Vancouver Sun Mon Jan 2 2012
By Margaret Munro
The alerts from U.S. Strategic Command now arrive every couple of weeks – warnings that space junk is hurtling toward one of Canada’s multi-million-dollar satellites.
The mathematical whizzes at the Canadian Space Agency assess the odds of their space-craft being hit by the debris, much of it from missile tests, rocket launches and mid-orbit collisions. More often than not, they sit tight.
But five times this year the space agency has fired up the thrusters on Canada’s $500-million Radarsat satellites to move them out of harm’s way.
“The numbers of near-misses are going up, rather alarmingly,” said David Kendall, the CSA’s director general of space science and technology.
Space debris is already a big problem, and threatening to get so much worse that engineers are now sizing up the possibility of sending tow trucks into orbit to clean up the heavens.
“The problem is not going to go away,” said Kendall, who chairs the Inter-Agency Debris Coordination Committee, which includes representatives from space agencies around the world.
Collecting trash may not have the glory of walking on the moon, or rocketing off to the International Space Station, but it is a potential growth industry.
More than 16,000 chunks of debris, ranging from baseball-sized to bigger than a refrigerator, are circling the planet. The growing list includes everything from dead satellites to rocket boosters to a tool kit dropped by astronauts.
Some regions of space now contain so much trash it could set off what researchers call a “cascade effect” where one collision leads to another, creating more and more pieces.
“This is pollution that almost, in a way, reproduces,” says Daniel Rey, systems manager for space exploration at the Canadian Space Agency.
Those fragments become smaller with each collision; Rey notes that the objects are moving so fast that one just 10 cm across can cause “catastrophic” collisions. “It is enough to make something explode,” he said.
How quickly the cascade effect will kick in is a subject of debate among space scientists but Kendall said “credible” models predict there will be “so much junk, so many particles whizzing around” in some regions that they could be off-limits within the next 10 to 30 years.
The area 800 to 1,000 kilometres above Earth is one of the most vulnerable, he said. It is also one of the most important spots for satellites monitoring everything from icebergs to floods to military operations.
“There is a lot of traffic up there,” said Kendall.
There is also a lot of trash, he said, noting two recent events have added significantly to the collection.
A widely criticized Chinese anti-satellite missile test in 2007 blew up an old weather satellite about 850 kilometres above the Earth.
In February 2009, a defunct Russian satellite, Cosmos 2251, smacked into one of the satellites relaying conversations for the US Iridium telephone network.
The two events resulted in an almost 50 per cent increase in the number of pieces of track-able debris, which jumped from 11,000 to 16,000 pieces, said Kendall, citing data from the European Space Agency.
And that, he said, does not include the hundreds of thou-sands of smaller bits of debris travelling at speeds of thou-sands of kilometres an hour.
Surveillance and warning systems have expanded along with the threat. U.S. Strategic Command now issues alerts almost daily about objects that are on track to collide.
Such alerts used to be to rare events at the flight operations centre at the Canadian Space Agency in Montreal, which controls the remote sensing satellites RADAR-SAT-1 and RADARSAT-2 and SCISAT, which studies Earth’s atmosphere.
From 1995 until 2007, there was just one alert, which prompted operators to change the course of Radarsat 1 to move it out of path of danger, said Michel Doyon, manager of CSA flight operations.
Now, he said, alerts are issued almost every other week about space trash heading for one of the Canadian satellites.
There were 22 warnings in 2010, and 27 in the first 11 months of 2011.
It often turns out the satellites are not in real danger, said Doyon. But over the last two years, Radarsat 1 and 2 have been moved out of harm’s way nine times.
One of the closest calls was in the spring of 2010, when a U.S. telecommunications satellite was on a collision course with one of the RADARSAT satellites, which travel an incredible 7.5 kilometres a second, circling the planet every 90 minutes.
The two satellites were on track to pass within 50 metres of each other, give or take several metres – far too close for Doyon and his team watching from the ground 800 kilometres below.
“It was a very risky one,” he said, recalling how his team collaborated with the U.S. operators to avert a potential disaster.
“In the end we both manoeuvred. We went up and they went down,” said Doyon. The two satellites safely cruised past each other with 500 metres between them.
He said the majority of alerts involve “pure space debris” that has been building up in orbit since the first artificial satellite, the Sputnik 1, soared into space in 1957.
Kendall said rocket stages left by space launches, which he describes as “giant gas cans,” are particularly nasty as they can retain enough fuel to explode.
Defunct satellites also pose big problems, though inter-national rules now require that they be built with the capability, and enough fuel, to be moved to a safe location before they die.
Telecommunications satellites, which keep the world’s phones and televisions humming, are in geostationary orbits 36,000 kilometres above Earth – meaning they’re “parked” in orbit and appear stationary to an observer on the ground.
When they die they are boosted several hundred kilo-metres into higher “grave-yard” orbits to make way for new satellites.
The Pacific Ocean is the destination of choice for dead spacecraft in lower orbits – such as a six-tonne NASA research satellite which plunged to Earth in September.
Then in October, the defunct German ROSAT satellite, carrying an enormous heat-resistant mirror used to search for black holes and neutron stars, made a fiery re-entry over Southeast Asia.
A Russian spacecraft is next in line and is expected to plunge back into the atmosphere between Jan. 6 and 19. The Phobos-Grunt spacecraft was launched in November on a mission to retrieve a soil sample from the Martian moon Phobos. (“Grunt” is Russian for “soil”) but the spacecraft’s engines failed to ignite and it is slowly falling back to Earth.
Many spacecraft and objects, however, get stuck in orbit.
One of the biggest and potentially most dangerous is Envisat, a European Earth observation satellite the size of a bus that could hang around in orbit for more than 100 years.
It is due to retire in 2013 but does not have enough fuel left to be boosted into a grave-yard orbit or down into the Pacific.
And once Envisat runs out of thruster fuel it will no longer be able to dodge debris, and could shatter into a huge cloud of space junk if hit.
Such nightmare scenarios have several countries, including Canada, exploring the idea of sending service vehicles into orbit to deal with the most dangerous trash.
Rey said that recent studies suggest that removing five big pieces of debris each year from the most crowded parts of space might “prevent the cascade event from multiplying the junk.”
Several options are being assessed, ranging from spraying debris with foam to increase drag and quicken the descent back to Earth, to catching and moving trash with “smart” robotic vehicles. “Canada has a great heritage here,” said Kendall, pointing to the Canadian-made robotic arms and vision systems that have been moving and grappling materials on the Inter-national Space Station.
Dealing with space debris is the focus of three of the six $250,000 contracts the CSA awarded in October to explore ideas that the agency says “could become Canada’s next revolutionary technologies.”
One contract, led by Burnaby-based MacDonald, Dettwiler and Associates Ltd. (MDA) of Canadarm fame, is to design an “on-orbit, automated servicing experiment” for the International Space Station to demonstrate the technologies needed to capture a satellite.
The space agency says this could help pave the way for the repair and refuelling of aging satellites and removal of debris from crowded orbital slots.
MDA also is leading a “clear sky project” to design a robotic vehicle that could get on with the cleanup.
The third contract, led by COM DEV International Ltd, an Ontario-based space firm, is to develop concepts for a “mission for orbital debris elimination.” Ronald Holdway, COM DEV vice-president, envisions an unmanned craft with a vision system and robotic arm able to sidle up to space junk, assess its size, speed and movement, then use its arm to “grab it.”
“You could hook up a cable like you would with a tow truck,” Holdway said.
The trash could then be pulled up to a graveyard orbit or towed into in a lower orbit to quicken re-entry into Earth’s atmosphere.
Along with the technical questions, Holdway’s group is exploring some of the legal and financial issues.
Who is responsible if diverted trash inadvertently crashes into something else, or makes a mess when it plunges back to Earth?
And who would pay for cleanup missions in an era of shrinking government budgets?
No one has ever been killed or injured by falling space debris, said Kendall, but it does threaten important space services people tend to take for granted, such as communications and remote-sensing satellites used for disaster management and environmental monitoring.
He said a space cleanup mission could be relatively inexpensive – in the $200 mil-lion range, he suggested – a bargain compared to the satellites themselves, which can cost upwards of half a billion dollars.
“It doesn’t have to be huge. It has to be smart,” Kendall said of the space age tow truck.
It could probably be designed, built and launched within a few years, he said, “if people got motivated.”