The Medium-Class Explorer (MIDEX) Announcement of Opportunity (AO) will be
modified from the Draft AO which was released for community comment on
February 14, 2001. The changes to the final AO will include the following.

1. The cost cap for MIDEX missions will be increased to $180M (FY02 dollars).
2. MIDEX missions will be allowed as attached payloads on the International
Space Station.
3. There will be additional International Space Station opportunities for
Mission of Opportunity proposals including the Express Palette, the Window
Observational Research Facility, the Japanese Experiment Module - Exposed
Facility, and astrobiology flight experiments.
4. The Spartan 400 spacecraft will not be available as government furnished
equipment (GFE).
5. Space Shuttle launches will be allowed for MIDEX missions. However,
availability of launch opportunities in the appropriate years is not
assured, and the proposer must work with the Space Shuttle Office to
identify potential opportunities.
6. With the exception of International Space Station payloads, Space
Shuttle launches and expendable launch vehicles will not be available for
Mission of Opportunity investigations.

There will be additional changes and clarifications in the final MIDEX
AO. Prospective proposers are encouraged to read the AO carefully when it
is released. Questions and answers concerning the MIDEX AO will be posted
at http://explorer.larc.nasa.gov/explorer/ppconf.html within the next two
weeks.

Questions concerning the MIDEX AO should be directed to Paul Hertz,
Explorer Program Scientist, Code SR, NASA Headquarters, Washington, DC,
20546; (phone) 202-358-0986; (FAX) 202-358-3097; (e-mail)
paul.hertz@... .