest of

Olympus Mons and the threevolcanoes on the Tharsis Ridge, an area ofparticular interest for its large, river-like channels. That sequence will continuethrough July 12.

Project officials pian a full program for Orbiter 1's final days. How much of the programcan be completed will depend onthe amount of attitude-control gasremaining. Here is a timeline of eventsthat are proposed to be carriedout if the orbiter continues to be cooperative:

July 138 14: The spacecraft will take a series of high- resolutionphotos of the summit caldera of Olympus Mons. These should be thehighest-resolution ever obtained of thecaldera of thesolar system's largest known volcano.

A- 2 (more ) July 15 through 18: The spacecraft will performthree

controlledburns of itsrocket engines. Those burnsare part of

a seriesof engineering tests to provide data that will benefit

future spacemissions. One effectof the burns will be to change

thespacecraft's orbit from its present 370 kilometers (230 miles)

periapsis and 34,000 kilometers (21,127 miles)apoapsis to 350

kilometers (220 miles)periapsis and 56,000 kilometers (34,800

miles)apoapsis. The new orbit will satisfy the condition, in ac-

cordance with planetary-quarantineprovisions, of notimpacting,

and thereby not contaminating,the planet before the year 2019.

July 20 to 23: Additionalengineering tests will becon-

ducted,principally on the radio system,and the final orbit will

be determined.

Currentextrapolation of thesupply andusage rate of

attitude-controlgas indicates July 23 isthe approximate date of

depletion, but flight controllers saythere isprobably a one-week

uncertainty i-n thatdate, so the orbiter could run out of gasas

earlyas July 16 or as late as July 30.

If it should turn out that there is still gasremaining,

thenabout July 27 Orbiter 1 will make a final high-altitude global survey of the visible portion of theMars disk -- 25 pictures

througheach of three filters, for a total of 75 frames.

When thegas is exhausted, the orbiter'sradio transmit-

ter will be commanded off forthe last time, and thespacecraft will continue silently orbiting Mars for many decades.

Viking 1 was launched to Mars Aug. 20, 1975, and arrived

June 198 1976. VikingLander 1 touched down onthe Martian surface

A- 3 July 20, 1976, with a 90-day missionexpectation. That mission com-

pleted, it has now observedthe planet for more thantwo full Mars

years -- fourEarth years on July 20.

As .longas it survives,Viking Lander 1 will continueto

collectphotos and weatherdata from the Martian surface and, on

command fromEarth, transmit them onapproximately a weeklybasis.

Viking Orbiter 2 ran out of attitude-control gas and wascommanded offJuly 24, 1978. VikingLander 2 was turnedoff afterits last relay transmission April 11, 1980.

The VikingProject -- todaywith fewer than 30 people engaged in flight operations and sciencedata processing -- is man-

aged for NASA's Office of Space Scienceby Jet Propulsion Laboratory.

#####

#940/7/9/80/DB

A- 4 APPENDIX B

VIKING LANDER MISSION SUPPORT EXTENSION REQUEST

LANDER (VL-1) MONITORING MISSION

JULY 20,1979 THROUGHDECEMBER 29,1990

B-1 OBJECTIVES

1. Obtain S-band rangingdata from the surface of Mars periodicallyover a longtime span for theconduct of RadioScience.

2. Obtainmeteorology and imaging data from the surface of Mars periodically over a longtime span to monitor and disseminate information relative to any significant changes with time.

SUPPORTREQUIREMENTS

1. Retainexisting DSS landertelemetry and command softwarecapability.

2. At least two64-meter passes of.3hours duration per month through 1980.

3. At least one 64-meter pass of 3 hoursduration per month through 1981.

4. Subsequentyears - tobe negotiated on a yearlybasis. -MCCC 1. Supportrequirements contained within theorbiter requirements until 2/1/80. No MCCC dependency orrequirements thereafter.

PROJECT/DSNINTERFACE

1. meproject shall provide a personto act as a focalpoint for al-1 lander/ -DSN interactions.

2. The projectinputs to the DSN shallinclude scheduling, predictions, sequences, commands and operationaldirection during passes.

3. The DSN shallprovide lander IDRsand datapackages to this person.

R. S. Watkins Thomas A. Mufch Viking Project Manager AssociateAdministrator for SpaceScience

~Zuce Nurray, Director " W. C. Schneider JetPropulsion Laboratory AssociateAdministrator for Space Trackingand Data System6

B-2 APPENDIX C*

VIKING LANDERMONITOR MISSION DIRECT-LINK REQUEST SUMMARY

*The information in this appendix was taken from Interoffice Memorandum 3394-82- 122 from P. Eshe to G. Gianopulous,"Viking Lander Monitor Mission Direct Link," JetPropulsion Laboratory, Pasadena, Calif.,Oct. 7, 1982.

c- 1 First year of the VLMM August 13'to December 28, 1980:

19 total passes available

9passes scheduled

9passes unable to schedule(information not available)

1 pass was out of station viewperiod

Good low-rateand/or high-rate data: 8 passes

Good rangingdata: 7 passes

Bad low-rateand/or high-rate data: none

Bad rangingdata: 1 rangingpass bad due tolocked sideband

Lostdirect link: 1 - badpass due to digitally controlled oscillator (DCO) sweep problem

Second year of the VLMM January 4 to December27, 1981:

48 total passesavailable

31passes scheduled

17 passesunable to schedule. Reasons:

4 passesgiven up to Pioneer

7 passesgiven up to Voyager

1 pass given up to Helios

3passes given up due to Station 14 being down

2passes were out of station viewperiod

Good low-rateand/or high-rate data: 22 good passes of low-rate and high- rate data

1 pass good high-rate data

Good rangingdata: 23 passes

Bad low-rateand/or high-rate data: 1 pass no low-ratedata; no sync

1 wrong TPA configuration; lost battery data

Bad rangingdata: 1 pass PRARED

c-2 Lost direct link:

1 - Sun-Earth-probe (SEP) angle 1.2 deg

1 - transmitter tripped off

1 - wrong command sent

2 - DCO sweep problem

2 - DSS 14 was scheduled; station wasdown

Third year of the VLMM January 4 to December 28, 1982:

48 total passes available

41passes scheduled at this time (Dec. 12 to Dec. 28 have not beenscheduled yet). To this day, we havehad 36 passes available.

3 passesunable to schedule. Reasons:

1 passgiven up to radio astronomy for Australian experiment

1 passout of station viewperiod

1 passunable to schedule DSS 63 due to gearboxrepair. Tried for DSS 61 instead of DSS 63, but Voyagerneeded DSS 61.

Good low-rateand/or high-rate data: 32 passes

2 passes of good low-ratedata

Good ranging: 29 passes

Bad low-rateand/or high-rate data: 1 - unableto lockup on high rate data, probably due to being only one way.

1 - no high-rate data due to only 34-m station available

Bad ranging: 1 - unknown

1 - PRA declared RED

1 - wrong tuning

1 - downlink only

Lostdirect link: 1 pass DSS-14 radialbearing problem

c-3 APPENDIXD*

VIKING LANDERMONITOR MISSIONDIRECT-LINK REQUEST DETAIL

"The information in this appendix was taken from Interoffice Memorandum 3394-82- 122 from P.Eshe to G. Gianopulous,"Viking Lander Monitor Mission Direct Link," JetPropulsion Laboratory, Pasadena, Calif., Oct. 7, 1982.

D- 1 Day of Sol Y ea r Date Year Date Year No. DSS Scheduled Comments

198 0 8/131980 226 1445 12 Yes Good pass

8/20 233 1452 No

8/28 241 1460 No

915 249 1468 63 Yes Good pass

9/12 256 1475 No

9/20 264 1482 42 Yes Good pass

9/27 271 1489 No

1015 279 1497 63 Yes Good pass

10113 287 1505 No

10/20 294 1512 14 Yes No good DCO sweep problem

10128 302 1519 No

1114 309 1526 43 Yes Good pass 1:lO late

11/12 317 15 34 No

11/20 325 1542 No No viewperiod

11/27 332 1549 14 Yes Good pass 00:35 late

1215 340 1556 No

12/12 34 7 1563 43 Yes LR/HR data OK. No rangingdata locked on sideband

12/20 355 1571 63 Yes Good pass

12/28 363 15 79 No

1 98 1 1/41981 004 1586 43 Yes Wrong TPA config.; lost batterydata; good ranging

D- 2 ~~~~ ~ ~ Day of Sol Y ea r Date Year Date Year No. DSS Scheduled Comments

193 1 1/121931 012 1593 43 No Gave up for PN-12

1/19 019 1600 43 Yes Good pass

1/27 027 1608 63 Yes Good pass

214 035 1616 14 No Gave up for PN-12

2/11 04 2 1623 14 Yes Good pass

2 119 050 1630 43 Yes Good LR/HR date; no ranging (PRARED)

2/26 05 7 1637 No No viewperiod

3 16 065 1645 63 Yes Good pass

3/14 073 1653 14 No DSS-14 maintenance

3/21 080 1660 14 Yes SEP 2.6 deg; acceptable LR/HR data;no ranging

3/29 088 1667 43 Yes SEP 1.2 deg; no LR/HR Data

095 1674 63 Yes SEP 0.8 deg; No data. High-powertransmitter tripped off

4/13 103 1682 63 No Gave up forPioneer 12

4/21 111 1690 14 No Gave up for Pioneer 12

4/28 118' 1697 43 Yes Good pass One rangkng point

516 126 1704 43 No Gave up for Voyager 2

5/13 133 1711 63 Yes Good pass

5/21 141 1719 63 Yes Good pass

5/29 149 1727 14 Yes Good pass

615 156 1734 43 Yes Good pass

6/13 164 1741 No No viewperiod

D- 3 Day of Sol Yea r Date Year Date Year No. DSS Scheduled Comments

198 1 6/201981 171 1746 63 Yes Good pass;gave up

6/28 179 1756 63 No ForVoyager 2

7/6 187 1764 14 Yes Good pass

7/13 194 1771 43 Yes Good pass

7/21 202 1778 63 Yes Good pass

7/28 209 1785 63 No Gave up for Voyager

815 217 1793 63 No Gave up for Voyager

8/13 225 1801 14 No Gave up for Voyager

8/20 232 1808 43 No Gave up for Voyager

8/28 240 1815 63 Yes Good pass

914 247 1822 63 No Gave up for Voyager

9/12 255 1830 14 Yes DSS 14 down

9/20 263 1838 14 Yes DSS 14 down

9/27 270 1845 43 Yes Good pass

1015 278 1852 63 Yes Good pass

10112 285 1859 63 Yes Good high rate and ranging; no low rate

10/20 293 1867 14 No DSS-14 gearboxrepair

1/28 301 1875 43 Yes No good Wrong command sent

1114 308 1852 43 Yes Good pass

11/12 316 1889 63 Yes No good; DCO problem

11/19 323 1896 63 Yes Good pass

11/27 331 1904 14 No DSS 14 down

12 /05 339 1912 43 Yes Good pass Day of Sol Ye ar Date Year Date Year No. DSS Scheduled Comments

1 981 12/131981 347 1919 63 Yes Good pass

12/20 354 1926 63 No Gave up for Helios

12/27 361 1933 14 Yes No good; DCO problem

1 982 1/41982 004 1941 43 Yes Good pass

1/12 012 1949 43 Yes Good low- and high-rate data;ranging no good

1/20 020 1956 63 Yes Good pass

1/27 027 1963 63 Yes Good pass I

213 034 1970 14 Yes Good pass

2/11 042 1975 43 Yes Good pass

2/19 050 1936 43 Yes Good pass

2/27 058 1993 63 Yes Good pass

316 065 2000 14 Yes Good low- and high-rate data;ranging no good

3/13 072 2007 14 Yes Good pass

3/21 080 2015 42 Yes Good pass

3/29 088 2023 63 Yes Good pass

416 096 2030 14 Yes No good; radialbearing ~r problem

4/13 103 2037 14 Yes Good pass ~'LY?

4/20 110 2044 43 No Gave up for Radio Astronomy Australian Experiment

4/28 118 2052 63 Yes Good pass L.

516 126 2060 63 Yes Good pass bc

5 /14 134 2067 14 Yes Good pass L/

D- 5 Day of Sol Y ear Date Year Date Year No. DSS Scheduled Comments L 19 82 5/211982 141 2074 43 Yes Good low-and high-rate data;ranging no good; commanding no good

5/28 148 2081 43 2081 148 5/28 ‘Yes Good low-and high-rate data;ranging no good

615 156 63 2089 ‘Yes Good pass LJ‘

6/13 164 12 2097 ‘Yes Good pass L,

6/21 172 43 2104 ‘Yes Good pass t

6/28 179 43 2111 Yes Good pass t.

7 15 186 63 2118 ‘Yes No uplinkavailable; r/ noranging available; lost high-ratedata, low-rateok

7/13 194 2126 63 Yes Good pass L/

7/21 202 2134 12 Yes Good pass

7/29 210 2141 43 Yes Good pass r/

8 15 217 2148 43 Yes Good pass fl

8/12 224 2155 63 Yes Good pass

8/20 232 2163 63 ’le s Good pass -

8/28 240 2171 14 Ifes Good pass; two rangiqg points J

915 248 2175 43 Yes Good pass / \ 9/12 255 2185 43 Yes Good pass . b c L” :. . ,I v

9/19 262 2192 61 Yes Good pass;no HR data

9/27 270 2200 No No viewperiod ?- .. \ 10/5 278 2208 14 Yes \

101 13 28610113 2215 43 Yes ‘. , , , L-

D- 6 Day of Sol Y ear Date Year Date Year No. DSS Scheduled Comments

+. 19 82 10120 203 2222 20310120 1982 43 Yes ,. ./. .

10/27 300 2229 30010/27 61 No I- Unable to have DSS 63 !" due to gearboxrepair; VGR needed DSS 61 for test

1. I '. 11/4 308 2237 14 Yes 1 ~. ,

11/12 316 2245 14 Yes

11/20 324 2252 43 Yes

11/27 331 2259 43 Yes '.I , I

1214 338 2266 63 Yes

12/12 346 2274 14

12/20 354 2282 14

12/28 362 2289 43

D- 7 APPENDIXE

AN EXAMPLE OF VIKING LANDERSEQUENCE OF EVENTS

E- 1 JPL001A 4:;; 4:;; iJEE JZED OUTGOING MESSAGE 02/00012 FM J NASH/R hEVAREZ TO ANBE/STADIR/43 OPS JOCC/NOC~TRKCHF/NATCMD/NATRK/NATEL INFO JZED/PAG DLD W JENSEN/G REED/E BURKE/A BERMAN/D MUDGWAY/K LUDWIG/R GfLLETTE/ P ESHE/A BRITTING/GGIANOPULOS/J BRENKLE/E HAMPTON/R HOLLINCSWORTH/ J HODDER/S BENEDICT/T BOREHAM/COMMCONTROL

SUBJECT: VIKING LANDER SOE FOR DSS-43, SOL-2178 DOY-248 1. ON DOY 248 DSS-43 WILL BE SUPPORTING A VIKING LANDER RADIOSCIENCE RAtiGINC PASS. PROJECT HAS REQUESTED THAT BATTERY CONDITIONING COMMANDS BETRANSMITTED DURING THIS TRACKING PASS. THREE TRANSMISSkONZ WILL BEREQUIRED. THE FIRSTTRANSMISSION WILL BE THE DOW~LINK ON COMMANDS, THE SECOND TRANSMISSION WILL BE THE BATTERY CONDITIONIl4G,,COMMANDS, AKD THE THIRDTRANSMISSION WILL BETHE DOWNLINK "ON COMMANDS FOR THE TRACKINGPASS SCHEDULED OVER DSS-43 ON DOY 255. IT I$REQUIRED THAT 9 LANDER (S/C-26) COMMANDS BE MANUALLY LOADED INTO THE MANUAL BUFFER DURINGPTP. 2. UPLINK TRANSMITTER POWER WILL BE 10KW. 3. DURINGTHE FIRST'HOUR OF THE 1 1/2 HOUR PTP, CONFIGURETHE STATION FOR LAWDERSUPPORT. CONFIGURE ONE TPA FOR LANDERSUPPORT (CH-1, IK AND CH-2, 8.33 HSD).USE SOFTWAREBLOCK DECODING FOR LAhDER lK CODED DATA. ENSURE THAT THE SSA TO BEUTILIZED IN SUPPORT OF THE IK CODED DATA IS SET WITH A THKESHOLD OF 0.0 DB. 4. CONFIGURE THE PRIME CPA FOR LANDERCOMMANDIKG. MANUAL COMMANDS WILL ENTERED FOR THE FIRST ANC SECOND TRANSMISSIONDURING THE PTP AND AFTER NATCMD HAS VALIDATED THE COMMANDS SYSTEM PEil SOE. THE THIRD SET OF COMMANDS WILL BE LOADED INTO THEMANUAL BUFFETi DURING THE LAST HOUR OF THE TRACKING PASS, 5. DURINGTHE PTP PERFORM RAKGING PRE-CALS FOR LAhiDER. COMP: 0 6 TO: 3E T1: 90 T2 : 9 T3 : 60 CARRIERSUPRESSION: 9DB 6. SEQUENCE OF EVENTS FOR LANDER SUPPORT 02:25:00 DSS-43 CONFIGURE STATION FOR LANDERSUPPORT 03:10:00 DSS-43 TURN COMMAND SYSTEM OVER TONATCMD FOR VALIDATION 03:20:00 DSS-43 AFTER COMMAND VALIDATION, RETURN TO MANUAL AND ENTER THE COMMANDS INTO TEE FOLLOWING OhDER.

MOUDLE MSG NBR BITTIME PATTERN 1 I 248:04:23:00 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 E 2 5 2 NONTIMED 68201'7016F4500BD8 3 NONTIMED. 5F4400B95FACE8CA8 MODULE MSG NBR BITTIME PATTERN 2 4 248:04:38:00.4 2 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 E 2 5 5 NONTIMED 68201D727D3900D98 6 NONTIMED 71EAZBC6B4DD0BFA8 7 NONTIMED CZDC00EZF4DDBaA28 8 NONTIMED 000@00DEC9B9€3a958 9 NONTIMED ZZDC0D1914BE09068

MORE en B- L JPL003A RR ANBEJOCC JZED DE JJPL 0038 02/0001z

PAGE TWO @3:35:00 DSS-43REMAIN IN MANUAL AND RETURN COMMAND SYSTEM BACK OVERTO NAT CMD FOR MODULES 1 AND 2 VALIDATION. @3:36:00 NATCMDRECALL MANUAL BUFFER AND VALIDATE COMMAND BIT PATTERNS. 03:51:00 DSS-43AFTER NATCMD HAS VALIDATED COMMAND BJT PATTERNS,, RETURNTO REMOTE. 03:52:@0 NATCMDVERIFY CORRECT COMMAND TRANSMITTIME DISPLAYED ON FORMAT 301. 03:55:00 DSS-43START OF LANDERTRACK SOL-21'78 04:01:00 DSS-43TRANSMITTER ON (10KW) LANDERFLAG S/C-26, S-BAND ONLY, Z-WAY, BADDATA, ROL IN THE MDA. MDA DATA RATES: 1 SAMPLE/10 SEC. AT AOSTO LOS OF LANDERPASS. 04:01:2? DSS-43 STARTACQUISITION SWEEP AS PER SWEEP MESSAGE. 04:18:00 DSS-43COMMAND MODULATION ON 04:19:08 DSS-43SEND IDLE-2/ACTIVE ON 04:24:00 NAT/DSSCONPIRM FIRST COMMAND TRANSMISSION 04:39:00 NAT/DSSCONFIRM SECOND COMMAND TRANSMISSION 04:48:00 TRKCONVERITY BANGING PARAMETERS 04:41:@0 NATCMDAFTER ALL NINE (9) COMMANDS HAVE BEE^ TRANSMITTED ANDCOKFIEMED, RETUSN TO IDLE-l/ACTIVE OFF. 04:45:00 DSS-43 RANGINGMOD ON B4:49:58 DSS-43 TRAKSMITFIRST RANGE ACQUISITION @5:12:52 DSS-43 STARTSWEEP FOR DOWNLINK ACQUISITION @5:14:22 DSS-43 AOS(2-WAY) S/C-26 LOW RATECHANNEL 8 1/3 UNCODED 05:14:52 DSS-43 RECIEVEFIRST RAEGE ACQUISITON 05:15:00 DSS-43RETURN COMMAND SYSTEMsTOMANUAL MODE @5:16:00 DSS-43CLEAh THE MANUALBUFFER AND ENTER THE THIRD SET OF COMMANDS IN THE FOLLOWINGORDER.

MODULE MSGTIME NBR BIT PATTERN 1 10 248:05:34:30 5 5 5 5 5 5 5 5'5 5 5 5 5 5 5 E 2 5 11 NONTIMED 68201'7016F4500BD8 12 WONTIMED 5F4400B95FACE8CA8 05:16:57 DSS-43 RANGINGMOD OFF 05:21:00 DSS-43REMAIN IN MANUALMODE AND RETURN COMMAND SYSTEM OVER TONATCMD FOR MANUAL BUFFER VALIDATION. 05322308 SATCMDRECALL MANUAL BUFFER AND VALIDATE COMMAND BIT PATTEEN 05:27:00 DSS-43AFTER NATCMD HAS VALIDATED COMMAND BIT PATTERN, TRANSFEil MANUAL 3UFFER TO MODULE-1 AND RETURN TO REMOTE. 05:29:00 BATCMDVERIFY CORRECT COMMAND TRANSMITTIME DISPLAYED ON FORMAT 301. 05:30:00 NATCMD SENDIDLE-Z/ACTIVE ON 05:35:@0 NAT/DSS CONB'IBM THIRD COMMAND TRANSMISSION 05:3?:00 NATCMD AFTERALL THRE (3) COMMANDS HAVEBEEN TRANSMITTED ANDCONFIRMED, RETURN TO IDLE-l/ACTIVE OFF. 05:41:51 DSS-43 HIGHRATE CHANNEL ON (1K) DUAL SUBCARRIER SSA THRESHOLDSHOULD BE SETAT 0.0 DB.

MORE

E-3 JrL005A RR ANBEJOCC JZED OUTGOING MESSAGE DE JJPL 005A 02/0001z PAGE THREE 06:04:0@ DSS-43 COMMAND MOD OFF 05:54:00 DSS-43 TRAKSMITTER OFF 06:14:53 DSS-43 LOS S/C-26 7. TELEMETRY IDR REQUIREMENTS(NOCC) A. LOW RATEENGINEERING DOY-248/05:14:222 TO DOY 248:@6:15:002 B. H.IGH RATE SCIENCE DOY-248:05:41:002 TO 248:06:15:002 8. IF THERE ARE ANY QUESTIONSCALL J. NASH X-4491 OR R. E. NEVAREZ X-7163 REGARDS, REN . END OF MESSAGE 02/01052 SEP 82 JJPL

E-4 APPENDIX F

RECOVERYSTRATEGY LOG FOR VIKING LANDER 1

NovemberThrough February 1983

F- 1 The chronologyof events that followed the spacecraft emergency declared on November20, 1982, and thesubsequent efforts to recover the spacecraft signal are given below:

November 19:DOY 324:SOL 2252: DSS 43: No downlinkobtained during this regular downlink pass.

November 20:DOY 325:SOL 2253: Spacecraftemergency declared by the Viking Project at 0000 hoursbecause of failure to receive a scheduleddownlink transmission from VL 1. The opening of an undervoltage switch on the lander electrical equipment buss was suspected.

November 23:DOY 325:SOL 2256: DSS 43: Transmit uplink onlyto Lander. The commands were toincrease battery- chargingfrequency, close the undervolt.age switch, and cause a downlinkto occuron DOY 331.

November 26:DOY 331:SOL 2253: DSS 43: Whiletransmitting commands to initiate the downlink, the DSS 43 antenna halted due to a hydrauliccoolant leak; the pass was canceled.Project dis- coveredthat the lander antenna pointing parameters in thelander computer memory had inadvertently been overwritten with the battery-charging parameters. A new strategythat recognizes the lander antenna as being off point will have to be developed for all future uplink transmissions.

December 02:DOY 336:SOL 2264: DSS 63: Transmit commands for a downlink on DOY’ 338 with VL-1 antenna in a parked position.

December 04:DOY 338:SOL 2266: DSS 63: No downlinkobserved during this pass.

December 06:DOY 340:SOL 2268: DSS 63: Transmit commands for downlink on DOY 341 with VL-1 antenna in a parked position.

December 07:DOY 341:SOL 2269: DSS 63: Further set of commands for a downlink on DOY 343 with antenna in parked position.

December 09:DOY 343:SOL 2271: Ops teamdiscovers that 256-bit idle sequence was inadvertentlyomitted from theuntimed commands senton SOL 2264,2266, and 2268, thusinvalidating those uplink sequences.

December 11:DOY 345:SOL 2273: DSS 14 Command transmissionsfrom DSS 14 now included the correct 256-bit idle sequence.This sequence was to move the VL-1 antennato a known favorable Earth-pointposition, for a downlink on SOL 2274.The attempt to reposition thehigh-gain antenna was only partially successful because the high-power transmitterfailed several times during this pass.However, 36 commands of theplanned 60were successfully transmitted.

F- 2 December 12:DOY 346:SOL: 2274: DSS 14: This was intendedto be adownlink-only pass. However, the commands to initiate the downlink flag were not transmitted because an operations problem prevented the proper idle sequence being executed before the command windowclosed at 20042.The failure to initiate the command sequencecor- rectly was subsequentlyinvestigated, but noconclusive problem could be found .

December 17:DOY 351:SOL 2279: DSS 63: Commands were transmitted to park the antenna and initiate adownlink on SOL 2282.

December 20:DOY 355:SOL 2282: DSS 14: Searched for adownlink after transmitting the downlink flag, but no downlink detected.

December 23:DOW 358:SOL 2285: DSS 14: This uplink sequence was topark the antenna and cause adownlink to occur on SOL 2289. Approximately2/3 of this pass was conducted with thetransmitter on right circular polarization (RCP) and1/3 on left circular polarization (LCP).

December 27:DOY 362:SOL 2289: DSS 43: Searched for adownlink after transmitting the downlink flag, but no downlink detected.

December 31:DOY 365:SOL 2292: DSS 43: Uplink commands topark the antenna. First part of this pass in RCP, second part in linear polarization at the 45-degand 90-deg phase positions, with transmitter at 80 kW.

January 04:DOY 004:SOL 2296: DSS 43?63: This was a split pass with DSS 43 transmitting the uplink turn-on commands. The second part of the pass with DSS 63 initiated adownlink search with the SSI andopen-loop recording, but no downlink could be detected.

January05, 1983 Project announcedsuspension of further DSN supportpending an in-depth investigation into the lander antenna pointing program.

February 1:DOY 003:SOL 2324: DSS 43: The passover DSS 43 onFebruary 1 was satisfactory, with 23 of theplanned 25-command sequences beingtransmitted. The high-powertransmitter tripped offfour times causing the lost sequences. The automatic command facility workedperfectly. Any one ofthe commands wouldhave been sufficient to reprogramthe VL. The 11-hourpass allowed for a full-Earth pass as viewed from Mars.

February 03:DOY 035:SOL 2326: DSS 43: This was thesecond of theautomatic D/L transmissions following an 8-week U/Labsence. (Assumed by thelack of responseof the spacecraft.) No signal was seenon the SSI by DSS 43.

F- 3 February 06:DOY 036/37:SOL2328: DSS 43: Thispass consisted of a continuous command to close the UV switch and park theantenna. (It will becompleted over DSS 63 on February 11) TX power was 80 kW, and the new automatic CMD S/W was used. Commands wereseparated by 40 min to ensurethat the spacecraft could execute one command beforere- ceivingthe next andbefore.processing the next. 312 commands weresent. Therewere no transmitter trips.

February 10:DOY'41:SOL2332: DSS 63: This was theremainder of the CMD sequence sentFebruary 6. Because the DCO did not start ontime, the first block of commandswas missed;otherwise all commands weresent ok.

February 11:DOY 42:SOL2333: DSS 63: The sequence consisted of a TX sweep followed by an idle sequenceand short setof commands toactivate the downlink. Even if thespacecraft had not received any of the commands in thepast, an automatic downlink should have occurredat this point. None was found. A two-way sweep was then made and a search for the downlink using the spectrum signal indicator andopenloop receivers. No downlink was found.

February 16:DOY 047:SOL2338: DSS 63: Following an uplink acquisition sweep, a 25-command sequence was sent to

I change thespacecraft radio configuration from TWTAl/I4OD-EXCl and acti-to

~ vate a downlink. However, an intensivesearch failed findto a downlink i signal.

February 18:DOY 49:SOL 2340: DSS 63: A 1ong.series of commands to move theantenna to its limit and then park at Earthpoint were now sent from DSS 63. This shouldhave enabled the antenna andcomputer drive to come into registration at the limit point. It hadbeen thought that some kind of sticking and friction may havecaused the antenna andcomputer driveto lose alignment. Since the antenna pointing direction was not known, commands weresent through the whole view period (10 h). On thenext available pass, an immediate downlink will be initiated.

February 25:DOY 56:SOL 2347: DSS14: A short uplink-acquisition sequence followed by a search for the downlink failed to find a signal. The RFI van at Goldstone was alsoused to search for the downlink with its spectrum analyzer at a minimum detection level of -186 dBm. No signal was detected.

F- 4 APPENDIX G

ANNOTATED BIBLIOGRAPHY

G1 The entries below may beordered from the Superintendent of Documents, U.S. Government PrintingOffice, Washington, D.C., 20402.

Images of Mars (1980, 32 pp.)

NASA SP-444, Stock NO. 033-000-00793-1 A collection of 39 of the best orbiter photographs from the Viking Extended Mission, 1977 to 1979, with descriptivetest.

Mars: The VikingDiscoveries (1977, 32 pp.)

NASA EP-146, Stock NO. 033-000-00703-5 A nontechnical account of the findings of the first few months of the Viking Mission with 28 pictures, including 7 i.n color.

The Martian Landscape (1978,160 pp.)

NASA SP-425, Stock NO. 33-000-00716-7 A large book containing over 200 VikingLander photographs in color and black and white,including 19stereopai.rs. Includes a first-personaccount of the preparations for and actualphotographing of Mars from its surface.

Viking-MarsExhibit Package(1977)

Stock NO. 033-000-00711-6 A setof posters, including one 76.2 by 101.6 cm, two 61 by 89 cm, and many smaller ones. In additionto pictures, mostly in color,there are descrip- tions of each scientific instrument on the orbiters and landers and some of the results of eachexperiment.

VikingOrbiter Views of Mars(1980, 182 pp.)

NASA SP-441, Stock NO. 033-000-00795-7 The varioustypes of geologic features on Mars aredescribed and illustrated by some of the best orbiter pictures from the first year of the Viking mission; more than 200 illustrations.

VikingPictures of Mars: Set No. 1 (1977)

Stock NO. 033-000-00691-8 A set of four color and five black-and-whitereproductions, 30.5 by 63.5 cm, of Marstaken by the cameras on the Viking Orbiters and Landers.

Viking 1 EarlyResults (1976, 67 pp.)

NASA SP-408, Stock NO. 033-000-00675-6 The Viking Project, the orbiting and 1a.nding spacecraft, and the results obtained in the first few weeks at Marsare described with photographs, graphs, and diagrams.

G- 2 The entries below may be ordered from the National Technical Information Service,Springfield, Virginia, 22151.

The Mosaics of Marsas Seen bythe Viking Lander Cameras (1980, 75 pp.)

Stock NO. N80-32311 Thispublication describes the 10 panoramic mosaics and various other image products that were derived by computer processing from the individual pic- turesobtained by theViking Landers. 20 illustrations.

Viking Lander Imaging Investigation During Extended and Continuation Automatic Missions, Volume 1: Lander 1 PictureCatalog of Experiment Data Record (1981, 650 pp. Available soon)

The format is the same as thatof the primary mission catalog, below. It details the operation of the Lander 1 cameras from December 1976 to February 1979. Volume 2 onLander 2 will beissued later.

Viking Lander Imaging Investigation Picture Catalog of Primary Mission Experiment DataRecord (1978, 560 pp.)

Stock NO.78N-20042 A technicalencyclopedia of the performance of the cameras onthe two Viking Landersduring the first four months ofthe mission. Included is a repro- ductionof every photograph (small size and mediocre in quality) along with completeinformation about where, when, and how each picture was taken.

G- 3 \

APPENDIX H

VIKING FACTS

H- 1 E ve nt Viking Event 1 Viking 2

Launch Aug.Sept. 20, 1975 1975 9,

Arrival 1976 June 19, Aug. 7, 1976

Landing JulySept. 20, 1976 3, 1976

Site Planitia UtopiaChryse Planitia

Coordinates 225.8" 47.7"N,22.3"N, 48.0"

Orbiter in orbitdays 718.8 days1,509.9

La nd er on surface Landeron 2,100(4/20/82 1,316.1daysdays

End landeroperations (predicted) 1994) April 11, 1980 (. &JQL" aa, l%%L- End orbiteroperations Aug. 7, 1980 July 25, 1978

O rbiter photos Orbiter 51,539

La nde r photos More than More photos Lander 4,500

Photocoverage 97% of planet with resolution of 300 m (1,000 ft) or better.

25% of planet with resolution of 25 m (82 ft) orbetter.

Landerweather reports: more than 1 million

Orbiterinfrared observations: more than 1 million

Orbiterweight: 2,325 kg

Landerweight: 571 kg

Orbiters built by Jet Propulsion Laboratory

Lander built by Martin Marietta Aerospace

H- 2 NASA-JPL--Coml.. L.A.. CslS