August 15, 2007

Dear Colleagues,

In recognition that the Spitzer cryogenic mission will be ending at roughly the end of 
March 2009, and that Cycle 5 is the last call for cryogenic operation of Spitzer, I 
convened a special advisory committee in July to address the question "What Must Spitzer
Do Before the Helium Runs Out?"  The committee was drawn from senior members of the 
astronomical community. The group was unanimous in finding the research pursued by 
Spitzer to be imaginative, balanced and highly productive.  No gaping holes were 
identified in the Spitzer science program.

The main recommendation of the committee, already adopted in the Cycle-5 Call for 
Proposals, was that priority for Spitzer observations in the time left for cryogenic 
operations should be:

 1. to fill scientific gaps in the Spitzer program
 2. to pursue follow-on observations of uniquely Spitzer discoveries, and
 3. to exploit the unique capabilities of Spitzer during the final cryogenic
      observing cycle.

I especially encourage you to submit proposals for Spitzer Cycle 5 that address the 
above priorities.  As a reminder, the selection criteria for Spitzer science proposals 
are clearly stated in the appropriate section of the Cycle 5 call for proposals.

Summaries of all approved programs, sorted by cycle and science category, were generated
for the committee meeting.  These summary materials are provided here and will be made 
available to members of the Cycle-5 review panels and TAC.  These summaries are provided
for your convenience, and are a supplement to searching for specific observations from 
the Spitzer observations database with Leopard.

Sincerely yours,

B. T. Soifer
Director, Spitzer Science Center