Mark K. Mulrooney (ESCG/MEI, Houston), Mark J. Matney (NASA Johnson Space Center), Matthew D. Hejduk (SRA International), Edwin S. Barker (NASA Johnson Space Center)
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Abstract:
Mulrooney and Matney [1] developed a technique for estimating the intrinsic size distribution of orbital fragmentation debris and among the conclusions of their study was the recommendation of a global albedo value of 0.13 for these debris objects. In 2008 this value was revised upward to 0.175 [2] after revisions were made to the basis set of supplied brightness data (NASA-Liquid Mirror Telescope photometry data [3-5]). These revisions primarily involved uniform application of Lambertian phase function correction as opposed to the specular/Lambertian mixture in the original dataset. While these two studies demonstrated the soundness of their approach, uncertainties in the optical and radar data used for the calculations led the studies to produce only a provisional, rather than definitive, global albedo value for fragmentation debris. Calculations using alternate photometric and RCS (Radar Cross Section) data is required to support the use of their albedo in a truly global context. As a first step in this vetting process we perform an albedo consistency check by utilizing RCS values from an alternate source – the United States Air Force Space Command Studies and Analysis Division (AFSPC/A9A) high-precision RCS catalogue. As with prior work, these values will be passed through NASA’s Size Estimation Model which primarily provides a diameter correction (downward) for objects in the Rayleigh scattering regime. Analysis using other photometric sources, such as the GEODSS visual magnitude data repository, will be performed in future.
In addition to fragmentation debris, there is utility in exploring the albedo distribution of non-fragmentation objects – including intact rocket bodies, payloads, and mission related objects. Queries about space object size are often tendered against object types other than merely fragmentation debris; frequently, full-catalogue size profiling is desired, which includes payloads and rocket bodies. When published size information about these objects is available, these actual measurements can be used for such profiling; but since they are often unavailable, it would be helpful to have an expansion of the Mulrooney and Matney technique available for this class of objects. As a first step in this process, we will determine the character of the albedo distribution for non-fragmentation targets based on LMT photometry and available data from the A9 high-precision RCS catalogue. Since the size distribution for this object class does not follow a simple power-law, a suitable subset will be extracted whose behavior is approximated by a weak power-law and a bias corrected albedo will be derived.
Date of Conference: September 16-19, 2008
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