Estimation and Analysis of Two-Line Elements for Small Satellites

Abstract

This paper presents an assessment of two-line element sets for one nano- and two micro-satellites in low Earth orbit. Both the publicly available element sets issued by the North American Aerospace Defense Command and element sets estimated from GPS tracking data are assessed. The nanosatellite, which carries an intermittently operated dual-frequency GPS receiver, presents one of the first opportunities to assess two-line-element accuracy for an object measuring only $10\times 10\times 35\mathrm{cm}$ using precise reference orbits. The larger satellites provide continuous GPS coverage as well as insight into the impact of maneuvers and formation flying on two-line element sets. It is found that, overall, the North American Aerospace Defense Command two-line element sets provide reliable position information accurate to a few kilometers for small satellites in low Earth orbit and that, with an arc length similar to the North American Aerospace Defense Command, two-line elements estimated from continuous GPS data or even intermittent GPS data collected sufficiently often can improve the spread of five-day along-track propagation errors from 10 km down to 2 km for a nanosatellite.