Kathryn Poole (Northrop Grumman), John Woloschek (Northrop Grumman), Elizabeth Murphy (Northrop Grumman), Jerry Lefever (Northrop Grumman), John Breslin (Northrop Grumman)
Keywords: Orbital Debris
Abstract:
An effective debris search strategy at GEO requires the balance of objectives that are often at odds with one another. Ideally, the strategy would allow for both high search rates (greater coverage, leak proof fence) and sufficient dwell times within a sensors individual pixel (greater sensitivity). In this study we simulate various search strategies to evaluate their effectiveness in meeting these two objectives. We initially evaluate three basic search strategies using a continuous scan: (1) one dimensional scans centered on the GEO belt, (2) one dimensional scans centered off the GEO belt and (3) a square wave scan pattern centered on the GEO belt. We evaluate each of these methods using various encounter statistics to determine which method provides the greatest coverage. We also investigate the possibility of minimizing solar phase angles during the search to achieve maximum sensitivities. Based on these results we focus on the one dimensional scans centered on the GEO belt. We analyze the effect on sensitivity and coverage of using a step stare method (both fixed and sidereal stares) rather than a continuous scan method. Included in this analysis is an assessment of a specialized step stare based on the method used by the ESA Space-Debris Telescope on Tenerife, Canary Islands1. Lastly we look at the likelihood that satellites with high inclinations and/or drift rates (both typical characteristics of debris objects) will not stay in a sensors instantaneous field of view for the sensors full integration time. We developed analytical equations to (1) calculate the expected dwell time within a single pixel and (2) calculate the likelihood that a streak will dwell within a single pixel for the full integration time, given the relative angular rate of the satellite and the sensor detector size and integration time. An expected pixel dwell time that is less than the full integration time could be justification for reducing the integration time, which would result in a reduction of the duration of individual scans without sacrificing sensitivity. Results are presented for simulations that take into consideration the primary objectives of an effective GEO debris search and provide insight into methods for improved success.
%Z Flury, W., et al., Searching for Small Debris in the Geostationary Ring Discoveries with the Zeiss 1-metre Telescope, ESA Bulletin 104 November 2000
Date of Conference: September 10-14, 2006
Track: Orbital Debris