Observation and characterisation of space debris

Between July and December 2022, GAL Hassin conducted observations of artificial space objects to monitor the ‘traffic’ of artificial satellites and space debris crowding the space around Earth.

This type of observation has become essential to avoid collisions and damage to operational satellites and, in particular, to ensure the survival of human beings on planet Earth and aboard the International Space Station (ISS).

In particular, 11 artificial objects with different sizes (up to 10 cm) and orbital heights distributed between low (LEO) and medium (MEO) Earth orbit were selected.

Of these objects, the change in brightness over time due to the rotation of certain rocket pieces was measured, obtaining the light curves. From this measure, the rotation period and an estimate of the geometry of rotation around their axes.

The collection of this type of data will be useful for an active removal of these old and long-abandoned objects in space, which is already planned by the European Space Agency (ESA) and the American Space Agency (NASA) which have been called Active Debris Removal missions.

Then, the different ‘colour’ that some satellites and debris show depending on their rotation was measured. From this colour measurement and the different reflection of sunlight on them, an estimate of the material of which the satellite (or debris) is composed was obtained.

Finally, the measurement of the position in space and time (astrometry) of space debris returning to Earth is used to accurately predict the falling orbit.

In this way, it is possible to estimate the areas on Earth at greatest risk of impact with these bodies, an event that has become rather frequent in recent years given the large amount of junk present and now out of control.

Image: Credis and copyright: NASA – Micrometeoroids and Orbital Debris (MMOD)  

OneWeb Satellite Constellations

The GAL Hassin Foundation was commissioned by the OneWeb Company to carry out the observation and measurement of the brightness of the OneWeb constellation satellites for a period of approximately one year (2021) and under different angles of incidence of sunlight.

At present, at European level, GAL Hassin is the only institute to have carried out photometric work on low-altitude satellites. It is expected that the OneWeb – GAL Hassin collaboration will continue with the observation of the second generation of satellites to verify whether technical modifications on these satellites have led to a reduction in the brilliance of their surfaces.

The publication of this work between GAL Hassin, Politecnico di Milano and OneWeb in 2022 is a kind of milestone for the aerospace-satellite sector, as it represents the first example of synergy between astrophysics, engineering, the environment and private enterprise.