Giampiero Sindoni

Satellite laser-ranging is successfully used in space geodesy, geodynamics and Earth sciences; and to test fundamental physics and specific features of General Relativity. We present a confirmation to approximately one part in a billion of the fundamental weak equivalence principle (uniqueness of free fall) in the Earth's gravitational field, obtained with three laser-ranged satellites, at previously untested range and with previously untested materials. The weak equivalence principle is at the foundation of General Relativity and of most gravitational theories.

In 2016, we published “A test of general relativity using the LARES and LAGEOS satellites and a GRACE Earth’s gravity model. Measurement of Ear

We summarize a laser-ranged satellite test of frame dragging, a prediction of General Relativity, and then concentrate on the estimate of thermal thrust, an important perturbation affecting the accuracy of the test. The frame dragging study analysed 3.5 years of data from the LARES satellite and a longer period of time for the two LAGEOS satellites. Using the gravity field GGM05S obtained via the Grace mission, which measures the Earth's gravitational field, the prediction of General Relativity is confirmed with a 1-σ formal error of 0.002, and a systematic error of 0.05. The result for the value of the frame dragging around the Earth is μ = 0.994, compared to μ = 1 predicted by General Relativity. The thermal force model assumes heat flow from the sun (visual) and from Earth (IR) to the satellite core and to the fused silica reflectors on the satellite, and reradiation into space. For a roughly current epoch (days 1460 - 1580 after launch) we calculate an average along track drag of -0.50pm/sec².

In this paper we present a nanosatellite for cosmic ray detection. The main payload is constituted by a particle detector. A second payload may be constituted by the control unit of an innovative type of photovoltaic cells that will have a twofold objective: test the performances and provide additional power to the nanosatellite. It is under investigation the possibility of using a propulsion module in case, later in the phase A study, will be realized an additional advantage to transfer the orbit from circular (the most commonly used in commercial launches) to elliptical. Launch opportunities are relatively frequent since the market of nanosatellites is rapidly increasing and launch providers are including those into their business. The service module will provide power, radio communication, on board computer and attitude control. Thermal control will be achieved passively by the use of paint with proper absorptivity and emissivity and thermal blankets. The problem with this approach is that paint and solar cells have to share the external surface of the nanosatellite, unless a deployable solar array will be included. Besides being an important carrier of information from sources in our galaxy and beyond, cosmic rays may have influence in the terrestrial environment as well as in the technologically advanced human activities, such as orbiting satellites and human spaceflight. The objective of the satellite will be twofold: to train students with hands-on activities through all the phases of a space mission and the development of particle detectors as well as to study the properties of the detected cosmic rays with possible implication in fundamental physics and Earth environmental studies.

Space debris represent a big concern for future space activities. Particularly at low Earth orbit there is a concentration of debris. Although the probability of impact are today relatively low some occurrences have been registered. The problem was addressed since the beginning of the space age and international treaties regulate the responsibilities of the spacefaring nations. LARES (LAser RElativity Satellite) mission was launched in 2012 and is currently operational. The scientific requirements and the mission design required a waiver to the European debris mitigation regulation for the launch. To date, four close approaches of LARES with space debris have been registered. In the case of a collision with a debris, the resulting controversial is not predictable. The paper addresses possible legal scenarios in case LARES would be involved in an impact with a space debris.

This work has been developed in the framework of the LARES mission of the Italian Space Agency (ASI). The LARES satellite has been built to test, with high accuracy, the frame–dragging effect predicted by the theory of General Relativity, specifically the Lense–Thirring drag of its node. LARES was the main payload in the qualification flight of the European Space Agency launcher VEGA. A concern arose about the possibility of an impact between the eight secondary payloads among themselves, with LARES and with the last stage of the launcher (AVUM). An impact would have caused failure on the payloads and the production of debris in violation of the space debris mitigation measures established internationally. As an additional contribution, this study allowed the effect of the payload release on the final manoeuvers of the AVUM to be understood.