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International Space Station Tight Pitch Attitude Oscillation Improves Valuable Science Data Collection
RAIDS mounted in the open end of HREP aboard the International Space Station. RAIDS mounted in the open end of HREP aboard the International Space Station. (NASA)
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The attitude control requirement of the International Space Station is ±3.5 degrees. Earth remote sensing instrument studies have sometimes viewed this performance as a disadvantage, since they require precise pitch angles for accurate measurements and have to modify instruments or pointing devices to compensate for the space station attitude fluctuation. The actual on-orbit performance of the station attitude control system is significantly better, however, making it much easier for instruments to track and meet their objectives.

With orbital coverage over 90 percent of the populated Earth, the space station offers an outstanding science platform to prove remote sensing technologies before new instruments launch on free-flying satellites. Experiments like the Remote Atmospheric and Ionospheric Detection System or RAIDS, currently take advantage of space station orbiting capabilities. Data from this investigation will improve knowledge of Earth's atmosphere, as well as improve NASA models for planetary exploration in long-duration space flight.

Seemingly small station attitude oscillations can create a large adverse impact to the RAIDS viewing altitude. Recent updates by space station Guidance, Navigation and Control improved station attitude control of oscillation to an impressive ±0.20 degrees. For RAIDS, this means an increased return in science data by a factor of two. This upgrade in performance from pitch oscillation control makes it easier to develop remote sensing instruments that use the external attachment sites on the space station.

Over the long term, the predicted station momentum management capability allows for pitch oscillation control within three different ranges (±1.25, ±0.88, or ±0.25 degrees), depending on the attitude controller design, space station inertia and aerodynamic properties, and environmental conditions.

For more information on RAIDS and other space station research news, go to http://www.nasa.gov/mission_pages/station/research/index.html.

by Jessica Nimon
NASA's Johnson Space Center
ISS Program Science Office