Abstract:
Presented here is an improved planning and characterization tool that can be used to estimate the satellite encounter operational tempo for a given orbit against a satellite catalog. The spherical encounter volume in our original work is replaced with an ellipsoid that is constant in size, shape, and orientation in the satellite’s Radial-InTrack-CrossTrack frame. For a given pair of satellites we accomplish this by defining a traveling ellipsoid about the second satellite’s orbit and assessing if/when the first satellite’s orbit traverses it. To ensure that no encounter is missed, the ellipsoid is moved along the second satellite’s circular or elliptical orbit in increments of true anomaly corresponding to in-track movement much smaller than the ellipsoid’s minor axis. An incremental determination of encounter probability is made if/when the first satellite’s orbit track contacts the ellipsoid. When this takes place, the orbit true anomalies extant at ellipsoid entry and exit are captured for both satellites and converted to their respective mean anomaly ranges. The likelihood that both satellites will simultaneously be inside that encounter region is then determined from these ranges. In addition to determining probability, the method also estimates the number of expected encounters over a given time span. The method is valid for both coplanar and non-coplanar orbits. However, our assumption of uniformly distributed relative in-track positions is not applicable in all satellite pairings. This method is useful in identifying such regions as graveyard orbits that are least likely to produce encounters. It can also be used to estimate how often neighboring satellites will trigger volumetric warnings when considering a candidate orbit. We make a limited version of this tool publicly available through a non-subscriber website Graphical User Interface, where only spherical encounter regions in LEO circular orbits are considered.
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Alfano, Sal and Oltrogge, Dan, “Volumetric Encounter Analysis Enhancements,” 2015 Astrodynamics Specialist Conference, Vail CO, AAS 15-581, 23 Aug 2015, accessible at https://comspoc.com/Resources/Content/Private/C-20220424T083315/Paper/20150823_Volumetric%20Encounter%20Analysis%20Enhancements%20AAS%2015-581_PROOF.pdf.
