recommendations of the CAIB that must be implemented prior to returning to flight. NASA Administrator Sean O’Keefe committed the agency to following the CAIB recommendations.

In mid-January 2004 O’Keefe announced that, as a consequence of safety considerations, NASA would reduce its shuttle manifest to only the 25 to 30 (the precise number of flights required is uncertain at this time) planned missions required to build the ISS. The decision was also made, on the basis of risk, to not pursue the Hubble Space Telescope SM-4, but instead to investigate other options for extending the life of HST. That announcement was followed by considerable expression of public concern in many media outlets about the future of Hubble, and astronomers and other scientists also raised many questions about the decision. Senator Barbara Mikulski (D-Maryland) asked O’Keefe to seek an independent opinion on whether the decision to cancel SM-4 was, in fact, required for compliance with the CAIB’s recommendations. In response, O’Keefe asked the CAIB chair, Adm. Harold Gehman, to review the matter. In his March 5, 2003, letter to Mikulski, Gehman said that “the Board is split on the merits of flying this mission.” He also indicated that “whether to fly another mission to the Hubble is one of the public policy debates this nation should have,” and he called for a “deep and rich study of the entire gain/risk equation (to) answer the question of whether an extension of the life of [HST] is worth the risks involved.”

Subsequently the National Research Council was asked to perform such a study. To do so, it appointed the Committee on the Assessment of Options for Extending the Life of the Hubble Space Telescope. This final report, together with an interim report released in July 2004,2 represents the outcome of that effort.


The principal goal of this study is to assess options for extending the life of HST. The assessment considers issues of safety in the use of the space shuttle for servicing HST with an astronaut crew, the feasibility of robotic servicing approaches, the impacts of servicing options on HST’s scientific capability, and risk/benefit relationships between servicing options that are deemed acceptable. The specific tasks addressed in the course of the study are listed in Appendix A.

During the development of the most recent decadal strategy for astronomy and astrophysics,3 it was assumed that the Hubble SM-4 mission, long considered an integral element of the U.S. space astronomy program, would be conducted at the time necessary to prevent the demise of the telescope and to enable Hubble’s ongoing operation for conducting astronomical research in the wavelength range covered by HST. The next major facility initiative in space astronomy given priority in the 2001 decadal strategy was the James Webb Space Telescope (JWST). The advisory panel convened by NASA in 2003 to advise it on the transition from HST to the JWST concurred with the decadal survey on the need for the SM-4 servicing mission and noted the work that had already been done, and was currently in progress, toward this servicing.4 The advisory panel recommended that a servicing mission SM-5 also be pursued, but only “in a peer-reviewed competition with other new space astrophysics proposals.”


See Appendix C, National Research Council, “Assessment of Options for Extending the Life of the Hubble Space Telescope,” letter from Louis J. Lanzerotti, chair of the Committee on the Assessment of Options for Extending the Life of the Hubble Space Telescope, to Sean O’Keefe, NASA administrator, July 13, 2004. Available online at


National Research Council, 2001, Astronomy and Astrophysics in the New Millennium, National Academy Press, Washington, D.C.


HST-JWST Transition Panel, Report of the HST-JWST Transition Panel, August 14, 2003. Available online at

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