AIP FYI #158: Hubble Servicing Report

FYI
The American Institute of Physics Bulletin of Science Policy News
Number 158: December 14, 2004

NRC Panel Endorses Shuttle Servicing Mission to Hubble

“A shuttle astronaut servicing mission is the best option for
extending the life of Hubble and preparing the observatory for
eventual robotic de-orbiting….  Given the intrinsic value of a
serviced Hubble, and the high likelihood of success for a shuttle
servicing mission, the committee judges that such a mission is worth
the risk.”  – Committee on the Assessment of Options for Extending
the Life of the Hubble Space Telescope

A National Research Council panel evaluating the options for
extending the scientific life of the Hubble Space Telescope (HST)
finds that, in the time available, the likelihood of success of a
proposed robotic servicing mission is “remote.”  The Committee on
the Assessment of Options for Extending the Life of the Hubble Space
Telescope reviewed NASA’s plans for a proposed robotic servicing
mission versus a manned servicing mission using the space shuttle,
and warns that the “very aggressive” development schedule, as well
as the required level of technological complexity, maturity,
sophistication, and ability to adapt to unforeseen events, “make it
unlikely that NASA will be able to extend the science life of HST
through robotic servicing.”  It further concludes that a space
shuttle servicing mission would be “highly likely to succeed,” and
could be flown “as early as the seventh flight after return to
flight [of the shuttle fleet] without a critical operational impact”
on the International Space Station (ISS).

The committee, composed of 21 experts from industry, academia and
government, was asked to “conduct an independent assessment of
options for extending the life” of the HST, including a benefit/risk
assessment of whether servicing the Hubble, by a shuttle mission or
other means, “is worth the risks involved.”  The committee submitted
an interim report in July (see
http://www.aip.org/fyi/2004/096.html ).  After a lengthy and
comprehensive analysis, its final report is now in prepublication
form.  The report runs over 130 pages with appendices.  Its eight
chapters include background information on the Hubble, its past and
future scientific impacts, projections of component failure,
evaluations of robotic and shuttle servicing options, a benefit/risk
assessment of the options, and final recommendations.

The Hubble is “the most powerful space astronomical facility ever
built,” says the report.  It “provides wavelength coverage and
capabilities that are unmatched by any other optical telescope
currently operating or planned,” and discoveries with the Hubble
rank “among the most significant intellectual achievements of the
space science program,” the report continues.  Given the growth in
capabilities due to previous servicing missions and the potential
for even greater scientific power with new scientific instruments,
the committee finds the Hubble “a national asset well worth
maintaining in operation.”

According to the report, certain Hubble components are expected to
fail in the coming years, leading to an anticipated termination of
scientific operations in the 2007-2008 time frame if the telescope
is not serviced.  A space shuttle servicing mission, SM-4, was
originally planned to replace aging components and install two new
science instruments, but in the wake of the Columbia shuttle
accident, NASA Administrator Sean O’Keefe announced that SM-4 would
be cancelled for safety reasons.  Upon expressions of concern by
members of the science community, the public, Senator Barbara
Mikulski (D-MD) and other Members of Congress, O’Keefe requested an
analysis of servicing options from the National Research Council.
At the same time, NASA went ahead with consideration of proposals
for a robotic servicing mission.

The projected component failures, along with other strategic
considerations, prompted the committee to urge NASA to conduct a
servicing mission “as early as reasonably possible.”  The report
notes that a robotic servicing mission, as currently envisioned by
NASA, would require a 39-month development schedule.  The committee
finds that this schedule, combined with the anticipated failure of
Hubble gyroscopes in mid to late 2007, would “result in a projected
29-month interruption of science operations.”  Additionally,
consideration of past experiences and historical data led the
committee to conclude that “the likelihood of successful development
of the HST robotic servicing mission within the baseline 39-month
schedule is remote.”  The committee also notes that the proposed
robotic mission would not install all the upgrades planned for SM-4,
and would have “minimal capacity for responding to and repairing
unforeseen anomalies.”

On the other hand, the committee expects “no interruption of science
operations…for a realistically scheduled SM-4 shuttle mission.”
Based on the experience of previous shuttle servicing missions, the
committee finds that the risk of failure “in the mission phase of a
shuttle HST servicing mission is low.”  It also believes that NASA
could meet the relevant Columbia Accident Investigation Board and
Return-to-Flight requirements for a shuttle servicing mission, and
it concludes that “the difference in risk of loss of the vehicle and
crew between a single servicing mission to the Hubble and a single
mission to ISS is extremely small.”  The committee “further believes
that adding a shuttle flight for an HST SM-4 mission adds a percent
or fraction more to the total risk of losing astronauts in the
course of completing the already planned ISS program,” and,
“compared to the total cost of flying a shuttle flight, the
resources required to overcome unique technical or safety issues
involved in flying a shuttle mission to HST are small” and well
within NASA’s experience base.

The committee concludes that “the benefit/risk ratio for the human
mission is high, and the benefit/risk ratio for the robotic mission
is low.”  The committee makes three final recommendations:

1.      “…NASA should commit to a servicing mission to the
Hubble Space Telescope that accomplishes the objectives of the
originally planned SM-4 mission.”

2.      “The committee recommends that NASA pursue a shuttle
servicing mission to HST that would accomplish the above stated
goal.  Strong consideration should be given to flying this mission
as early as possible after return to flight [of the shuttle fleet].”

3.      “A robotic mission approach should be pursued solely to
de-orbit Hubble after the period of extended science operations
enabled by a shuttle astronaut servicing mission, thus allowing time
for the appropriate development of the necessary robotic
technology.”

The entire report is not yet available, but a press release can be
found at the link below:
http://www4.nationalacademies.org/news.nsf/isbn/0309095301?OpenDocument

Audrey T. Leath

Media and Government Relations Division

The American Institute of Physics

fyi@aip.org
www.aip.org/gov

(301) 209-3094