The sticky issue of Space debris

Tuesday 17th August, 2021

Our speaker (on Zoom) was James Blake from Warwick University who talked to us about "The Sticky Issue of Space Debris". He has nearly completed his doctorate which focuses on the imaging and tracking of space debris in geosynchronous Earth orbits (GEOs), around 36,000 km above the equator. His work is part of that carried out by a relatively new department at the University named the "Centre for Space Domain Awareness". He also founded the astronomical society at the University and will be moving on to become a Research Fellow.

He began by saying that the area of space surrounding our planet is getting a lot more crowded. He listed the main various orbits as: Low Earth Orbit (LEO), Geosynchronous Orbit (GEO), Medium Earth Orbit (MEO), Highly Eccentric Orbit (HEO) as well as an irregular orbit known as a "UFO".

Out of all these orbits the most crowded are the GEO and the LEO with around 1 million objects orbiting that are greater than 1 cm in size. The LEO orbits are becoming very crowded, as companies such as SpaceX and OneWeb are launching thousands of satellites to provide communications for sites on Earth with very poor coverage. The US Space Force has the most complete catalogue of space debris and tracks objects of 10cm or more in LEO and objects between a half and 1 m in size in GEO. Large Earth-based radar installations can track a range of sizes from 1-10 mm.

Apart from actual observations on the ground the debris can be analysed and tracked when equipment that has been in orbit (such as external experiments on the International Space Station) is returned to Earth. Sometimes spacecraft also have onboard cameras to track debris and the amount of debris in orbit can also be modelled on computer in laboratories.

Just as on Earth, satellite and spacecraft operators are beginning to implement the environmental motto of "reduce, reuse, recycle". In February 2020 Northrop Grumman sent a satellite called MEV-1 (Mission Extension Vehicle-1) to dock with a client satellite, the Intelsat IS-901, and it was carrying fuel to extend the Intelsat's lifetime until it is no longer required. After that, MEV-1 will move the Intelsat to what is known as a "graveyard orbit", undock and move on to another satellite. This went so well they then launched another in April 2021 that docked with another Intelsat satellite.

Another option to avoid collisions is for each satellite to have on board some sort of automatic collision avoidance system, as implemented on Starlink satellites. Of course not every satellite will work properly and may fail completely but the advantage of them being in LEO is that they will relatively quickly fall back down to Earth and burn up in the atmosphere.

Some companies are also starting to work on systems to capture inoperative satellites or pull them out of orbit to burn up in the atmosphere. In 2019 a RemoveDEBRIS spacecraft designed by Airbus Stevenage and Surrey University successfully deployed a harpoon in LEO to target a piece of satellite panel 1.5 m away. It had already used a net to capture a piece of debris the year before but its deployment of a large sail structure that would attach to a failed satellite and use atmospheric drag to deorbit a satellite failed.

James ended his talk by saying that he is involved with the GNOSIS organisation (The Global Network on Sustainability in Space, https://gnosisnetwork.org) which bring together scientists and industry to understand and solve problems related to the ever growing problem of space debris.