Wednesday, December 22, 2010

Compelling Planetary Science Missions: Mars Geophysical Network and Mars Polar Climate Missions

This continues a series of posts inspired by a similar set of posts at Future Planetary Exploration blog selecting the 5 most compelling missions from the Planetary Science Decadal Survey list.  This follows 3 reviews of potential Mars missions.  Here I make my personal selection from that list.

After some consideration, I decided not to include the MAX-C rover in my list of most compelling Planetary Science missions from the Decadal Survey list.  The mission science is compelling, the raw idea of a rover exploring and selecting Martian samples for return to the Earth is right, the mission is in a reasonably advanced state of development, and it has international cooperation and multi-mission implications.  Thus, it is not to be set aside lightly, and as you'll eventually see I'm not setting it aside lightly.  However, the estimated mission cost is just too much for me, and I'm worried about the new rover delivery mechanism.  Demonstration of the Sky Crane at Mars, combined with validation that a Network Pathfinder could be added to the mission with minimal risk and cost, might be enough to squeeze MAX-C into my top 5 most compelling missions, but those things haven't happened yet.

It's all about opportunity cost and risk.

This is easy for me to do because I haven't been waiting for those Mars samples for half a career.  I suspect that if I had been, I'd have made a different choice.

Having dealt with MAX-C, the question now becomes which Mars mission will I choose for my "most compelling" list - Mars Geophysical Network or Mars Polar Climate Mission?

The answer: All 3 of them.  Or all 4 of them.

I think I'd better explain.

In the last couple posts, I described a number of potential Mars Polar Climate and Mars Geophysical Network mission options.  Some key options include:

2 Mars Geophysical Network powered landers - $1,015M (New Frontiers)
1 Mars Geophysical Network powered lander - $720M (Discovery)
Mars Polar Climate Orbiter - Climate and Weather - $613M (Discovery)
Mars Polar Climate Orbiter - Energy Balance and Composition - $629M (Discovery)
Mars Polar Climate Orbiter - Polar Science - $866M (New Frontiers)
Mars Phoenix Class Lander - Sightseer - $751M (Discovery)
Mars Phoenix Class Lander - Subsurface Sampler - $860M (New Frontiers)
MER Class Rover - $1,049 (New Frontiers)

My selection for the 3rd most compelling mission from the Decadal Survey list is a combined Mars Polar Climate mission consisting of an orbiter and a lander.  Thus 2 of the Mars Polar Climate options above would be selected.  These should be mutually supportive with remote sensing and ground truth in-situ observations of the same physical entities.  The orbiter can also help the lander through its telecommunications capability (which would be supplied by NASA to the mission as standard procedure for Mars orbiters).

I selected the Mars Polar Climate mission for a variety of reasons.  It addresses science questions about climate that are relevant to our situation on Earth.  Mars offers another extreme environment and history to compare to Earth, just as Venus does as explained in the Future Planetary Exploration blog's choice of a Venus Climate mission as the second compelling mission.  In addition, the mission has potential as an astronaut scout sort of operation (i.e. a science substitute for a robotic precursor mission).  The missions could be a good fit for collaboration with any funding that may appear in NASA's Exploration Technology Demonstration or Robotic Precursor efforts.  With additional mass budgets, they offer plenty of opportunity for super-charging with instruments from non-NASA space agencies, too.  Of course the missions go after big Planetary Science questions about Mars, too.  The missions follow up on technology and science demonstrated and advanced in earlier Mars missions, so the risk of cost overruns, mission failure, or unimportant science is lower than it otherwise might be.  Also, assuming no cost overruns, the missions are affordable.  For example, if we select the "Climate and Weather" orbiter as a revival of the "Mars Scout" line, and also select the subsurface sampler as our New Frontiers mission (since these Decadal Survey selections are supposed to be for New Frontiers and Flagship missions), we are only (if I may use that word when talking about huge amounts) at $613M + $860M = $1,473M.

My selection for the 4th most compelling mission is the Mars Geophysical Network Mission.  Since the science value of this mission goes up considerably with 2 landers rather than 1 lander (as, for example, the seismometers will return much more valuable data with simultaneous, time-synchronized data collections at different locations than the mere location of 2 landers at 2 distinct geographical locations would suggest), I'll select the $1,015M New Frontiers powered landing option with 2 landers.  Still the 3 missions combined are $2,488M, which isn't much more than the estimated MAX-C cost.  Had I selected the single Geophysical Network lander delivered on a Falcon 9 rocket (i.e. the Discovery class version), the 3 missions would cost less than MAX-C.  Like the Mars Polar Climate missions, the Mars Geophysical Network Mission addresses fundamental Mars science, gives lots of opportunities for international collaboration and thus more capable missions, and presents interesting possibilities for collaboration with potential NASA Exploration Technology Demonstration and Robotic Precursor efforts.

I've picked particular variants from the selections above, but I think the basic idea would work with other choices.  For example, we could switch the polar deposit Subsurface Sampler to the Mars Polar Climate rover (exchanging instrument mass for mobility).  This might be justified on grounds of mission science return or keeping our ability to develop Mars rover missions.  We could switch back and forth between Discovery and New Frontiers levels as funding allows and external participation (or lack thereof) encourages.  Call it the Flexible Path at Mars.

Tuesday, December 21, 2010

Compelling Planetary Science Missions: Mars Background, Part 3 (Mars Polar Climate Mission)

This continues a series of posts inspired by a similar set of posts at Future Planetary Exploration blog selecting the 5 most compelling missions from the Planetary Science Decadal Survey list.  This is the 3rd of 3 reviews of potential Mars missions, building up to a selection from that list (and I've already revealed that Mars will not be skipped in my overall selection of 5 compelling missions).

The Mars Polar Climate Mission Concepts report doesn't focus on a single mission, but instead gives a broad overview of the types of missions that could study the Martian polar deposits to reveal information about the planet's climate.  Six potential missions, covering Discovery and New Frontiers classes, are investigated: 3 orbiters roughly similar to Mars Odyssey or Mars Reconnaissance Orbiter, 2 landers roughly similar to Mars Phoenix, and 1 MER-class rover.

Clearly the MAX-C rover is a more well-developed plan than these conceptual missions, but that may be balanced somewhat by the argument that these missions are simpler and use a great deal of heritage hardware.

These missions would all study the Martian climate through its polar layers, but they would do that in quite different ways.  Science questions include the age, energy budget, and mass of the polar deposits, volatile movement between the polar layers and other regions, historical Mars climate change as reflected in the polar layer records, and how the layers might be affected by influences like erosion, dust and carbon dioxide cycles, and liquid run-off.  Orbiters tend to be better at measuring large-scale processes like water and dust transport in and out of the polar regions.  Landers would be better at measuring composition of the layers, isotope ratios, and other characteristics that require sample handling or close observation.  Quite a few measurements could be made by either orbiters or landers.

Two Discovery class orbiter missions are described.  One mission selects instruments that emphasize current weather, climate, and polar change over the course of a season.  The other mission emphasizes current movement of water and dust into and out of the polar layers, comparing this information to polar layers that record the history of similar movements.  The single New Frontiers class orbiter addresses both of these areas.  The estimated FY15 costs with reserves for the orbiter missions are $613M, $629M, and $866M, respectively.

The body of 2 static landers described in the report would be similar to the Phoenix lander.  One Discovery class static lander is described.  This would land next to a polar layer region and observe the layers from below using a high resolution multispectral imager.  It would also include a meteorology instrument suite.  The New Frontiers class static lander would land on one of the polar layered deposits and sample the deposit using melting or drilling, laser, camera, microscopic imager, meteorological suite, and spectrometer.  Rough FY15 mission cost estimates with reserves are $751M and $860M, respectively.  Based on the power and mass capabilities of the Phoenix landing platform and the limits placed on the instrument suites by the expected Discovery and New Frontiers cost limits, considerable additional capabilities (drills, robotic arms, sensors, etc) could be added to the landers if funded by external sources.  For example, the mass of the strawman instrument suite for the Discovery mission is 11.3 kg, and the mass of the instrument suite for the New Frontiers mission is 31.2 kg, but the Phoenix platform allowed 65.0 kg.

The New Frontiers class rover, costed at $1,049M, would bring a rock corer like the one planned for the MAX-C rover, a mass spectrometer, imagers, and a meteorological package, all with heritage from other Mars rover missions.  The rover itself would be based closely on the MER rovers.  The mission would be expected to last at most 90 sols if based on solar power because of the encroachment of the polar cap and lack of sunlight near the pole as winter approaches.  The value of the rover is that it would be able to directly access multiple polar deposit layers.

The next post in this series will include my selection of the most compelling mission from among the MAX-C rover, Mars Geophysical Network, and Mar Polar Climate missions.

Monday, December 20, 2010

Compelling Planetary Science Missions: Mars Background, Part 2 (Mars Geophysical Network)

This continues a series of posts inspired by a similar set of posts at Future Planetary Exploration blog selecting the 5 most compelling missions from the Planetary Science Decadal Survey list.  This is the 2nd of 3 reviews of potential Mars missions, building up to a selection from that list (and I've already revealed that Mars will not be skipped in my selection of 5 compelling missions).

The Mars Geophysical Network Options Decadal Survey study presents a number of options beyond the Network Pathfinder described in the previous post to study the interior of Mars.  The science to be addressed by these mission options includes seismology, precision tracking to measure Mars rotation rate, precession, nutation, and polar motion, meteorology to determine atmospheric effects to the seismology instrumentation, subsurface heat flow analysis, and electromagnetic sounding.  Science goals including measuring the structure, composition, and size of the crust, mantle, and core, and measuring heat flow through the crust.  For simplicity, only the key seismology and (telecommunications-based) precision tracking capabilities are considered in cost comparisons, although there is ample room for more instrumentation in the landing mass allowances.  Because multiple simultaneous seismology measurements increase the value of these measurements considerably, from 1 to 3 distributed landers are considered in the options (hence the Geophysical Network).  Other variations beyond the number of landers include landing method (airbag or powered), mission "class" (New Frontiers, Discovery, or Mission of Opportunity hitching a ride), and method to get to Mars (shared vehicle, free flyer, or secondary payload)

Interestingly, the basic "Mission of Opportunity" scenario estimated costs ranged from $522M to $627M, far higher than the Sky Crane Network Pathfinder option described in the previous post.  New Frontiers class scenarios with 2-3 landers ranged from $1,015M to $1,347M; only the scenario with only 2 powered landers fit the New Frontiers cost limit.  For the Discovery mission class options which all had only 1 lander, only the Falcon 9 launch and powered landing approached (but, at $720M, still exceeded) the anticipated FY15 Discovery mission cost limit.  It is noted that for these missions with high heritage from systems already used on Mars (e.g.: Mars Phoenix, Mars Exploration Rovers, and Mars Pathfinder), the Decadal Survey's required development phase reserves (50%) might be more than is needed for these mission options with little technology to develop.  Also, costs were made based on all U.S. development, but it's expected that the main instrument, the seismometer, would be contributed by a European agency.  It's possible that additional instruments would use funding sources from outside NASA Planetary Science, too.

Sunday, December 19, 2010

Compelling Planetary Science Missions: Mars Background, Part 1 (MAX-C Rover)

This continues a series of posts inspired by a similar set of posts at Future Planetary Exploration blog selecting the 5 most compelling missions from the Planetary Science Decadal Survey list.

As should be no surprise, Mars is well represented in the Planetary Science Decadal Survey Mission and Technology Studies.  My personal selection of the most compelling Planetary Science missions probably goes against the prevailing preference of the Planetary Science community, so I'm certainly not going to be so rash as to skip favored Mars in my list of compelling missions.  The question then becomes which Mars mission should I select from the Decadal Survey's list?

The Survey includes 7 papers on Mars missions, but the choice isn't going to be as hard as that makes it sound.  Two of the papers are on the same general topic - a Mars Geophysical Network mission.  Three are on a 3-part series of missions to return Mars samples to Earth, and I'm simply going to rule out selection of the 2nd and 3rd of these missions in case the 1st fails or does not find samples that are interesting enough to deserve 2 additional missions to return.  There is a study on Sky Crane capabilities for the 2018 Mars opportunity which really boils down to a potential augmentation of the first of the Mars sample return missions.  Finally, there is an investigation on a variety Mars Polar Climate missions.  In other words, there are 3 basic missions to choose from, possibly followed by additional choices on the details of the selected mission.

Out of the 3 basic mission choices, the first of 3 Mars Sample Return missions surely has the most backing within the Mars science community.  That community has hungered for Mars Sample Return since, well, the Noachian period, it seems.  Not only that, but the 2018 MAX-C Caching Rover, which is to perform this first phase of the sample return sequence, is part of a multi-component international collaboration between NASA and ESA.  In 2016, NASA and ESA plan to launch the ExoMars Trace Gas Orbiter and an ESA Mars landing technology demonstration.  The Mars Trace Gas Orbiter is intended to investigate methane and other trace gases on Mars.  This will help select interesting destinations for the 2018 mission.  The orbiter will also serve as a telecommunications relay for the 2018 lander elements.

The 2018 NASA-ESA collaboration uses the Sky Crane landing method of NASA's Mars Science Laboratory.  However, instead of one larger rover, this time the payload is 2 smaller rovers.  ESA will contribute the ExoMars Rover, which will be able to drill 2 meters and collect soil samples.  The rover includes a variety of instruments to analyze the samples, drilled hole, and region around the rover.

NASA's 2018 contributions include the rocket, Sky Crane, and Mars Astrobiology Explorer-Cacher Rover.  This rover would be able to rove 20 km over 500 sols, retrieve 19 ten-gram rock core samples, and store them in a cache that is easily fetched by the next phase of the sample return (with a backup cache that also holds 19 samples).  The proposed rover instruments include a Panorama camera like the MER and Phoenix lander cameras to identify good sample sites and to give sample context, a NIR spectrometer for mineralogical mapping, an arm-mounted microscopic imager like the MER one, an Alpha-Particle X-Ray Spectrometer (APXS) similar to the MER and MSL ones to show what elements make up rocks the instrument is placed on, a Raman/fluorescence instrument to assess organics in rocks, and a sample caching system using an arm, drill, and caches. 

All of this in-situ science and sample return preparation is compelling, but the decision becomes more difficult when costs are considered.  The estimated FY15 cost (with the usual reserves) for NASA's contributions to the 2018 mission is about $2.2B.  That's quite a lot.  Now to be fair, the mission doesn't just do top quality in-situ science and take a big step towards the Mars sample return holy grail.  It also delivers an entirely separate and capable rover from ESA that can do work that MAX-C can't, which probably makes the 2 rovers more valuable as a team than they would be as rovers at separate locations.

Still. $2.2B ...

The Sky Crane study raises an interesting possibility.  Apparently, even with 2 rovers, there is plenty of room for additional payload for the mission.  For an additional $150M, a basic geophysical Network Pathfinder could be delivered to the Martian surface with the 2 rovers.  Mass delivery margin would be 29%, which is less than the 30% that is required, but this is close enough that a more detailed investigation might find ways to fit the additional payload comfortably within the mass margin like merging the Network Lander and landing pallet.  The Network Pathfinder would include a seismometer and meteorological sensors.  (More ambitious Network Pathfinder scenarios are also presented should the ESA rover not be assigned to the mission). 

Still, it might be nice to see that Sky Crane actually work on Mars for MSL before developing the MAX-C plan.

The bottom line is that this is a compelling mission, but it's expensive.  Is it compelling enough to be worth the expense (and therefore missed opportunities)?  Will I let my emotional annoyance at the fact that the mission uses a whole new rover design after all the trouble we went to design and build MSL and the MER rovers before that, and even uses the Sky Crane in a different way (2 rovers instead of 1) get the best of me?  Find out as I take a look at the Mars Geophysical Network and Mars Polar Climate mission concepts in the next 2 posts.

Tuesday, December 14, 2010

Compelling Planetary Science Missions: Enceladus Orbiter

For my first choice of compelling missions from the Planetary Science Decadal Survey Mission List, I picked the Lunar Polar Volatiles Explorer mission to send a rover to the Moon to assess the volatiles there.  This mission has great science and "astronaut scouting" potential.  However, in my first post in the series, I said that

Planetary Science should not have to be warped beyond recognition into a substitute Robotic Precursor program just because Congress isn't wise enough to adequately fund Robotic Precursors. 

While robotic "astronaut scouting" has a great deal of value, we should let Planetary Science be Planetary Science, and the Jupiter and Saturn systems (if I may group them together) are certainly top-tier Planetary Science subjects.  As a result, it's just a matter of choosing one of the Jupiter and Saturn missions from the Decadal Survey list for the second-place spot.

The front-runner for a Jupiter or Saturn mission is probably the Jupiter Europa Orbiter (JEO). There are a number of reasons to pick this one as my second most compelling mission:

The Vision for Space Exploration that this blog takes its name from specifically identifies robotic missions to Jupiter's moons (in that case the Jupiter Icy Moons Explorer (JIMO):

Conduct robotic exploration across the solar system for scientific purposes and to support human exploration. In particular, explore Jupiter’s moons, asteroids and other bodies to search for evidence of life, to understand the history of the solar system, and to search for resources;

However, the VSE also mentions missions to Saturn to follow Cassini, such as a Titan balloon.  I'd suggest that the VSE would have also considered Enceladus had it been written long enough after Cassini's work at Saturn started. 

A Europa orbiter has been studied in detail for many years.  Such a mission has been a high priority for the Planetary Science community for years, too.  JEO also has the potential for mutual observations with ESA's Jupiter Ganymede Orbiter if that mission is selected.  JEO would not only study Europa from orbit with instruments like a laser altimeter, ice-penetrating radar, and many others to find out about Europa's likely subsurface ocean, deep interior, ice shell, and surface, but it would also conduct numerous flybys of Ganymede, Callisto, and Io, and would be able to study the entire Jupiter system during its long tour towards Europa orbit.  It would also be able to conduct its mission years before an Enceladus orbiter.  In addition, researchers have had many years to consider the Galileo results, whereas Cassini is still in operation and could still change our perspective on just how an Enceladus mission should be conducted.

Now that I've made the case for JEO, I'm going to select an Enceladus orbiter as my second most compelling mission instead.  Enceladus wins me over for 2 reasons: the JEO price tag is a bit scary (even the Enceladus orbiter is not cheap), and Enceladus has those plumes!  The Titan Saturn System Mission would also study the plumes of Enceladus, to say nothing of also conducting a staggeringly ambitious investigation of Titan and the entire Saturn system with a spacecraft bristling with instruments and carrying a Titan lake lander and a balloon, but again the estimated cost is too high ($3.248B for the floor mission, not counting partner costs) for my faster-better-cheaper instincts.

The Decadal Survey looked into a number of Enceladus missions, including flybys, landers, and orbiters (see "Enceladus Flyby and Sample Return Concept Studies" on the Planetary Science Decadal Survey Mission & Technology Studies page).  The conclusion was that Enceladus landers would be better done after an orbiter mission, and orbiter missions would return more science than sample return missions of similar cost.  The "Enceladus Orbiter Concept Study" available on the same page gives more details about orbiter mission options.

Like JEO, an Enceladus Orbiter would conduct a tour of its destination planetary system before intense study of its destination moon.  The tour presented includes 40 flybys of Titan, Rhea, Dione, and Tethys, and 20 flybys of Enceladus itself, before the Enceladus orbit phase.  The main goals of the orbiter would be to study the source of the plumes, the composition, rate, and dynamics of the plumes themselves, the geology of Enceladus, the internal makeup of Enceladus including the subsurface ocean, scouting for future landers, and studies of other moons it would fly by.  Instruments would include a camera designed for the tiger stripe region of Enceladus, a thermal imaging radiometer, a mass spectrometer to measure the makeup of the plumes while the orbiter goes through them, a dust analyzer, and a magnetometer to study the moon's magnetic field for clues about the subsurface ocean as Galileo did for Jupiter's icy moons. 

Little technology development would be needed for the mission.  The baseline mission cost in FY15 dollars is projected to be $1.613B, including a significant amount for post-launch work like conducting the journey to Saturn and the science phase over many years.

Sunday, December 12, 2010

Compelling Planetary Science Missions: Lunar Polar Volatiles Explorer

See Part 1: Compelling Planetary Science Missions in this series of posts.

My first selection for the most compelling planetary science mission on the Decadal Survey list is the Lunar Polar Volatiles Explorer (LPVE).  From the Executive Summary:

The Lunar Polar Volatiles Explorer concept involves placing a lander and rover (with an instrument payload) in a permanently sun-shadowed lunar polar crater. The rover will carry a suite of science instruments to investigate the location, composition, and state of volatiles. While previous orbital missions have provided data that support the possibility of water ice deposits existing in the polar region, this LPVE concept seeks to understand the nature of those volatiles by direct in-situ measurement. A prospecting strategy is employed to enable lateral and vertical sampling only where higher hydrogen concentrations are detected, thus eliminating the criticality of statistically significant numbers and distributions of samples required by stochastic approaches.

As with most or all of the Decadal Survey mission concepts, there are more and less capable variants of this mission.  For example, some instruments that are in more capable variants could be dropped for a more affordable but less capable mission, and the rover power system could be based on batteries or ASRGs. 

Lunar volatiles are of scientific interest

because they record not only those released from the interior of the Moon during its geologic evolution, but also species derived from the solar wind, cosmic dust, and comets. Thus, the volatiles in the cold traps provide a record of the evolution of the Moon, the history of the sun, and the nature of comets that have entered the inner solar system over the last several billion years.

They are also of interest as potential resources for later exploration missions or even lunar and cis-lunar space infrastructure development.

The LPVE mission seeks to answer questions about the distribution, chemical and isotopic composition, physical form, and deposition rate of the volatiles.  We don't know the distribution of the volatiles, so we need a mobile explorer so we can test multiple locations.  That's where the rover comes in.  A neutron spectrometer on the rover is used to identify locations in the regolith with hydrogen.  The rover positions itself at the locations.  It's able to drill 2 meters into the regolith.  Instruments like another neutron spectrometer and an imager can be put in the drill hole to assess any volatiles there.  This allows the rover to identify the best sample locations within the hole.  The rover is able to retrieve samples from the drill hole and bring them to a gas chromatograph / mass spectrometer that heats them for analysis.

In addition to these "core" capabilities, "priority 2" instruments include X-Ray diffraction to measure the mineralogy of the retrieved samples, ground-penetrating radar and surface imaging for geological context, and a mass spectrometer to measure the lunar exosphere.

The fully-capable mission variant with an ASRG would be expected to last over a year and to be able to travel nearly 200 km.  It would be able to take 460 samples.  Battery variants would last a few days, be able to travel a few km, and be able to take about 20 samples.  Since this is my most compelling mission pick, I would be inclined to go for the full instrument suite and ASRG power supply in this case.  The difference in mission cost (at least in the estimates presented in the report) is minor, and the increased capability is significant.  The fully capable mission cost is estimated to be $1.132B in FY15 dollars; the battery mission cost is estimated to be $0.972B.  That's a lot of money in either case, but all of the missions in the Decadal Survey list are in the more expensive New Frontiers or Flagship mission classes.  If any funds are available from the Robotic Precursor line in upcoming years, one might imagine that funding line contributing an instrument or 2, making it easier for Planetary Science to run a fully capable LPVE mission.

In addition to the science, "astronaut scouting", and resource potential of this mission, I find the idea of a capable rover moving across hundreds of kilometers while drilling into the dirt to be compelling at a more basic level.  It seems that this sort of mission speaks to the handyman or "Dirty Jobs" part of our nature.  It just looks like a lot of fun.

Compelling Planetary Science Missions

The blog Future Planetary Exploration has a series of posts that present one view of the 5 most compelling planetary science missions from the list that the Planetary Science Decadal Survey is considering.  The posts describe missions that would most fundamentally advance our understanding of the solar system.  Using this measure, they do a good job of justifying the selection of the 4 missions described so far:

Thoughts on the Most Compelling Proposed Planetary Mission - This initial post in the series gives some background, and proposes the first of 3 missions for Mars Sample Return, the 2018 MAX-C rover, as the most compelling mission.  In spite of some skepticism about technical difficulty and cost, the opportunity to take advantage of the favorable 2018 Mars launch window, the Mars Surface Laboratory team's capabilities that would otherwise be dispersed, and the ability to work with Europe's ExoMars with subsurface sample capabilities is too tempting to pass up.

Compelling Missions - Part 2 - The Venus Climate Flagship, a scaled-down version of an ambitious Venus Flagship mission concept, is presented as the second most compelling mission.  This was posted a bit before the Decadal Survey list was released, so my interpretation is that it isn't so much a selection of the specific Venus Climate mission that's on the Survey's list, but rather that NASA would at least make some significant contribution to Venus studies, perhaps as part of a multinational Venus mission.

Compelling Missions 3 and 4: Icy Ocean Worlds - Missions to explore the icy Jovian moons and Saturn's Titan and Enceladus are next on the list.  The preference is for the Europa Jupiter System Flagship mission and one of the Enceladus orbiter missions with significant Titan capability, but

this combination would cost almost $6B.  Combine that with a $3-4B investment in Mars missions (which I predict will be the Decadal Survey's top priority) and a couple of Discovery missions, and that's pretty much the entire budget for missions next decade.  I also think that the Flagship missions may face have a couple of programmatic challenges.  First, NASA's last two choices for Flagship-scale missions, the Mars Science Laboratory and the James Webb Space Telescope, both experienced large cost overruns. ...

Several later posts look at lower-cost options to achieve some of the goals at the moons of Jupiter and Saturn.

While waiting for the last compelling mission, I decided to make my own series of "most compelling mission" posts with a different perspective.  These are supposed to be Planetary Science missions, so science return is an appropriate measure to use to compare the various missions.  However, I'd like to bring other factors into play, too.

I'd like to consider the Planetary Science missions in the context of our overall exploration and development of space.  A mission that helps NASA's human spaceflight program (whether Vision for Space Exploration, Flexible Path to Mars, or other approach) and/or traditional and new commercial space efforts will have an edge in my evaluation.  On the other hand, we are talking about Planetary Science, not Robotic Precursor missions.  Therefore, I will stick to the Decadal Survey list, which is full of missions with high-priority science content.  Planetary Science should not have to be warped beyond recognition into a substitute Robotic Precursor program just because Congress isn't wise enough to adequately fund Robotic Precursors.

For a fair comparison, I won't even consider the current 3 New Frontiers finalists (SAGE, a Venus lander mission, MoonRise, for sample return from the lunar South Pole-Aitken Basin, and OSIRIS-REx, for sample return from the asteroid 1999 RQ36), although I would otherwise be inclined to put them near or at the top of my list.

Decadal Survey: The Candy Store Posted - In order to play this game, you have to know what the proposed missions are.  This Future Planetary Exploration post gives the links and information needed to find out about the missions the Decadal Survey is evaluating.  The Decadal Survey reports are here.  The post also includes a handy table that summarizes the missions, their anticipated launch, arrival, and end dates, and a cost estimate or cost range for each mission.  Certain missions' cost estimates can be considered to be more reliable than others for various reasons (heritage, maturity of the particular mission proposal, etc), but I'll just take them as presented here.

Saturday, December 11, 2010

Twitter Account

I have a new twitter account: VisionRestore.

Also, I have some ideas for posts that have been simmering for quite a while, waiting for a chance to be written down.  I won't make any promises on when I'll finish, but I've finally started.