Dealing with the space junk
The European Space Agency is currently building a radar system to catalogue and track hazardous objects in Earth orbit. At the moment the US Space Surveillance Network (SSN) tracks 26,000 objects, and its Space Fence radar system, becoming operational in March 2020, will track as many as 200,000 objects. To mitigate the problem of space junk the Inter-agency Space Debris Coordination Committee (IADC) was formed in 1993 to produce a set of guidelines. It advocates several preventative measures, including reducing the amount of hardware ejected or rendered inoperative by a space mission. Since accidental orbital explosions have accounted for at least 500 incidents, it is recommended that explosive gases or fuels be vented to stop this happening. The deliberate explosion of satellites should be stopped, and where possible satellites should be steered clear of debris. As LEO satellites are the biggest culprit, they should be designed to only have an orbital life of 25 years and carry drag devices or a propulsion system to send them into re-entry if their orbit is not low enough for them to naturally re-enter. Higher satellites should be designed to enter a ‘graveyard’ orbit at the end of their operating life. Several ideas have been proposed to dispose of existing space junk. They range from shooting debris down using lasers, scooping it up with Aerogel material or netting it with ‘trawler’ satellites. For the smallest debris, large panels of porous foam could slow down junk that passes through it, making it re-enter the atmosphere. For larger debris, it could be collected by the robotic arm of an unmanned spacecraft.