Ricerc@Sapienza

Nowadays, the space debris issue is on top of the list of all space agency in the world. Even more so with the advent of the new space economy which will increase even more the number of objects around the Earth and consequently impact risk between operative satellite and space debris. S5Lab has developed several tools in order to identify, classify and monitor object in orbit. Measurements acquisition occurs by means of a network of telescope around the Earth surface.

In recent years, the increase in space activities has brought the space debris issue to the top of the list of all space agencies. The fact of there being uncontrolled objects is a problem both for the operational satellites in orbit (avoiding collisions) and for the safety of people on the ground (re-entry objects). Optical systems provide valuable assistance in identifying and monitoring such objects. The Sapienza Space System and Space Surveillance (S5Lab) has been working in this field for years, being able to take advantage of a network of telescopes spread over different continents.

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.

The constant increase of the amount of space debris is becoming a threat for both ground and space infrastructures. The non-negligible risks of collisions in orbit, involving possible damages for active space systems, and concerns over re-entry of large objects are leading to an increasing international interest in Space Surveillance and Tracking.

Optical observations represent a passive method for space debris tracking and monitoring. Although being con- strained to limited time intervals, e.g. when the target is in sunlight and the observatory is in darkness, a debris observatory network distributed over multiple locations can improve the observational interval and favor the data integration for more consistent and significant results.

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.

The interest in determining the attitude of an orbiting object has grown significantly in recent years. Besides being one of the key parameters needed to obtain a precise orbital determination, the attitude is also crucial in the perspective of planning a space debris removing mission. In this paper, we present a method to retrieve the attitude of an orbiting object, based on a virtual reality simulation together with a global optimization. The attitude will be determined using the object's lightcurve derived information, i.e. the total reflected light variation in time.

The space debris environment is one of the main issues in present and future space missions in Earth orbit. The threat posed by these objects to operational satellites is getting more and more severe due to their increasing number, which determines, as consequence, an increase in the risk of potential accidental collisions. Some orbits are of particular interest for many applications and then more exposed to the space debris threat.

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.

Recently, the focus of Space Research has been set both on scientific and commercial fields. When planning a mission in space, it is necessary take into account the environment in which the instrumentations and the satellite that carries them will go to work. About 25% of operating anomalies are in fact due to the space environment that affects the control and management systems of the spacecraft and of the instrument.