ASTROBIOLOGYVolume 7, Number 4, 2007© Mary Ann Liebert, Inc.DOI: 10.1089/ast.2007.0153

Research Paper

A Concept for NASA’s Mars 2016 Astrobiology Field Laboratory

LUTHER W. BEEGLE, MICHAEL G. WILSON, FERNANDO ABILLEIRA, JAMES F. JORDAN, and GREGORY R. WILSON

ABSTRACT

The Mars Program Plan includes an integrated and coordinated set of future candidate mis-sions and investigations that meet fundamental science objectives of NASA and the Mars Ex-ploration Program (MEP). At the time this paper was written, these possible future missionsare planned in a manner consistent with a projected budget profile for the Mars Program inthe next decade (2007–2016). As with all future missions, the funding profile depends on anumber of factors that include the exact cost of each mission as well as potential changes tothe overall NASA budget. In the current version of the Mars Program Plan, the AstrobiologyField Laboratory (AFL) exists as a candidate project to determine whether there were (or are)habitable zones and life, and how the development of these zones may be related to the over-all evolution of the planet. The AFL concept is a surface exploration mission equipped witha major in situ laboratory capable of making significant advancements toward the Mars Pro-gram’s life-related scientific goals and the overarching Vision for Space Exploration. We havedeveloped several concepts for the AFL that fit within known budget and engineering con-straints projected for the 2016 and 2018 Mars mission launch opportunities. The AFL missionarchitecture proposed here assumes maximum heritage from the 2009 Mars Science Labora-tory (MSL). Candidate payload elements for this concept were identified from a set of rec-ommendations put forth by the Astrobiology Field Laboratory Science Steering Group (AFLSSG) in 2004, for the express purpose of identifying overall rover mass and power require-ments for such a mission. The conceptual payload includes a Precision Sample Handling andProcessing System that would replace and augment the functionality and capabilities pro-vided by the Sample Acquisition Sample Processing and Handling system that is currentlypart of the 2009 MSL platform. Key Words: Mars—In situ science investigations—Astrobiol-ogy Field Laboratory. Astrobiology 7, 545–577.

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Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California.

INTRODUCTION

TWO QUESTIONS HUMANITY HAS STRIVEN to an-swer since it became self-aware are “Are we

alone in the universe?” and “How did life on theEarth begin?” Until recently these questionscould only be asked in theological discussions, asthe technological means to begin to answer them

were not available. The recent explosion in tech-nological advances makes it possible for us to be-gin to address these questions. As such, overrid-ing goals of the National Aeronautics and SpaceAdministration (NASA) include search for evi-dence of how life started here and determinationas to whether we are alone in the universe. Marsis now the focus of these life searches. Discover-ies of previous martian epochs with standing sur-face water, along with tentative observations ofatmospheric methane; preliminary evidence ofnear-surface liquid water; and higher-than-ex-pected cratering rates not only suggest the possi-bility that habitable zones may have existed onMars, but also suggest that they may still exist inthe near-surface environment, where they couldbe accessed with currently available technology(Malin and Edgett, 2000, 2003; Formisano et al.,2004; Malin et al., 2006).

NASA’s Mars Program is designed to exploreMars by way of a systematic set of missions thatwill launch at every Earth-to-Mars ballistic trans-

fer opportunity (approximately every 26months). Each mission will build upon the tech-nology and scientific results of previous missionsthrough a strategic planning process that, in gen-eral terms, is characterized by a scientific strategywhereby we will begin by “following the water”and then move on to “finding the carbon.” TheAstrobiology Field Laboratory (AFL) is the nextlogical in situ search platform that will follow theMars Reconnaissance Orbiter (MRO) (launchedin 2005), Phoenix Scout-class mission (to launchin 2007), Mars Science Laboratory (MSL) (tolaunch in 2009), and the Mars Science Orbiter(MSO) (to launch in 2013) projects in this strate-gic effort. (Note: the detailed objectives of theMars Scout Program’s 2011 mission are unknownat this time.)

In a current draft of the Mars exploration strat-egy, there is the option to send the AFL to Marsin the 2016 launch opportunity (Fig. 1) (Beaty etal., 2006; McCleese, 2006). We have developed anAFL mission concept which can fit within current

BEEGLE ET AL.546

2013 2016 2018 2020+2011

Mars Science Orbiter

Compacted Scout Mission

Twin Mid Rovers

Long-Lived Surface Network

Astrobiology Field Laboratory

Mars Sample Return

MAVENor TGE

ESAExoMars

SAG/SDT to beformed Early in

2007

1 Mission inEach Opportunity

Selected from4 Options

1 Mission inEach Opportunity

Selected from4 Options

FIG. 1. Mars Exploration Program pathways for potential next-decade missions. The AFL is an option for eitherthe 2016 or 2018 opportunity (Beaty et al., 2006; McCleese, 2006). ESA, European Space Agency; SAG, Science Analy-sis Group; SDT, Science Definition Team.

and projected Mars Program planning fundingconstraints. Strawman payload elements wereidentified from a set of recommendations putforth by the Mars Exploration Program AnalysisGroup (MEPAG) Astrobiology Field LaboratoryScience Steering Group (AFL SSG) in 2004 (Steeleet al., 2004), for the express purpose of identifyingoverall rover mass, power, and other technical re-quirements for such a mission. Candidate payloadsuites consistent with the full complement of rec-ommended measurements, and selected subsetsand augmentations to those measurement goals,have all been investigated as part of this missionconcept. The development of the AFL missionconcept allows us to identify technology thatneeds to be developed to meet identified missiongoals. It also gives potential instrument providersa broad mission overview so as to focus instru-ment development activities that may be capableof contributing to the mission goals.

The AFL SSG developed the goals for the AFLmission based upon the anticipated goals andpayload of the MSL rover. However, the findingsof the 2004 AFL SSG were submitted prior to theselection of the MSL payload suite, and it is an-ticipated that a future AFL SSG is expected to be-gin later in 2007 (Fig. 2) (Arvidson, 2007). The2007 SSG will revisit the science objectives andmeasurement strategies for the AFL, taking intoaccount the actual characteristics of the MSL pay-load that will launch, as well as the wealth of in-formation gathered about Mars by the suite of

spacecraft currently in orbit and on the surface ofMars. However, the fundamental rationale andobjectives for the AFL are not expected to changesignificantly.

The selected payload for the MSL will attemptto determine the habitability potential of a spe-cific site at Mars. That is, could Mars have beenhabitable in the past, or is it habitable now? TheAFL SSG mission goals are

1. To make a major advance in astrobiology byexploring a site with high habitability poten-tial as determined by results from MRO,Phoenix, or MSL missions.

2. To search for evidence of past or present lifeby identifying the presence of potential biosig-natures. If definitive biosignature detectionsare made, they will be accomplished throughmutually confirmed measurements.

3. To test for habitation by investigating whetherthe environment could have been or currentlycould be habitable.

In any search for extraterrestrial life, the de-velopment of search strategies that give maxi-mum flexibility to find “life as we may not knowit” is the real key to formulating a mission con-cept that will be flexible enough to meet missiongoals. Accordingly, the AFL SSG developed thefollowing set of search strategies and assump-tions for increasing the likelihood of detectingbiosignatures:

1. Life processes produce a range of biosigna-tures, which leave imprints on geology andchemistry. However, the biosignatures them-selves may become progressively destroyedby ongoing environmental processes.

2. Sample acquisition will need to be executed inmultiple locations and at depths below thatpoint on the martian surface where oxidationresults in chemical alteration.

3. Analytical laboratory biosignature measure-ments require the pre-selection and identifica-tion of high-priority samples. These samplescan be subsequently subsampled to maximizedetection probability and spatially resolve po-tential biosignatures for detailed analysis.That is, the AFL must identify the best possi-ble sample for analytical analysis.

The AFL will be an integral part of the strate-gic exploration of Mars and feed forward tech-

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FIG. 2. High-level near-term AFL mission conceptschedule and relevant MEP activities. Planning activitiesand dates are approximate and subject to change byNASA MEP (derived from information presented by D.Beaty at MEPAG meeting, January 2007, Washington,DC). SAG, Science Analysis Group; SDT, Science Defini-tion Team.

nologically and scientifically to the next landedmissions, as is evidenced in several aspects of themission architecture.

2. SCIENCE

Mars is a natural first target in the robotic ex-ploration and search for extraterrestrial life. It isthe most Earth-like of all the objects in our solarsystem, a rocky body with appreciable atmo-sphere (95% CO2 at 5 Torr), 25-hour days, and acurrent obliquity to orbit of 25.19°; and Mars ex-ists within the assumed habitable zone aroundour Sun (Kasting et al., 1993; Kasting, 1997a). Or-bital missions NASA has sent to Mars—theViking Orbiters, Mars Global Surveyor, MarsOdyssey, and MRO—have all imaged evidenceof ample liquid water on the surface. The recentrelease of Mars Global Surveyor Mars OrbiterCamera images also adds to this evidence and in-dicates that recent surface water may be possible(Malin et al., 2006).

Geomorphological land forms show evidenceof past active gullies, river beds and deltas, lakebeds, and even potential seas, which indicatesthat a warmer and wetter Mars existed in the past(Higgins, 1982; Parker et al., 1989; Gulick andBaker, 1990; Parker et al., 1993; Squyres and Kast-ing, 1994; Malin and Edgett, 2000, 2003). Recently,both Mars Exploration Rovers (MER) found am-ple chemical and mineralogical evidence in sur-face rocks that standing water was present atMeridiani Planum and Gusev Crater (Squyres etal., 2004a; Squyres et al., 2004b; Haskin et al., 2005).The European Space Agency’s Mars Express(MEx) orbiter has identified, in the martian at-mosphere, trace amounts of methane that couldbe the result of near-surface volcanism, abioticprocesses, or, possibly, life processes taking placein the near surface (Welhan, 1988; Kasting, 1997b;Max and Clifford, 2000; Kotelnikova, 2002;Duxbury et al., 2004; Formisano et al., 2004;Krasnopolsky et al., 2004; Bar-Nun and Dimitrov,2006). Mars Express orbital investigations indi-cate that this aqueous period occurred shortly af-ter the planet’s formation and may have been pre-sent for substantial periods of time on the surface,approaching 500 million years (Bibring et al.,2006). What makes this even more exciting is thatthis aqueous period is believed to have existedaround the time when life began on Earth (Walshand Lowe, 1985; Schidlowski, 1988; Schopf, 1993;

Mojzsis et al., 1996; Rosing, 1999; Westall et al.,2001; Garcia-Ruiz et al., 2003; Tice and Lowe,2004; Van Kranendonk and Pirajno, 2004; VanKranendonk, 2006).

One overriding question the Mars ExplorationProgram (MEP) hopes to address is, if life startedon Earth, then might it have started on Mars aswell? And if so, might life on Mars still survivein protected environments where chemical en-ergy and water exist, such as in the subsurface,in rocks, or under the polar caps? Furthermore,if life never began on Mars, what conditions pre-vented a second genesis there, and might knowl-edge of those conditions on early Mars help toconstrain the potential geochemical environmentat the time of the origin of life on Earth?

Life on Earth inhabits virtually every terrestrialenvironment where food and energy exist, anddestroys chemical and geological evidence of theearly Earth. Plate tectonics, the hydrological cy-cle, and other geological activity further destroygeologic and chemical evidence of early life. Asa result, we can only infer what conditions werepresent at the time of origin of life. Some of theseissues, however, do not appear to apply to Mars,where no plate tectonic activity has been identi-fied and a relatively dry environment has per-sisted for the last !4 billion years. As we beginto address questions with regard to whether lifeexists, or has existed, on Mars, we will gain a bet-ter understanding of conditions on Earth at thetime of the origin of life here.

In 1976, NASA sent two Viking landers to Marsto characterize the surface and determinewhether life existed in the unconsolidated surfacematerial that covers the entire planet (Klein, 1977,1978; Klein et al., 1992). The set of experiments onthe two landers were identical and included theLabeled Release, Pyrolytic Release, and Gas Ex-change experiments. These experiments acquiredunconsolidated surface material (conventionallycalled martian soil) and tested it for signs of life.In addition, a gas chromatograph/mass spec-trometer (GC/MS) was used to analyze thevolatiles released from several samples on thesurface.

In the Pyrolytic Release experiment, small sam-ples were exposed to CO and CO2, which wereradioactively labeled with C14 to determinewhether organic matter could be synthesized inthe martian soil under ambient martian condi-tions (Horowitz et al., 1976; Klein et al., 1992).Trace amounts of carbon-containing substances

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were formed for those samples that were studiedunder ambient martian conditions as well asthose heated to 625 °C, which indicated that lifeprocesses were most likely not present in the soil.

In the Labeled Release experiment, soil sam-ples were introduced to a nutrient-rich solutionthat contained radioactively labeled carbon, andthe evolved gases were analyzed by two solidstate beta detectors (Horowitz et al., 1976; Levinand Straat, 1976, 1977). This process resulted in arapid release of CO2 followed by a slow releaseof CO2, which is what was expected if organismswere present in the soil. While there are somewho feel that the results are indicative of biology,conventional wisdom is that there was no biol-ogy in those samples (see Klein, 1978 and Kleinet al., 1992 for a more thorough discussion on thisand on all of the Viking life-detection experi-ments.)

In the Gas Exchange experiment, soils were ex-posed to H2O and, upon humidification, releasedO2 (Oyama et al., 1977; Oyama and Berdahl,1979).

The GC/MS analyzed two samples on eachlander; samples were heated to 200 °C, 350 °C,and 500 °C (Biemann et al., 1976; Biemann andLavoie, 1979). Although there was a detection ofthe solvent that was used to clean the spacecraft,the GC/MS detected no organic material in anysample. This was unexpected because current es-timates of the amount of exogenic organic mate-rial delivered to Mars through the infall of mete-orites and interplanetary dust particles is 2 ! l05

kg yr"1, which almost certainly was higher in thepast (Hayatsu and Anders, 1981; Mullie andReisse, 1987; Flynn, 1996). Furthermore, thereshould be, by some estimates, almost 500 parts-per-billion of carbon-bearing species in the uppermeter of the planet (Benner et al., 2000). The re-sults of these three experiments, taken togetherwith the GC/MS results, indicate the presence ofone or more surface oxidants, though not neces-sary life.

The AFL payload will attempt to minimize anyconflicting positive detection of life by includinga suite of instruments that provide mutually con-firming analytical laboratory measurements. Fi-nally, while the results of the Viking GC/MS in-dicated that no organic material was detected inthe surface material sampled, oxidation productsfrom meteoritic in-fall would have been unde-tectable by that particular instrument (Benner etal., 2000; Navarro-Gonzalez et al., 2003). Under-

standing the limits of detection for instrumentmeasurements on complex samples is criticallyimportant for the AFL mission so that any possi-ble biosignature measurements made can be in-terpreted in the proper context.

The Mars Exploration Program AnalysisGroup (MEPAG) defines science goals and mea-surements for Mars for consideration by NASAprogram planners. The current MEPAG docu-ment, Mars Science Goals, Objectives, Investigations,and Priorities: 2006 MEPAG (MEPAG, 2006) statesthat the determination of whether life arose onMars is a key and challenging goal. If life existsor has existed on Mars, scientific measurementsto be considered would focus on understandingthose systems that support or supported it. Fi-nally, if life never existed while conditions weresuitable for life formation, understanding why amartian genesis never occurred would be a fu-ture priority.

In 2004, NASA charged MEPAG to convene aScience Steering Group (SSG) that would beginto define the desired measurement characteristicsand scientific objectives for an AFL mission(Steele et al., 2004). The results and recommen-dations from this SSG effort have been used toguide the design efforts described in this paper,with the understanding that such recommenda-tions will be revisited as results from MER, MEx,and MRO are factored into the strategic planningprocess. An example of the process by which anupdate to the AFL measurement objectives mightbe incorporated into the Mars Program Plan is il-lustrated in Fig. 2 (based upon MEPAG planninginformation), with some key planning milestoneshighlighted. The outcome of this planningprocess, in this scenario, would be available inlate 2008 and provide supporting rationale for se-lecting a particular mission and objectives to bemet by the mission to be launched 2016.

With the understanding that the Mars Programplanning process is not complete, we have takenthe 2004 AFL SSG recommendations of the mis-sion scope and goals and formed a mission con-cept that meets the identified measurement goals.This provides input into the overall advancedplanning process for the NASA Mars Program. Itshould be noted that, as budgetary influences be-come better known and more focused in the com-ing budget planning cycles, and the predecessorMSL heritage becomes better understood, themission design of the AFL would also inevitablychange as constraints are better matched with

ASTROBIOLOGY FIELD LABORATORY 549

available resources. Though the fundamentalmission goals of the AFL are not likely to change,a basic change in the high-level mission design ofthe AFL could occur during the National Envi-ronmental Policy Act (NEPA) compliance stageof mission planning.

It is fundamental to the AFL concept to un-derstand that organisms and their environmentconstitute a system, within which any one partcan affect the other (Steele et al., 2004). The over-all AFL science investigation will focus on char-acterization of environments where organismsmay be or may have been, and any possiblebiosignatures of extant and extinct life detectedin those environments. Though the current AFLscience justification does not include a pre-defin-ition of potential life forms that might be foundon Mars, the following assumptions were made:

1. Life utilizes some form of carbon.2. Life requires an external energy source (that is,

electromagnetic, chemical, etc.) to survive.3. Life is packaged in cellular-type compart-

ments.4. Life requires liquid water.

The current understanding of Mars is that itwas, at one point in its history, warmer and wet-ter, with ample energy in the form of volcanismand volcanically produced chemical species.

The AFL’s objective must balance the need forthe project to be a significant extension beyondcurrently planned missions, yet not an unrealis-tic extension of current technology. The detailedobjectives proposed include (in no order of im-portance):

• Within the region of martian surface opera-tions, identify and classify martian environ-ments (past or present) with different habit-ability potential, and characterize theirgeologic context.

• Quantitatively assess habitability potential by:! Measuring isotopic, chemical, mineralogical,

and structural characteristics of samples, in-cluding the distribution and molecular com-plexity of carbon compounds.

! Assessing biologically available sources ofenergy, including chemical and thermalequilibria/disequilibria.

! Determining the role of water (past or pre-sent) in the geological processes at the land-ing site.

• Investigate the factors that will affect thepreservation of potential signs of life (past orpresent) on Mars.

• Investigate the possibility of prebiotic chem-istry on Mars (including non-carbon chem-istry).

• Document any anomalous features that can behypothesized as possible martian biosignatures.

The goal of this AFL concept, as proposed, isto search for the potential, rather than definitive,biosignature, and characterize the supporting en-vironment where the signature resides.

The Mars surface environment appears to havebeen cold and dry from !4 billion years ago tothe present. From a programmatic perspective,understanding the potential for preservation ofbiosignatures is vital for the development of thenext generation of missions. The surface is oxi-dizing as a consequence of the intense photodis-sociation by solar UV radiation and the absenceof global shielding from harmful space radiationin the form of galactic cosmic rays, which maywell render the surface sterile (Hunten, 1979; Mc-Donald et al., 1998; Benner et al., 2000; Yen et al.,2000; Pavlov et al., 2002; Kminek and Bada, 2006).Further, understanding the nature of the surfaceis a goal of the AFL mission concept. This in-cludes the identification and characterization ofspecific biomolecules (lipids, proteins, aminoacids) and potential kerogen-like material.

3. FLIGHT SYSTEMS

The AFL flight system as currently conceivedconsists of three major components that are mod-eled after the MSL system currently under de-velopment. It is not the purpose of this article todefine the MSL heritage system, but rather, toprovide a basic description of the system to en-able an understanding of why certain constraints(landed mass, landing site latitude, etc.) exist. Thefundamental characteristics of the system de-scribed here include an Earth-Mars cruise stage;an atmospheric entry, descent, and landing (EDL)system; and a mobile science rover with an inte-grated instrument package.

Cruise stage

Following launch and during the interplanetarytransfer to Mars, the cruise stage provides the nec-

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essary functions to deliver the entry system to theatmospheric entry interface at Mars. The spinningcruise stage has minimal capabilities (e.g., power,propulsion, telecommunication) and takes advan-tage of the rover systems to implement many ofits data-handling and commanding functions. Thecruise stage propulsion system is separate fromthe EDL system and is used for spin-rate control,attitude control, and all trajectory correction ma-neuvers on approach to Mars. The AFL cruisestage as currently conceived is modeled as a di-rect heritage design from the MSL. As will be dis-cussed later, the mission design for this AFL con-cept constrained the trajectory option space tominimize any fundamental changes that might berequired to the MSL cruise stage. In this example,the trajectory design for this concept precludedthe use of sizable deep-space maneuvers to avoida modification of the cruise stage propellant tankdesign and accommodation interface.

Entry vehicle and descent

The AFL EDL phase begins when the space-craft reaches the Mars atmospheric entry inter-

face point. This AFL concept mimics the EDL con-cept (Fig. 3) that is planned to be used for the 2009MSL mission (Mitcheltree et al., 2006). The designemploys an aeroshell/heat shield and a para-chute to guide and decelerate the lander throughthe martian atmosphere. The diameter of the AFLparachute has been scaled up from that of theMSL to approximately 23 m (from !20 m) to ac-commodate the possibility of heavier AFL entryand rover masses and a shift in atmospheric mod-eling conditions from those consistent with alaunch in 2009 to those appropriate for launch in2016.

Like the MSL, the AFL would use an offset cen-ter of mass to generate an aerodynamic lift vec-tor during the hypersonic entry phase (Mitchel-tree et al., 2006). The entry vehicle lift vector ismodulated through use of roll-control thrustersto guide the vehicle and compensate for unpre-dictable vehicle performance, navigation accu-racy, and environmental variations that ulti-mately affect AFL surface targeting accuracy.Lift-vector modulation would be the primarymeans for meeting the AFL landing accuracyneeds, which are currently assumed to be con-

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Cruise Stage Separation

Entry Interface

Peak Heating

Peak Deceleration

Heading Alignment

Deploy SupersonicParachute

Entry

Exo-atmospheric

Despin (2 rpm 0 rpm)

Cruise Balance Mass Jettison

Turn to Entry Attitude

FIG. 3. EDL sequence concept of events for the MSL 2009 mission representing the cruise stage separation to su-personic parachute deploy (Steltzner et al., 2006). This series of events is identical to the EDL sequence for the AFLconception design described here.

sistent with the MSL landing accuracy capabilityapproximated by a 10 km radius footprint on thesurface. This AFL concept does not attempt toguide the vehicle following parachute deploy-ment. When investigating a specific site, the nec-essary landing accuracy requirement is driven byterrain and mobility considerations. If the high-est-priority landing sites that support science andmission objectives require increased landing ac-curacy, this technology would need to be addedto the technology development trade space. Thevehicle design would also need to be modified tosupport this capability.

Following the parachute phase, the vehiclewould employ the skycrane architecture for shed-ding the remaining velocity of the system and de-ploying the rover on the surface. No modifica-tions to the MSL skycrane phase depicted in Fig.4 are anticipated for this concept. For other AFLconcepts with stricter landing accuracy require-ments, such as those that require pinpoint land-ing techniques for highly constrained hazardouslocations (i.e., landing accuracies on the order of100 m), a departure from strict MSL heritage de-

sign may need to be considered. Further elabo-ration of pinpoint landing technology is summa-rized in the technology development discussionto follow. For the AFL concept to be describedhere, a summary of Key Design Assumptions andResults is given in Table 1.

A key difference between the MSL flight sys-tem and the flight system concept for the AFL hasto do with the anticipated need for the AFL toperform a vehicle-level sterilization activity priorto launch. This key difference is discussed in thetechnology development section.

Rover

The AFL rover for this mission concept is a di-rect descendant of the MSL rover system cur-rently under development for launch in 2009. Al-though no analysis has been performed toexamine the power options for the AFL, we areconsidering the MSL Radioisotope Power System(RPS) as a concept to enable the same landing siteflexibility and surface operations performance ca-pability that was selected for the MSL. As this

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Flyaway

Sky Crane

Powered Descent

SupersonicParachuteDescent

Deploy SupersonicParachute

Heatshield Separation

Entry Balance Mass Jettison

Radar Activation and Mobility Deploy

MLE Warm-Up

Backshell Separation

Cut to Four Engines

Rover Separation

Rover Touchdown

FIG. 4. EDL Sequence concept of events for the MSL 2009 mission representing the supersonic parachute deployto touchdown (Steltzner et al., 2006). This series of events is identical to the EDL sequence for the AFL conceptiondesign described here. MLE, Mars Lander Engines.

mission concept is further developed, the power-generation options will be investigated thor-oughly for suitability to the specific objectives ofthe AFL.

As currently conceived, the AFL rover wouldbe expected to conduct its mission over a periodof one martian year (669 Mars sols or 687 Earthdays). The fundamental rover design features ofthe MSL are expected to carry forward to this AFLconcept. These include the basic size of the rover(Table 2).

The mass of the rover is expected to be greaterthan that of the MSL, as the payload and the sam-ple acquisition and processing systems are aug-mented to meet the challenging science objectivesdiscussed earlier. At the time of the detailed de-sign for this concept, the AFL was approximately10% more massive than the MSL heritage con-cept. For an MSL rover in the 850 kg class, thiswould correspond to an AFL rover in the 935 kgclass. For EDL and flight system design consid-erations, the rover for this concept was assumedto be constrained to less than 1,000 kg.

Strawman instrument payload

Part of the mass increase is due to the possibleinclusion of the full desired science payload andthe associated precision sample acquisition andprocessing system. The AFL SSG 2004 reachedconsensus on a suite of core AFL instruments thatmet a set of key measurement objectives of thenominal AFL mission (Steele et al., 2004). As dis-cussed earlier, these were defined for planningpurposes only and are not meant to pre-judge

future budget considerations, science analysisgroup activity, or the instrument selectionprocess. For this concept discussion, the straw-man instrument payload measurement objectivesare defined below:

Remote Sensing Suite (site characterization)

• color and stereographic images• reconnaissance scale mineralogy

Contact Suite (sample selection, context)

• obtain mid-scale imaging and spectroscopy ofsamples

• identify geochemistry and mineralogy of sam-ples

Biosignature Analytical Laboratory (detailedsample analysis)

• meso-scale structure of samples• definitive mineralogy

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TABLE 1. APPROXIMATE DESIGN PARAMETERS FOR THE 2016 AFL MISSION CONCEPT DESCRIBED HERE

Design parameter Design value Comment

Launch mass (wet) 4400 kg Enable C3 # 14.2 km2/sec2, max.DLA # 15.6°

Entry mass (wet) 3800 kg Limit Mars atmosphere relative entry speed to $6.2 km/sec.

Rover landed mass 1000 kg Assume 150 kg rover mass(for sizing EDL system) increase beyond current

MSL rover allocation(placeholder).

Approximate parachute 23 meters Stretch MSL capabilitydiameter beyond 19.7 meters. No

flight test re-qualification.Inertial entry flight path "14.5°

angle

TABLE 2. AFL MISSION CONCEPT APPROXIMATEROVER SYSTEM DIMENSIONS

Characteristic Size (meters)

Height to top of deck 1.1Height of mast 2.1Wheel diameter 0.5Clearance 0.7Approximate deck dimensions 2.0, 1.2, 0.5

(L, W, H)Approximate wheel base (L, W) 2.3, 2.5

• oxidation/reduction potential, advanced car-bon chemistry

• abundance/molecular structure of carbon• isotopic composition of carbon

The AFL concept described here has looked ataccommodating all measurements, as well as se-lected subsets of these measurements. In addi-tion, the SSG called for the analysis of 100 sam-ples, with analysis of over 10 samples in the fullanalytical laboratory, and a rover with greaterthan 10 km linear traverse distance.

While the exact instrument package would beselected through Announcements of Opportunity(AO), we have sized several potential instrumentpackages to ensure that they meet the above mea-surement objectives. When a well-characterizedinstrument with high technology readiness levels(TRL) met one of the measurement objectiveslisted above, we carried that instrument and itsaccommodation characteristics (i.e., mass, vol-ume, power) as a placeholder. For a more com-plete discussion of TRL concepts with respect toinstrument development and future flight readi-ness, please see Mankins, 1995. For example, thephysical parameters of the panoramic cameraaboard MER were used to size the AFL remotesensing suite (color and stereographic imagingmeasurement). This gave us the most confidencein sizing the payload, while allowing us to ac-knowledge that further improvements on the per-formance characteristics of instruments (whichwould be over a decade old at the time of launch)would occur. In those instances when compara-ble instruments have not yet flown, we combinedphysical characteristics of instruments that will

fly aboard the MSL, or obtained best estimatesfrom current instrument developers and mergedthem into a single instrument. This was done pri-marily for analytical instruments that could ana-lyze over 50 samples and wet chemistry instru-ments that have not flown or are yet to bedeveloped to a high TRL. Again, this is for thepurpose of discerning a reasonable estimate onwhich to base our mass estimates. Instrumentcosts were estimated in a similar manner, withcurrent best estimates for instruments taken fromvarious MSL-proposed instruments and flightheritage for the MER and Phoenix mission space-craft. The total payload cost estimates for thestrawman suite, which meet every measurementobjective, only fit within the scope of the most op-timistic Mars Program budget. Reduced capabil-ity payloads were also costed, and most fit withinour presumed Mars budget. Table 3 includes thepayload mass, power, and volume summary forthe complete instrument suite. The volume ofrover subsystems is an important design concernfor rover missions due to the severe engineeringpackaging constraints associated with hypersonicentry vehicles. While we have not identified anyvolume concerns for the instruments identified inthis concept, there have been significant packag-ing issues on past missions, and volume can beexpected to be an ongoing concern as this devel-opment continues and changes are introduced.The expected instrument volume envelope forthis concept is included in Table 3 as a reference.

Of importance here is the need to improve ourunderstanding of the accommodation needs forall potential instruments aboard the AFL. Severalinstruments we were aware of had “special

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TABLE 3. PREDICTED BEST ESTIMATES (PBE) FOR SEVERAL PAYLOAD ELEMENTS

PBE mass PBE average powerbudget budget PBE volume budget

(kg) (W) (m3)

PSHPS, mast, IDD, and 125 TBD TBDsample acquisition

Remote instruments 10 12 0.018Contact instruments 7 18 0.028Analytical instruments 98 60 0.430

This includes the Current Best Estimates (CBE) with a 30% contingency on all values.The power budget is the average power consumption during daily operations and isdependent on the length of operations. (Here assumed to be no more than 6 hours.) Forthe PSHPS system we only provide the estimated mass due to the low TRL of that con-cept.

needs,” which included increased radiationshielding from a potential radioisotope powersystem, extreme tolerances on the particle size foranalysis, and radius of curvature for the storageof arm-mounted instruments. The need to un-derstand potential thermal tolerances for astrobi-ology themed instruments is of special interest,particularly with regard to how they may relateto potential Planetary Protection (PP) require-ments. In the event that an instrument is intoler-ant to heat sterilization, it is conceivable that theinstrument could be sterilized on the componentlevel, aseptically assembled, and accommodatedinto the flight systems in a thermally isolatedmanner. Early understanding of these issues canlead to design modifications of the flight systems,but it is conceivable that certain instruments maybe disqualified from consideration because of PPrequirements on the system and subsystems thatcannot be met.

Since this is an ongoing study, any instrumentdata that we receive from instrument developersonly makes for a more realistic platform and,hence, more realistic costing data. Finally, it is in-tended that the physical parameters listed in thiswork inform instrument developers of this par-ticular concept and its constraints and provide adiscussion data point for further instrument de-velopment activities.

4. MISSION DESIGN AND DESCRIPTION

Launch/Arrival strategy

This AFL concept has a primary objective ofplacing an advanced mobile science laboratory onthe surface of Mars. Current planning efforts in-clude the use of the 2016 launch opportunity(which includes late December 2015 launch op-portunities) to launch and deliver the rover to aselected site on Mars. As noted previously, theplanning for the AFL assumes that surface oper-ations would be conducted over a primary mis-sion duration of at least one martian year (687Earth days).

The design of the launch strategy for the AFLmust consider many of the same issues that faceany of the surface missions going to Mars. Thereare numerous engineering and science con-straints that are placed upon the mission design,which manifest themselves in the design of the

launch period and launch vehicle. Engineeringconstraints and considerations can include

• Entry, Descent, and Landing (EDL) telecom-munications visibility during the entry andlanding phases of the mission (both relayedand Direct-To-Earth communications).

• Entry speed at the vehicle interface to the Marsatmosphere.

• Entry flight path angle.• Landing target conditions (e.g., altitude).• Time of day of landing (e.g., landing aid sen-

sors such as passive optical cameras must haveadequate lighting conditions).

• Atmospheric dust loading (typically manifest-ing itself through a Mars atmospheric dustmodel such as MarsGRAM (Justus and John-son, 2001)) results in environmental consider-ations associated with the arrival season for aparticular landing site.

• Landing site Mars season at the arrival time(e.g., a potential landing during the predictedMars dust storm season is an important eventthat the AFL may need to be designed to with-stand).

The Earth-relative departure conditions thatmust be achieved by the upper stage of the launchvehicle are specified by defining the launch en-ergy (or C3, which is the departure trajectory hy-perbolic excess velocity, or V-infinity, squared)and the direction of the hyperbolic departure tra-jectory (typically characterized by the declinationof the launch asymptote (DLA), and the right as-cension of the launch asymptote (RLA), at a spe-cific time).

The AFL launch period for this concept is sum-marized and described in Table 4 and depictedgraphically in Fig. 5. The figure also shows rele-vant geometric events that affect the orbital tra-jectories between Earth and Mars.

The selected launch period falls within thelaunch/arrival space as indicated in Fig. 6. Animportant characteristic of past landed missionsis the ability to freeze the arrival date across thefull 20-day launch period. This in turn enables the supporting infrastructure (e.g., orbiter over-flights, specific Deep Space Network antennacoverage) for the critical EDL phase to be plannedindependent of the actual launch date within thelaunch period. For a constant arrival date, andother design constraints, the launch/arrival date

ASTROBIOLOGY FIELD LABORATORY 555

for the AFL was designed to maximize the space-craft injected mass.

Trajectory design

The 2016 AFL concept follows a Type II inter-planetary transfer trajectory to Mars (i.e., the he-liocentric transfer angle is between 180° and360°). This selection was made to keep the flighttime to Mars at a reasonable duration (interplan-etary trajectories that arrive later or at compara-ble times to a 2018 Type I or II trajectory wereexcluded) while satisfying the other key engi-neering constraints. Table 5 summarizes the tra-jectory trades that were considered for this AFL2016 concept.

All cases analyzed were optimized for maxi-mum entry mass and constrained the arrival V-infinity to 3.75 km/sec (entry speed of approxi-mately 6.2 km/sec). The arrival V-infinityconstraint will be revisited for this concept as thedesign of the MSL heritage system progresses andthe heat shield thermal constraints for the AFLare better defined. The option selected for thisconcept (corresponding to Case 2 in Table 5) is aType II transfer, with a maximum C3 of approx-imately 14.2 km2/sec2 and a fixed arrival date.The Mars landing site latitude is allowed to vary

from 36°N to 75°S for this option. The absence ofspecific high-priority sites that would have re-quired potential AFL landing site latitudes to beas far north as those under consideration for theMSL (i.e., 45°N) allowed us to avoid a significantlaunch mass penalty (e.g., compare with Case 4of Table 5 where the landing site included ahigher northern latitude constraint for the trajec-tory design). For this preliminary concept defin-ition, the adopted latitude band encompassedmost MSL sites under consideration, as well aspossible AFL-specific sites associated with the re-cently discovered gully regions (e.g., see Dietrichet al., 2006). The interplanetary trajectory for thecruise to Mars for the opening of the launch pe-riod is illustrated in Fig. 7. Figures 8, 9, 10, and11 show some key parameters for this trajectoryduring transit to Mars.

Entry, descent, and landing design

A high-level illustration of the MSL-developedEDL sequence is shown in Figs. 3 and 4, whichhighlight the key phases of the EDL timeline. Ap-proximately 9 months after launch, the spacecraftwill enter the martian atmosphere directly fromthe interplanetary trajectory. Like the MSL, theAFL would be expected to follow a guided entry

BEEGLE ET AL.556

TABLE 4. 2016 ASTRONOMICAL FIELD LABORATORY CONCEPT: 20-DAYLAUNCH PERIOD CHARACTERISTICS (CASE 2 OF TABLE 5)

Launch Arrival C3 DLA VHP DAP VEntrydate date (km2/sec2) (deg) (km/sec) (deg) (km/sec)

29-Dec-2015 13-Oct-2016 14.25 0.05 3.72 "27.25 6.1830-Dec-2015 13-Oct-2016 14.00 0.56 3.71 "27.48 6.1731-Dec-2015 13-Oct-2016 13.75 1.09 3.71 "27.72 6.1701-Jan-2016 13-Oct-2016 13.52 1.65 3.70 "27.97 6.1702-Jan-2016 13-Oct-2016 13.30 2.24 3.69 "28.23 6.1603-Jan-2016 13-Oct-2016 13.09 2.87 3.69 "28.51 6.1604-Jan-2016 13-Oct-2016 12.89 3.52 3.69 "28.80 6.1605-Jan-2016 13-Oct-2016 12.71 4.21 3.68 "29.11 6.1506-Jan-2016 13-Oct-2016 12.54 4.93 3.68 "29.43 6.1507-Jan-2016 13-Oct-2016 13.38 5.69 3.68 "29.77 6.1508-Jan-2016 13-Oct-2016 12.24 6.49 3.68 "30.13 6.1509-Jan-2016 13-Oct-2016 12.12 7.32 3.68 "30.50 6.1510-Jan-2016 13-Oct-2016 12.01 8.20 3.68 "30.90 6.1611-Jan-2016 13-Oct-2016 11.92 9.12 3.69 "31.32 6.1612-Jan-2016 13-Oct-2016 11.85 10.09 3.69 "31.76 6.1613-Jan-2016 13-Oct-2016 11.79 11.10 3.70 "32.22 6.1714-Jan-2016 13-Oct-2016 11.77 12.16 3.71 "32.71 6.1715-Jan-2016 13-Oct-2016 11.76 13.27 3.72 "33.23 6.1816-Jan-2016 13-Oct-2016 11.78 14.42 3.73 "33.78 6.1917-Jan-2016 13-Oct-2016 11.83 15.64 3.75 "34.36 6.20

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BEEGLE ET AL.558

FIG. 6. AFL 2016 Earth-to-Mars ballistic transfer launch/arrival trajectory data. C3, Launch Energy; Ls, Areocen-tric Longitude of the Sun (Global Dust Storm Season occurs between Ls # 185° and Ls # 345°); TTIME, Flight Timeto Mars; VHP, Arrival V-Infinity (hyperbolic excess velocity).

trajectory (pre-parachute deploy) through the at-mosphere. The spacecraft would rely on a heatshield and parachute to slow its descent throughthe martian atmosphere and would fire retro-rockets to reduce its landing speed while de-ploying the MSL-developed skycrane system(Mitcheltree et al., 2006) to place the rover on thesurface of Mars. Following a soft landing, the AFLrover would be poised to commence its surfacemission.

A number of EDL engineering constraints aredependent upon the mass of the entry and landedsystems, and it is not a straightforward processto capture all of those constraints in a list of fixeddesign values. As any part of the mission designchanges, there can result a waterfall of changesthroughout the EDL system. For example, the en-try speed constraint is influenced by the allow-able thickness and materials used for the designof the entry heat shield. Across their respectivelaunch periods (and their corresponding arrivalconditions at Mars), the Mars atmosphere-rela-tive entry speeds for AFL in 2016 are higher thanthose for the MSL in 2009. The heat shield mustbe designed within manufacturing constraintsand account for expected heat flux and rate. Thisin turn constrains the amount of mass that canstrike the atmosphere and be delivered to the sur-face. Retrograde entry conditions tend to exacer-bate these constraints and can limit the launch/arrival space or landing sites that can be consid-ered. Increasing the landing accuracy require-ments to a level such that pinpoint accuracy is anecessity (i.e., 100-meter accuracy range) may re-

quire additional landing propellant and tankmass to counter expected local near-surface windenvironments. Such considerations can manifest,ultimately, in larger elements for the EDL system(i.e., parachute), a larger launch vehicle class, orinterplanetary trajectory design changes. Scienceconstraints and considerations also influence thelaunch/arrival design strategy and include land-ing site altitude and landing site latitude.

A much more complete discussion of the EDLproblem for an MSL-type entry system can befound in Mitcheltree et al. (2006) and Steltzner et

ASTROBIOLOGY FIELD LABORATORY 559

TABLE 5. TRAJECTORY DESIGN OPTIONS CONSIDERED FOR THE ASTROBIOLOGY FIELD LABORATORY MISSION CONCEPT

Departure Arrival Traj Max. C3 Max. VHP Min. inj. Mass Max. LatsCase dates dates type (km2/sec2) (km/sec) (kg) (deg)

1 29-Dec-2015 to 02-Oct-2016 to II 13.9 3.75 4539 36 to "7517-Jan-2016 17-Oct-2016

2 29-Dec-2015 to 13-Oct-2016 II 14.2 3.75 4510 36 to "7517-Jan-2016

3 10-Mar-2016 to 1-Oct-2016 to I 18.2 3.75 4197 67 to "6329-Mar-2016 13-Oct-2016

4 6-Dec-2015 to 16-Sep-2016 II 20.0 3.74 4063 45 to "8525-Dec-2015

Case 1: Floating arrival date, no bounds on achievable latitudes.Case 2: Fixed arrival date, no bounds on achievable latitudes.Case 3: Floating arrival date, minimum achievable latitudes % 45 degrees.Case 4: Fixed arrival date, minimum achievable latitudes % 45 degrees.Case 2 selected; fixed arrival date, unconstrained landing site latitude, Type II trajectory.Type III and Type IV trajectories rejected and excluded due to excessive Earth-Mars cruise duration.

FIG. 7. Graphical representation of AFL concept in-terplanetary cruise trajectory for the opening of the pro-posed launch period.

al. (2006). For this AFL concept, a snapshot ofsome key parameters and results are summarizedin Tables 1 and 2. This set of assumptions showsa point design for this AFL concept that is con-sistent with the MSL heritage system, with iden-tified departures, and with the 2016 Mars oppor-tunity. As the precise limitations of the MSLheritage system evolve during the developmentof that mission, so too will the design evolve forthis AFL concept.

Telecom during EDL

Similar to previous Mars landed missions,there is an expectation that the mission designwill plan for Earth to be in view during EDL,which will allow for the transmission of direct-to-Earth signals during all phases of EDL, as wellas during a post-landing time period. It may bepossible to rely on relay systems during thisphase, but for this conceptual design it is an as-sumed requirement for both communicationpaths. A preliminary trajectory design shows thata relay orbiter in an MRO science orbit offers thepossibility for meeting these telecommunicationsconstraints, consistent with the rest of the designfor this concept. Figure 12 shows how, for manyAFL landing scenarios under consideration here,the possibility for an orbiter in an MRO, Odyssey,or a candidate MSO orbit can meet these AFL crit-ical event relay requirements. Key coverage gapsexist for landings at mid-latitudes with this ex-

ample, but may be addressed by other assets inorbit at that time (e.g., 2011 Scout or 2013 MarsScience Orbiter).

This is a proof-of-concept design that takes intoconsideration this telecom requirement duringthe design phase of the interplanetary trajectoryfor this option, which highlights a key criterionin the final selection of the AFL landing site andthe necessity for coordination among other ele-ments of the Mars Program.

Landing site selection

The final landing site selection for most NASAMars missions takes place close to launch and af-ter a thorough site selection process that includesinput from the full science community and con-sultation with the flight system engineering de-velopment team (Grant and Golombek, 2006). Itis expected that a 2016 AFL landing site wouldbe chosen by way of data returned from MEx,MRO, and perhaps 2013 MSO orbital observa-tions, with input from MSL surface chemistry re-sults. However, since MRO will have nominallycompleted its primary science and initial two-year relay mission by the end of 2010, it may bebeneficial to select a landing site early in AFLPhase A/B (see Fig. 13) while MRO high-resolu-tion imaging is still capable of performing at therequired imaging resolution levels. This wouldenable the characteristics of potential landingsites to be thoroughly vetted, with contributions

BEEGLE ET AL.560

FIG. 8. AFL range to Earth during the cruise phasefrom Earth to Mars. AU, Astronomical Units.

FIG. 9. AFL range to Sun during the cruise phase fromEarth to Mars. AU, Astronomical Units.

from maximum resolution data sets. Here, wediscuss some advantages to an early site selec-tion, as well as potential site characteristics thata 2016 AFL would be able to reach.

The advantages of making an early site selec-tion first become apparent in the selection of aspecific and highly focused science payload opti-mized for site-specific measurements. Differenttypes of sites require different types of instru-ments to maximize scientific investigations. TheAFL SSG strawman payload that was selected tosize this mission concept was formulated for an“average” non-specific martian environment,while there were four specific site types individ-ually discussed. For each of these individual sites(stratigraphic, ancient hydrothermal, ice, and current water/current hydrothermal), differenttypes of measurements had higher priority,which required different instrumentation formeasurement objectives. For example, in theevent that a near-surface, volcanically active spe-cial region is the target landing site, it would beimportant to include a thermal emission spec-trometer to determine the exact location of hotspots. However, that instrument concept may notbe as vital in a gully region, where a long focallength imager that can identify processes occur-ring in geological regions that are out of reachmay be more appropriate (Malin et al., 2006). Fi-nally, in an ice-dominated region, special sampleacquisition and handling strategies will have to

be developed to ensure ice sample interrogationin a 5 Torr CO2 environment (Taylor et al., 2006;Peters et al., 2007).

Also, early site selection carries a benefit to theengineering of the rover systems. The engineer-ing development team necessarily constrains pa-rameters of all potential landing sites so that theyare consistent with the technical capabilities ofany system that affects the ultimate success of theEDL phase, as well as the ultimate use of the roversystem on the surface. These engineering con-straints span many flight subsystems and includesuch diverse elements as interplanetary naviga-tion, heat shield design, parachute design, avail-able propellant, telecommunications visibility, aswell as local environment concerns such asslopes, rock abundance, rock size, and winds. Ifthe landing site options are focused and highlyconstrained, the engineering of the rover does notoverdesign a system that takes into account allpotential EDL characteristics (including atmo-spheric pressure, wind speed, and hazard avoid-ance) but rather opts for a highly focused design.This design scenario would reduce developmen-tal cost and, potentially, mission risks. Program-matic and technical considerations related toplanetary protection may also argue for earliersite selection than has been customary for pastMEP missions especially if a special region is thetargeted landing site. (For a more thorough dis-cussion on this, please see the section titled For-

ASTROBIOLOGY FIELD LABORATORY 561

FIG. 10. AFL range to Mars during the cruise phasefrom Earth to Mars. AU, Astronomical Units.

FIG. 11. AFL Sun-Earth-Probe (SEP) angle during thecruise phase from Earth to Mars.

ward planetary protection for life-detection mission toa special region). From a program risk standpoint,the Mars Program may consider an early site-se-lection campaign, or the program can consider in-cluding MRO-class imaging resolution as a pay-load element on the proposed 2013 MSO mission.

One key difference between potential AFLlanding sites and MSL landing sites is that, whilethe MSL must avoid special regions, the AFL mayspecifically target a “special region.” From a PPstandpoint, a special region is defined as a regionwithin which terrestrial organisms are likely topropagate or a region that is interpreted to havea high potential for the existence of extant mart-ian life forms (COSPAR 2005; MEPAG special re-gions-science, 2006). Given our current under-standing of Mars, this definition is applied toregions where liquid water is present or whereliquid water may result if potential long-lived ra-dioisotope heat sources are put in contact withthe local environment. Special regions may in-clude ancient hydrothermal systems, areas where

near-surface ground water may reside, volcani-cally active regions, or methane hot spots (Beatyet al., 2006). Because of the PP restrictions, theMSL will not land within a special region’s land-ing site that requires horizontal traverse by theunsterilized rover. In these regions, vertical mo-bility through the martian regolith may be possi-ble through the use of sterilized sampling hard-ware.

If the landing site selection process is consis-tent with that which the MSL project (Grant andGolombek, 2006) is currently exercising, the AFLflight systems will be consistent with engineeringdesign constraints applicable to the MSL flightsystem. (Mitcheltree et al., 2006). The engineeringconstraints are derived from the natural environ-ment conditions at all potential landing sites andfrom the capabilities and characteristics of thespacecraft and EDL system. Some key, high-levellanding site constraints for this conceptual studymirror those of the current MSL design. Whetherthese capture the regions of interest for the AFL

BEEGLE ET AL.562

Earth & Sun

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EDL Coverage - Terminal Descent Only2016 AFL Mission

2 3 4 5 6 7 8 9 10 11 12

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Latit

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13 14 15 16 17 18 19 20 21 22 23 24

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Earth Only Sun Only

AFLLaunch Period

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AFLLaunch Period

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FIG. 12. EDL relay orbiter telecommunications coverage during AFL concept terminal descent with MRO andOdyssey represented as examples. While key coverage gaps exist for landings at mid-latitudes, it is expected thatthese gaps may be addressed by other assets in orbit at that time (e.g., 2011 Scout or 2013 Mars Science Orbiter). LMST,Local Mean Solar Time; ODY, Mars Odyssey.

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BEEGLE ET AL.564

FIG. 14. Artist’s conception of a corebeing analyzed by the PSHPS on theAFL rover. Since this system is not yetundergoing development, the actualsystem may hold no actual resem-blance to this conception. The corerepresentation here is from an en-dolithic colony collected from the DryValleys in Antarctica and was pro-vided by H. Sun at the Desert ResearchInstitute.

FIG. 15. Artist’s conception of the AFL mission concept. The rover systems are based upon 2009 MSL heritage sys-tems.

will be a subject of discussion for the key missiondevelopment science analysis groups. For currentplanning purposes, the desired landing sites areconstrained to %45° latitude, elevation with re-spect to the Mars Global Surveyor Mars OrbiterLaser Altimeter (MOLA) &1.0 km, 10-km land-ing ellipse radius. It is important to note that thecurrent launch period is not able to reach 45° inlatitude in the northern hemisphere without adramatic change in launch capability. The abilityof the AFL to land within a 10-km landing ellipseradius is consistent with the rover engineering ca-pability to traverse a total of 20 km. This ensuresthat the AFL has the ability to drive to any de-sired target within the landing ellipse.

Daily operations on Mars

Once EDL is complete, the day-to-day surfaceoperations of the AFL are constrained mainly bythe power available to the rover and the data vol-ume generated by the instruments. Data upload-ing to Earth would primarily be achieved usingan orbiter such as MSO, which would act as a re-lay link (analogous to the way the MER missioncurrently uses the Odyssey orbiter). It is expectedthat, once in its telecom orbit, an orbiter such asMSO would be able to relay as much as 1–2 gi-gabits of daily science data. Any direct-to-Earthcommunications would be done via X-Band andwould primarily be used for EDL and as a backupcommunication system. The largest single dailydata volume generation is expected to occurwhen the full-resolution color panorama imagingis obtained, at an estimated volume of 500–750megabits. If an instrument exceeds this value, op-tions for data storage would have to be exploredthat are either instrument specific or occur at thesystem level.

Several daily operational power scenarios werestudied to determine the power-generation re-quirements. We compared the power require-ments with several potential instrument conceptsto the power required for traverse, and foundthem to be roughly similar. Like all previous Marsrovers, the AFL drive train was assumed to be a6-wheel rocker-bogie design. All wheels have twomotors: one for driving the wheel and one forturning the wheel. All motors are expected to bebrushless with 2, 4, or 6 wheels operational at anytime, depending on the terrain. Power profiles as-sume that, in a worst-case scenario, each wheelwill consume 18–25 W or 100–150 W 'Hrs for all

wheels during traverse, depending on the surfacecharacteristics of the site (i.e., slop, rock distribu-tion, surface material, etc.). In addition to indi-vidual wheel power draws, NavCam, HazCam,and other image processing occur during thesetraverses, which increases the total power drawduring traverse. The MSL is currently assumingslopes as great as 30° and a total traverse lengthapproaching 90 m during a fully autonomousdrive (please see the mission website http://mars-program.jpl.nasa.gov/msl/index.html for up-dates to these values). During the assumed one-martian-year lifetime of the mission, it is expectedthat (10 km of total linear distance will beachieved. The AFL would expect to match any ofthe final characteristics of the MSL rover for tra-verse, if not improve on the capability when op-erations are developed and refined in the courseof that mission.

2018 opportunity

The current Mars Program Plan shows an op-portunity for AFL launch in either 2016 or 2018(Fig. 1), thus, as part of this effort, there has beenhigh-level mission design for the later opportu-nity as well. The performance results across thetwo launch opportunities are similar. While thepreliminary analysis showed that the 2018 op-portunity is more energetically favorable (lowerlaunch C3 and lower arrival V-infinity), it occursduring a season of increased dust storm activityand changed lower atmospheric parameters ofimportance to the EDL problem. The net effect onthe ability to land the desired payload, within thesame engineering constraints, is minimal.

5. SCHEDULE AND PROGRAMMATICCONSIDERATIONS

Schedule

A strawman 2016 AFL schedule of major mile-stones has been developed to support long-rangeplanning efforts that may be considered by theMars Program for this concept (Fig. 13). It is im-portant to identify those long lead items thatwould enable a launch in the late 2015 / early2016 time frame and ensure that the necessary re-sources are in place to support those efforts in atimely manner. An early allocation of resourcesmust be consistent with the scope of the mission

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objectives as well as the projected budget profileavailable for the development of this mission,which will ultimately lead up to the launch andsubsequent operations. Budget assumptions forthe Mars Program would dictate whether the fullcomplement of proposed AFL core measure-ments discussed above would be feasible.

The strawman schedule developed for the AFLties into the long-range planning efforts of theprogram outlined in Fig. 1. This AFL schedule isconsistent with a plan to provide an update to theMars Program Plan by the end of calendar year2008. At that time, it can be expected that suffi-cient data from MER, MEx, MRO, and Phoenixwill be in hand to provide more specific guidanceto the mission selection or goals for the 2016launch opportunity. The developmental stagesfor a typical NASA mission proceed sequentiallyfrom Pre-Phase A through Phase E, where Pre-Phase A is the advanced study or conceptualstudy phase; Phase A is the mission and systemsdefinition phase; Phase B is the preliminary de-sign phase; Phase C is the detailed design phase;Phase D is the assembly, test, and launch phase;and Phase E is the operations phase of the mis-sion. In the scenario discussed here, the AFL isdesignated as a compelling mission opportunitybased on the data from MER, MEx, MRO, andPhoenix, and begins a Pre-Phase A effort in early2009. As discussed in the current update to theMars Program Plan, this is consistent with aschool of thought that the selection of AFL in-vestigations need not be dependent on MSL re-sults (Beaty et al., 2006; McCleese, 2006). A redi-rection of the program away from the currentAFL concept would be expected to occur no laterthan mid-2011, one year after MSL EDL and suf-ficiently early to redirect development effortstoward a newly defined 2016 objective (i.e., oneof the other missions under consideration for2016/18, such as the Mid-Rover concept). TheAFL Pre-Phase A effort would support flight sys-tem advanced technology development activities,instrument technology efforts, and project devel-opment in support of the Mission Concept Re-view (a key project review supporting entry intoPhase A). These activities would be complete bythe end of 2009 and would enable instrument pro-curement activity to begin during the first part of2010 (e.g., an AFL Instrument Announcement ofOpportunity). This would also kick off a 72-month development cycle (i.e., Phase A–Phase D)for the AFL project. The AFL development sched-

ule for this concept is approximately 1–2 monthslonger than the MSL development currently un-derway. The phase durations within this time pe-riod are expected to be different than those of theMSL in order to reflect some of the key advan-tages of having the MSL development as a her-itage system and to reflect some of the key dif-ferences with respect to the MSL. For example,the candidate instrument selection process de-fined for this concept would be completed by late2010. This enables a slightly longer (10%) instru-ment development activity of 44 months for thepotentially more complicated AFL instrumenta-tion (as compared with the MSL), by which timethe flight instruments would have to be deliveredfor the final assembly, test, and sterilizationprocess. To support such a schedule, a mid-levelTRL development effort for instrument technolo-gies should be initiated in early to mid-2007, witha technology development effort nearly completeby the time of the kickoff of the instrument se-lection activity in early 2010.

Spacecraft subsystem and system cleaning andsterilization will be a key challenge for the AFLand its payload. The cleaning and recontamina-tion avoidance procedures for AFL introduceschedule pressure relative to MSL developmenttimelines, as these are new and necessary stepsin the assembly, test, and acceptance processesfor both instruments and flight systems. As a re-sult, our conceptual design anticipates a relativeincrease in the duration of Phases C/D (as com-pared with the MSL) leading up to launch. As thetechnology efforts for PP and organic contami-nation control proceed, this will need to be re-visited. As part of long-range planning for AFLdevelopment, the major milestones for steriliza-tion facility construction must also be considered.A Viking-like sterilization facility would need tobe constructed at the launch facility (NASA,1990). A candidate schedule for the steps leadingup to the construction and initial operations ca-pability of such a facility (in this case a dry-heatmicrobial reduction, or DHMR facility) has beendeveloped as shown in Fig. 13. The initial stepsfor facility requirements development and earlybudget planning would begin before 2009.

In this concept, technology development forthe AFL would begin in earnest at the beginningof 2010, which would be early enough to achieveTRL-6 maturity at the time of an AFL PreliminaryDesign Review (or PDR, a key project review sup-porting entry into Phase C) in late 2012. It may

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be desirable to consider initiation of some AFLadvanced developments even earlier than 2010 toensure that critical/low TRL/high risk technolo-gies are brought to the required readiness levelwell before the system PDR. The precision sam-ple handling and processing system (PSHPS)would be an example of technology that fits intothat category.

Another key long-lead development effort wasdiscussed earlier. One of the key trades to be con-ducted for the AFL mission concept will be theevaluation of the power source alternatives forsurface operations. This trade is slated to beginearly in Phase A and will be completed in timeto support System Definition Review (a key pro-ject review supporting entry into Phase B) in mid-2011. This plan is also consistent with the devel-opment schedule for Nuclear Launch Approval,should the studies show that RPS or other ra-dioactive sources are required in this mission. Acandidate Launch Approval Schedule (whichconsiders data and products in support of NEPAand Presidential Directive NSC/25 launch ap-proval processes) has been developed for thisconcept in consideration of the possibility thatsuch systems may be proposed for the baselinedesign of the rover.

Science feed-forward

As with any mission that is part of the coordi-nated MEP, there is a plan for AFL science mea-surements and results which the Mars Programcan build upon and develop follow-up investi-gations consistent with overall agency objectives.The AFL would impact future missions by:

1. Improving the understanding of Mars biosig-nature preservation potential by providing:a. A thorough understanding of the nature,

structure, and concentration of near-surfacecarbon.

b. An assessment of the amount of chemicalalteration a site has experienced since itsformation.

c. Identification of sites with high preserva-tion potential such as those that containaqueously deposited chemical sediments.

2. Identifying specific sample types for possiblereturn. The potential for caching high-valuesamples for targeted sample return is in themission architecture trade space. This wouldbe an added consideration for a Mars Sample

Return (MSR) landing site selection or missionarchitecture definition.

3. Detecting potential biosignatures. If the AFLidentifies potential biosignatures, the devel-opment of a mission to characterize extant orextinct life would be the next logical develop-ment.

4. Further exploring the martian surface forchemical and mineralogical diversity, includ-ing environmental characterization for futurehuman missions.

5. Spurring development of robotic tools for theexploration of life on other bodies (e.g., a Eu-ropa or Enceladus Lander). This includes de-veloping sample acquisition, handling, andprocessing hardware and infrastructure thatwill lead to better scientific measurements offuture missions and sample contaminationcontrol and cleaning processes.

6. TECHNOLOGY AND TECHNOLOGYDEVELOPMENT

The required technologies for Mars missionsare developed by the Mars Technology Program(MTP), which is an element of the MEP. MTP de-velops technologies via two subprograms: Baseand Focused Technology Programs. The BaseTechnology Program is an on-going program thatfunds low-TRL technologies to mature technol-ogy concepts to breadboard or early brassboardlevels. These technologies are acquired via NASAResearch Announcements (NRAs) such as Re-search Opportunities in Space and Earth Sciences(ROSES). The Focused Technology Programfunds and develops technologies for specific mis-sions. This advanced technology developmentprogram is designed to raise the TRL of enablingand strongly enhancing technologies to level 6 atthe PDR stage of the mission development. For abrief review of all technologies currently in de-velopment, see http://marstech.jpl.nasa.gov.

The AFL mission will benefit from many tech-nologies that have been developed and success-fully infused into MER and the upcoming MSLmissions. In the area of EDL, these include moreaccurate landing (20 km landing ellipse for theMSL) via guided entry technology and soft land-ing of !850 kg rovers on the surface of Mars. Soft-landing technologies include sensor, parachute,and propulsion advanced development efforts. In

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the area of rover technology, these include au-tonomous navigation, instrument placement,ground control tools, and power storage devices.The AFL can also benefit from technologies be-ing developed outside of the Mars Program (e.g.,the Crew Exploration Vehicle heat shield and ma-terials development).

To meet the challenging AFL-SSG-derived sci-ence objectives and remain consistent with thenecessary engineering constraints of the observa-tion platform, a number of key technology devel-opment activities must take place. At this stage ofdevelopment, the following items must be con-sidered preliminary and are summarized here toprovide insight into some of those challenges.Early identification of potential technology devel-opment needs helps to support the next decadeMEP planning efforts (i.e., budget and scheduleplanning). The technology funding profile to sup-port these activities will need to be synchronizedwith the AFL development and funding scheduleif this concept is to be implemented. Also, itshould be noted that advanced developmentplans for certain technologies (e.g., the need forpinpoint landing with a 100-m landing accuracylevel, subsurface access to 2 m, or extreme terrainaccess) may shift in priority as appropriate and asthe needs of the mission are better defined andunderstood. Some of these technologies are in-cluded in the discussion below. For this AFL con-cept, the technology development effort includes

1. Precision Sample Handling and ProcessingSystem (mission-enabling technology).

2. Forward Planetary Protection for Life-Detec-tion Mission to a Special Region (mission-en-abling technology).

3. Life Detection-Contamination Avoidance(mission-enabling technology).

4. Astrobiology Instrument Development (mis-sion-enabling technology).

5. MSL Parachute Enhancement (possibly mis-sion-enabling technology).

6. Autonomous safe long-distance travel (mis-sion-enhancing technology).

7. Autonomous single-cycle instrument place-ment (mission-enhancing technology).

8. Pinpoint landing (100–1000 m) (mission-en-abling technology if necessary to reach specificscience targets in hazardous regions).

9. Mobility for highly sloped terrain (30° (mis-sion-enabling technology if required to reachscience targets).

Here we focus our discussion on mission-en-abling technologies, while only briefly touchingupon those technologies currently considered tofall within the mission-enhancing category forthis concept.

Precision sample handling and processing system (PSHPS)

To date, only simple sample acquisition, han-dling, and processing have been attempted onMars. Viking had a robotic arm and a simplescoop, MER had an Instrument Deployment De-vice (IDD) with a Rock Abrasion Tool (RAT) forcleaning off the outer few mm of weathering onsurface rocks, Phoenix has a robotic arm with ascoop and a simple Icy Soils Acquisition Devicefor obtaining samples with tensor strength above!10 MPa, and the current design for the MSL isconfigured with an IDD, RAT corer, and a jawrock-crusher (Peters et al., 2007). The centerpieceof the AFL design would be the most ambitioussample acquisition, handling, and processinghardware flown to date.

MSL’s rock corer was designed to acquire acore from rocks, bedrock, and sediments with a1-cm diameter and a length of up to 5 cm. Thiscore would then be fed into a simple jawrock-crusher that creates fines for analysis by MSL’sCheMin XRD/XRF and SAM GC/MS instru-ments (Hansen et al., 2007). However, it is rea-sonable to assume that the MSL will have a de-sign that is much different than what wasoriginally baselined in order to maintain overallsystem mass limitations and cost. This may resultin the use of a powdering drill bit on the MSL in-stead of a corer or crusher. This would not be anoption for the AFL. For the AFL to reach its sci-ence goals as defined by the 2004 AFL SSG, it isimperative that the AFL have the capability to ac-quire and analyze a core (Steele et al., 2004). Fur-thermore, the ability to subsample that core is apriority measurement goal of the mission. ThePSHPS on the AFL would allow us to make spa-tially resolved measurements that were simplynot possible on previous missions.

The AFL would acquire an intact core of 5–30cm in length. Since small-diameter cores tend tofracture rather than be collected intact, we haverelaxed the 1-cm diameter requirement on thecore and left that as a manufacturer design pa-rameter that would likely be defined only withpower and mass as the driving requirements.

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Once collected, and after any surface obscurationis removed (e.g., coring dust layer), the corewould be analyzed to determine its meso-scalestructure by identifying stratigraphy and miner-alogical variations along the core axis. This corewould then be subsampled within an area ofroughly 4 mm2. That powderized subsamplewould then be transferred to the analytical in-struments for analysis. Depending on this analy-sis, further samples may be acquired and a chem-ical/mineralogical map of the core constructed.Once completed, this core is to be ejected and anew one obtained. As of yet, we know of no sys-tem that can accomplish these tasks. It is plannedthat a specific Mars advanced development taskwill be requested as part of the long lead-timetechnology necessary to implement the AFL,which could augment any Planetary InstrumentDefinition and Development Program (PIDDP) orMars Instrument Development Program (MIDP)tasks that may be funded in the meantime. Othersample processing technologies, such as the ac-quisition and processing of petrographically im-portant thin sections, have not been consideredfor this particular concept, though they may beincluded as the need develops. For an artist’s ren-dition of the PSHPS please see Fig. 14.

Forward planetary protection for life-detectionmission to a special region

A fundamental difference between the 2009MSL mission and the 2016 AFL mission is thatthe AFL mission would be designed to preservethe option to explore special regions on Mars andmake measurements that may search for extantlife. To preserve the option to implement a mis-sion of this type, it will be necessary to developthe capability to implement the required PP con-trols (COSPAR 2005; MEPAG special regions-sci-ence, 2006). Should a choice be made to target aspecial region, implementation of the necessarycontrols would almost certainly involve steriliza-tion of the landed system and encapsulation ofthe system in a bioshield until after launch toavoid recontamination by live organisms. To pre-pare for this scientific option, it would be neces-sary to conduct any required long lead-time plan-ning and capability development in advance ofthe pertinent 2016 mission-planning decisions.The long lead-time items include technologies as-sociated with pre-launch system cleaning andsterilization; flight qualification of parts, materi-

als, and processes; and design of facilities to ac-complish the required planetary protection con-trols prior to launch.

To achieve maximum mission flexibility (i.e., totarget a special region and perform extant life-de-tection measurements), AFL mission engineeringis currently planned assuming both PlanetaryProtection Category IVb and IVc requirements.Because the mission may target a special region,the entire spacecraft (rover, payload, descentstage, aeroshell, and probably the cruise stage)would need to satisfy requirements for totalbioburden reduction comparable to those of theViking lander missions. This implies that space-craft design would include a biobarrier thatwould envelope the aeroshell and permit system-level terminal sterilization using heat (i.e.,(110°C). Full PP implementation planning forthe AFL would include many of the following:

• development and qualification of a system-level DHMR facility at Kennedy Space Center.

• development and qualification of bioshield.• system design changes to accommodate bio-

shield (i.e., thermal, propulsion, separations).• identification of hardware elements incompat-

ible with or sensitive to DHMR.• definition and qualification of DHMR-compat-

ible parts, materials, and practices.• qualification of sensitive, high-risk instruments

at card/assembly level.• qualification of sensitive, high-risk engineering

subsystems and sensors at card/assemblylevel.

• design, development, and qualification of asterile fueling and de-fueling operation.

This latter process must consider the possibil-ity that the AFL will require an RPS with the as-sociated handling and safety considerations. Allof these tasks inherently imply a possible depar-ture of the AFL system from MSL heritage.

Contamination avoidance in support of organicsor life detection

For AFL contamination control, it will be cru-cial that potential sources of prelaunch contami-nation on the landed spacecraft be identified andexcluded. This includes organic material that re-mains on the spacecraft after sterilization, as themeasurements to be made by the AFL can be cor-rupted if those remnants of the sterilization

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process (e.g., spores, terrestrial organics) producefalse positives. This would entail that the criticalpath of contamination (i.e., the path the sampletakes to the instrument) be cleaned of organic ma-terial to a level below the detection limit of all in-struments before mission launch.

Measurements that the AFL would make mustinclude appropriate methods to identify and ex-clude contamination as a source of any potentiallypositive detection. To identify potential contami-nants, instruments may be required to produceprocedural blanks that allow potential contami-nates to be identified and characterized. Thisblank analysis would be undertaken upon the be-ginning of AFL surface operations and follow thesample acquisition, handling, and processing pathto the instruments themselves. In the event of apositive detection, the procedural blanks may beused before a confirming second analysis to en-sure a blank measurement. Additionally, cross-sample contamination caused as multiple samplesare acquired and processed by the system mustbe held at a level consistent with the sensitivity ofthe selected instruments. It is anticipated that or-ganic contamination issues for the AFL will ex-ceed those addressed by the current 2009 MSLmission development effort (Mahaffy et al., 2004).

Astrobiology instrument development

The 2004 AFL SSG (Steele et al., 2004) high-lighted examples of development shortcomingsin critical areas of science instrument develop-ment. To meet the objectives as described in the2004 AFL SSG report, there must be a focused ef-fort to fund science instruments for the AFL mis-sion concept. New instrumentation techniques aswell as methods to integrate techniques are de-sired and encouraged to meet the objectives of theAFL as currently conceived. This necessitates awell-funded, well-advanced instrument develop-ment and integration program. It is expected that,in addition to MIDP (which is an element of theMars technology program), other programs suchas the Astrobiology Science and Technology In-strument Development (ASTID) and the Astrobi-ology Science and Technology for ExploringPlanets (ASTEP) programs will step in to meetthese long-term needs. Funding for this AFL in-strument development effort, regardless of theform, must be sufficiently early to enable a timelyattainment of TRL-6 (i.e., in time to support sys-tem PDR) that is consistent with the AFL devel-

opment schedule. To meet a late 2015 / early 2016launch date, as discussed earlier, the proposedAFL instrument PDRs must be in the 2012 timeframe. In addition, these instruments must be ata TRL sufficient to enable a competitive risk man-agement assessment by the NASA selection au-thority during the instrument selection process(this date is unknown, but it could be justifiedplanning for this to occur as early as fall 2010).

MSL parachute enhancement

As discussed above, the increased mass of theAFL concept payload and flight systems wouldrequire additional landed mass capabilities be-yond those provided by the MSL heritage system.Our current understanding of the science mea-surement objectives and technologies drives thisaugmentation in capability. This parachute-en-hancement technology item is an enabling capa-bility with the objective to increase the landedpayload mass by increasing the parachute diam-eter and parachute deployment Mach numberabove that necessary for the MSL. The current ex-pectation is that parachute performance increasesfor the AFL are developed and validated throughanalysis and actual MSL performance results only(i.e., only a limited parachute re-qualification pro-gram is assumed necessary).

AFL technology parking lot

As indicated above, the AFL concept is subjectto modification as the science objectives, high-level requirements, and budget for the missionare defined in the coming years. As the characterof the mission changes, the expectation is thatnew technology thrusts will be identified to meetthe changed mission objectives. Some enhancingtechnologies that fit into this category have beenidentified for the AFL and are relegated to thetechnology parking lot (i.e., are not being inte-grated into this particular concept or are notfunded in our concept cost estimates) until a spe-cific need and direction are identified. For the cur-rent AFL concept, the technology parking lot in-cludes these technologies:

• Larger-diameter (e.g., (23 m) Supersonic Para-chute: This is a high-leverage option that willsignificantly improve payload mass beyondthat of the MSL (currently baselining a 19.7 mdiameter chute) and counter the adverse effects

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of dust loading in the atmosphere associatedwith the 2016/2018 launch opportunities.Other technologies, such as inflatable aerody-namic braking devices, can also be consideredfor this application. Based on internal analysesand trades, as well as a current understandingof MSL parachute development and extensi-bility, this full development and qualificationeffort for a large-diameter parachute has beenput on a lower priority at this time. It is ex-pected that a modest diameter and capabilityenhancement beyond that of the MSL can beimplemented, following a successful MSLlanding, through analysis and simulation. AsMSL development proceeds and information isupdated, this technology prioritization assess-ment will be revisited.

• We could not identify technology currentlyavailable at (or near) TRL-6 to support acquisi-tion of (10 cm cores on the robotic arm. TheAFL SSG called for acquiring 10–30 cm cores.While it currently is unlikely that the MSL isgoing to acquire a core, this AFL concept re-quires a core delivered to the PSHPS. Develop-ment of a corer would be a high priority in fu-ture technology developments. The MTP BaseTechnology Program has been, and will con-tinue, funding technologies to access the sub-surface, including coring required for the AFL.

• The Mars 2007 Phoenix mission is flying a toolthat could be developed into a simple rock-,permafrost-, or ice-sampling system, referredto as a RASP or Rapid Active Sampling Pack-age (Peters et al., 2007). Our concept has not yetidentified the RASP as an enabling technologythat is required to support the measurementobjectives. However, since a properly devel-oped RASP could do precision sampling for theAFL PSHPS, RASP, or similar technology de-velopment for the AFL should continue to helpreduce overall mission risk. This technologyenhancement can be developed by the MTPBase Technology Program.

• The recently discovered gully regions on Marsmay be key areas of interest for AFL explora-tion. As an example, MSL landing site discus-sions indicate that gullies are located at mid-dle and polar latitudes and may be key sitesfor water and habitability science and explora-tion (Dietrich et al., 2006; Grant and Golombek,2006). The MSL will not visit these sites becauseof planetary protection and terrain access is-sues. Future AFL science analysis groups, or

science steering groups, may recommend thatthese new features be key targets for AFL ex-ploration. Although no specific terrain modelshave been identified for many of these specificareas of possible AFL interest, it is expectedthat an MSL heritage system will have diffi-culty accessing either the source or the depositsidentified from orbit (landing accuracy issuesand post-landing accessibility issues). Terraincharacterization and extreme terrain accesstechnologies may need to be pursued to enablethis specific mission option (see also pinpointlanding discussion below). The technologies toaccess extreme terrain are planned to be ad-dressed by the MTP Base Technology program.

• The Mars Program is nurturing a capability toenable a pinpoint landing technology devel-opment with the objective of achieving 100 mlanding accuracy error (99% probability). Thiscapability provides for landing at scientificallyinteresting targets unreachable with MSL-heritage landing accuracy or through rovermobility systems (Wolf et al., 2006). Assuring a hazard-free landing area as determinedthrough pre-arrival site reconnaissance andlanding accuracy analyses will determine theneed for this technology for AFL applications.The development of this capability also pro-vides feed-forward technology for a static AFLlander option that must land near specifiedtargets, such as deep-drill lander sites, or formissions retrieving samples previously cachedby an earlier mission. The SSG-derived conceptand mission objectives for the AFL have notidentified a driving requirement for pinpointlanding. Pinpoint landing requirements alsointroduce flight system design and masschanges that include the addition of an opticalnavigation sensor for precision Mars approachnavigation (and a consequent design changefrom a spinning to a 3-axis stabilized cruisestage) and larger EDL propellant tanks for re-moving and countering residual and environ-mental landing accuracy error sources, follow-ing the jettison of the descent parachute.

• Site certification and science objectives will dic-tate whether an investment in budget and, ul-timately, of spacecraft resources to enable Haz-ard Detection and Avoidance for the AFL isnecessary. There are ongoing efforts withinother NASA programs that are pursuing thistechnology (see for example Epp and Smith,2007) for earlier missions. There is a strong con-

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nection between pinpoint landing and landingsafety.

• As more and more is learned as to how to op-erate rover systems on Mars, more types ofautonomy are possible. The MER have beendriving autonomously using GESTALT, (Mai-mone et al., 2006) a stereo hazard avoidanceprogram that allows for the evasion of steepslopes and rocks. As MSL operation softwareis developed, it is hoped that recent develop-ments in single-cycle arm placement and po-tential autonomous science investigations willbe at a heritage level so as to increase the sci-entific output of the AFL (Pedersen et al., 2006;Castano et al., 2007; Estlin et al., 2007).

7. TRADES

As with any mission in Pre-Phase-A develop-ment, there are multiple trade options that arecontinually being studied and can change themission concept. These options, while originallyoutside the base mission concept, augment themission’s return and allow for greater return oninvestment. Some of the trades we have plannedor studied include the utilization of a 2 m drillthat would reduce the instrument payload, solarversus nuclear power generation, and the possi-bility of caching samples for future analysis orsample return. The augmentation that these con-cepts provide increases mission potential if moreresources become available.

Drilling

The need for subsurface access is apparentgiven current martian surface conditions. Theseconditions may result in a sterile layer that existsdown to a depth greater than 1 m (Kanavariotiand Mancinelli, 1990). To get under that poten-tial sterile layer, a 2 meter drill design is currentlybeing studied. An advantage to this drill is itsability to collect samples at 25 cm intervals, whichwill provide an opportunity to produce a map ofthe subsurface chemistry, measure the depth ofthe oxidizing layer, and determine the extent ofdestruction due to galactic cosmic rays (Kanavar-ioti and Mancinelli, 1990; Kminek and Bada, 2006;Dartnell et al., 2007). As with any trade, the in-clusion of the drill would come at the monetaryand mass expense available for other payload el-ements. While the payload monetary costs are

something that can be estimated, the cost to otherpayload elements is something that needs futurediscussion. The inclusion of a drill presents apackaging problem with the current rocker-bogietype rover system. The only attachment point fora drill may be where the fully instrumented IDDwith corer is currently located, away from thecurrent mast location (Fig. 15). Hence, the pay-load cost of the drill may be the exclusion of aninstrumented robotic arm (IDD) that can thor-oughly investigate surface features. Therefore,before a drill can be included in the payload, ascientific debate will have to take place to decidewhich acquisition apparatus maximizes the sci-ence return for the AFL. Other locations wherethe drill could be included are near the “back” ofthe rover, near a potential RPS. In this scenario,it is unclear how sample transfer would takeplace and if there would be any sample alterationdue to the location of a potential RPS.

Sample caching

The possibility that the AFL will make a majordiscovery related to Mars habitability and poten-tial biosignatures may require a follow-on mis-sion to confirm or validate results from the AFLmission. One way to accomplish this would be tocache samples that have been analyzed by theAFL payload, retrieve them in a future MSR mis-sion, and bring them back to Earth for analysis instate-of-the-art laboratories. This scenario greatlyreduces the potential cost of MSR because theMSR rover would be less complex than a roverthat would be required to perform complex sam-ple acquisition and initial analysis to maximizethe probability of returning the highest-prioritysample (Mattingly et al., 2004). Individual samplecontainers would have to be sealed to preventcross-sample contamination and degradation ofsamples as a result of exposure to the martian sur-face environment. These containers could eitherbe dropped on the martian surface or stored onthe rover for later retrieval. Designs for thecaching concept have been developed, but aworking system needs to be developed anddemonstrated (Backes and Collins, 2007). MSL iscurrently considering a design for a samplecaching system for inclusion in the 2009 mission.

Solar power versus nuclear power

Our preliminary designs made the assumptionthat the conditions that resulted in the MSL be-

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ing designed as a RPS-powered rover may alsoexist for the AFL. As a proof of concept, instru-ment power profiles for AFL were determined tofit with the MSL RPS capability envelope. As thescience and technology objectives and engineer-ing constraints for the AFL concept are furtherdefined, there will necessarily be a rigorous tradeanalysis for the power system.

8. COSTS

The MEP encompasses all NASA Mars roboticmission activities and data analyses with regardto understanding Mars and its evolution, and di-rectly supports NASA’s Vision for Space Explo-ration. As described in the Mars Exploration Pro-gram Plan (Beaty et al., 2006; McCleese, 2006), itis a science-driven, technology-enabled effort tocharacterize and understand Mars. The AFL mis-sion is a concept that meets strategic objectives ofNASA and MEP, and a key part of an integratedset of missions that are mutually supporting andworking toward the program’s scientific goals.The AFL concept described here is a facility-classmission and is not merely a re-flight of the MSL.At a minimum, this mission concept as definedhere carries a more sophisticated and astrobiol-ogy-focused science payload, a more complexsample acquisition and processing payload, amore challenging EDL environment, and a muchmore challenging organic contamination and PPprotocol than that of the MSL (one that is cur-rently assumed to include full system DHMR,similar to that performed by Viking). However,this AFL concept is also leveraging a tremendousamount of flight system development heritagefrom the MSL that offers significant developmentsavings over a non-heritage system concept. Thenet effect is that this facility-class mission tendstoward a cost expectation consistent with anMSL-class development effort ($1–2 billionrange). This is a key consideration in planning therelative timing of missions in the 2016/2018 time-frame, as illustrated in Fig. 1.

ACKNOWLEDGMENTS

The research described in this paper was car-ried out at the Jet Propulsion Laboratory, Cali-fornia Institute of Technology, under a contract

with the National Aeronautics and Space Ad-ministration. This paper has been cleared for pub-lic U.S. and foreign release by JPL document re-view services under clearance number CL#07-0985. The authors have drawn upon a wealthof material produced by other projects and ac-tivities and wish to acknowledge their contribu-tions. These include a tremendous input from theMSL project and the AFL 2004 SSG, as well ascontributions from MER, MRO, the Mars Explo-ration Program Office, Karen Buxbaum, DavidBeaty, Samad Hayati, Sylvia Miller, MEPAG, andJPL Team-X. We wish to thank Sherry Cady andChris McKay for critical editorial comments thatimproved the overall quality of the paper. A spe-cial thanks to Richard Barkus for the illustrationof the AFL mission, to Judy Greenberg for ad-ministrative support, and to Kirsten Badaraccofor account management. Any opinions, findings,and conclusions or recommendations expressedin this paper are those of the authors and do notnecessarily reflect the views of the National Aero-nautics and Space Administration, the Mars Ex-ploration Program, or the Jet Propulsion Labora-tory.

ABBREVIATIONS

AFL Astrobiology Field LaboratoryAO Announcement of OpportunityARR ATLO Readiness ReviewASTEP Astrobiology Science and Technol-

ogy for Exploring PlanetsASTID Astrobiology Science and Technol-

ogy Instrument DevelopmentATLO Assembly, Test, Launch, OperationsC3 Launch Energy (Earth departure V-

infinity, squared)CBE Current Best EstimateCDR Critical Design ReviewCheMin Chemistry and Mineralogy (MSL In-

strument)COSPAR Committee on Space ResearchCY Calendar YearDAP Declination Arrival AsymptoteDHMR Dry Heat Microbial Reduction (sys-

tem level sterilization technique)DLA Declination of the Launch Asymptote

(Earth departure hyperbola)EDL Entry, Descent and LandingEIS Environmental Impact StatementEM Engineering Model

ASTROBIOLOGY FIELD LABORATORY 573

FM Flight ModelGC/MS Gas Chromatograph/Mass Spec-

trometerGESTALT Grid-based Estimation of Surface

Traversability Applied to Local Ter-rain (rover navigation software)

IDD Instrument Deployment DeviceJPL Jet Propulsion LaboratoryLs Areocentric Longitude of the SunMCR Mission Concept ReviewMEP Mars Exploration Program (NASA)MEPAG Mars Exploration Program Analysis

GroupMER Mars Exploration Rovers (Spirit and

Opportunity)MEx Mars Express (European Space

Agency)MGS Mars Global Surveyor (non-opera-

tional)MIDP Mars Instrument Development Pro-

gram (NASA, MTP)MOLA Mars Orbiter Laser Altimeter (MGS

instrument)MRO Mars Reconnaissance OrbiterMSL Mars Science LaboratoryMSO Mars Science Orbiter (2013 Launch)MSR Mars Sample ReturnMTP Mars Technology Program (NASA)NASA National Aeronautics and Space Ad-

ministrationNEPA National Environmental Policy ActNRA NASA Research AnnouncementODY Mars OdysseyPBE Predicted Best Estimate (includes

growth uncertainty)PIDDP Planetary Instrument Definition and

Development ProgramPDR Preliminary Design ReviewPMSR Preliminary Mission And System Re-

viewPP Planetary ProtectionPSHPS Precision Sample Handling and Pro-

cessing SystemPSR Pre-Ship ReviewRASP Rapid Active Sampling PackageRAT Rock Abrasion ToolRLA Right Ascension Launch Asymptote

(Earth departure hyperbola)ROD Record of Decision (NEPA process)ROSES Research Opportunities in Space and

Earth Sciences (NASA)RPS Radioisotope Power System

SAM Sample Analysis at Mars (MSL in-strument)

SAR Safety Analysis ReportSSG Science Steering GroupTRL Technology Readiness Level (Levels

1–9 represent a qualitative assess-ment of technology readiness forspaceflight. For example, TRL-6 indi-cates that the system validationmodel has been successfully demon-strated in a relevant environment)

VHP Arrival V-Infinity (hyperbolic excessvelocity)

XRD X-Ray DiffractionXRF X-Ray Fluorescence

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