At orbital speeds a tennis-ball-sized piece of space junk packs enough energy to obliterate a satellite…Even tiny bits of debris can do damage. In May 2021 the Canadian Space Agency said an untracked piece of junk had punched a hole 5mm across in Canadarm2, a robotic limb attached to the International Space Station (ISS).
As orbiting objects multiply, the danger grows. Roughly a dozen sizeable pieces of space debris break up every year as a result of collisions, exploding rocket fuel, or the rupturing of pressurized tanks or old batteries. Solar radiation chips off bits of paint and metal…Today there 4,500 active satellites orbiting Earth and this does not include defunct satellites…There could be 100,000 active satellites in orbit by the end of the decade…
Radars operated by the US Department of Defense have improved ‘space situational awareness’…One big advance has been “Space Fence”. This is a system built in the Marshall Islands for America’s air force. It is billed as the world’s most advanced radar…In April 2021, LeoLabs, a firm in Silicon Valley, switched on its fourth debris-tracking radar station. ..LeoLabs sells data to satellite operators, space agencies, America’s armed forces and insurers keen to calculate better actuarial tables for spacecraft….
Besides using radar, debris can also be tracked optically. In collaboration with Curtin University, in Perth, Lockheed Martin runs FireOpal, a system of 20 cheap cameras aimed at the sky from various parts of Australia. For several hours at dawn and dusk, when these cameras are in the dark but sunlight still illuminates debris orbiting above, the cameras take pictures every ten seconds. The closer an object, the more it appears to move relative to the stars, allowing triangulation of its position…fire
Lasers are another option….For finding stuff in high orbits, though, neither lasers nor radars are much help. But telescopes work. ExoAnalytic Solutions, a Californian firm, tracks junk up to 170,000km away—nearly halfway to the Moon—using instruments “just laying on the shelves” at astronomy shops...Northstar Earth & Space, a new firm in Montreal, is to raise money to build, at $25m a pop, three 100kg satellites that will use telescopic cameras to track junk from orbit..
Naturally, this orbital-tracking technology has military value as well. Knowing objects’ orbits can reveal much about an adversary’s capabilities—including, perhaps, orbital combat. Movements that represent any deviation from normal patterns are most telling…To illustrate why, he points to an object that had been considered to be just a piece of debris from a Russian military launch. In May 2014 the “debris” sprang to life. Its movements since then have fuelled fears that it could be an anti-satellite weapon. Whether other such “sleepers” are hidden in plain sight among the clouds of rubbish orbiting Earth remains to be seen.
Excerpts from Orbital housekeeping: Tracking space debris is a growing business, Economist, Sept. 18, 2021