Ricerc@Sapienza

The tracking of LEO objects, by means of large field of view (FOV) optical telescopes, is very challenging. Generally, optical tracking is only possible when the LEO satellite is in sunlight and the ground station is in darkness. This limits the tracking availability to morning and evening twilight for maximum five minutes at a pass. At worldwide level, several activities and studies are currently under development in order to improve the space surveillance capabilities. To this aim, Sapienza - University of Rome, together with the Astronomy Department of University of Michigan, are collaborating in the framework of the LEDSAT (LED-based SATellite) project. A LEO 1U CubeSat, equipped with LEDs (Light Emitting Diodes) is used as calibration target for optical observations for tracking the CubeSat. Through active illumination on the nanosatellite, the possibility to observe LEDSAT, by using ground-based telescopes, will increase since direct Sun illumination is no longer needed. The payload will flash with different patterns, on the basis of an accurate timing generated on-board. In this way, high timing precision on the ground-based system is not necessary. Thus, very simple and currently operating optical telescopes can be used for tracking, i.e. those in the amateur astronomy community. This paper describes the LEDSAT concept and the related science case. Moreover, the detectable LED-based payload configuration and the studies performed on the orbit determination feasibility are presented. In particular, the detectability is validated by Signal to Noise Ratio and Apparent Magnitude analyses. In addition, simulations of a tumbling LEDSAT with different flash patterns are shown. The reliability of the orbit determination is demonstrated by a batch filter. Furthermore, Monte Carlo runs show the achievable accuracies on the basis of different frequencies measurements and instruments precisions. Moreover, the architecture of the LEDSAT ground segment is outlined, with particular emphasis on the optical Ground Stations Network, which includes six observatories.