●

John B. McNanNc* and Richard A. Cook**

Jet Propulsion Laboratory California lnslitutc of Tcchnolofw L,. ‘asadcna, California

Abstract

q’hc objective of the Mars Environmental FY 1994 project start, ~’hc objcctivc of the Survey (MESIJR) Network mission is to establish Pathfinder mission is to concluct the cnginccring a global network of small scicncc stations on the demonstrations required prior to the full surface of Mars to operate concurrently over a commitment of funds to develop and proccccl with minimum of onc martian year, MFNUR Network the MESUR Network mission. ‘J’hc primary is viewed as an evolutionary and affordable step in cnginccring test performed by Patbfinclcr will bc of the scientific characterization of the rnartian an entry, dcsccnt, and landing approach whic}~ environment following Viking and Mars Observer cmp]oys an acroshcll, parachute, solid tractor and prcccding sample return and human rocket, air bags, and a ]andcr petal system. This exploration missions. The full network is entry, descent, and landing system is required to envisioned to consist of an intcrnationa] clccelc.rate the vchiclc from high entry velclcity, complement of 16 or more landers providing polc- achicvc a scrni-hard lancling on the martian surface, to-pole covcragc of the planet. The broad scicncc and establish an upright configuration for the objectives of the MIXUR Network mission arc to surface opcrationa] phase of the mission. characterize the martian environment in terms of atmospheric structure, intcrna] structure, global atmospheric Circulation, surface chemistry, and !mtJMQc~lK!.iQjti.vd Lltion ol.MMU.R surface morphology, ‘1’hc strawman scicncc payload for the Network mission includes an In 1978, the National Acadc!my of Science’s atmospheric structure package (pressure, Committee on Planetary and Lunar Exploration tcnpcrature, and acceleration rncasurcmcnts cluring (COMP1 XX) provided direction to the post-Viking clcsccnt), cameras for ctcsccnt and surfi~cc imaging, Mars exploration program in stating: 3-axis seismometer, mcteoro]ogy package, Alpha/Proton/X-Ray Spcctromcter, l’hcrmal “’J”hc primary objectives in order of scientific Analyzer/J3volvcd Gas Analyzer, radio scicncc priority for the continued cxp]oration of Mars am: cxpcrimcnts, and others. The MESUR Network project start is targeted for FY 1996 with the first (1) The intensive study of local areas: launch occurring no earlier than the 1998/99 (a) “J’o establish the Chcmica], mincralogica], opportunist y. and pctrological character of different components of the surface material, A precursor to the MHSLJR Network mission, rcprcscmtativc of the known ctivcrsity of designated MESUR Pathfinder, is targeted for an the planet; (b) To establish the nature and chronology of .— —-—. .— the major surface forming proccsscs; (c) To dctcrminc the distribution, abundance, * Mission Design Manager, Mars and sources and sinks of volatile 1 invironmcntal Survey Project. materials, including an assessment of the biological potential of the martian * * Mcn~bcr of “J’ethnical Staff, Mission environment, now and during past epochs; Design Section, Member AlAA. (d) q’o establish the interaction of the surface material with the atmosphere and its Copyright Cl American institute of Aeronautics and radiation environment; Astronautics, IJ]c., 1993. All rights rcscrvcd. . t (2) To explore the structure and general circulation upper atmosphere, surface morphology, of the martian atmosphere; geochemistry, and the clcrncntal composition of rocks [4]. ‘l’he strawman instrument payload (3) To explore the structure and dynamics of designed to accomplish these objectives inc]udc: Mars’ interior; Ihrec-axis scismomctcr (4) To cslablish the nature of the martian magnetic ficlct and the character of the upper atmc)sphcre ‘I%c Network scismomctcr measures ground and its interaction with the solar wind; motion with high sensitivity, large clynamic range, and large banclwidth. ‘1’hc scismomctcr requires a (5) To establish the global chemical and physical deployment mechanism to cmplacc the instrument characteristics of the martian surf ace.” [1] in clircct contact with the soil a fcw rnctcrs from the lander, ‘1’hc data volume associated with the in 1983, the Solar System Exploration seismology investigation is estimated at 10 Comrnittcc of the NASA Advisory Council megabits pcr day per lander after event triggering recognized that the dcgrcc to which Mars scicncc logic and data compression algorithms are objectives could bc accomp]ishcd depended on the crnploycd. The data volume associated with the establishment and operation of a network of long- scismo]ogy investigation is a significant mission livcd scicncc stations at diverse locations on the clrivcr to develop a high capacity direct-to-F,arth surface of Mars to perform seismic, mctcorologica], downlink or to deploy a Mars Relay Satellite and gcoscicncc observations [2]. Various concepts (MRS). In addition, the seismology investigation to establish a global Mars landed network were requires instrument operations over a significant studied as part of the so-called “90 Day Study” [3]. period of time (one Mars year basclincd) to insure In 1991, the NASA Ames Research Center a high probability that Marsquakcs arc dctcctcd, dcvclopcd an innovative concept for a Mars ~nvironmcnta] SURvcy (MESUR) mission that Meteorology instruments invo]vcd the phased cmplaccmcnt of a 16 larrdcr network on Mars beginning with the first launch in The full meteorology cxpcrirnent is designed the 1998/1999 opportunity and ending in 2006 to perform high frequency surface pressure, after onc Mars year (1.8 Earth years) of full tcrnpcraturc, wind velocity, humidity, and network concurrent operations [4]. atmosJ~hcric opricity mcasurcmcnts. The baseline mctcoro]ogy investigation requires a pole-to-pole Responsibility for the Phase A study of the cmplaccmcnt of Iandcrs and instrument operations MESLJR Network mission was assigned to the Jet over a minimum of onc Mars year. 1.andcrs placed Propulsion Laboratory (JPL) in November of at ]atituclcs greater than +/-45° cannot rely on solar 1991, In early 1992, JPL. was dircctcd to study the power for operations during all seasons. q’hc feasibility of launching a MESUR Network “n~ini-Met” lrrndcr concept was devised to allow the precursor mission under tight schcdulc and cost year-round acquisition of high priority mctcorc)logy constraints to demonstrate cnginccring systems and data at high latitudes. ‘1’hc n~ini-Met lander is tcchno]ogics key to the Network. The precursor powered either by a primary battery or a “power mission, designated MESUR Pathfinder, is slated stick” which is a standard Radio-Isotope }Ieatcr for a ncw start as the first Iliscovcry class mission (RIIU) unit attached to a thermocouple., ‘J’hc power in October 1994 with a launch in late 1996. The provided by the primary battery or power stick is MESIJR Network start is targeted for 1996 with sufficient to provide hourly rncasurcrncnts of the first launch targeted for no earlier than the pressure, tcmpcraturc, and opacity and allow the 1 998/99 opportunity. transmission of these data to a relay satellite or directly to Earlh (at low data rates).

MESUR Nctwor- Alpha/Protcm/X-Ray (APX) Sp@ron~ctcr

“1’hc broad scicncc objectives of the Network ~’hc AT’X spcctromctcr measures the clcmcntal mission arc to characterize the environment of Mars composition of surface soil and rocks for most in terms of the intcrna] structure of the planet, the major elements cxccpt hydrogen, The spcctromctcr global atmospheric circulation, the structure of the must be placed in direct contact with the soil and

2 t rock samples to obtain a measurement. Thus, a Specifically, a single Delta 11 (7925) launch in 1999 surface rover, rnechanizcd arm, or ot}mr deployment would inject four free-ftying acrocraft on a trans- mechanism is required. Mars trajectory. TWO Dc]ta launches in 2001 would deploy four additional acrocraft and a single ~q~nlal Analyzer/Evolved Gas Analvzcr (TM iGA) communications relay orbiter to Mars. F’inally, two Delta launches in 2003 would deploy eight The TA/EGA dctcrmincs the mineralogical acrocraft to cornplctc the 16 lander Network, composition of the martian soil. A soil sample is Operations of the landed stations would continue placed in an oven, heated, and changes in heating for a minimum of onc Mars year after the arrival of and gas rclcascs arc monitored. The gas analyzer the final complement of eight landers. Thus, a measures the water, carbon, nitrogen, oxygen, surface lifetime in cxccss of 6 I~arth years is organic, and oxidant content of the released gas. A required by the four landers ]aunchcd in 1999 to mechanism is required for obtaining samples. satisfy the onc Mars year concurrent Network operations rcquircmcnt. IIcsccnt lma~cr The current buclgct climate, as well as technical The dcsccnt imagcr obtains nested imigcs of issues such as the cxtcndcd surface lifetime the martian surface during the parachute dcsccnt. rcquircmcnt of the landed stations, have led to the These images arc used to establish the geologic decision to revisit the MES~JR Network design. context of the science mcasurcmcnts taken by the. ‘l’he MIiSUR l’rojcct Team at J]’I,, the Mars landed slation. Scicncc Working Group, the MliSUR Science IIcfinition Team, the International Mars ~dcc lma~cr }lxploration Working Group, and others arc stuclying alternative mission architectures and The multiband surface imagcr provides a 360° vchic]c (icsigns, In addition, on August 6, 1993, panorama from the lander edge to the horizon in JPL announced the selection of Ilughcs Aircraft order to determine the surface characteristics of the Company and Rockwell international Corporation landing site. as the two associate contractors for the MIiSUR Network Phase 131 study and MESUR Pathfinder Atmospheric Structure instrument (AS]) supporl cfforl. During Phase 1;1, schcdulcd to begin in November 1993, cac}~ of the two The AS] obtains pressure and tcrnperaturc contractors will support NASA and JPL in defining profiles of the martian atmosphere along the entry the MEStJR Network architecture and future vchic]c trajectory to the surface. In addition, an implementation plans. The overall goal of the atmospheric density profile is derived from 3-axis rcdmign effort is to utilize innovative designs and acceleration measurements taken during entry and intcrntitiona] cooperation to define an affordable dcsccnt. Network mission in terms of both dcvclopmcnt and total mission )ifc cycle costs that accomplishes the Radio Scicncc major scicncc objectives of the Mars exploration program, ‘1’radc issues which have major cost and Sirnultancous 2-way cohcrcnt Doppler science impacts and arc an integral part of the tracking of three (or more) landers from a single redesign effort have been identified as follows: Darth antenna once pcr week for onc Mars year provides information which yields dccirnctcr ICVCI Science determination of Mars rotational pararnctcrs. ● Number of landers ● latitude dispersion of landers Satisfitction of the MESUR scicncc objectives ● Science, instrument suite requires the concurrent operation of rnultiplc landed ● instrument dcp]oymcnt schcmc stations for an cxtcndcd period of time (nominally one Mars year). The original scenario for the ~owcr ernplaccmcnt of the Network involved a phased ● Radioisotope Thcrmoclcctric Generators (R’I’G’s) deployment over three launch opportunities duc to vs. solar powered Iandcrs anticipated annual funding rate constraints,

3 t Qlmlunications 3’llc primary objcctivc of MHSUR Pathfinder ● Dircc(-to-F,arth downlink vs. Communications is to demonstrate critical functions, particularly the relay orbiter(s) entry, dcsccnt, and landing function, required for t}]c successful dcvclopmcnt and deployment of the ?hcrmal Cent@ MESUR Network stations. Scientific objectives ● R’1’G vs. Radioisotope IIcating Unit (R1lU) + and the instrument payload for Pathfinder include: solar vs. Phase Change Material (}’CM) + solar ● Acquisition of atmospheric structure data 1 ~unch Vchiclcs along the Pathfinder entry trajectory from ● Delta, Taurus, Atlas, Titan, Arianc, Proton, etc. an entry instrument package (pressure, temperature, and vchiclc acceleration), &rfacc 1 & ● ● 1 month vs. 1 Mars year vs. multiple Mars years Characterization of surface morphology and geology at meter scale from a surface ~>cploynlemt imaging camera, ● Full vs. phased Network cmplaccmcnt ● Cruise carrier vs. Free-fl icr b Determination of the elemental conmosition of rocks and/or surface matcria~s from ~lardwarc alpha/proton/X-ray spcctromctcr ● Common landers vs. landers based on focused nlcasurcmcnts, surface function ● lntcgratcd landers vs. landers based on available A single MESUR Pat}lfindcr acrocraft will be hardware ]aunchcd on a Dc]ta class launch vehicle in ● Redundancy vs. sing]c string Dcccmbcr/January 1996. I’hc I’athfindcr acrocraft consists of a cruise stage, acroshcll (heat shield and “1’hc near term schcdulc for the Network back cover), dccclcrator systcrns (parachute, solid architecture rc-definition effort includes a MIWUR rctrorockct, ancl air bags), and a lander as shown in Scicncc Definition Tcarn Meeting in September, l;igurc 1. “1’hc acrocraft will bc spin-stabilized and 1993, a meeting of the international Mars l~arth-pointed during the cruise to Mars. Ilxploraticm Working Group in Graz, Austria, in Pathfinclcr will enter the rnartian atmosphere on October, 1993, and the initiation of the MESUR July 4, 1997 directly from the hyperbolic transfer Network Phase Ill study in November, 1993, orbit and descend to the surface using the acroshcl], parachute, and solid retrorocket to slow the dcsccnt and an air bag systcrn to attenuate the landing MESUR Pathfinder shocks as shown in Figure 2. The Pathfinder landing site will bc sclcctcd from available low As part of the MESUR program, JPI. is elevation areas large enough to accomrnociatc studying the feasibility of landing a single vchiclc anticipated targeting dispersions near the sub-solar on Mars in 1997 as a demonstration of the enabling point at 15° North latitude. 1,anding sites near lSO systems, tcchnologics, and rnanagcmcnt approaches North latitude provide good solar and liarth for the MESUR Network mission, Ilccausc the visibility conditions for the primary solar power planned Network mission will have a different, and direct-to-liarth communications for the more stressful landing proccdurc than was used by duration of the Pathfinder 30 day primary mission, Viking, it is important to demonstrate critical entry, A free-ranging, solar powered rover surface vehicle, dcsccnt, and safe landing functions prior to the full- dcvclopcd with NASA Code C funding, will bc up irnplcmcntation of the MESUR Network flown on Pathfinder, ‘1’hc rover, as shown in Figure fabrication activity, The demonstration mission, 3, will bc deployed from the lander to conduct rover designated MESUR Pathfinder, is the first of the technology cxpcrimcnts, dctcrminc the viability of Discovery class missions, Discovery missions arc rover operations in the martian environment, and to defined as fast schcdulc (3 year development cycle), serve as deployment platform for the low cost ($1 50 million dcvclopmcnt cost cap) alpha/proton/X-ray spcctromctcr. ‘J’hc acquisition missions with significant, but focused, scicncc and return of scientific data and rover operations object ivcs. will cornrncncc imrncdiatcly following the playback of kcy engineering data regarding the condition and

4 configuration of the lander and the characteristics of the entry, Figure 4 provides an artists conception of the MESUR Pathfinder lander and deployed rover on the surface of Mars.

Acknowledgment

The research dcscribcd in this paper was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

References

[1] COMPLEX, 1978, Strategy for Exploration of the ]nncr Planets: 1977.1987. Natio,,a] Academy of Sciences, Washing[on, DC.

[2 “Planetary Exploration Through the Year 2000: A Core Program,” Part One of a Report by the Solar System Exploration Committee of the NASA Advisory Council, Washington, DC, 1983.

[3 “A Robotic Exploration Program: In Response to the NASA 90-Day Study on IIurnan Exploration of the Moon and Mars,” JPI. Technical Report D-6688, Jet Propulsion laboratory, Pasadena, CA, Dcccmbcr 1989.

[4] “Mars Environmental Survey (MIiSUR) Science Objectives and Mission Description,” NASA ATTICS Research Center, July 1991.

5 Cluisc Stage

Backshcll

1,ander

Hcatshield

Figure 1. Ilxplodcd View of MESUR Pathfinder Flight Systcm .-.,

Jettison Cruise ~ *3O minutes prior to entry. Stage 6 -130 km altitude, *7.6 knds at 17°~ 1° entry angle, ballistic coefficient 40-45 kg/m A2 (type 1 trajectory). Entry “%#.. :,,, Tractor Rocket deployment. Deployment estimated by timer after max. deceleration for DepIoy Parachute dynamic pressure of 660 N/mA2, Mach number 1.9, altitude 8-9 km.

25- Estimated by timer after max. deceleration. Time allowed for parachute to stabilim. Altitude 7-8 km. Rebse Heat Shield & Estimated by timer after max. deceleration. Time allowed for Heat Shield to fa!l clear. Altitude 5-6 km. Release Lander on 40 m Incremental Bridle

b Release Touchdown Sensor (TDS) on -30 m Immediately after Lander release, *5 km altitude. Tether 4

.&

,,’ :, .,::, Cut TDS, Deploy Airbags, and fire RAD motors. I Upon TDS contact t , /,, ( % ~ ,..:’., $ Immediately after Airbags touch ReIease Chute. RAD motors carry chute away. surface (additional sensor may be reauired for this). or bv timer Impact er TDS contact (4).?5 seconds) 0-20 rnls VerticaI velocity, up to 50 mh Horizontal (Due to winds) Airbazs crush to mitizate shock. Lander can roll and tumble to remove horiz&tal velocity, S;me redundancy inherent due to overlap of airbags. Impact occurs *MO seconds after entry. Lander is self righting upon pets! dep!oynent. Release High Gain Antenna, DepIoy Camera. Retract Airbags, Open Petals and * L%cage Rover and drive off petal. Begin Surface Operations , .

ox m-J m m z l\ Ln d\b&1 u u e -1 I

E-. /

( 11 r )

Figure 3. MFHJR Pathfinder Micmrovcr %hcmatic

8 Figure 4. MESUR l’athfinclcr 1.ankl Configuration

9