Ricerc@Sapienza

Time Difference of Arrival (TDOA) networks could support spacecraft orbit determination or near-space (launcher and suborbital) vehicle tracking for an increased number of satellite launches and space missions in the near future. The evaluation of the geometry of TDOA networks could involve the dilution of precision (DOP), but this parameter is related to a single position of the target, while the positioning accuracy of the network with targets in the whole celestial vault should be evaluated.

Two-Line Elements (TLEs) of LEO objects, consisting in the object orbital parameters released by the North American Aerospace Defense Command (NORAD), are often characterized by low accuracy and short-term reliability. This is mostly due to sparse tracking data and relevant contribution of either unmodeled or poorly modelled perturbations of the orbital dynamics. Frequent updates of the dynamic state estimate are necessary for Space Situational Awareness (SSA) analyses and reliable orbit propagation.

LEDSAT (LED-based small SATellite) is a 1-Unit CubeSat project conceived by the Sapienza - Space Systems and Space Surveillance Laboratory (S5Lab) research team at Sapienza - University of Rome, with the collaboration of the University of Michigan (USA). The project has been accepted for the European Space Agency Fly Your Satellite! Programme, it is under development with the support of the Italian Space Agency (in the framework of the IKUNS project) and it will be launched within 2020.

Optical observations are intensively applied to space debris monitoring for the achievement of orbit determination and for gathering information on their attitude motion, even if constrained by light conditions. Light Emitting Diodes (LEDs) installed on the external surfaces of a satellite could increase the visibility interval to the whole eclipse time. LEDSAT (LED-based small SATellite) is a 1-Unit CubeSat aimed at demonstrating the effectiveness of LEDs for the improvement of space debris optical monitoring algorithms.

LEDSAT is a 1U CubeSat developed by S5Lab team of Sapienza – University of Rome in collaboration with the Astronomy Department of University of Michigan. The main goal of the mission is to demonstrate that a LED-based active illumination system may be used to achieve orbit and attitude determination. LEDSAT will be placed into a Low Earth Orbit (LEO) and observed by a network of ground-based telescopes. A LED-based system may improve the accuracy in monitoring LEO spacecraft.

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.

The optical orbit determination is one of the most important ways for noncooperative object tracking. One of the main problems with noncooperative object tracking is its recognition through different nights. In this study, the conditions that ensure the recognition of a geostationary satellite inside a cluster were assessed through a hard real case study. This study was developed through a three-phase approach. The first phase was the observation campaign for the images acquisition.