In keeping with the statement of task given to the committee, this report does not address, or support, any changes in priorities for astronomical research or facilities. The committee assumed that NASA, in order to strive for frontier achievements in astronomy and astrophysics, would follow the 2001 decadal survey’s advisory recommendations. If NASA concludes that it cannot move forward with portions of the decadal survey strategy, then NASA will have to carry out an examination of priorities for the research field. The committee does not endorse such a re-examination. The committee notes that if a re-examination should occur it would have to be conducted in a very timely and very expeditious fashion in order to ensure the continued operation and integrity of Hubble (see discussions in Chapter 4).


To address the various aspects of its task required that the committee engage in considerable analysis of a large volume of technical material and information provided in various briefings. Two key documents to which the committee referred frequently were the report of the Columbia Accident Investigation Board and a NASA document titled NASA’s Implementation Plan for Space Shuttle Return to Flight and Beyond.5 In addition, the committee had access to numerous additional reports and technical documents on topics ranging from the test data on Hubble battery recharging cycles to industry proposals for the development of robotic missions.6 The committee’s work also benefited from the input of many experts at NASA and in academia and industry, who gave extensive briefings (listed in Appendix B), and from information received from many other individuals who made themselves available by telephone and e-mail to answer specific questions posed by committee members. The committee’s analysis was limited by the dearth of data in some areas, such as the lack of a probabilistic risk assessment that took into account the differences in the safety risk of shuttle missions to ISS versus to Hubble, and the lack of detailed cost estimates for the SM-4 shuttle mission. A study by the Government Accountability Office (previously the General Accounting Office) being prepared for release in late 2004 assesses the costs of such a mission, and its findings are expected to be considered along with those of this committee when a decision is made regarding HST servicing.

Those issues that involved the most data, or required the most complex analysis, are treated in separate chapters of this report: (1) the scientific benefits of servicing Hubble, in Chapter 3; (2) the servicing needs and operational status of Hubble, in Chapter 4; (3) the prospects for Hubble servicing via a robotic mission, in Chapter 5; (4) the prospects for Hubble servicing via a shuttle mission, in Chapter 6; and (5) a discussion of the various types of risks involved in servicing Hubble, in Chapter 7. Although robotic servicing and shuttle servicing were the options to which the committee devoted the most time and energy, other options for extending the life of Hubble were considered, and discussion of these is included where appropriate throughout the report. Each section of the report contains findings relevant to the task statement. The final conclusions and recommendations of the study, stated simply in Chapter 8, derive directly from the findings and analysis presented in the preceding chapters.


NASA, NASA’s Implementation Plan for Space Shuttle Return to Flight and Beyond, Volume 1, Revision 1, October 15, 2003. This and subsequent revisions (2.1, July 28, 2004; 2.2, August 27, 2004) are available online at During the course of this study, this document underwent a number of revisions, each of which was supplied to the committee.


See, for example, Steven J. Gentz, NASA Engineering and Safety Center, “Technical Consultation of the Hubble Space Telescope (HST) Nickel Hydrogen (NiH2) Battery Charge Capacity Prediction,” RP-04-08, June 17, 2004, NASA.

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