becomes more complicated if the mission is extended beyond late 2005. The TRMM spacecraft is sufficiently large that it will not burn up completely on reentry. Thus NASA will face a second decision point in roughly December 2005 when it must weigh in the element of the additional risk to life and property. For this second decision NASA must choose whether to (1) use TRMM’s remaining fuel to conduct a controlled reentry into the atmosphere that directs the remains of the satellite into the ocean far from human settlements1 or (2) continue TRMM operation until the fuel runs out in 2010 or 2011 and accept the added risk of an uncontrolled reentry because of the operational and scientific benefits of doing so.

THE ROLE OF THE NATIONAL ACADEMIES

In August 2004 NASA Administrator Sean O’Keefe requested that the National Academies provide advice on the anticipated scientific and operational contributions from extending TRMM beyond 2004. The charge to the Committee on the Future of the Tropical Rainfall Measuring Mission in the first phase of its work was to conduct a workshop and prepare an interim report to be delivered in December 2004 on how best to use the remaining TRMM spacecraft life. The Academies were able to begin the study process in October 2004, and immediately assembled the committee and planned an information-gathering workshop. The committee and workshop participants were asked to consider

  • scientific and research contributions of TRMM to date and those expected if TRMM is continued;

  • operational contributions of TRMM to date and those expected if TRMM is continued;

  • assessment of expected benefits of continuing TRMM operation until (1) fuel is depleted to the level needed for a controlled reentry (around December 2005), and (2) all fuel is depleted (estimated to be 2010-2011).

A second phase of the committee’s work will focus on needs for satellite-based measurements of tropical rainfall beyond TRMM (see Appendix B).

The committee hosted its phase I workshop in Washington, D.C., on November 8, 2004,2 and subsequently drew on information and discussions from the meeting and other written inputs and information sources to address its task for phase I.

1

In this scenario controlled reentry would be in 2008 after the satellite had drifted to a lower orbit for roughly two years.

2

See http://dels.nas.edu/basc/trmm for presentations from the workshop.



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