FINDING: The proposed HST robotic servicing mission involves a level of complexity that is inconsistent with the current 39-month development schedule and would require an unprecedented improvement in development performance compared with that of space missions of similar complexity. The likelihood of successful development of the HST robotic servicing mission within the baseline 39-month schedule is remote.

Based on extensive analysis, the committee concluded that the very aggressive schedule for development of a viable robotic servicing mission, the commitment to development of individual elements with incomplete systems engineering, the complexity of the mission design, the current low level of technology maturity, the magnitude of the risk-reduction efforts required, and the inability of a robotic servicing mission to respond to unforeseen failures that may well occur on Hubble between now and the mission, together make it highly unlikely that NASA will be able to extend the science life of HST through robotic servicing.

The risks that must be considered in making a decision to service Hubble with the shuttle are the risk to the safety of the crew and the shuttle, as well as the risk of failing to accomplish the servicing objectives. As part of its assessment of safety risk, the committee looked carefully at the findings and recommendations of the Columbia Accident Investigation Board (CAIB)⁵ and at NASA’s return-to-flight (RTF) requirements. Strong consideration was given to understanding differences in the safety risk factors between shuttle missions to the International Space Station (ISS)—to which NASA still plans to fly 25 to 30 missions—and a shuttle mission to Hubble. Technical considerations examined by the committee included comparisons of on-orbit inspection and repair capabilities at ISS and Hubble, various safe-haven and rescue options, and the likelihood of the shuttle being damaged by micrometeoroid orbital debris (MMOD). With regard to mission risk, the committee considered both the known on-orbit operations required for Hubble servicing and past experience with Hubble shuttle astronaut servicing, including such factors as unforeseen on-orbit contingencies.

The committee developed a large number of findings based on the various analyses cited above. Some of the key findings relevant to the question of the risk of shuttle servicing of HST are as follows:

FINDING: Meeting the CAIB and NASA requirements (relative to inspection and repair, safe haven, shuttle rescue, MMOD, and risk to the public) for a shuttle servicing mission to HST is viable.

FINDING: The shuttle crew safety risks of a single mission to ISS and a single HST mission are similar and the relative risks are extremely small.

FINDING: Previous human servicing missions to HST have successfully carried out unforeseen repairs as well as executing both planned and proactive equipment and science upgrades. HST’s current excellent operational status is a product of these past efforts.

FINDING: Space shuttle crews, in conjunction with their ground-based mission control teams, have

Front Matter (R1-R16)

Executive Summary (1-7)

1 Introduction (8-10)

2 Hubble Space Telescope (11-15)

3 The Impact of Hubble: Past and Future (16-39)

4 HST Observatory Assessment and Lifetime Projection (40-55)

5 HST Robotic Servicing Assessment (56-73)

6 Space Shuttle Servicing of Hubble (74-91)

7 Benefit/Risk Assessment of Hubble Space Telescope Servicing Options (92-108)

Appendix A: Statement of Task (109-111)

Appendix B: Briefings to the Committee (112-115)

Appendix C: Interim Report (116-125)

Appendix D: State of the Art in Robotics (126-129)

Appendix E: Acronyms (130-133)

Appendix F: Glossary (134-136)

Appendix G: Biographical Information for Committee Members and Staff (137-144)