www.satellite-evolution.com | November 2018 1

Space Debris

Photo courtesy of Goonhilly

From errant paint flecks to defunctspacecraftA piece of debris the size of a marble – 1cm in diameter – has the power to critically damage anyspacecraft while any item over 10cm diameter could shatter a satellite or spacecraft intosmithereens. An indication of the scale of the problem is that at present, very few pieces of debrisunder 10cm are tracked yet estimates of their quantity go as high as the hundreds of millions.Dr Bob Gough, Head of Business Development, Australia & Asia-Pacific at Goonhilly explainswhy we need to collaborate and accelerate efforts to discover and remove space debris.

Our dependency on satellites for GPS, TV and othercommunications has come at a price. The amount of spacedebris that has built up is making us vulnerable to a human-made risk that could wipe out space initiatives in one fellswoop.

The issue of space debris has come to a head becauseour industry is gearing up to launch over 15,000 new lowearth orbit (LEO) satellites during the next decade, not onlyfor Earth Observation but also our insatiable appetite forinternet communications.

A piece of debris the size of a marble – 1cm in diameter– has the power to critically damage any spacecraft whileany item over 10cm diameter could shatter a satellite orspacecraft into smithereens. An indication of the scale of theproblem is that at present, very few pieces of debris under10cm are tracked yet estimates of their quantity go as highas the hundreds of millions.

At the APSCC 2018 conference in Jakarta in September,space debris was high on the agenda including a panel

discussion, in which I participated. The goal was to raiseawareness and encourage more regional organisations tocollaborate and participate in industry and governmentinitiatives. As countries including Myanmar and Bangladeshbegin to fulfil their ambitions to put satellites in orbit, there isa heightened imperative for information sharing on bestpractices and training.

During the debate, one delegate asked the panel whatthe chances are that the Kessler Syndrome will occur.

This theory is raised in NASA scientist Donald Kessler’spaper about the impact of increasing space debris, publishedin 1978, following a number of Delta rocket explosions.The Kessler Syndrome presents a scenario where the densityof objects in LEO reaches such a level that any collision goeson to generate more space debr is and leads to anirrecoverable chain reaction of more collisions.

The result is that space activity, including the operationof satellites, will become unfeasible in specific orbits.

As my co-panellists hesitated to predict the likelihood of

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Space Debris

Dr Bob Gough, Head of Business Development, Australia &Asia-Pacific at Goonhilly

Kessler Syndrome, I stuck my neck out and said, “What wasthe chance of the 2008 global financial crisis occurring andwho saw that coming?”

Hindsight isn’t going to help us when a single piece ofdebris just millimetres wide, travels ten times faster than thespeed of a bullet.

What’s out there?I have a personal interest in the issue of space debris andhave a piece sitting on my desk as a reminder. In addition,Goonhilly has an overarching incentive to help resolve thisissue since our business relies on the welfare of our

customers’ billions of dollars worth of satellites in orbit.We take seriously our responsibilities to characterise the

risks of SSA (Space Situational Awareness) for regulatoryand insurance purposes and to plan now for the end of life ofany deep space missions.

Although we are over six decades into the space age,there has recently been some real progress in spacesituational awareness (SSA) as we improve techniques tofind, measure, share and predict the impact of space junk.

Although many objects transit out of Earth’s orbit or re-enter Earth’s atmosphere, there are more than 23,000 objectscurrently being tracked at altitudes between 100km and120,000km. This figure includes 1,150 active spacecraft aswell as thousands of retired spacecraft such as 25 metrerocket upper stage rockets. The reduced atmospheric dragin higher orbits means that much material will stay in spacefor decades and those objects in geosynchronous orbit (GEO)could remain there for hundreds of years.

The SSA challenge is increasing as it becomes moreviable for academics, students, entrepreneurs and otherinnovators to access space with small, inexpensive payloadscombined with the proliferation of 10cm CubeSats.

The challenge is to track those smaller pieces and to maketracking more accurate in lower orbits where there is a biggerchallenge and a more substantial risk.

Industry collaborationThe keys to success include collaboration in the capture andtransparent reporting of reliable, granular data. No singleorganisation can take on this task alone and military, civiland commercial organisations all have different approachesand standards. Only with cooperation, regulation and datasharing will it be possible to track space debris and makespace programmes safer.

A piece of debris the size of a marble – 1cm in diameter – has the power to critically damage any spacecraft.Photo courtesy of Shutterstock

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Space Debris

OTS1 solar panel fragment

The key player is the US Combined Space OperationsCentre (CSpOC) – formerly the Joint Space OperationsCentre JSpOC – which actively tracks all objects of 10cm orlarger in orbit, using a combination of ground radar and opticalsystems and some space-based sensors. Others, includingthe Space Data Association (SDA) also monitor debris usingpassive and active radars. SDA and CSpOC notify spacecraftowner/operators continuously with information to feed intocollision avoidance manoeuvres.

In general, warnings are issued when object distancesare under 5km apart at GEO or less than 1km apart in LEOand within 72 hours of the closest approach. Currently, theestimated day-to-day statistical chance of a collision is onein a million. If only this statistic were as comforting as it firstmight seem.

There are many other important players contributing too;an internet search will quickly reveal who they are and whatthey are doing.

Tracking debris re-entry is another challenge. As part ofGMV’s collaboration with France’s National Centre for SpaceStudies (Centre National d’Etudes Spatiales: CNES), it hasdeveloped a tool to estimate space debris re-entry timingbased on the orbital data published by the US governmentand others.

GMV is also involved in defining a SSA simulation testbed. This would be used to define a future system that couldmodel the space object population, evaluate collision andre-entry risk and detect risks of explosions and collisions.

Goonhilly has the potential to play an important role inSSA information sharing in the future. Thanks to our on-sitedata centre and our unique position at the junction of multiplesub-sea cables with satellite communications, we can deliverlow latency data to operators around the globe, ensuring theyhave real-time updates on debris so they can move theirsatellites if there is a risk of collision.

Cleaning up the clutterAn accurate picture of the celestial scrapyard is just one halfof the puzzle. Eliminating this man-made junk is the other

part. Some of the best brains in the business are applyingthemselves to this challenge and there are a range of creativeideas for how to remove debris being explored, although it isstill early days. One project is ESA’s Clean Space Initiativeand its proposed e.Deorbit mission using a robotic arm tocatch derelict satellites.

Even sooner, a test mission called RemoveDEBRIS, ledby a consortium of European industry and governmentorganisations, will test a “chaser” satellite equipped with aharpoon. A successful test has already been completed usinga net.

A third initiative is Astroscale’s plans to affix a small,lightweight plate with a ferromagnetic coating on satellitesprior to launch. If the satellite fails before its nominal end oflife, Astroscale will launch a retriever satellite – a chaser –that will track the dead craft and attach to the plate with amagnet. Then the two craft will burn up together as they fallinto the Earth’s atmosphere.

A better solution would be a reusable chaser but that’s achallenge still waiting to be solved, perhaps when there arerefuelling stations in orbit or new forms of electric propulsionto deliver the change in velocity required.

There’s no doubt that many challenges remain. But if ourindustry stands together and commits to collaborating onSSA, while technologists develop creative solutions formanaging debris, then we can continue on our currenttrajectory, and deliver on the promise of space as a utilitythat benefits all of humankind.

Tracking debris re-entry is another challenge.Photo courtesy of Shutterstock