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M&D SIG - Meteoroid & Debris Special Investigation Group (1989 - 1994)

The Long Duration Exposure Facility (LDEF) exposed a number of dedicated experiments designed to study the hypervelocity particle environment in low-Earth orbit (LEO). While most of these experiments were intended to investigate natural micrometeoroids, a substantial concern regarding the contributions of man-made orbital debris emerged following the conception and placement of these experiments in LEO. These developments made it paramount that LDEF’s cumulative impact history be quantified to the greatest extent possible. Because of the stochastic nature of the bombardment process, this quantification required that efforts be made to obtain the best statistical information possible from LDEF.

Micrometeoroid Impacts

Photos of impact-related features on LDEF spacecraft surfaces

Prior to the retrieval of LDEF it was realized that the dedicated meteoroid experiments would not suffice to accomplish these objectives, and that the systematic scanning of the entire LDEF spacecraft would be necessary to obtain information complementary to, or in addition to, that expected from the dedicated M&D instruments. In addition, previous experience with the impact record on planetary surfaces and retrieved spacecraft components (e.g., Solar Max) revealed the somewhat subjective nature of simple crater counts. Thus, it was decided that a limited number of experienced individuals would be best suited to perform the global LDEF survey in a systematic and internally consistent fashion. This group (e.g., the M&D SIG “A-Team”) resided at the Kennedy Space Center (KSC) during the entire LDEF deintegration (i.e., February through April, 1990). The A-Team optically scanned and photodocumented all exposed LDEF surfaces for impact-related features (i.e., measured and photographed approximately 4,600 individual impact events; craters >0.5 mm and penetrations >0.3 mm in diameter, as well as other related features [debris, secondaries]), and identified and secured surfaces of special interest. The long-term curation of these materials and all documentation was subsequently transferred to the Johnson Space Center (JSC), which is responsible for open and continued access to these materials by qualified investigators, and for maintaining an up-to-date database of impact data.

To this end, the LDEF Micrometeoroid and Debris Special Investigation Group (M&D SIG) was organized. Among the major goals of the M&D SIG were:

  1. The documentation of the impact record of the entire LDEF spacecraft
  2. Characterization of the LEO particulate environment
  3. Dissemination of this information, primarily to those interested in the collisional hazard represented by these particles

Efforts toward the accomplishment of these goals include:

  1. A publication (See et al., 1990) describing all observations of impact features made during LDEF’s deintegration at KSC by the M&D SIG A-Team
  2. The continued examination and documentation of impact features on LDEF hardware
  3. Archives of this data, as well as similar information provided by LDEF Principal Investigators, in a public-domain database
  4. The generation of compact disks (CD’s) which contain copies of all of the stereo images acquired at KSC during LDEF’s deintegration
  5. The access to all of this information through the Internet

The original M&D SIG was formed and supported by the LDEF Project Office located at NASA’s Langley Research Center in Hampton, Virginia. The work done via the LDEF M&D SIG has been completed, and we archived the pertinent microparticle-bearing surfaces at JSC in the MIC Lab.