IAC–08–A3.6.9

MISSION ARCHITECTURE AND TECHNOLOGY OPTIONSFOR A FLAGSHIP CLASS VENUS IN SITU MISSION

Tibor S. Balint, Johnny H. Kwok, Elizabeth A. Kolawa, James A. Cutts & David A. SenskeJet Propulsion Laboratory, California Institute of Technology

4800 Oak Grove Drive, M/S 301–170U, Pasadena, CA 91109–8099e-mail: tibor.balint@jpl.nasa.gov

ABSTRACT

Venus, as part of the inner triad with Earth and Mars, represents an important exploration target ifwe want to learn more about solar system formation and evolution. Comparative planetology couldalso elucidate the differences between the past, present, and future of these three planets, and canhelp with the characterization of potential habitable zones in our solar system and, by extension,extra–solar systems. A long–lived in situ Venus mission concept, called the Venus Mobile Explorer,was prominently featured in NASA’s 2006 SSE Roadmap and supported in the community WhitePaper by the Venus Exploration Analysis Group (VEXAG). Long-lived in situ missions are ex-pected to belong to the largest (Flagship) mission class, which would require both enabling andenhancing technologies beside mission architecture options. Furthermore, extreme environmentmitigation technologies for Venus are considered long lead development items and are expected torequire technology development through a dedicated program. To better understand programmaticand technology needs and the motivating science behind them, in this fiscal year (FY08) NASA isfunding a Venus Flaghip class mission study, based on key science and technology drivers identi-fied by a NASA appointed Venus Science and Technology Definition Team (STDT). These missiondrivers are then assembled around a suitable mission architecture to further refine technology andcost elements. In this paper we will discuss the connection between the final mission architectureand the connected technology drivers from this NASA funded study, which — if funded — couldenable a future Flagship class Venus mission and potentially drive a proposed Venus technologydevelopment program.

INTRODUCTION

As discussed in the Solar System ExplorationDecadal Survey [1] by the National ResearchCouncil (NRC) of the National Academies,Venus represents an important exploration tar-get, which can help us to learn more aboutthe formation and evolution of our solar sys-tem, and by extension, other extra–solar sys-tems. Comparative planetology between Venus,Earth, and Mars could also elucidate the differ-ences between the history and evolution of theseplanets, thus, for example, help constrainingour models of potential habitable zones and thegreenhouse effect. In response to these goals,both NASA’s 2006 Solar System Exploration(SSE) Roadmap [2] and the community White

Paper by the Venus Exploration Analysis Group(VEXAG) [3], prominently featured a long–livedVenus in situ mission concept, called the VenusMobile Explorer (VME).

Due to its complexity and projected cost, VMEbelongs to the Flagship (largest) mission classfor solar system exploration. Strategic Flagshipclass missions are usually directed by NASA andlarger in their scope, with a projected cost capbetween ∼$1.5B and $3B. Smaller Discovery and(Mars) Scout class, and medium class New Fron-tiers missions — capped at ∼$425M–$475M forthe former (with launch vehicle), and ∼$650M(without L/V) for the latter, respectively — arecompetitively selected through periodic NASAAnnouncements of Opportunity (AO).

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Technology planning for Flagship class missionsis reasonably well defined and constrained withinmission development phases, and the missionimpacts are well understood. (In comparison,Discovery and New Frontiers missions are typ-ically planned an opportunity ahead and witha significantly lower cost cap, which may in-troduce limitations to technology development.)Relevant technologies for extreme environmentmitigation were assessed and reported in [4]. Inaddition, the Science Mission Directorate (SMD)Science Plan [5] also identified technologies forextreme environments, as high–priority systemstechnologies needed to enable exploration of theouter solar system and Venus.

Since long–lived Venus in situ missions are sig-nificantly affected by the extreme environmentof Venus, and the development of relevant tech-nologies may take longer than for missions toother planetary targets, in FY’08 NASA ini-tiated a mission study with an explicit goalof identifying and assessing a science drivenFlagship mission architecture and its technologydrivers. As a deliverable, the NASA appointedVenus Science and Technology Definition Team(STDT) was tasked to deliver a final reporton a recommended point design and to derivea related technology plan, which could lead totechnology investment over the next decade, andconsequently enable a potential Venus flagshipmission in the 2020–2025 timeframe.

Although the study is still ongoing, this paperaddresses relevant Flagship class mission archi-tecture concepts and related technologies for anin situ mission to the extreme environments ofVenus.

EXTREME ENVIRONMENTS

Proposed in situ missions to Venus could en-counter some of the most hostile environmentsin our solar system. Environments are con-sidered “extreme,” if they present extremes inpressure, temperature, radiation, and chemi-cal or physical corrosion. In addition, certainplanned missions would experience extremes inheat flux and deceleration, leading to their in-clusion as missions in need of technologies for

extreme environments.

At Venus, the super rotating atmosphere con-sists mainly of carbon dioxide (CO2 ∼96.5%)and nitrogen (N2 ∼3.5%), with small amounts ofnoble gases (e.g., He, Ne, Ar, Kr, Xe) and smallamounts of reactive trace gases (e.g., SO2, H2O,CO, OCS, H2S, HCl, SO, HF). The cloud layeris composed of aqueous sulphuric acid dropletsbetween the altitudes of ∼45 km and ∼65 km.The zonal winds near the surface are ∼1 m/s,increasing up to ∼120 m/s at an altitude of ∼65km. Due to the greenhouse effect, the surfacetemperature reaches ∼460◦C to 480◦C. The av-erage surface pressure can be as high as ∼92bars. (Pressure, temperature and wind condi-tions as a function of altitude are illustrated inFigure 1.) At these conditions near the surface,the CO2 becomes supercritical, which could fur-ther complicate missions planned to explore thisregion. Furthermore, the dense atmosphere isexpected to introduce significant entry heatingand potentially high g–loads for the aeroshelland for the in situ elements it carries.

From a technology point of view it is also impor-tant to point out that Jupiter and Saturn DeepEntry Probes at a 100 bars pressure elevationwould experience similar coupled high pressureand temperature conditions, as those for Venusin situ missions near the surface.

Therefore, mission architectures and relatedtechnologies must address ways to mitigate theseenvironmental conditions.

STUDY OBJECTIVES

At the beginning of this fiscal year (FY’08)NASA HQ formed the Venus STDT and taskedit to address six objectives for a Venus Flagshipclass mission study, with support provided byJPL. Specifically:

1. To develop and prioritize science goals,investigations and measurements, whichare consistent with the recommendationsof the NRC Decadal Survey [1], and theVEXAG community White Paper [3];

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2. To identify suitable mission architec-tures and related instrument capabilities,through assessing their performance, cost,risk drivers and technology readiness;

3. To identify technology investment areasand maturation schedule required to sup-port potential mission architectures in the2020–2025 timeframe;

4. To assess and identify potential precursorobservations and technology validation ex-periments that could be implemented ona prior medium class New Frontiers Venusmission, that could enable or enhance a fu-ture Flagship class mission;

5. To chart a path from proposed New Fron-tiers and Flagship class missions to a po-tential Venus Surface Sample Return Mis-sion; and

6. To document the findings in a final studyreport and in a technology developmentplan that NASA HQ could utilize for po-tentially developing a Venus TechnologyProgram.

ASSUMPTIONS

The mission architecture trade–space for thisFlagship class mission study was constrained byNASA HQ by a number of given assumptions,as described below. The launch period was as-sumed between 2020 and 2025. The life cyclemission cost range — or cost cap — was setbetween $3B and $4B (in FY’08 dollars). Thelaunch vehicle (L/V) for a single launch optionwas limited to a Delta IV-H L/V or smaller, andfor a dual launch option to two Atlas V-551 orsmaller. For telecommunications it was assumedthat the Deep Space Network (DSN) would beavailable to support the mission with a 34 m an-tenna, and including Ka band. In addition, theimpact of optical communication on the missionperformance could be also considered. Regard-ing technology maturation, the instruments andsystems would have to be at least at a Tech-nology Readiness Lever (TRL) of 6. While inthis particular study international collaborationis not considered, it is likely that by the timethis mission becomes reality it could morph into

an international mission, in the same fashion asCassini–Huygens and the proposed Outer PlanetFlagship Mission (OPFM) targeting either Ti-tan or Europa are.

METHODOLOGY

In this section we describe the methodology usedby the Venus STDT and the JPL Study Teamto derive a final mission architecture for a pointdesign [6]. The assessment process is furtherillustrated in Figure 2.

Science Figure of Merit Process

Since NASA’s missions are predominantly sci-ence driven, the science members of the STDTtook the VEXAG community White Paper [3]as a starting point for a list of science goals, ob-jectives and measurements. The STDT then re-grouped these investigations to eliminate dupli-cations, and updated their prioritizations. Thescience measurements were also assigned to mis-sion architecture elements (which are definedlater). Then, a simple Figure of Merit (FOM)was constructed for each investigation and plat-form combination, using the formula of

FOMs = 5− P ×G

where P is the priority; and G is goodness. Thepriority ranking represented the scientific rank-ing of a given investigation and was assigned anumerical value between 1 and 4. If the investi-gation was considered essential, it was given pri-ority (1), while highly desirable; desirable; andvery good to have; were assigned (2), (3), and(4), respectively. The goodness value, summedfor each instrument or measurement technique,yielded a science value against a given missionscience goal. The assigned values scaled up-wards from 0 to 3. For these instrument andplatform goodness scores (0) was assigned if aninvestigation was not addressed; (1) was givenfor minor contribution or supporting observa-tion; (2) for major contribution; and (3) fordirectly answering an investigation. Summingup these FOM values for each platform providedan overall FOM for that platform. Higher FOMrepresented higher science return.

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Technology Figure of Merit Process

In parallel to the science FOM, a technologyFOM was also constructed by the technologymembers of the STDT for each mission archi-tecture element, using the formula of

FOMt =C

M

where C is technology criticality and M is tech-nology maturity. For criticality the ranking from0 to 3 meant: not needed; useful; desirable; andmust have. Similarly, maturity was defined onthe basis of Technology Readiness Levels (TRL),and ranked from 0 to 3, representing TRL rangesfrom TRL 1–2 for (0); TRL 3–4 for (1); TRL5–6 for (2); and TRL 7–9 for (3). Criticalitywas assessed by the mission architecture teambased on mission impact, while maturity valueswere assigned by the STDT technology sub-group. Higher FOM meant higher technologydevelopment requirements. While the technol-ogy FOM did not impact the science drivenselection of mission architectures, it gave an in-dication about how much technology needs tobe developed to achieve them.

Mission Architecture Elements

As discussed above, the STDT established sci-ence and technology FOMs and mapped themagainst 13 mission architecture elements, whichare listed and defined in Table 1. (The table alsoshows the corresponding science and technol-ogy FOMs, discussed above, and the estimatedmission architecture element costs, discussedbelow.) These mission architecture elements in-cluded an orbiter or flyby spacecraft and a setof in situ platforms from which science measure-ments could be taken. In situ mission elementcomplexities varied from a simple descent probeto a highly complex near surface mobile aerialplatform with long traverse and periodic accessto the surface. The STDT also differentiated be-tween a single element and multiple elements ofthe same kind, since the latter could significantlyenhance science by performing synergistic mea-surement at different locations. Mission lifetime— short or long — was an important differen-tiator. On one hand long lifetime enabled a long

observation platform, on the other it introducedsignificant technology challenges, thus increas-ing mission cost and complexity.

These platforms were then used to assemblea broad range of multi–element Flagship classmission architectures within the assumed costrange, while carrying out science investigationsat a significantly higher scope than achievableby smaller New Frontiers or Discovery class mis-sions.

Rapid Cost Assessment Process

Approximate mission costs were estimated bythe mission architecture team at JPL, using arapid cost assessment method, which was cus-tomized for Venus missions. This approach wassuccessfully used during NASA’s SSE Roadmap[2] process, and documented in [7].

For each Venus mission architecture concept,a set of cost drivers were established, identi-fying key capabilities that a mission would re-quire to achieve its objectives. The three identi-fied primary cost driver categories included (1)launch operations; (2) flight systems; and (3)mission operations. Additional categories ac-counted for (a) the operating environment; (b)technologies; (c) flight heritage from past mis-sions; and (d) technology feed forward to futuremissions. These categories were set to dividepotential missions into distinct categories andnon–overlapping and comprehensive cost con-tributors. This ensured a detailed accountingof the various mission cost contributors, whileeliminating potential double counting of thesefactors.

Each applicable cost driver was then associatedwith a cost driver index, acting as a measure forthe overall magnitude of the perceived complex-ity. Cost driver indices were allocated based onan arbitrary five level exponential scale, whereLevels 1 to 5 were assigned points from 21(= 2)to 25(= 32).

Using these definitions, the rapid cost assess-ment process consisted of four steps:

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1. Establishing a Reference Mission Set:which included (a) identifying historicreference missions (e.g., MER, Stardust,Viking, Galileo, Cassini-Huygens); (b) as-signing cost indices to each cost driver;(c) summing the cost indices; (d) plottingthem against historic mission costs; and(d) calculating the slope of the curve fitover the data set.

2. Calculating cost indices for each of the13 Venus mission architecture element (seeTable 1).

3. Identifying new Venus Flagship class ar-chitectures, by combining multiple missionarchitecture elements until the target costcap (between $3B and $4B) is reached.This assumed cost cap also included 10%allocation for science payload.

4. Estimating costs for these mission archi-tectures, from the slope of the referencemissions multiplied by the cost indices.

It was found that this approach could predictrelative mission costs between the various archi-tectures when the missions are still in their pre-liminary study phase and not yet fully defined.However, this method should be used for scop-ing only and not to replace higher fidelity meth-ods, such as parametric costing or a grass rootmethod. The estimated accuracy of the rapidcost assessment is ∼10%–20% for relative costs,and ∼30%–40% for absolute costs. Therefore, amore accurate cost estimation is still required ata later phase of the study.

MISSON ARCHITECTURES

In this section we provide an overview of typ-ical Venus mission architectures, followed by adiscussion on the STDT recommended missionarchitecture, which will serve as the basis for adetailed point design that will be performed bythe JPL Study Team.

Selecting the most optimal mission architectureis a multi–disciplinary effort, because it has toaccount for targeted science investigations byselecting a suitable payload; it has to employappropriate technologies which are relevant to

the operating environments and measurementrequirements; and it has to address program-matic considerations, including cost caps, mis-sion development phases, and phasing betweenmissions.

To date, a significant number of Venus missionswere either flown or proposed, including missionarchitectures from orbiters to probes, balloonsand landers, as shown in Table 3. While themission architecture elements on these missionsare found to be similar to potential future mis-sions, the main differences will be accounted forthrough the payloads in support of the sciencequestions they will target to answer. Therefore,these example architectures are not expected tocover the full mission architecture trades space,instead, they try to demonstrate the flexibilityof how future mission concepts can be formu-lated in support of science.

Potential future missions can also vary in sizeand scope as well, from Discovery to Flagshipclass missions for NASA, although this study fo-cuses on Flagship class architectures only. Otherspace agencies are also proposing missions to ex-plore Venus. Under ESA’s Cosmic Vision Pro-gram [8] an ESA lead team proposed a multi–element international mission, called the Euro-pean Venus Explorer, or EVE [9]. Although itwas not selected, it received high ranking fromthe selection committee and will likely be re–proposed for a potential launch after 2020. Themission concept for EVE included a Europeanorbiter and cloud level balloon, a Russian shortlived lander, and potentially a mid–level balloonunder the cloud deck by the Japanese AerospaceExploration Agency. JAXA is also planning tolaunch an orbiter in 2010, called Planet–C orVenus Climate Orbiter (VCO). [10]

Returning to the current study, the STDT andthe JPL Study Team identified 17 multi–elementmission architectures that would fit within theassumed cost cap of the a Venus Flagship mis-sion. Among these architectures, three wererecommended by the STDT science subgroups,one each, and a forth one which was jointly pro-posed by the STDT. The science and technologyFOMs and estimated costs for these four archi-

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tectures are shown in Table 2. The STDT alsofound that single element architectures, such asa near surface mobility platform alone, cannotanswer all of the key science questions for Venus,and thus were not selected for this year’s study.

Recommended Mission Architecture

It is evident from Table 2 that the STDT recom-mended multi–element mission architecture hasthe highest science FOM, and provides flexibilityfor payload accommodation on the various mis-sion architecture elements. This allows for scal-ability in response to mission cost cap changes,and could lend itself to international collabora-tion in the future. In addition, this architecturesupports synergies between measurements andscience, therefore, further increasing the sciencereturn from the mission.

Specifically, the recommended architecture in-cludes a highly capable orbiter with a designlifetime of ∼4 years; two cloud level super–pressure balloons floating at a constant altitudebetween 52 and 70 km with a design lifetime of1 month; and two landers which would also per-form science measurements during atmosphericdescent. The baseline architecture called forshort lived landers, because most of the landedscience could be carried out during the expected5–10 hours period. However, two instruments— a seismometer and a meteorology station —operating for up to ∼243 days (i.e., Venus’ side-real rotation period, or length of day), couldsignificantly enhance the science return. There-fore, the feasibility of long lived elements on theshort lived landers will be assessed as part of thestudy. This, however, should be evaluated in theframework of its full mission impact, includingnot only science, but also mission cost, technol-ogy development requirements, complexity andrisk.

The proposed mission architecture would includetwo launches. The study baselined launches in2021, ∼6 months apart, although backup launchoptions are available in every 19 months (in 2022and 2024) due to orbital phasing between Venusand Earth. Each of the two Atlas V–551 launchvehicles could deliver up to ∼5500 kg mass to

Venus. The carrier spacecraft with two Venusentry systems, each accommodating a balloonand a lander, would be launched in late April,2021, on a Type IV trajectory, and arrive atVenus after a 456–days cruise in late July, 2022.The two aeroshells would be released from thecarrier 20 and 10 days before arrival, targetingtheir predetermined entry and landing sites onthe day side of Venus. This was required byscience, in order to allow for imaging during de-scent and after landing. During the flyby, thecarrier spacecraft could be equipped to providebackup telecom support from the landers andballoons, and confirmation that the entry wassuccessful. The orbiter would be launched inlate October, 2021, on a Type II trajectory, andwould arrive to Venus in early April, 2022, fol-lowing a 159–days cruise. This earlier arrivalwould provide sufficient time for the orbiter toset up a 300 km × 40000 km elliptic orbit, withthe apoapse optimized for up to ∼5–6 hours ofcontinuous visibility of the in situ elements (asa function of their landing location).

Following atmospheric entry, the entry, sepa-ration, then the descent and inflation for theballoon, and the descent and landing for thelander, would follow similar steps and timelinesas those of the historic Russian VeGa missions.The balloons could deploy in about 15–20 min-utes and start operating. The landers wouldtake ∼1–1.5 to descend, while performing de-scent science. This would be followed by surfaceoperations, while communicating the data tothe orbiter. After completing in situ sciencesupport, the obiter would circularize its orbit at∼300 km, and begin its own long science phase.

A preliminary payloads for these platforms wererecommended by the STDT, based on the high-est priority science objectives and measure-ments. Notional payloads for the three missionarchitecture elements (orbiter, balloons and lan-ders) are provided in Table 3.

Because the study is still ongoing, this paperonly addressed generic features of the concept.Full details on the proposed mission architec-ture, operating scenarios, and data rates and vol-umes for the point design will be provided in the

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final report.

TECHNOLOGIES

Preliminary results indicate that the proposedscience driven mission architecture has a lowtechnology FOM, which means that the base-line configuration may not introduce significanttechnology challenges. It is also expected thatfor this configuration all instruments could bebrought to at least TRL 6 before 2015 (i.e., 5years before the earliest assumed launch date).

In the second phase of the study, the STDTwill address enabling and enhancing technolo-gies for instruments, components, and subsys-tems, based on the point design, and documentthe findings in a technology development plan.

Technologies can be divided into two major sub-groups, such as,

• Technologies for science measurements: in-cluding instrument operation; sample pro-cessing; data acquisition; etc., and

• Technologies for operations and surviv-ability: of subsystems on architectureelements, including thermal mitigation;power; telecom; command and data han-dling; mobility; etc.,

Specifically, technologies for science measure-ments address aspects of instrument designs tooperate in extreme environments, and opera-tional constraints to perform a desired sciencemeasurement. For example, silicon based elec-tronics can’t operate at Venus surface temper-atures and should be protected in a thermalenclosure, while certain imagers may require ac-tive cooling of the focal plane to perform theirmeasurements.

Technologies for operations and survivability aretypically coupled with suitable system architec-ture approaches.

System architecture approaches could include:

• Full tolerance: where components are de-signed to survive the extreme environ-ments. Full tolerance might not be tech-

nically feasible, since some of the compo-nent can’t be developed to operate at 460◦C and 92 bars.

• Full protection: where components wouldbe placed inside a protective environment(e.g., to mitigate pressure and temper-ature). Full protection could be pro-hibitively expensive to develop, and mightnot be practical either, since the missionarchitecture requires components, such assensors, sample acquisition systems, to beplaced outside of the thermally controlledpressure vessel.

• Hybrid system: is where some of thecomponents would be protected and somewould be tolerant. For the Venus landersof this study a hybrid system approach isrecommended as it combines the benefitsfrom the other two approaches.

In general, it is expected that any lander config-uration would require technology developmentfor pressure and temperature mitigation andsample acquisition and handling.

While the landers in the baseline mission ar-chitecture could utilize passive thermal man-agement, the long lived elements would likelyrequire active thermal control (cooling) coupledwith a Venus specific Radioisotope Power Sys-tem (RPS). If implemented, it could increasethe lifetime of the landers or parts of the landedelements from several hours to weeks or months,therefore, it could significantly increase the sci-ence return. However, due to the low TRL ofthis technology, the full mission impact shouldbe carefully assessed.

Beside the landers, the recommended architec-ture also includes cloud level balloons. Othermission architectures could use aerial mobilityplatforms at lower altitudes and near the surface.Since extreme environment conditions and thetechnology difficulty to mitigate them increasewith the decrease of altitude and the increase ofmission lifetime, these aerial platforms shouldbe specifically designed to address these specificconditions, as discussed in [11].

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A general overview of Venus related extreme en-vironment technologies is given in [4] and [12].

CONCLUSIONS

In the first phase of the Venus Flagship study theNASA HQ appointed Venus Science and Tech-nology Definition Team assessed science goals,objectives and measurements, potential technol-ogy needs, and the relevant Figures of Meritsfor both science and technology. These factors,cross referenced with estimated mission costs,pointed to a mission architecture that includedan orbiter, two cloud level balloons and two lan-ders. This recommended mission architectureprovided the highest science FOM, with a rela-tively modest technology requirement, and thus,the basis for a point design in the second phaseof the study. The orbiter and the two balloonswere baselined for operational lifetimes of 4 yearsand 1 month, respectively. The two landers werebaselined to operate for about 5 to 10 hours onthe surface, but an option was also identifiedwhere a long lived element could operate for upto∼243 days, while performing seismometry andmeteorology observations.

FUTURE WORK

In the second phase of this still ongoing VenusFlagship study the JPL Study Team will carryout a point design on the STDT recommendedmission architecture. Beside documenting thefindings, the STDT will also recommend a tech-nology development plan to enable such a flag-ship mission. The technology plan is expectedto reach beyond the point design, in order toprovide sufficient flexibility for enabling a futureflagship architecture, which might be differentfrom the architecture recommended here. Whilethis architecture represents the current best es-timate for a flagship mission concept, future ar-chitecture changes could reflect possible shifts inscience focus, for example, in response to poten-tial precursor Discovery and/or New Frontiersmissions, or to NRC recommendations from asoon to be updated Decadal Survey. Further-more, findings from this study may point to afollow up study next year, where additional flag-ship architectures could be addressed to broadenour understanding of potential science returns

from various configurations, and to augment thetechnology development plan. The final studyreport could also provide an important input tothe next Decadal Survey.

ACKNOWLEDGMENTS

The authors of this paper wish to thank all mem-bers of the Venus Science and Technology Defi-nition Team (STDT), and the JPL Study Team,whose contribution to the Venus Flagship mis-sion study provided the basis for this paper. TheSTDT is divided into three science subgroupsand a technology subgroup. The AtmosphericSubgroup included: David Grinspoon (DMNS)[lead]; Mark Bullock (SWRI) [STDT Chair]; An-thony Colaprete (NASA ARC); Sanjay Limaye(U.of Wisconsin); George Hashimoto (KobeU., Japan); Dimitri Titov (ESA); Eric Chas-sefiere (U. of Nantes–France); Hakan Svedhem(ESA). The Geochemistry Subgroup included:Allan Treiman (LPI) [lead]; Steve Mackwell(LPI); Natasha Johnson (NASA GSFC). TheGeology and Geophysics Subgroup included:Jim Head (Brown University) [lead] and DaveSenske (JPL) [STDT Co-chair] . The Technol-ogy subgroup included: Elizabeth Kolawa (JPL)[lead]; Viktor Kerzhanovich (JPL); Gary Hunter(NASA GRC); and Steve Gorevan (HoneybeeRobotics). Ex Officio: Ellen Stofan (VEXAGChair) and Tibor Kremic (NASA GRC). TheJPL Venus Flagship Study Core Team consistedof Johnny Kwok and Jeff Hall (consecutive studyleads); Tibor Balint (mission lead); Craig Peter-son (rapid costing); Tom Spilker (architectures);and Ted Sweetser and Stacia Long (trajectories).NASA and JPL study sponsors were: AdrianaOcampo (NASA HQ) and Jim Cutts (JPL).

This work was performed at the Jet PropulsionLaboratory, California Institute of Technology,under contract to NASA. Any of the opinions,findings, and conclusions or recommendationsexpressed in this paper are those of the authorsand do not necessarily reflect the views of theNational Aeronautics and Space Administration.

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REFERENCES

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[2] SSE Roadmap Team. Solar System Explo-ration – This is the Solar System Explo-ration Roadmap for NASA’s Science Mis-sion Directorate. Technical Report JPLD-35618, National Aeronautics and SpaceAdministration, Washington, D.C., August2006.

[3] VEXAG. Venus Exploration AnalysisGroup. http://www.lpi.usra.edu/vexag/,August 2008.

[4] E.A. Kolawa, T.S. Balint, G. Birur,E. Brandon, L. Del Castillo, J.L. Hall,M. Johnson, R. Kirschman, R. Manvi,M. Mojarradi, A. Moussessian, J. Patel,M. Pauken, C. Peterson, J. Whitacre,E. Martinez, E. Venkapathy, P. Newdeck,and Okajie R. Extreme Environment Tech-nologies for Future Space Science Mis-sions. Technical Report JPL D-32832, Na-tional Aeronautics and Space Administra-tion, Washington, D.C., September 2007.

[5] NASA-SMD. Science Plan for NASA’s Sci-ence Mission Directorate 2007–2016. Tech-nical report, National Aeronautics andSpace Administration, Washington, D.C.,May 2007.

[6] M.A. Bullock, D. Senske, and J.H. Kwok.Venus Flagship Study — Interim Brief-ing. Presentation at NASA HQ, SMD–Planetary Science Division, May 2008.

[7] C. Peterson, J. Cutts, T. Balint, andJ. Hall. Rapid Cost Assessment of SpaceMission Concepts through application ofComplexity–Based Cost Indices. In IEEEAerospace Conference, number IEEEACpaper #1632, Big Sky, Montana, March2008.

[8] ESA. Cosmic Vision, Space Science for Eu-rope 2015–2025. Technical Report ESA BR-247, October 2005.

[9] E. Chassefiere, O. Korablev, T. Imamura,K. H. Baines, C.F. Wilson, D.V. Titov,K.L. Aplin, T. Balint, J.E. Blamont, C.G.Cochrane, Cs. Ferencz, F. Ferri, M. Gerasi-mov, J.J. Leitner, J. Lopez-Moreno,B. Marty, M. Martynov, S. Pogrebenko,A. Rodin, J.A. Whiteway, L.V. Zasova,J. Michaud, R. Bertrand, J.-M. Charbon-nier, D. Carbonne, P. Raizonville, andand the EVE team. European VenusExplorer (EVE): an in-situ mission toVenus. Experimental Astronomy, ESA Cos-mic Vision - CV07 special issue, (ISSN0922-6435 (Print) 1572-9508 (Online); DOI10.1007/s10686-008-9093-x), 2008.

[10] M. Nakamura and Planet-C project team.Present status of Venus Climate Orbiter(Planet-C). In 37th COSPAR Scientific As-sembly, Symposium C31: Planetary Atmo-spheres, Montreal, Canada, July 2008.

[11] J.A. Cutts, T.S. Balint, J.L. Hall,V. Kerzhanovich, J. Jones, E.A. Ko-lawa, and J. Nott. Technology Challengesfor Exploration of Planets with AerialPlatforms. In 37th COSPAR ScientificAssembly, Symposium B06: Scientificinvestigations from Planetary Probes andAerial Platforms, Montreal, Canada, July2008.

[12] J.A. Cutts, T.S. Balint, E. Chassefiere, andE.A. Kolawa. Chapman Monograph – Ex-ploring Venus as a Terrestrial Planet, chap-ter Chapter 13: Technology Perspectives inthe Future Exploration of Venus. Booksand Monographs. AGU, ISBN 978-0-87590-441-2 edition, 2007.

[13] T.S. Balint, J.A. Cutts, and J.H. Kwok.Overview of Flagship Class Venus MissionArchitectures. In 6th International Plane-tary Probe Workshop (IPPW–6), Atlanta,GA, June 2008.

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Figure 1: Pressure, temperature and wind conditions at Venus

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Figure 2: Flowchart for the Venus STDT Figure of Merit (FOM) process

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Table 1: Mission architecture elements, FOMs, and cost estimates.

ArchitectureElement

DescriptionScienceFOM

Tech.FOM

Costest.

OrbiterSelf–evident, but can dip into the exospherefor in situ sampling

177 0 $0.48B

High–LevelAerial

Altitude >70 km, above clouds 169 3 $0.55B

Mid–LevelAerial

Altitude 52–70 km, in clouds (about the samealtitude as the VeGa balloons)

191 3 $0.91B

Low–LevelAerial

Altitude 15–52 km, below clouds, limited viewof surface due to attenuation

176 14 $1.4B

Near–SurfaceAerial

Altitude 0–15 km, NIR imaging of surface ispossible, no surface access

170 20 $2.1B

Single EntryProbe

No surface access, descent science only 136 2 $0.51B

Multiple EntryProbes

No surface access, descent science only 171 2 $0.54B

Short–LivedLander

Single lander, about 5–10 hours lifetime onsurface, passive cooling

153 12 $1.02B

Short–LivedLanders

Multiple landers, about 5–10 hours lifetime onsurface, passive cooling

214 12 $1.05B

Long–LivedLander

Single lander, days to weeks lifetime, may re-quire active cooling and RPS

223 21 $2.3B

Long–LivedLanders

Multiple landers, days to weeks lifetime, mayrequire active cooling and RPS, long lived net-work possible

264 21 $2.33B

Surface Systemwith Mobility

Active or passive cooling, mobility with sur-face access at multiple locations (e.g., roverwith short traverse or metallic bellows withlong traverse)

209 53 $3.59B

CoordinatedAtmosphericPlatforms

Large number (e.g., swarm) of in situ ele-ments, with simultaneous measurements

129 21 $1.98B

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Figure 3: Venus mission architecture examples [13]

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Table 2: Potential Flagship class mission architectures, FOMs, and cost estimates.

Recommendedby

Mission architecture conceptScienceFOM

Tech.FOM

Costest.

Mission architecture choices by STDT Science SubgroupsGeologySubgroup

Multi–element architecture with 1 orbiter;and 1 near surface aerial platform

347 20 $3.2B

AtmosphericSubgroup

Multi–element architecture with 1 orbiter; 2mid–level aerial platforms; and 2 entry probes

539 5 $2.9B

GeochemistrySubgroup

Multi–element architecture with 1 flyby; and1 short lived lander

214 12 $2B

STDT recommended mission architecture for detailed Flagship study

Full STDTMulti–element architecture with 1 orbiter; 2mid–level aerial platforms; and 2 short livedlanders (could include long lived elements)

753 15 $3.7B

Table 3: Notional payload for the orbiter, two balloons, and two landers (by the STDT).

Orbiter 2 Balloons 2 Landers

Lifetime (∼4 years) (∼1 month)Descent Phase(∼1–1.5 hour)

Landed Phase(∼5–10 hrs)

Long Lived Pack-age (∼243 days)

InSAR — Interfer-ometric SyntheticAperture Radar

ASI — Atmo-spheric ScienceInstrument (p; T;wind; acceleration)

ASIMicroscopic im-ager

ASI (long life; notin baseline)

Vis–NIR ImagingSpectrometer

GC/MS — GasChromatograph /Mass Spectrometer(long life)

Vis–NIR Cam-eras with spotspectrometry

XRD / XRFSeismometer(long life; not inbaseline)

Nutral Ion MassSpectrometer

Nephelometer GC / MS Heat Flux Plate

Sub–mm Sounder Vis-NIR camera MagnetometerPassive GammaRay Detector

Magnetometer Magnetometer(Descent phaseonly)

Sample acqui-sition, transfer,and preparation

Langmuir Probe Radio tracking(Net Flux Ra-diometer)

Drill to ∼ 10 cm

Radio Subsystem(USO — UltraStable Oscillator)

(Nephelometer)Seismometer(short life)

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