(Image: NASA, public domain)
On March 17, 1958, the United States launched Vanguard I – the fourth man-made satellite and the first to be solar powered – into medium Earth orbit. Communication was lost in 1964, and Vanguard I has become the oldest man-made object still in orbit and one of the longest surviving pieces of space junk.
It was estimated that in July 2009, operational satellites accounted for 902 of the 30,000 man-made objects in space, making them a small minority amid a sea of orbital debris. In a bid to limit the probability of collisions between operational spacecraft and space junk, the Inter-Agency Space Debris Coordination Committee have sought to move defunct satellites to graveyard orbits.
(Image: US Air Force, public domain)
Also referred to supersynchronous orbits, junk orbits or disposal orbits, graveyard orbits occupy a portion of space several hundred kilometres above synchronous orbit. Moving a craft to a graveyard orbit requires less effort than de-orbiting the object, and is generally attempted when the change in velocity required to perform a de-orbit manoeuvre is too high.
But transferring derelict spacecraft to a graveyard orbit can be challenging, requiring reliable attitude control and the same amount of fuel needed by the satellite for approximately three months station-keeping. As a result only one in three satellite operators succeed in moving their craft to graveyard orbits at the end of their useful lives.
Other Space Junk
During the 1970s and ’80s the Soviet Union launched a series of naval surveillance satellites as part of its RORSAT programme, equipped with nuclear reactors to provide enough energy to operate their radars. While most of these craft were ultimately boosted into a graveyard orbit, several – notably Kosmos 954 - failed, its radioactive material falling to Earth.
But even those that successfully reach a graveyard orbit risk being punctured and leaking their coolant over any 50-year period. Forming droplets several centimetres in size, the coolant may even create its own debris field.
(Image: NASA, public domain)
Space junk in the form of lost equipment poses an additional risk. Examples include a glove lost by astronaut Ed White during the first American space-walk, a camera lost by Michael Collins during the Gemini 10 mission, and garbage bags jettisoned from Mir space station.
(Image: NASA, public domain; Mir space station showing impact damage)
A wrench and toothbrush are also orbiting the Earth, along with another camera lost during STS-116 flown by the Space Shuttle Discovery. Meanwhile, a pair of pliers and a tool box joined the realm of orbital debris during STS-126, flown by Endeavour.
Lower stage solid rocket boosters are designed to fall to Earth after launch, but Inertial Upper Stage rockets like the Ariane booster begin and end their useful lives in orbit, making them a known source of space junk. NASA and the USAF have taken steps to improve the survivability of their boosters, but this isn’t the case with all launchers.
In March 2000 a Chinese upper stage created a debris cloud after exploding in orbit. A similar event occurred in February 2007, when a Russian booster exploded while orbiting above South Australia. Astronomers filmed the explosion, over 1,000 fragments of which have thus far been identified.
Eight break-ups occurred in 2006, the most since 1993. Another Russian booster exploded in 2012, although the severity of the debris field has not yet been determined. A major source of junk stems from the testing of anti-satellite weapons by the US and Russia during the Cold War. China, meanwhile, conducted a test in 2007, creating a huge amount of debris.
On a positive note, however, it was reported in March that a satellite system called Sling-Sat could potentially remove orbital debris from space at an affordable price (above). Click here for a full inventory of spent satellites orbiting Earth.
Commemorating Vanguard I
(Image: NASA, public domain; above: Vanguard I)
On March 17, 2008, 50 years to the day after Vanguard I was launched from Cape Canaveral, the Naval Research Laboratory commemorated the event with a day-long meeting in Washington, D.C. The meeting concluded with a simulation of the satellite’s orbital track across the sky above the capital, just one among tens of thousands of pieces of space junk, most of which will receive no such recognition.