On-Orbit Observations of Conjuncting Space Objects Prior to the Time of Closest Approach
Abstract
In this paper, an examination how an at-risk LEO primary satellite could obtain optical tracking data on a secondary object prior to the Time of Closest Approach (TCA) and assess its own collision risk without the need for additional ground-based space surveillance data is performed. This analysis was made possible by using in-situ optical measurements of space objects conjuncting with the Canadian NEOSSat Space Situational Awareness R&D microsatellite. By taking advantage of the near "constant-bearing, decreasing range" observing geometry formed during a LEO conjunction, NEOSSat can collect astrometric and photometric measurements of the secondary object in the time prior to TCA, or in the multiple half-orbits preceding TCA. This paper begins by describing the in-situ phenomenology of optically observed conjunctions in terms of the observing approach, geometry and detected astrometric and photometric characteristics. It was found that conjuncting objects are detectable to magnitude 16 and astrometric observations can improve position covariances used for the computation of Probability of Collision. In orbits prior to TCA, in-track positioning error is improved by a factor of two or more by processing space-based observations on a filtered position estimate of the secondary. However, cross-track positioning knowledge is negligibly improved due to the inherent astrometric precision of the NEOSSat sensor's observing geometry during conjunction observations.
- Publication:
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Advanced Maui Optical and Space Surveillance Technologies Conference
- Pub Date:
- September 2019
- Bibcode:
- 2019amos.confE...7S
- Keywords:
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- Small Satellites;
- Conjunctions;
- Optical Measurements;
- Space Debris