As part of the fulfillment of the "better, faster, cheaper" approach to space exploration, NASA recently revamped the venerable Explorer program. Two categories of major missions are now defined within this program: the Small Explorer (SMEX) missions, which will cost no more than $35 million to launch, excluding the launch vehicle, and the Medium-Class Explorers (MIDEX), which are limited to $70 million.
Approximately one SMEX and one MIDEX mission will fly each year. Multiple SMEX missions have already been chosen, and NASA recently completed the selection of the first two MIDEX missions. Dr. James Thieman of the NSSDC has supported this process by serving as the MIDEX program scientist since April 1995, when the MIDEX pre-proposal briefing was held. Dr. Thieman replaced Dr. Peter Vedder in this position when he left NASA Headquarters.
The MIDEX Announcement of Opportunity involved several new approaches in the selection process. For example, proposers could either use a NASA-provided spacecraft for their mission or they could propose to take the responsibility of procuring the spacecraft from industry. The selection process itself was broken into two steps for the first time. In the first step were submitted proposals that defined the science merit of the mission and only briefly summarized the cost and technical details. A scientist peer review of the Step-One proposals was the basis for selection of proposals to proceed to Step-Two. The Step-Two proposals then provided details of the technical, cost, management, etc., considerations as well as any changes to the science proposed in Step One.
Dr. Thieman's main task as program scientist was to arrange for the Step-One science peer review and any subsequent review made necessary by changes to the proposed science in Step Two. Forty-three proposals were submitted for Step-One review. From these Dr. Huntress, administrator of the Office of Space Sciences, chose 13 to proceed to Step-Two. After the final review process Dr. Huntress chose two missions for flight from among these 13. Two backup missions were also chosen if, for some reason, the prime choices were found not to be feasible during the definition phases of the mission.
The Imager for Magnetosphere-to Aurora Global Exploration (IMAGE) was chosen for the first flight, presently scheduled for launch in late 1999. This mission will explore the Earth's magnetosphere for the first time using coordinated imagery of neutral particles, charged particles, aurora, etc., to get a global picture of the dynamic processes taking place there. The principal investigator is Dr. James Burch of the Southwest Research Institute.
The Microwave Anisotropy Probe (MAP) will be launched in 2000. This mission will measure the structure within the cosmic background radiation with much higher resolution than was done by that of the Cosmic Background Explorer (COBE). The results promise to provide much better values for basic cosmological constants that determine the age of the universe, whether it is open or closed, etc. The principal investigator is Dr. Charles Bennett of Goddard Space Flight Center.
"It is unfortunate that only two missions could be chosen at the present time," said Dr. Thieman. "There were so many fundamental, compelling, and exciting missions proposed which could be done within the cost caps. The ingenuity of the science community when faced with a constrained environment bodes well for the future of space science research."
Author:Miranda Beall (email@example.com)