Sunday, November 16, 2008

New Frontiers mission options

Release Date: November 17, 2008
The National Aeronautics and Space Administration (NASA) Science
Mission Directorate is releasing a Draft Announcement of Opportunity
(AO) for community review and comment for the next mission in the New
Frontiers program (NNH09ZDA003J). The science objectives covered by
the Draft New Frontiers AO include South Pole -- Aitken Basin Sample
Return, Venus in Situ Explorer, Comet Surface Sample Return, Network
Science, Trojan/Centaur Reconnaissance, Asteroid Rover/Sample Return,
Io Observer, and Ganymede Observer.

Note the opportunity to vote for your favorite mission on this blog page.
The rules for the selection are:

o In November 2009, up to three missions will be selected for a 9 to 11 month Phase A that will be funded up to $2.5M each. Down selection to a single mission for flight will occur in January 2011. Launch is to occur no earlier than 2015 and no later than 2018.

o This NF-3 AO will solicit only missions that do not require nuclear sources for power generation or propulsion, although Radioisotope Heating Units (RHUs) and calibration sources will be allowed.

o The Principal Investigator (PI) Mission Cost for all phases of the mission will not include the launch vehicle and will be capped at $650M in FY09 dollars.

o Proposers will be given the option of selecting none or one of two specific technologies for insertion into their mission. The two technologies are the NASA Evolutionary Xenon Thruster (NEXT) and the Advanced Materials Bipropellant Rocket (AMBR) engine. For missions that insert NEXT, the cap on the PI Mission Cost will be raised up to $15M. For missions that insert AMBR, the cap on the PI Mission Cost will be raised up to $5M.

To refresh your memory, New Frontier’s missions are non-Mars (with a possible exception noted below) missions with a price tag of $500M-$1B. (The price envelope changes with each mission.) NASA announces that it will select a mission targeted to a pre-selected group of destinations, and scientists (paired with laboratories such as the Johns Hopkins Applied Physics Lab or JPL or paired with an aerospace company) propose missions. NASA then selects the mission with the best science return given the budget and development risk. The New Horizon’s Pluto mission was the first New Frontiers mission selected and the Juno Jupiter mission the second.

The price cap in particular seems very tight (although the launch is not included). My guess is that this will limit the complexity and development R&D of the missions. I expect that a fairly simple mission will be selected.

NASA preselects a group of target missions from which it selects the winning mission. (Mars has been excluded from previous selections.)

Which mission gets selected is hard to handicap in advance since it requires knowledge of the details of the proposals. Often issues of cost or risk not generally known to the public can be the deciding factor. Several of the targets have mission studies in progress as part of concept studies for the Discovery program but would use Stirling RTG power sources. I would not be surprised to see those proposals adapted for the New Horizons competition but with the use of solar panels.

It is fun to speculate about what you personally would like to see based on the thrill of exploration and expected scientific return. So for the next selection, here is my assessment; it is strictly personal and everyone is encouraged to present their own views:

Asteroid Rover/Sample Return – Returned samples can tell us much more than can a simple orbiter or lander. However, this mission probably has several challenges. The easy to reach near Earth asteroids probably are not the most interesting asteroids, and the main belt asteroids would be very challenging to do for a round trip mission. Grabbing the most scientifically meaningful sample from an asteroid is challenging. Also, laboratories have lots of asteroid samples already in the form of meteorites. Rovers on the small asteroids are technically challenging -- hoppers are easier. Rovers on larger main belt asteroids face the costs of reaching the destination and implementing a descent system.

Comet Surface Sample Return Mission – The New Frontiers competitions generally allow creativity in meeting the goals so an alternative mission that has been proposed to collect the samples from the coma might be an alternative. Here, I think that the diversity of comets and our new knowledge that they may have substantial dust covers makes it questionable whether or not a mission would get meaningful samples of the ice. I think this mission is unlikely to be chosen before the Rosetta comet rendezvous/lander mission tells us a lot more about the surfaces of comets. It would also be very challenging to return cryogenically frozen ice samples in a New Frontier’s budget. The review panels have said that it would be okay to propose a mission that returns melted samples, but the proposers would have to show that such samples would still have scientific merit.

Ganymede Observer/Io Observer – I put these together because they have similar challenges. The challenge for both these missions is to convince review panels that more flybys of these moons is a good way to spend $650M+. Based on past mission studies, an orbiter for Ganymede would not seem to fit within the budget (and is technically impossible for Io given the radiation). Both missions have the challenge of making solar panels work in the radiation belts of Jupiter (a much more severe challenge for an Io mission). I will point out that the two missions could be combined. A craft could initially do a series of Io flybys, raise perijove, and then do a series of Ganymede flybys (or alternatively, a series of Europa flybys) with continuing long range observations of Io and Jupiter. This more complicated mission probably busts the budget, but follow-on flybys of Ganymede might be funded as a Discovery program mission of opportunity. If the Jupiter system is selected as the target for the next flagship outer planets mission, then I don't either of these missions would be selected. If the Saturn system flagship mission is selected, then the appeal of a Jovian system may rise considerably.

Lunar South Pole-Aitken Basin Sample Return Mission – Sample return missions always rank highly in terms of scientific merit. This mission was a finalist for the last competition (losing out to Juno). Why it lost wasn’t clear based on scientific merit. The complexity of landing on the moon, selecting samples that answer the key scientific questions, and then returning to the Earth may have been too great.

Network Science (including Mars) for seismology and meteorological observations distributed across a globe (other observations also possible) – Mars is the obvious candidate. A network science mission is the second highest ranked scientific goal for Mars after a Mars Sample Return. However, this mission has been estimated to have a budget above $1B and it requires an orbiter to provide communications relay (not included in the >$1B estimate). Mars also already receives a substantial portion of NASA’s planetary science budget. My guess is that the next New Frontiers mission will be used to round out the list of targets NASA is exploring. ESA’s ExoMars 2016 mission also will include a single surface station that could teach us a lot about how to tune the instruments and design of a full network.

Trojan/Centaur Reconnaissance – These are an interesting series of targets, but I don’t know if NASA will be willing to use it’s ~2 times a decade chance to fly a New Frontiers mission to do reconnaissance.

Venus in Situ Explorer – A pair of short-lived Venus landers were proposed for the last New Frontiers competition. I’ve heard through the grapevine that the mission wasn’t selected because the timing was wrong to take advantage of alignments of planets for a launch within the budget timeframe. (There may also have been substantial mission cost and implementation risk – Venus’ surface is not a friendly place!) The exploration of Venus’ atmosphere in situ and surface has been ignored (by the next time a New Frontiers mission flies) for decades. Counting against this mission is the fact that the Venus scientific community is pushing for a much more ambitious mission to Venus involving an orbiter, balloons, and more capable landers. A mission using just balloons to explore the atmosphere could be an alternative.

So which missions would I like to see if every one could fit within the dollar and risk budgets? My first choice would be a pair of Venus landers. It simply has been too long since we’ve done in situ Venus science. If not that mission, I’d pick the Io Observer, partially because Io is my second favorite moon (after Titan) and because the mission can do additional Jovian system science (Jupiter meteorological observations, for example).

My choice for the following New Frontiers mission isn’t a competition at all. I’d go with the Argo Jupiter-Saturn-Neptune/Triton-Kuiper belt mission. While it would be flybys to at all destinations, the chance to take modern instruments to Neptune/Triton is compelling as is the opportunity to explore a wider variety of Kuiper belt objects than New Horizons can (post Pluto). Observing changes in the Jupiter and Saturn systems would simply be icing on the proverbial cake.

My guess is that the final selection will go for the mission with the lowest price tag and development risk that meets the minimum bar for scientific return. Don't get me wrong -- such a mission will produce excellent science, but it's public appeal may be limited. I think the selection of the Discovery Grail mission in the last selection is an example of this criteria in operation. Superb science, but not exciting exploration. That, I think, is the price future missions will pay for past successes (all the cheap, exciting exploration missions have been done) and mistakes (the cost overruns on the Mars Science Laboratory, James Webb telescope, Kepler mission, etc.).

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