Thursday, August 26, 2010

A Loser in the Astronomy Decadal Survey

Source: JPL/NASA

One of my long time correspondents and readers of this blog, left a detailed comment on a recent blog I wrote on the implications of the recently released Astronomy Decadal Survey recommendations  Phil takes me to task for not bringing up a key loser in those recommendations, the SIM Lite Astrometric Observatory.  (Phil's thoughts have always proved to be good reading, and I recommend you check them out.)  This mission would have had the capability to accurately measure positions of stars with extreme precision.  A key contribution of this mission would have been the study of nearby stars for exoplanets, potentially as small as the Earth.

Here's a summary of this mission from it's JPL webpage (

"The SIM Lite Astrometric Observatory is 6-meter baseline Michelson interferometer capable of positional accuracies of 4 microarcseconds all over the sky and 1 microarcsecond for selected targets. SIM Lite addresses foundational problems across all of astrophysics:

  • SIM Lite will identify terrestrial planets in the habitable zones of their stars, as well as hundreds of other planets.
  • SIM Lite will determine masses and luminosities of stars at their extremes, including brown dwarfs, neutron stars, and black holes, permitting tests of models of stellar evolution.
  • SIM Lite will determine the age of the Milky Way, its formation history, the Sun’s place in it, the distribution of dark matter in the Milky Way and Local Group, and place limits on the mass of the dark matter particle.
  • SIM Lite will investigate the sources and mechanisms of energy release and jets from stellar masses to mega-solar-mass galactic nuclei.
  • SIM Lite will establish an optical astrometric grid accurate to 4 microarcseconds over the whole sky."

The Astronomy Decadal Survey gives little attention to this type of mission, and most importantly does not recommend it for flight in the coming decade despite years of technology development.  Instead, the Survey recommends limited funding in this decade to continue technology development with the potential that this might lead to flight recommendation in the 2020 Survey. The Survey does strongly recommend studying statistical patterns of exoplanet distribution with another proposed mission, an infrared space telescope, WFIRST.  This mission, however, cannot carry out detailed surveys of nearby solar systems that SIM Lite would have.

An on-line article at Scientific American explores the implications of the Survey's recommendations on exoplanet studies in more detail (

Editorial Thoughts: The SIM mission has a long and checkered history (see the 'Budget' section of the Wikipedia entry on the mission  It appears that the real death of this mission came several years ago with NASA science funding was reduced to fund development of new manned space systems.  Rather than killing SIM Lite, the Survey decided not to resurrect it following it's effective transformation to a technology development program.  Because of the cost overruns on the James Webb Space Telescope, the Survey effectively have budget room to recommend just one major space mission.  WFIRST, which can study a variety of astronomical issues including Dark Matter.  WFIRST serves a larger portion of the astronomy community than SIM Lite would have.

Phil is right that this is a loss for planetary exploration that will not be filled for a decade and probably two.

I think the lesson from the probable death of SIM Lite (NASA seems unlikely to go against the Survey's recommendations) is that Surveys have become about hard choices within limited budgets.  I think we'll see similar hard choices in the upcoming Planetary Decadal Survey.  Several key missions many of us would like to see fly may not be recommended.

Wednesday, August 25, 2010

Limited posts for next month

I'm headed back to parts of the world where the Internet has yet to extend its tentacles.  I do have some material queued up that I will post when I do have access, but I won't be able to follow breaking news.

In the meantime, here's a map of where readers of this blog reside.  The greatest concentration of readers are in southern California and the Washington, D.C. area.  I suspect that a number of these readers may be professionals in the field.  If so, corrections and additions are always welcome.

Tuesday, August 17, 2010

Thoughts on Astronomy Decadal Survey

The past few days, I've read through the Astronomy and Astrophysics Decadal Survey report released last week.  If you are interested in these fields, I encourage you to look through the report.  While it is long (225 pages), the 17 page executive summary and 32 page overview of the state of the field are worth reading.  You can download the complete report. or read good summaries of the recommendations at the journal Nature or at Spaceflightnow.

The recommendations of the Survey have been widely reported, and I won't rehash them here.  Instead, I'll look at the report for clues as to how the Planetary Decadal Survey may approach its recommendations.  Before doing that, there are three key differences in the astronomy and planetary programs that must be acknowledged.  First, the astronomy Survey covers both space missions and ground facilities.  The planetary Survey also can prioritize ground facilities, but in general, the trend is has been to ensure funding for access to facilities already built.  Second, the NASA astronomy program is expected to continue to spend the bulk of its funds on the James Webb Space Telescope through the middle of this decade.  As a result, the proposed space portion of the astronomy program appears modest with just a single major mission firmly recommended.  And third, the incremental cost of meaningfully increasing our knowledge in planetary exploration appears to be greater than in astronomy.  The report notes that the three highly successful Explorer astronomy missions of the past decade together cost $560M.  The budget for a single mission in the equivalent planetary program, the Discovery missions, is $425M.  (Astronomy missions can be expensive, though.  Two ground based telescopes recommended by the Survey would cost $465M and ~$1.1-1.4B and two lower priority space missions would cost several billion dollars.)

The astronomy recommendations are based on conservative budget assumptions that assume flat spending for the NASA portion of the budget.  It has been common in reports of this nature to request budget increases.  With this report, the optimistic scenario is that NASA astronomy and astrophysics budgets will increase for inflation and the pessimistic scenario is that they won't.

The astronomy recommendations are built around two recent key advances in our understanding of the universe: the discovery that dark energy is the major constituent of the universe and the rapidly expanding family of known extra solar planets.  These two areas have radically changed our perceptions of the universe and how solar systems form.  I don't believe that there has been equivalent discoveries in the planetary program in the past decade.  We have much stronger evidence that Mars likely preserves its ancient history and possible record of life and that water was and is abundant, but those discoveries could be viewed as expected.  We have also learned that Titan is a more fascinating world than expected and the geysers of Enceladus were truly unexpected.  These discoveries argue for continuing heavy funding for Mars exploration and perhaps shifting missions from the ice-ocean moons of Jupiter to the ice-ocean moons of Saturn rather than switching, for example, from a Mars focus to a Venus focus.  (If you disagree, please leave a comment!)

The astronomy Decadal Survey chose to make its highest recommendations for general purpose instruments -- as space borne Wide Field Infrared Survey Telescope (WFIRST) and an Earth-based Large Synoptic Survey Telescope -- that can address both the two focus topics and a variety of other questions.  In the planetary field, the trend is to more specialized missions that investigate one body in depth (e.g., a single comet) or a particular topic (trace gases at Mars or the lunar gravity field).  Proposed missions to explore wide ranging phenomena that include geology, atmospheric sciences, and fields and particles have become relatively rare and expensive.  Two examples of proposed missions that would be wide ranging are the Jupiter Europa Orbiter that would explore the entire Jovian system and the Venus Flagship mission that would explore the surface and atmosphere of Venus both remotely and in situ.  Both missions have price tags greater than $3B compared to the $1.6B WFIRST.

The astronomy Survey made clear choices between fields.  Survey instruments received preference over higher resolution instruments.  Infrared astronomy received preference over high energy (X-ray and gamma ray) astronomy missions that were ranked lower and would fly only if US funding permits and international cooperation occurs.  I believe that we are likely to see similar clear preferences from the planetary Survey.  Fiscal credibility will, I believe, be a major criteria for the planetary Decadal Survey.  Steven Squyres, head of the Survey, as warned of sticker shock, which could result in only one no large (>$2-3B) missions being recommended.  (See Sticker Shock and Decadal Survey Showdown.)

The astronomy Survey made as its second priority for space missions an expansion of the small PI-led Explorer program, with a request for funding increases from $40M per year to $100M per year starting in 2015.  Similarly expanding the planetary PI-led New Frontiers (~$650M each) and Discovery (~$450M each) missions from 2 and 3 per decade, respectively, likely would require a decision to forgo either the Jupiter Europa Orbiter or the Mars sample caching rover.

The astronomy Survey made international cooperation a key element of several of its recommendations.  WFIRST could be combined with a less ambitious ESA mission with similar goals.  The third and fourth priority space missions apparently would fly only with substantial ESA contributions and, in the case of one mission, Japanese contributions.  On the planetary side, NASA already is collaborating with ESA on 2016 and 2018 Mars missions and discussing collaboration with ESA to explore the Jovian system.  (All three ESA large class missions in competition for selection involve collaboration with NASA.  One is the Jupiter Ganymede Orbiter and the other two are the astronomy Survey's third and fourth space mission priorities.)  The planetary Survey may also prioritize missions that require substantial international collaboration.  Beyond the missions already in discussion, the planetary survey might, for example, prioritize a small scale orbiter to continue studies of Enceladus and Titan while also suggesting carrying along one or more foreign probes for in situ exploration of Titan.

The astronomy Survey prioritized development of technologies for key missions desired for the decade (2020s) following this coming decade.  The planetary Survey is considering similar recommendations.  Technologies that have been discussed for development in this coming decade to prepare for the next include Mars sample return, technologies for Titan exploration, and cryogenic sample return from a comet.  At the same time, the planetary Survey will have to decide whether or not to make use of key technologies developed in the past decade to allow an Europa orbiter and develop and operate rovers on Mars.  A recommendation not to use those investments may mean that the expertise may be lost if the supporting engineering teams are disbanded for the lack of an immediate flight opportunity.

To sum up, I would expect the planetary Survey to select clear winners and losers among the big ticket missions in response to a tight budget forecast, recommend a continued (and possibly expanded) program of small missions, strongly urge international cooperation, and recommend technologies for development to enable key missions to fly in the 2020's.

Saturday, August 14, 2010

Astronomical Decdal Survey 2010 Published

The lastest in a series of astronomical Decadal Surveys was published yesterday (8/13/10).  Like previous astronomy surveys, this one ranked space- and ground-based missions in priority order.  Unlike previous surveys, this one (like the concurrent planetary Decadal Survey) placed considerable emphasis on analyzing the technical maturity and probable cost of the missions it recommended.  Advances in astronomical research over the last decade has created a new set of priorities of future missions.

I will have my own analysis in a few days after I wind up some travel.  In the meantime, the journal Nature has a good overview of the reasoning behind the priorities and list of the recommended missions, facilities, and research programs.  You can also download the complete report.

Hayabusa 2 Mission Approved

Source: JAXA
Correction: A reader corrected the budget situation: So far, the Ministry of Edcuation, Science ... approved the mission. However the budget allocations are decided by the Ministry of Finance and the parlament. Usually at Dec. or January we know Jaxa´s next budget.

The Japanese government has approved the Hayabusa 2 mission that will attempt a second near Earth asteroid sample return.  The mission will launch in 2014 to visit the carbon rich (and believed to be a sample of the early primitive solar system) 1999 JU3 asteroid, which is believed to be one kilometer in diameter.  The samples would be collected in 2018 and returned to Earth in 2018.  A number of engineering modifications are planned to the Hayabusa 1 design to take advantages of lessons learned from that mission.

This mission has similar goals to the OSIRIS-REX proposal in the current NASA New Frontiers competition, especially in the goal to sample a body believed to be carbon rich.  The spacecraft would visit different a different asteroid (1999 RQ36).  If both missions fly, we would get an idea of the diversity of these primitive asteroid fragments.

For more information, check out the article at or the official Hayabusa 2 website.

Thursday, August 5, 2010

Mars Versus Europa had a recent article on the competition between Mars sample return and the Jupiter System mission for the next large NASA and ESA missions.  (The article primarily focuses on the Mars mission, but I'd like to explore the competition.)  Both missions are large: The sample return is likely to cost $6-7B while the combined costs to NASA and ESA of the Jupiter Europa and Jupiter Ganymede missions will be ~$4.5B.  The backers of a Mars sample return would like to see the three elements of the sample return fly in 2018 (the ExoMars rover and the sample cache rover, MAX-C), 2022 (an orbiter to carry the samples brought up from the surface back to Earth), and 2024 (a lander and ascent vehicle to deliver the sample to Mars orbit).  (I believe that the 2022 mission would have to enter development around 2018 in this scenario.)  The backers of the Jupiter system mission would like to see that mission fly in 2020.

The article and others (see Decadal Survey Showdown) have suggested that the two space agencies cannot afford both sets of missions.  The U.S Decadal Survey is seen as the body that will decide between the missions.  In this blog post, I consider whether it might be possible for both to fly without consuming the budget.

The ESA elements for the 2018 ExoMars rover are already budgeted, while ESA's Jupiter Ganymede orbiter (if chosen over two other missions) would be funded out of its large science mission budget.  Funding for subsequent ESA contributions to the sample return, would according to the article, require more money than is currently being budgeted for Mars exploration.

On the NASA side, there is room in a ~$12-13B (in current dollars) decade budget to fly both missions.  Doing so would consume most of that budget, probably crowding out all but a handful of low cost missions to other targets.  (And if these two large missions experience significant cost overruns, even those small missions may have to go.)

However, I wonder if there might be a sequence of missions that allows both to fly.  The currently discussed sample return mission series assumes that missions fly as quickly as budgets could allow.  Another option would be fly the 2018 sample mission and wait for its results to commit to the subsequent orbiter and lander/ascent vehicle.  The 2018 rover might crash on landing, become stuck in the mother of all dust pits for eternity, or simply fail to find compelling samples.  Committing to flying the subsequent sample return elements before the results of the 2018 mission are known would seem to commit NASA's resources to a single large program predicated on success in 2018.

An alternative might be to fly the sample cache mission in 2018 and the Jupiter Europa mission in 2020 (hopefully with their ESA counterparts).  The results of the 2018 mission should be known by 2020 or 2021, and then if compelling samples are safely cached, development of the subsequent missions could begin with flights in the later half of the 2020s.  (I don't know whether a decade or more waiting on the Martian surface would cause the cached samples to degrade.)  In this scenario, the NASA would need to commit $6-7B between the two missions, leaving room for a couple of New Frontiers and Discovery missions.  The majority of the remaining funds needed for the subsequent sample return elements would come from the following decade's budget.

It's easy to be an armchair mission planner.  There may be many reasons why this possiblity may be infeasible or unwise and there may be better alternatives.  The Decadal Survey may also conclude that it wants to recommend just one (or no) multi-billion dollar missions in the coming decade, eliminating the competition.  However, I have not seen a discussion of the question of whether or not results from the 2018 caching mission should be known before committing to the next sample return element.  I hope that the Decadal Survey will consider that question as it reportedly is considering whether to recommend either or both of these two large missions.

Wednesday, August 4, 2010

Mars Trace Gas Orbiter Instruments Selected

ESA-supplied MTGO orbiter releasing the ExoMars demonstration lander.  Credit ESA.

Earlier this week, ESA and NASA announced the instruments selected to fly on the proposed 2016 Mars Trace Gas Orbiter (MTGO) mission.  This mission has several goals.  It will follow up on discoveries of short-lived trace gases previously discovered in the Martian atmosphere that suggest either active geological processes or life to replenish them.  Another focus will be to continue measurements of the Martian weather and climate to provide context for the trace gas measurements, to aid current landed missions (for example, to predict atmospheric conditions for entry and descent or to monitor dust storms), and to extend similar measurements that currently operating orbiters provide.  A high resolution camera will continue studies of selected spots on the planet in detail.  And finally, the orbiter will carry a communications package to relay data from future landers and rovers to and from Earth.

Previously measured methane concentrations in the Martian atmosphere.  Credit NASA.

The detection of methane in the Martian atmosphere has made trace gas measurements at this world a priority.  The discovery implies that Mars is currently active -- methane has a short lifetime in the Martian atmosphere and must be regularly refreshed.  However, the discovery brought with it two mysteries.  First, is the source of the methane geological or biological activity?  Either would have major implications for our understanding of this planet and the latter would have major implications for our understanding of our place in the universe.  The second mystery is what is removing the methane so quickly, much more quickly than known processes could account for?  The issue of trace gases is not limited to methane.  Other important concentrations to measure include CO2, CO, H2O, H2O2, NO2 N2O, O3, CH4, C2H2, C2H4, C2H6, H2CO, HCN, N2S, OCS, SO2, HCl, and CO.

Two instruments will study the trace gases, with the first focused on measuring trace concentrations (it reportedly could detect the the methane emitted by three cows) and the second on the sources of the trace gases:

  • Mars Atmospheric Trace Molecule Occultation Spectrometer (MATMOS) An infrared spectrometer to detect very low concentrations of molecular constituents of the atmosphere. Principal Investigator: Paul Wennberg, California Institute of Technology, Pasadena, USA. Participating countries: US, CA.
  • High-resolution solar occultation and nadir spectrometer (SOIR/NOMAD) An infrared spectrometer to detect trace constituents in the atmosphere and to map their location on the surface. Principal Investigator: Ann Vandaele, Belgian Institute for Space Aeronomy, Brussels, Belgium. Participating countries: BE, IT, ES, GB, US, CA.

Two instruments will make weather and climate measurements:

  • ExoMars Climate Sounder (EMCS) An infrared radiometer to provide daily global measurements of dust, water vapour and chemical species in the atmosphere to aid the analysis of the spectrometer data. Principal Investigator: John Schofield, Jet Propulsion Laboratory, Pasadena, USA. Participating countries: US, GB, FR.
  • Mars Atmospheric Global Imaging Experiment (MAGIE) A wide-angle multi-spectral camera to provide global images in support of the other instruments. Principal Investigator: Bruce Cantor, Malin Space Science Systems, San Diego, USA. Participating countries: US, BE, FR, RU. 

The final instrument continues high resolution mapping of the Martian surface to study possible sources of trace gases, examine future landing sites, and continue geological studies of the planet:

  • High-resolution Stereo Color Imager (HiSCI) A camera to provide 4-colour stereo imaging at 2 m resolution per pixel over an 8.5 km swathe. Principal Investigator: Alfred McEwen, University of Arizona, Tucson, USA. Participating countries: US, CH, GB, IT, DE, FR.

HiSCI will have lower spatial resolution (2 m) than the current HiRISE instrument (0.3 m), but will cover a larger area in each image.  The HiSCI instrument apparently will have color imaging over the entire image area while HiRISE has just three colors over a 1.2 km swathe and a single color, red, over a 6 km swathe.  Where HiRISE could image only a tiny fraction of one percent of Mars a year, HiSCI will be able to image around two percent per year.  HiSCI will also be able to obtain stereo coverage for every image, while HiRISE must acquire images on different orbits that may be months apart.  (It's not clear if HiSCI will have the stereo channel built into the instrument, or takes a second image on a the next orbital pass.  See the University of Arizona press release for what details are available.)

The orbiter will carry a communications package to relay data from future landers and rovers to and from Earth. has an article with additional information on some of the instruments.  You can read the original press releases from ESA and NASA.  A presentation on the goals and implementation of the mission can be found at the MEPAG website.

Editorial thoughts: The status of this mission is currently unclear.  If I understand the Decadal Survey process, this mission must be recommended by the Survey for NASA to proceed with development.  However, I personally think it is unlikely that it won't be recommended.  The communications relay is needed for future Mars landers and rovers and the weather monitoring and high resolution camera would be useful to those missions.  The discovery of trace gases also begs for follow up measurements to determine concentrations and sources.  This is also an international mission, and the Survey would have to ask NASA to cancel plans on which ESA depends to fly its ExoMars mission elements.

As currently planned, NASA will provide the launch vehicle and the instrument package.  NASA will pay for the US instrument development; it's not clear whether it will pay for foreign instrument development.  NASA also will provide tracking services.  Together, these investments probably total several hundred million dollars (see this blog entry to get an idea of instrument costs).  ESA will pay for the orbiter and its ExoMars landing demonstration package.  This mission appears to be true partnership with each party contributing major elements.

You can find more information on the goals and measurement techniques of the classes of instruments selected in a report that analyzed possible instruments for the mission to guide the two space agencies in their final selection.

Sunday, August 1, 2010

Latest Decadal Survey Update

The following open letter from the Survey's chair, Steve Squyres, was published today.  You can read the original at

Dear Colleague:

This is the sixth newsletter to the community regarding SolarSystem2012, the planetary science decadal survey. The key points in this newsletter are these:
  1. The five decadal survey panels have completed their integration of the inputs from the community, and have provided their recommendations to the steering committee.
  2. Cost and technical evaluations for the highest priority missions recommended by the panels are nearing completion.
  3. Final prioritization of mission candidates and other activities by the steering committee is underway, and will be completed within the next few weeks.
  4. A report is being drafted, and we expect it to begin a comprehensive peer review process beginning in late September.
  5. We hope to have a final report ready to present to the community by next spring.
  6. More information is available on the SolarSystem2012 web site:

Late spring and early summer were an exceptionally busy time for the five panels, as they finished working through all of the inputs from the community, integrating them for inclusion in the final decadal survey report. The statistics on the community inputs were impressive, with 199 white papers written by 1691 unique authors and co-authors. The panels also worked closely over this period with the Applied Physics Laboratory, Goddard Space Flight Center, and the Jet Propulsion Laboratory to perform detailed studies of a large number of candidate missions that arose from the community inputs.

After receiving the mission studies from the panels, Aerospace Corporation, under contract to the NRC, has performed a number of detailed cost and technical evaluations of the candidate missions. Most of these evaluations are now done, and the final few will be completed within the next two weeks.

Once the steering committee has received all of the scientific inputs from the panels and all of the technical and cost evaluations from Aerospace, the final prioritization of mission candidates will take place. The challenge, of course, is finding the best solar system exploration program that fits the projected budget.  Much of the prioritization has already been done by the panels themselves, so the number of decisions that the steering group will have to make is small. As always, our decisions will be driven by our assessment of the community’s views on the science value and cost effectiveness of all the missions and other activities under consideration. The final prioritization will be completed within the next few weeks.

A report summarizing the current state of knowledge in planetary science, the key outstanding science questions, and the affordable mission candidates and other science activities that best address those questions is being drafted. Most of the report is now written, and we expect to have a final draft done within the next two months. Once that draft has been submitted to the NRC, it will undergo a long and rigorous peer review process, per NRC standards. Many of you in the community will be asked to review it; if you do get asked to provide a review, a timely response will be greatly appreciated!

As soon as the report has been through the review and revision process, it will be released publicly. We expect that the release date will be sometime in the early spring of 2011. After the report has been released, we will also be able to provide briefings about it to the community at major science conferences… so stay tuned for those.

I’d again like to thank everyone in the community for your many inputs to this process. The set of activities that we have studied is breathtaking in its scope, and finding the subset that best addresses your highest priorities while fitting into a limited budget is turning out to be both challenging and rewarding. I’m excited
about the recommended plan that is emerging, and I think you will be too.

As always, more details, including archived webcasts of meetings, agendas for past and future meetings, and materials presented to the Steering Group and panels, are available at the SolarSystem2012 web site:

Best wishes,
Steve Squyres
SolarSystem2012 Chair

Editorial Thoughts: The Survey is in the publicly quiet time where priorities are being set and justified.  We are unlikely to hear much about the missions selected until the release of the report next spring.

I suspect that the prioritization by the steering committee may not be as easy as suggested by this letter.  There are at least two or three Richter scale decisions: Should any of the flagship-scale missions (Mars sample return caching rover, MAX-C, Jupiter Europa Orbiter, Saturn-Titan-Enceladus orbiter) that likely will top at least some of the panel's priorities be funded and if so, how many?  Should substantial funds be committed to development of follow on elements of the Mars sample return to allow the fastest possible return of samples cached by MAX-C?  Should one or two destinations (or types of destinations, e.g., comets) be prioritized and receive substantial funding much like Mars was in the last decade?

The easiest solution would be to pick the top missions from each panel (Mars: likely Trace Gas Orbiter and ExoMars/MAX-C, Outer Planets: likely Jupiter Europa Orbiter, etc.) and fund them until the likely money is gone.  However, if any of the flagship-scale missions that may be the highest priority of a panel run into serious cost overruns, then paying for the cheaper lower cost missions may not be possible.  This happened with both the last astronomy (James Webb Space Telescope) and planetary (Mars Science Laboratory) surveys.  The technical and cost evaluations being done will help avoid this problem, but probably not eliminate the risk.

A recent report by the National Research Council showed that many missions experience their major overruns well into development when the designs are presumably well understood.  From the report:

  • "Past studies of cost growth in NASA Earth and space science missions calculated values for average cost growth ranging from 23 percent to 77 percent.
  • "Relatively little cost growth occurs between preliminary design review (PDR) and critical design review (CDR). 
  • "A majority of cost growth occurs after CDR, with the rest occurring prior to PDR.For one large set of 40 missions, 80 percent of the total cost growth (in absolute dollar terms) was caused by only 11 missions."

And, "So 75 percent of cost growth occurs after CDR. Primary Reference 5 also analyzed the evolution of cost growth over time and concluded that “it is important to notice that, unlike the mass and power growth time trends, cost growth is typically not recognized until after CDR."  (PDR is the preliminary design review that occurs early in the project while the CDR is the critical design review that occurs later before committing to development.)  Cost overruns on larger missions often are more damaging than overruns on small missions (25% of $3B is much more in absolute dollars than 25% of $650M).

At the same time, I personally would not like to see a list of missions that are all safe because the technologies are firmly developed.  If I were to wager a beer, my guess is that the Survey will prioritize only one flagship scale mission and fill out the rest of the program with smaller New Frontier and Discovery class missions.  But I wouldn't bet more than a beer on this prediction.

I look forward to seeing how the Survey balances these conflicting priorities.