Orbital Debris  Surface Examinations

Long Duration Exposure Facility (LDEF)

Debris smaller than about 1 mm cannot be detected easily by ground-based radars or optical telescopes. Space-based in-situ measurements, the study of surfaces that have been exposed to space in Earth orbit, have been the only means to describe sub-millimeter debris populations. All spacecraft collide with very small orbital debris particles and meteoroids; consequently, spacecraft surfaces returned to Earth are found to have many small craters resulting from hypervelocity impacts. In most cases, these craters are too small to have any effect on the operation of the spacecraft. However, by examining them, important clues can be obtained on the sources of orbital debris, and the rate that it is changing. In addition, residual material inside craters on the returned surfaces can be analyzed to obtain the chemical compositions of the impactors.

NASA has a long history of conducting space-based in-situ experiments on micrometeoroids and orbital debris, including instruments on the Explorer and Pegasus satellites in the early 1960's. The Long Duration Exposure Facility (LDEF) was a bus-sized spacecraft that was returned after ~5.7 years in low Earth orbit. Over 20,000 impacts have been documented on LDEF, approximately 1,000 of which have been chemically analyzed in an attempt to determine the origin of the projectile. These measurements have provided NASA scientists important information not only on the micrometeoroid and orbital debris populations, but their orbital distributions as well.

Critical surfaces, such as the windows, on the Space Shuttle are examined after every flight. Other surfaces examined include those from the Solar Max satellite and the Hubble Space Telescope. On average, two Shuttle windows are replaced per mission due to damages caused by micrometeoroid and orbital debris impacts. Impacts on Shuttle windows and radiators are examined after each mission. The analysis results are part of the database NASA scientists use to define the sub-millimeter micrometeoroid and orbital debris environment. Other notable surface examination experiments include the Orbital Debris Collector (ODC), which was part of the Mir Environmental Effects Payload (MEEP) experiment, and the Mir Solar Array Returned Experiment (SARE).

 

Orbital debris damage seen during Hubble Space Telescope repairs.		After in space repairs to the Hubble Space Telescope, the returned parts show many orbital debris impacts.
An impact that completely went though the antenna dish of the Hubble Space Telescope.		A close-up view of a panel from the LDEF spacecraft.