Satellite-threatening debris in high-Earth orbit is not being tracked closely enough, according to the results of a newly published survey. Probes orbiting in geosynchronous orbit – a region of space roughly 36,000 km (22,370 mi) above our planet’s surface – are responsible for providing a range of vital navigation, communication and weather services, and could be at risk from debris too small or dim to be easily tracked.
The relentless march of human technological progress seems to inevitably come at a heavy price to the natural environments we conquer along the way. The land and the sea are littered with plastics, and air travel has become a major source of pollution in the once pristine sky.
Industrialization has led to the wanton destruction of habitats, and is now fundamentally shifting the planet’s climate. It has even placed the future of our species at risk. Humanity is now slowly shifting into self-preservation mode, and seeking to rein in its polluting ways.
All of this is mirrored in our expansion into the space domain. Since we started lobbing rockets into orbit in the 1950s, the amount of human-made trash whipping around the Earth has been steadily increasing.
Orbital debris is comprised of old, defunct satellites and the rockets that put them there. They range in size from flakes of paint to huge fairing sections. In February 2009 a worst-case scenario occurred, wherein two large defunct satellites – the commercial Iridium 33 and the Russian military-owned Kosmos-2251 – smashed into each other, creating a vast cloud of hazardous debris.
Thankfully, novel strategies are being developed to track, and hopefully one day de-orbit troublesome debris, and guidelines have been put in place to reduce the influx of new debris from future launches.
Currently, the US Strategic Command boasts the most thorough record of orbital debris, with information regularly updated by over 30 ground-based observatories and a fleet of six satellites. With its impressive capabilities, Strategic Command is able to track objects in high orbit as small as 1 m (3 ft) in diameter. However, their records are far from complete.
The new survey focused on debris populating geosynchronous space around 36,000 km above Earth as part of the DebrisWatch collaboration between the University of Warwick and the Defence Science and Technology Laboratory in the UK.
The researchers hunted for small or unreflective chunks of debris that reflect little light, and so would ordinarily go undetected.
Images collected during the survey by the 2.54-m (8.3-ft) Isaac Newton Telescope located on La Palma island off the coast of Morocco, were run through specialized software capable of identifying and characterizing potential pieces of debris. By analyzing the light signatures of the tumbling objects, scientists were able to shed light on their size, shape and other surface properties.
Space trash whizzing around in low-Earth orbit is gradually slowed by resistance from particles in our planet’s atmosphere, which eventually causes them to de-orbit. However, in the higher altitudes of geosynchronous space, there is no atmospheric drag, and so debris left in this region is likely to stay there, and over time this could become a serious problem.
Roughly 95 percent of the debris pieces estimated to be around 1 m in size or less, making them more difficult to reliably monitor, failed to match a known object in the US Strategic Command database. When accounting for all objects spotted in the survey, including those over 1 m, it was found that more than 75 percent of the objects were unknown.
Following their discovery, the team are calling for more regular surveys aimed at discovering and characterizing threats in geosynchronous orbit. Data from the new study will help scientists to develop and upgrade algorithms used to analyze the light-fingerprints of distant space trash, and so gain a greater understanding as to what's out there, and how it behaves.
“It’s important that we continue to observe the geosynchronous region with large telescopes wherever possible, to start to build up a more complete feel for the faint debris environment,” comments James Blake, the lead author of the new study and PhD student at the University of Warwick Department of Physics. “With this survey, we’ve probed deeper than ever before, and still the population appears to be climbing as our sensitivity limit is reached. While we’re dealing with small number statistics here, it’s unsurprising that we see many more small, faint objects than large, bright ones.”
As it stands orbital collisions are still incredibly rare, though every now and then the International Space Station has to be shifted into a new temporary orbit to avoid oncoming debris or an errant satellite, as it did this week. Stepping up efforts to observe debris in low-Earth orbit and beyond is a vital step towards making space safer. However, the proliferation of rocket technology means that we are set to see an increase in space junk in the coming decades, and with it, an increased threat to vital infrastructure satellites.
The paper has been published in the journal Advances in Space Research.
Source: University of Warwick