FINDING: Astronomical discoveries with Hubble from the solar system to the edge of the universe are among the most significant intellectual achievements of the space science program.

FINDING: The scientific power of Hubble has grown enormously as a result of previous servicing missions.

FINDING: The growth in the scientific power of Hubble would continue with the installation of the two new instruments, WFC3 and COS, planned for the SM-4 shuttle astronaut mission.

Because a robotic servicing mission does not involve risks to the safety of an astronaut crew, the principal concerns are the risk of failure to develop a robotic mission capability in time to service Hubble, and the risk of a mission failure that results in an inability to perform the needed servicing, or worse, critically damages Hubble during the mission. Both schedule risk and mission risk are composed of a large number of factors that were studied in considerable detail by the committee.

Some of the critical components of mission risk include lack of adequate development time to validate the hardware, level of software and system performance required to rendezvous with Hubble, failure to successfully grapple and dock with Hubble, failure to successfully execute the combination of complex autonomous and robotic activities required to actually accomplish HST revitalization and instrument replacement, and the risk of unforeseen Hubble failures prior to mission execution that the robotic mission will not have been designed to repair. One example of a mission risk that concerned the committee is the complicated docking maneuver required for a Hubble robotic servicing, which has never been performed autonomously or teleoperated with time delays. Specifically, the use of the grapple system to autonomously perform close-proximity maneuvers and the final capture of Hubble is a significant challenge and is one of the key technical aspects of a robotic servicing mission that has no precedent in the history of the space program.

The components of schedule risk examined by the committee included the readiness levels of such technologies as the sensors, software and control algorithms, and vision-based closed-loop support for autonomous docking operations, as well as NASA’s relevant programmatic and technical expertise, resources, and specific development plans for a robotic servicing mission. From the risk mitigation viewpoint, the committee judged that the planned use of the mature International Space Station robotic arm and robotic operational ground system helps reduce both the schedule risk and the development risk for the robotic mission. In addition, the committee assessed the development schedule for the robotic servicing mission based on its experience with programs of similar complexity and the historical spacecraft development schedule data provided by both NASA and the Aerospace Corporation. The committee’s key findings regarding the question of the risk of robotic servicing are as follows:

FINDING: The technology required for the proposed HST robotic servicing mission involves a level of complexity, sophistication, and maturity that requires significant development, integration, and demonstration to reach flight readiness and has inherent risks that are inconsistent with the need to service Hubble as soon as possible.

FINDING: The Goddard Space Flight Center HST project has a long history of HST shuttle servicing experience but has little experience with autonomous rendezvous and docking or robotic technology development, or with the operations required for the baseline HST robotic servicing mission.

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)