Matt Hejduk (AFSPC/A9L,, RABA Technologies)
Keywords: Orbital Debris
Abstract:
Because most work on deep-space orbital debris has been in the form of debris surveys, relatively little effort has been directed to the photometric characterization of these debris objects. The present abundance of well-calibrated GEODSS satellite photometric data, however, can enable the beginnings of such an investigation. The brightness versus phase response of some 250 debris objects was studied and compared to the response for approximately 1000 payloads and 750 rocket bodies. Debris brightness response remains better circumscribed than that for payloads or rocket bodies, but with increased retrograde brightness-vs-phase behavior. Straight-line brightness versus phase response, typical for most payloads and rocket bodies, is not nearly so prevalent for debris but still constitutes the substantial majority of the debris cases. For brightness prediction, a straight-line phase function is a better predictor than the diffuse sphere approximation in about 80% of the cases, a figure similar to that for the other object types.
With the general behavior of the debris objects characterized, such objects were subdivided into three broad response categories, with further subdivisions into a total of nine categories, as a function primarily of the linear slope (or lack thereof) of the phase function and the spread about the fit line (or mean value). The categories were assigned by visual examination of brightness-versus-phase-angle plots, and the goal was to determine statistical quantities that could reliably separate both the larger and smaller categories. Fitted slope is a poor discriminator and t-test p-value a substantially better one, but the p-value at which discrimination is most reliable is much smaller than what would generally be used for hypothesis testing. Statistical discrimination among the smaller sub-categories is much less successful, but some of the natural groupings of the results are surprising.
Date of Conference: September 12-15, 2007
Track: Orbital Debris