8
Engineering Systems Integration
the 24-h, 7-day on-orbit operations. Lifecycle issues including costs, operational tempo, refurbishment strategy (transport the Hubble Space Telescope
back to Earth for upgrades and routine 3-year maintenance versus maintaining the system on-orbit from the space shuttle), and retention of key personnel needed to be integrated into all planning, including the development
planning, integration planning, and operational planning.
Additionally, the space shuttle crews needed to equip and train for space
walks of long duration, operate the remote arm to load and unload the
Hubble Space Telescope, and manage the controls that linked the Hubble
Space Telescope to the space shuttle.
Integration Management
The overall responsibility of management of systems engineering and systems integration was given to the prime contractor, Lockheed Missiles and
Space Company (Lockheed), and Perkin Elmer (contractor for the primary
mirror). Lockheed management needed to align the interests of a broad-base
of key stakeholders, including various NASA (National Aeronautics and
Space Administration) centers, the European Space Agency, representatives
from the U.S. Air Force, astronomers and scientists, contractors, and employees. One of the more innovative actions by Lockheed was to search through
the skills of their existing engineering staff to determine who could help
uncover problems with the design, architecture, and implementation of the
subsystems. Sometimes, small teams of Lockheed scientists and engineers
were formed with a mix of senior systems engineers and their recent hires
just out of college. Other times, lone systems engineers set out to consider the
consequences of various designs and specifications. The mix of skills and
enthusiasm on these teams helped inspire a quest for excellence that left nothing unturned within Lockheed’s domain as the prime contractor. Even when
the results of a mathematical model indicated that the specification for the
cleaning of the primary mirror was insufficient to meet the design requirement, Lockheed confirmed the model predictions and informed relevant parties about potential problems with the cleaning specification for Hubble Space
Telescope’s primary mirror. In a strongly collaborative environment, the integration of the Hubble Space Telescope moved forward. But in spite of resolute
persistence and scrutiny, a defect in the curvature (a spherical aberration
flaw) of the primary mirror went undetected at Perkin Elmer until the Hubble
Telescope was placed in operation after its 1990 launch into orbit. The users
were the first to point out the defect. The test configuration that was designed
to detect such an error had been set up incorrectly which resulted in the primary mirror being polished to the wrong shape. The integration and test procedures at Perkin Elmer were inadequate and documentation necessary to
reproduce the test configuration could not be found (Allen et al. 1990).
Some rules of thumb regarding integration activities for software provide
insight into the integration activities of the Hubble Space Telescope.