Thursday, May 28, 2009

Curiosity (MSL) Landing Site Candidates

Check out the great post by Ken Edgett on potential landing sites for the Curiosity (it will take me awhile to get comfortable with the now official name for the Mars Science Laboratory rover) at

Editorial Note: These are all great sounding candidate landing sites. However, I'm uncomfortable with the process for selecting a landing site for once in a decade or two decade flagship rover. I would have preferred to send cheaper rovers to several sites to scout out the terrain and chemistry before committing a flagship class rover. I know that this puts me at odds with the planetary community. But what happens if the clays at the site selected turn out to be thin veneers created by dew? The MER rover landing capabilities were substantially enhanced to allow landing by Spirit at Gusev Crater, it it turned out not to be an ancient lake bed.

Your dissenting views welcomed!

Friday, May 22, 2009

Top 10 thing Alan Stern wishes he knew about the solar system

Check it out at the Planetary Society blog,

My two favorites:

"How many worlds harbor life in our solar system?"

"Did Mars really ever have oceans -- rather than just lakes, rivers, and rains"

The questions that Alan poses are ones around which future planetary missions, or series of missions can be planned.

Alan list does not have any questions on Venus, so I'll add a couple of my own:

  • Did Venus ever support life?
  • What drives the geological cycle on Venus, which replaced almost the entire surface within the last few hundred million years, work?

Thursday, May 21, 2009

A Minimalistic Uranus Orbiter

Presentations from the March OPAG meeting continue to trickle onto the website. Today I found a short presentation on a concept study for a Uranus orbiter. JPL has a team that looks at possible mission concepts, both to see what could be done with today's technology and what technologies would be needed to enable certain missions. (Talk about a dream job!)

The goal of this study seems to have been two fold: First to see if a Uranus orbiter could be done within a New Frontiers budget cap ($650M not including launch vehicle) and second whether a solar powered mission could be done. The answer to the first question was not quite. The final mission price tag was around $715M. The answer to the second question was just barely. The solar panels would produce about 100W at Uranus. As the presentation says, "Power is a significant constraint, but batteries, radioisotope heating units, and phasing of instrument on/off times would allow the needed science return with solar panels producing only 100 W."

The mission that would fit into that price figure would be tightly constrained. The only instruments would be an ultra stable radio system for gravity studies, magnetometers, and a fields and particles instrument. This would be a Juno like mission without Juno's microwave radiometer for deep sounding into the Uranus atmosphere, the ultraviolet and near IR spectrometers, and the wide angle camera. (I have read that a microwave radiometer might not be useful for Uranus and Neptune because of the depth of the water layers in their atmospheres, but this is an old memory and I can't find the reference.)

Editorial Thoughts: I don't think that a $715M mission with this limited of an instrument set would be a competitive New Frontiers mission. I would want at least the instrument set of the New Horizons craft for a return to Uranus. Juno was a competitive proposal, in my opinion, because its microwave radiometer addressed fundamental questions about the structure and composition of gas giants and the mission carried out a number of other key studies enabled by the mission's orbit. I don't think that Juno without the microwave radiometer would have been a successful proposal.

This proposal does get me thinking about potential strategies for mid-cost missions to the outer solar system. The New Horizon flyby mission to Pluto and a KBO required a New Frontiers budget. This study says that a craft that is in many ways simpler would require a bit more than a New Frontiers budget. The Io Volcano Observer team says that it could do a Jupiter orbiter-Io flyby mission for around $500M, which puts it at the low end of estimates for outer planet missions.

Right now, the only options for outer planet missions are Flagship missions ($3B), or missions stripped to the bone to fit into New Frontiers budgets (or if the IVO estimates are correct) into Discovery-plus missions.

If the Decadal Survey wanted to increase the priority of outer planet missions, it could get creative. Generally, I've read, the cost of a second close copy of a spacecraft is around 60% of the cost of the first. Let's say that a reasonably instrumented outer planet craft mission cost $800. That price would bust a New Frontiers budget. However, for the price of two New Frontiers missions, two craft could be built if they were near duplicates of each other. The Decadal Survey could call for two New Frontiers competitions to be combined. NASA would provide two core spacecraft that presumably would allow some mission specific configuration (say, to carry enough fuel to enter orbit around an outer planet or two carry and atmospheric probe on a flyby mission). Then NASA could hold a competition to determine which specific missions each craft would conduct.

With a little thought, I can think of a number of possible candidate missions: A Saturn multiprobe to study the atmosphere, a simple Saturn orbiter to continue studies of Enceladus and Titan with 2-3 instruments with capabilities greater than those on Cassini, a Uranus orbiter, a Trojan or Centaur asteroid flyby or rendezvous, a Neptune-KBO flyby mission, and perhaps an Io observer if the radiation hardening could be done for a common design.

The easy answer out of the Decadal Survey would be to just continue the current planetary exploration program of regular Mars missions supplemented with three Discovery and two New Frontiers missions. (I still haven't figured out how the Jupiter-Europa mission gets included within this budget framework.) The ideas above, which are little more than day dreaming, are one example of alternative approaches. Are these daydreams better than the current direction, probably not. I do hope, though, that the Decadal Survey will look at lots of innovative approaches.

Resources: Solar Uranus Orbiter

NASA Details Plans for Lunar Exploration Robotic Missions

NASA has released the pre-launch press release for the Lunar Reconnaissance Orbiter, or LRO, and the Lunar Crater Observation and Sensing Satellite, or LCROSS missions scheduled for launch on June 17.

Press release:

LRO website:

LCROSS website:

Wednesday, May 20, 2009

Planetary Protection

The journal Nature has a nice article on the emerging rules for planetary protection and their possible impact on future Mars missions.

Tuesday, May 19, 2009

Budget Blues

Alan Stern left the following comment, which I think deserves to be placed with this post rather than just be in the comments:

"The budget my team built last year was intensely reviewed by NASA PA&E and by OMB; OSTP also had input. It was not overly optimistic, but it did rely on better cost control, which we were not allowed to ultimately implement. As a result, you have seen missions slip, be canceled, and R&A cut. "

At the Unmanned Spaceflight forum, Mariner 9 posted a quote from the Planetary Society's blog:
"While the previous FY 09 budget request included new initiatives including a Mars Sample Return mission, an Outer Planets Flagship mission, and a Joint Dark Energy mission, among others, that could not realistically be accommodated within the FY 09 budget proposal, the FY 10 budget plan for space science no longer includes these or other major new initiatives. For example, NASA selected the Europa Jupiter System target as the focus of an Outer Planets Flagship mission, but elected to proceed with technology development, further definition, and discussions on a potential partnership with the European Space Agency (ESA) on a potential future mission. The FY 10 budget plan for planetary sciences does not include a Mars Sample Return mission. NASA officials have indicated their interest in working more closely with ESA on potential Mars missions for the 2016 and 2018 launch opportunities."
Here is my reply to the post:

I think that the portfolio of missions put forth last year under Stern was a tad bit optimistic both in terms of funding that would be made available and the chances that no major missions would have cost overruns. (Alan, if you think I'm wrong, please let us know.) Hence, there is likely to be a number of missions pushed out.

If the Flagship launches in 2020, real money will be needed starting in 2015 or 2016. The current timing for the mission is based on trying to recover from the MSL slip plus aligning with ESA's budgeting for their portion (assuming they select this mission as their next large science mission).

I foresee two problems. First, if NASA's science budget stays roughly flat (with increases, hopefully, for inflation), then NASA will either have to forgo its aggressive Mars program for a few years or forgo New Frontiers and Discovery missions for a few years. I just don't see anywhere to stuff a $3B mission in the current funding profile without giving something up. This, I predict will be the biggest fight of the upcoming decadal survey (with the fight over a series of small or a sample return for the Mars program being almost as big of a fight).

The second problem that I foresee is that the Titan mission will be going through the same kinds of mission definition in the next few years that the Europa mission did over the last decade. That could bring the Titan mission to a high state of readiness. If so, I see the selection of the next Flagship target being revisited, again, which could delay the whole thing into the 2020s.

I hope that my pessimism proves to be unfounded.

Two Interesting Articles

Alan Stern has a guest blog at the Planetary Society talking about all the planetary encounters and launches for 2010 and 2011. It will be an exciting couple of years.

Wired magazine has an article on planetary rover concepts ( You can also read about these at JPL's website ( ).

Thursday, May 14, 2009

Ed Weiler on Future Mars Exploration Possibilities

The Planetary Society has an interview with Ed Weiler, associate administrator for NASA's science program. He discusses the thinking behind various Mars mission opportunities. Two interesting quotes:

"Weiler pointed out that "2018 is an excellent launch opportunity due to a very favorable orbital alignment", much like 2003 was when NASA launched the twin rovers Spirit & Opportunity which function still to this day 5 years later. He envisions a "very good possibility to send two rovers/orbiters by ESA and NASA, one of which could be equipped with a methane spectrometer". "

"The trade off to accomplish dispatching new spacecraft in the 2016, 2018 and 2020 timeframe would be to basically "take Mars Sample Return (MSR) 'off the table'. We'd have to give up on MSR for now", Weiler said. There is simply not enough money in anyone's budget to realize all these objectives simultaneously. "The cost of MSR would be on the order of at least $6 to 8 Billion and with a timeframe of the early 2020s". There is a debate within the Mars community on the wisdom of building one big Flagship class mission in a decade vs. multiple smaller and more focused missions more frequently."

Read the full interview at:

Wednesday, May 13, 2009

Interesting Charts

The National Research Council just released its report justifying the restart of production of plutonium 238 to enable future space missions. (Start up money for that production is in the proposed FY10 budget for the Department of Energy.) Several of the charts are interesting in their own right. Click on any of the images for a larger view.

This chart gives the current expectations for future planetary missions. It assumes that Discovery missions are started every three years and that every other selection will use ASRGs (Advanced Stirling Radioisotope Generator). New Frontiers missions would launch every six years. Unfortunately, the launch date for the fourth New Frontiers mission, 2021, would be too late to enable the Argo mission to Neptune and a KBO. Also, the list shows two outer planet flagship missions, but no follow-on Mars flagship mission after the Mars Science Laboratory.

The pressurized and Athelete rovers would be lunar rovers for manned exploration. (If you think I'm a cynic about Mars sample return missions, don't even get me started on manned lunar exploration on this scale. Sorties, maybe. Big bases? Yeah, sure.)

This chart is a laundry list of ideas for future planetary exploration. Unfortunately, only a small fraction of these missions are likely to fly.

This chart shows why plutonium production needs to restart.

Argo mission
Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration (click on 'sign in' button to download the report)

Tuesday, May 12, 2009

Next Discovery Mission Selection

NASA has posted a summary of an Announcement of Opportunity (AO) for the next selection of a Discovery mission. (Thanks to G. Clark for pointing this out.) This selection breaks with past practices in several important ways.

First, the highlights:
  • "It is anticipated that approximately two to three Discovery investigations will be selected for 9-month Phase A concept studies through this AO. At the conclusion of these concept studies, it is planned that one Discovery investigation will be selected to continue into Phase B and subsequent mission phases."
  • "Investigations may focus on any body in the Solar System, excluding the Earth and the Sun, and including Mars and the Moon. Investigations may not focus on extra-solar planetary systems."
  • "Discovery Program investigations may propose the use of Advanced Stirling Radioisotope Generators (ASRGs) for missions enabled by radioisotope power systems."
  • "Investigations are capped at a life-cycle cost of $425M (FY10), excluding standard launch services and, if required, ASRGs. Lower-cost investigations are encouraged."
  • Selection for competitive Phase A studies July 2010 (target); Down-selection November 2011(target); Launch date NLT December 31, 2016
Editorial Thoughts:

Three key departures from past Discovery program selections. First, missions to any place in the solar system can be proposed. In the past, Mars had been explicitly excluded. Second, the option to use radioisotope (ASRG) power systems opens up missions to the outer solar system and/or missions where solar panels would have been difficult. Third, while the budget for the mission has not increased, I believe that this is the first time that NASA is not including the cost of the launch vehicle within proposer's costs. (If anyone knows differently, please add a comment.)

Put together, these changes open up a much wider range of mission possibilities than we've had in the past. It will be very interesting to see which missions get selected in a little over a year for more in-depth study.

Resources: NASA intends to release a Discovery Program Draft AO

Network Science Missions

In the past, I've described mission concepts for all the New Frontiers candidate missions except one -- network science. This blog entry will begin a series that looks at plans and concepts for exploring planets with networks of stations.

To date, planetary lander missions have focused on exploring single sites as individual examples of locales. A long standing goal, however, has been to land networks of missions that can address questions that cannot be answered at a single location. In the 1970s, the Apollo Lunar Surface Experiments Package (ALSEP) was placed on the moon by the Apollo astronauts. The stations monitored seismic activity, heat flow, and the lunar environment until they were turned off in 1977, largely for budgetary reasons.

Since then, there have been many proposals for network missions, particularly for Mars. In fact, the number of concepts proposed may rival the number of Mars sample return missions proposed. I am less cynical about the chances of a network mission flying in my lifetime, though. The costs and technology issues for a network science mission are several times less than for a sample return mission.

In 2008, a panel of scientists recommended that NASA add network science missions to the list of candidate missions for New Frontiers competitions (which NASA did). The panel examined the rational and goals for network missions, and I'll quote from that report.

"Network Science missions to study the interiors of Mercury, Venus, and the Moon, with geophysics measurements as a primary objective, would address fundamental science questions. Although remote measurements of a planet’s gravitational field, magnetic field, and rotational state provide information on its internal structure, only seismologic observations can definitively determine the nature of a planet’s interior, including the size and physical state of its metallic core, the thickness of the crust, spatial variations in crustal thickness, and the occurrence and locations of subsolidus phase changes and regions of partial melting in the crust and mantle. The required seismic data can be obtained only with a globally distributed seismic network. The interiors of Mercury, Venus, Mars, and the Moon are poorly characterized, and geophysical network missions to these bodies are needed to learn what is inside them. A geophysical network can also be supplemented to measure planetary heat flow, magnetic field, atmospheric properties and winds, climate variations, surface-atmosphere interactions, and surface mechanical and thermal properties... Without the geophysical data from a network mission, the “foundation question” put forth by the Inner Planets Panel of the [early 1980s] decadal survey, i.e., How do the compositions, internal makeup, and geologic history of the planets explain the formation and sustainment of habitable planetary environments? cannot be answered."

"The scientific objectives of a Network Science mission should be drawn from a subset of the objectives (not in priority order) described in the decadal survey, as follows:

"For the Interior
  • Determine the internal structure including horizontal and vertical variations in the properties of the crust and mantle, and evaluate implications for how the core, mantle, and crust evolved.
  • Determine the characteristics of the metallic core (e.g., size, density, and presence and distribution of liquid) and explain the strength or absence of a present-day magnetic field.
  • Determine the heat flow and the distribution of heat-producing elements in the crust and mantle.
  • Determine interior composition and compositional variations to elucidate differentiation, crust-mantle evolution (plate tectonics, basin formation by impacts, conditions for life), and how the bulk composition relates to that of the Earth and other terrestrial planets and how planetary compositions are related to nebular condensation and accretion processes.

"For the Surface/Atmosphere
  • Measure the surface winds and their time variability and the near surface global circulation.
  • Measure the temperature, pressure, humidity, and radiative flux.
  • Measure the atmospheric, elemental, and isotopic compositions
  • Understand the relationship between the near-surface general circulation and the physical processes that force it.
  • Determine how the near-surface general circulation controls the exchange of dust, water, CO2, etc., between the atmosphere and surface.
  • Begin to establish a weather monitoring infrastructure to support future robotic and crewed missions.
  • Provide an enhanced assessment of year-to-year atmospheric mass exchange between the atmosphere and polar caps and regolith.
  • Determine the mineralogic composition of the surface and its thermophysical properties.
"The committee recommends that a Network Science mission be included in the forthcoming NASA New Frontiers announcement of opportunity. The decadal survey identified a network science mission’s primary objective as geophysics. For Mars, atmospheric measurements near the surface are a valuable supplement to the geophysics measurements but cannot be a substitute for them.

"In light of the decadal survey’s recognition of the importance of network science on all the terrestrial planets and the Moon, the committee recommends that network science missions to the Moon, Venus, and Mercury also be considered as candidate missions for the New Frontiers announcement of opportunity in addition to a Mars mission."


Opening New Frontiers in Space: Choices for the Next New Frontiers Announcement of Opportunity

Heads Up

When I logged in today, I noticed that since this blog started early last fall, I've posted 177 entries. The pace of postings is likely to slow down a bit because we are hitting a likely slow period for news. The next outer planets Flagship mission was selected, the various *PAGs (MEPAG, OPAG, etc.) have had their first half of the year meetings, and the next Decadal survey process isn't yet in high gear. So a post or two a week may be the norm for the next handful of months.

Monday, May 11, 2009

ExoMars article

Aerospace America has an article on ExoMars. It's pretty much a rah-rah overview rather than an in-depth analysis. I did learn, though, that ExoMars' solar panels will tip to follow the sun.

You can read the article at:

Friday, May 8, 2009

Restart of Plutonium-238 Production

The new budget includes money to begin the design work to produce new plutonium-238, which is used as a radioisotope for missions to the outer planets.

MSNBC has an article on the restart of production:

A look at the bigger NASA budget

Science Insider has a nice summary of the overall NASA budget. One item I missed yesterday was that the Obama administration has begun a three month re-examination of the human exploration program. The results of that review could either relieve pressure on NASA's budget or increase it. (Look here for an analysis of the overall mismatch between NASA's goals and budget:

For all the science programs, the budgets are essentially flat. Two programs, Earth Science and Astrophysics did benefit from a one time boost from the 2009 stimulus package.

The full article can be read at:

Thursday, May 7, 2009

Proposed FY10 NASA Planetary Budget

President Obama's proposed budget for NASA in fiscal year 2010 (which starts October 1, 2009) was released today. Before going into the details for future planetary missions, I'll give a brief overview of the U.S. budgeting process. The President proposes a budget for the entire federal government. However it is Congress which actually writes the funding bills. Since the U.S. Congress has two houses, each passes its own version of the budget. These are then reconciled in a final budget bill which doesn't become law unless the President signs it. The result is a series of compromises in which the final spending bill may be quite different than what was initially proposed. In recent years, the conflict between political parties has been so great that Congress has not been able to agree on a federal budget. In those cases, federal agencies, including NASA, are funded at the previous year's funding rates.

The proposed FY10 budget essentially is flat with the budgets of the last three years. (The budget projects gradual increases over the four years following FY10, but this projection is for NASA's planning purposes and has no force of law.) The budget continues the planetary program that has been in place over the last several years. The Mars program is the largest line item with 30% of the budget. The New Frontiers program is funded at a rate that allows for new missions of approximately $650M approximately every 3 - 4 years. New Discovery (~$450M) can be started approximately every two years.

One program that has received substantial new funding starting in this current fiscal year is the Lunar Quest program. This program funds research programs and modest robotic missions. (The latter will be the topic of a future blog entry.)

The Outer Planets program, which funds data analysis, Cassini operations, and preparatory work for the Jupiter-Europa orbiter (JEO) mission remains modest ($98M) in this and projected budgets. The primary funding for JEO starts after the current budget window.

Editorial Thoughts: The Obama administration has decided to continue the planetary program at its current levels. Within NASA's science program, only the Earth observation program was singled out for significant increase. (Most of that increase comes from the previously enacted Recovery Act.)

If the budget plan presented is funded at approximately these levels over the next few years, then the planetary program will continue to be robust. I see two potential threats to this plan. The first is the size of the federal budget deficit. NASA (and much of the federal government) is funded by a combination of borrowing and printing money. Any of several changes in the global finance system could make this more difficult. As a discretionary program, the planetary program could suffer as a result. The other threat I see is that NASA's budget is not sufficient to keep the manned Exploration program on schedule and fund the science program as envisioned. If the administration and Congress decided to prioritize the manned program, then the entire science program is likely to see substantial cuts in future years.

A final thought is that after 2014 (as far as the current budget projects go), JEO will need substantial funding averaging several hundred million dollars per year for around five years. If the planetary program continues to be funded as foreseen in this budget plan, then funding JEO will mean decreasing funding for other parts of the planetary program. My back of the envelope (and therefore wrong in the details) figures show that the needed funding would about equal what is projected for the Mars program in 2014 or the combination of the New Frontiers and Discovery programs in the same year. Put another way, building JEO would seem to require substantial cuts to other parts of the planetary program.

Sunday, May 3, 2009

What Next for Titan?

Science return and range of cost estimates for possible return missions to Titan. From Titan and Enceladus $1B Mission Feasibility Study Report JPL D-37401 B January 30, 2007. Click on image for larger version.

The last blog entry discussed the Titan Saturn System Mission review comments. One comment particularly caught my eye:

“The NASA-only mission, consisting of only a Titan orbiter as described in the Final Report, clearly makes fundamental advances in our understanding of Titan and Enceladus. However, in the absence of an in situ element, the mission falls short of providing the fundamental advances expected of flagship missions such as Galileo and Cassini.”

The proposed Titan-Saturn orbiter mission represented a $2.5B (FY07 dollars) mission. (If the issues listed in the previous blog entry were addressed, the mission may in reality have been more.) If $2.5B doesn't buy a Titan-Enceladus mission worth doing, is future exploration of Titan realistic? Is an investment of $3.5-4B (an approximate cost with the ESA lake lander and balloon added) the minimum increment needed to continue exploring Titan.

Based on recent and projected budgets, NASA and ESA do planetary missions of this scope just once a decade. That would put the launch of a return to Titan and Enceladus into the late 2020s or 2030s. That mission proposal would have to compete with other missions of this scope such as a Mars sample return or a Venus Flagship mission.

A NASA report published in 2006 looked at missions to either or both of these moons that would have cost substantially less than a Flagship mission ($2-4B). It also gave a range of estimated costs and judgement as to whether the mission would provide science value worth the cost. Here is a list of the missions (quoted from the report with costs reported elsewhere in the report added by me in brackets):
  1. Titan Orbiter: aerocapture and braking into Titan’s atmosphere; 1500 km orbit; 2-year global mapping and atm. measurements. [~$1.5-1.9B]
  2. Titan Aerobot: direct entry into Titan; Montgolfiere hot air balloon at 10 km altitude; 1-year in situ science survey of atmosphere and surface. [$1.35-1.75B]
  3. Lander: direct entry into Titan; Huygens style parachute soft landing; 3-month Viking-like surface sampling and imaging followed by 21-month seismic and meteorological monitoring [~1.4-1.8B]
  4. Titan Atmospheric Probe: simple fly-by s/c for Huygens-Like atmospheric probe delivery and comm. relay; 4-8 hr encounter. Note: science return is below guideline due to high bar set by Cassini-Huygens. [~1.1-1.3B]
  5. Saturn Orbiter/Multiple Enceladus Fly-Bys: aerocapture into Saturn’s orbit using Titan’s atmosphere; targeted plume and global science via >30 Fly-Bys of Enceladus over 2-year period. [~$1.5-1.9B]
  6. Enceladus Plume Sample Return: Stardust-like in situ sample capture >10 km/s; remote sensing and in situ measurements; Earth free-return trajectory [~1.5-1.7B]
  7. Enceladus Single Fly-By: NH-like mission using NH spacecraft with new but similar payload, single fly-by science return. Note: science return is below guideline due to high bar set by Cassini’s campaign of Enceladus fly-bys. [~$900M]

The unfortunate message is that any scientifically justifiable return to Titan and Enceladus seems to run between $1.3-1.9B. (My guess is that the high range of the estimates may be more realistic of actual costs given the propensity of costs to increase as serious design work and hardware manufacture and testing begins.) Given that the TSSM orbiter would have cost $2.5B, and it would not have sufficiently enhanced our knowledge for the cost, the bar for returning to these worlds could be unobtainable for the next decade.

Two possibilities, though, give me hope. First, Ellen Stofan has a Discovery-class Titan lake lander proposal. I've not seen the presentation, but a friend who has tells me that it is less capable than the ESA lake lander proposed for TSSM. (This would make sense – ESA had a budget of ~$1B for just the lake lander and balloon. Stofan has just $450M and has to fit a carrier craft and launch vehicle into that budget.) The 2007 report did not look at lake landers. I know of Stofan by reputation, and she's highly competent. However, fitting in a carrier, lander (with entry shell), and launch vehicle within a Discovery mission budget seems ambitious. Perhaps this could be done with a New Frontiers budget ($650M with the launch vehicle provided by NASA outside this budget), although the 2007 budget suggested that a budget twice this amount would be needed just for an atmopheric probe.

The other possibility that is see comes from the Io Volcano Observer mission, which is another Discovery-class mission proposal. Perhaps a craft of similar capability (included a tightly constrained instrument suite) could be flown to orbit Saturn and flyby Titan and possibly Enceladus as well. The 2007 report stated that this mission wasn't scientifically justified since the incremental return in information beyond Cassini would not be worth the approximately $1.5-2.0B cost. A return mission, however, could carry cameras that could make use of spectral windows in Titan's haze to better image the surface and a more capable mass spectrometer to analyze Enceladus' plumes. If such a mission could be done for $450-650M, the cost-benefit ratio would be favorable.

The issues listed above certainly are well known to the planetary science community. Now that there are no plans to return to Titan with a Flagship mission earlier than the 2030s, I expect that the community will be looking for clever, tightly focused missions to return earlier. I expect that we may see a proposal or two like this proposed for consideration in the Decadal Survey in progress.

Friday, May 1, 2009

Why Good Mission Concepts Sometimes Don't Fly


Most of us have seen concepts for planetary missions that simply sound too good not to fly. Some of my favorites are landers for Venus, comet sample returns, and networks of small landers for Mars. Word on the street has it that these missions have been proposed for NASA's New Frontiers (~$650M) and Discovery ($350-450M) programs. None have flown.

Sometimes the reasons good mission concepts don't fly is because of technical readiness (Neptune orbiters, for example), higher priority missions (Mars network landers), or simply too little money (Europa orbiters). Sometimes the proposers simply make silly mistakes in their proposals. Steven Squyres wrote in his book of a team he led proposing an instrument and simply reversing some key dimensions.

Usually NASA is quite tight-lipped about why missions aren't selected (or even disclosing which are proposed, except for those that become semi-finalists). We know that NASA conducts a thorough review (as does ESA in its competitions). The reviews concentrate on the importance of the science to be conducted, the ability of the mission to answer the key scientific questions, and the technical readiness of the proposal.

The recent competition between Jupiter System and Titan System missions for the next outer planets target provides a rare exception. In this case, NASA released the findings of the review boards for the NASA-led orbiter missions. (I don't know if ESA will release equivalent information for its contributions.) The Jupiter-Europa orbiter essentially received all thumbs up in all categories. This isn't surprising given that the mission had several previous full definition efforts over the last decade or so.

The Titan orbiter wasn't so fortunate. It received top marks for the science questions and for the ability of the proposed mission to address them. However, it fell short in a number of areas (see below) for technical readiness of the concept. That the proposing did so well starting from scratch just a couple of years ago speaks to the effort and expertise they put into the mission. I expect that once the Titan mission has had its own multi-year effort at definition and working issues, that it too will achieve high technical readiness.

The list of short comings found by the reiview team follows. Note how specific they are. I am told that it is not unusual for a mission proposal that would perform a great science mission to fail in a competition for similar reasons. The lesson is that putting together a winning proposal is hard. It must do something new to had exciting science, but at the same time the mission design and technology readiness have to be at a high level. This is a tough bar to clear.

Issues with the Titan orbiter proposal, from the presentation at the last OPAG meeting:

  • The dry mass margin is too low for a pre-Phase A mission concept with significant technical challenges.
  • The design drivers resulting from the inclusion of aerobraking in the TSSM mission have not been adequately defined and their resulting impact to the design has not been assessed.
  • The changes for TIRS from the heritage CIRS instrument on Cassini are large, and the ability to successfully implement these changes is not well supported.
  • The HGA pointing budget is extremely optimistic with little justification of the improvements presented.
  • The TSSM ability to meet the stringent pointing stability requirement is not supported.
  • Analysis, engineering, and test of the TSSM thermal subsystem will be challenging and the report does not acknowledge the complexity of the task to address the substantial thermal design constraints posed by solar insolation, Venus albedo, the Montgolfière Multimission Radioisotope Thermoelectric Generator (MMRTG) waste heat, capillary pumped heat pipes (CPHPs), and aeroheating.
  • Systems Engineering (SE) lacks the rigorous approach necessary for this highly complex mission, which leads to substantial technical, cost and schedule risk in both design and implementation.
  • The complexity of the SEP stage development and lack of technical maturity are not reflected in the project cost estimate.
  • The cost impact to accommodate the in situ elements seems unrealistically low.
  • The allocated budget for Project System I&T appears insufficient.

There was one additional issue that leads to bigger questions that I'll address in the next blog entry.