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This Informational Email is being distributed to AAS members as a community service. The contents were written by Alan Stern and Jon Morse and approved by them for broad release to the community. The AAS President and Executive Officer approve such occasional releases to the community.

New NASA Explorer AO
Alan Stern & Jon Morse, NASA Headquarters

Early this fall, NASAs Science Mission Directorate (SMD) will release a new Announcement of Opportunity (AO) for Principal Investigator (PI) led Explorer missions.

This is the first such call for new Explorer science missions in over four years. NASA had originally planned to issue this AO to select one MIDEX (medium-scale) Explorer mission, and one Mission of Opportunity (MO) instrument with a cost up to $35M. But instead the AO was restructured with an eye towards reinvigorating the Explorer launch rate by selecting three SMEX (small explorer) missions and any number of suitably meritorious MOs that fit within an expanded $70M funding pool. To further broaden the number of possible missions to be flown, the MO opportunity will also now allow teams to submit stand-alone micro-satellite missions. These moves will broaden both the number of experiments that fly and also the number of teams selected. In essence, we elected to revitalize the small science mission queue by refocusing the Explorer AO as described above, in concordance with recent community recommendations, such as in the NASA Astrophysics Performance Assessment (NAPA) report of the Space Studies Board of the National Research Council (NRC). We also accelerated the Explorer AO schedule to select the missions and MOs we will fly by January 2009 rather than mid-2009.

Explorer mission PIs direct their entire flight project, and the project manager and the entire project team of each Explorer mission
reports to the PI. The Explorer AO thus requires proposing mission PIs to meet minimum space flight experience criteria. This PI experience requirement is one part of an SMD-wide effort to better manage missions and mission costs so that more science can be accomplished within our budget. Although not every working astronomer and space scientist can meet these new mission PI experience requirements, many can. No experience prerequisites are placed on mission CoIs or mission scientists. Some teams may therefore choose to put a space flight experienced PI at the mission helm, but designate a deputy PI or a mission chief scientist who lacks the PI experience requirements but who would make the most natural science team leader as the mission science lead.

The 2006 NRC report on Principal Investigator-led Missions in the Space Sciences emphasized the importance of relevant experience for PIs for mission success, and recommended that NASA provide opportunities for scientists and engineers to gain practical spaceflight experience before they become involved in PI-led or core NASA missions. SMD is therefore putting in place on-ramps for those interested in being a mission PI. These on-ramps will include dramatically expanded suborbital rocket and balloon programs.

More information on this AO can be found by following the links at


Mailed to AAS members from 26 July 2007.

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