Phoenix lander self portrait. Courtesy NASA/JPL-Caltech/University Arizona/Texas A&M University
Spaceflightnow.com has an article on the end of the Mars Scout program. The article suggests that this was a recent event, while I recall the program having been canceled -- or perhaps more correctly being folded into the Discovery program -- a year or two ago.
Originally conceived of as a series of small missions similar in scope and cost to the Discovery program, the Scout program was envisioned to fly missions to supplement the large missionss. Each Scout mission would be lead by a principal investigator who would propose the mission and manage it through development and flight. This was in contrast to the large orbiters and rovers that were defined by committees of scientists and managed by the Jet Propulsion Laboratory. The Phoenix lander was the first mission in the program and the MAVEN orbiter planned for launch in 2013 will be the second and last mission.
The article states that the reason for cancellation was that the focus for Mars exploration will be landed missions, which don't fit into the Scout budget. (Phoenix slipped in under the budget cap because it used an already designed and mostly built lander from a canceled mission.) My understanding is that a changing budget situation ended the program. When it was initiated, the Mars program was expected to be funded at a higher level than turned out to be be case. In addition, cost overruns on the Mars Science Laboratory reduced funding for future Mars missions (although the MAVEN mission was protected from cuts).
NASA has not abandoned small missions to Mars. Now they must compete with other solar system targets within the Discovery program. The Spaceflightnow.com article notes that several proposals for Mars missions will be submitted as part of the current Discovery mission selection process.
The MAVEN orbiter will study the upper atmosphere of Mars. Courtesy NASA
Editorial Note: Small Mars missions may lack the inherent attraction of missions to less visit parts of the solar system such as Io, Titan, comets, and asteroids. However, Mars orbiters may represent excellent science return for the buck while representing low implementation risks. Our moon has been the most visited destination in the solar system, but the last Discovery competition selected the GRAIL lunar gravity mission, presumably on these criteria.
I was under the (perhaps mistaken?) impression that the last Discovery selection was essentially the cheapest available: extend two ongoing missions and the cheapest/quickest of the three new starts.
ReplyDeleteI am willing to be proven wrong...
G Clark
In the town hall Decadal Survey meetings, someone asserted that New Frontier selections have become the selection of the lowest risk mission among the final candidates. There probably is some truth to this. If you assume that the final candidates would all produce great science, then NASA would want the mission that has the greatest chance of not busting the budget.
ReplyDeleteAmong the last Discovery candidates, the review teams determined that the OSIRIS-REX asteroid sample return was unlikely to be implementable within a Discovery budget (per a subsequent presentation by the proposal team). That mission is now a finalist for the larger-budget New Frontiers program.
The remaining two missions were the VESPER Venus climate mission and the GRAIL lunar gravity mission. I don't know which of these was lower cost, but both were orbiters in the inner solar system. Neither may have been high risk. We could speculate on potential problems with the VESPER proposed implementation or perhaps that the science was two redundant given the ESA and Japanese Venus orbiters. Only the VESPER team knows what the review team concluded. The results are confidential. It may be that the VESPER proposal was excellent but that the GRAIL proposal was excellent, too, but at lower cost and risk. So I don't know why the decision went to GRAIL.
As for the smaller missions, NASA has a program for missions of opportunity to propose instruments for foreign missions or to propose extended missions. The two mission extensions were approved under this program.