A spectacular display of celestial fireworks? The momentous arrival of aliens? Or was it a work-in-progress sci-fi flick?
These questions weighed heavily on many minds as Melbourne's night sky lit up for almost a minute on the night of August 7. The flame raced across the sky before breaking into blazing fragments. A sonic boom shook the ground for a couple of seconds, setting off a panic among residents. A day later, the Australian Space Agency confirmed it was space junk, likely "remnants" of a giant Russian rocket which had hoisted a new navigational satellite into orbit.
A few weeks earlier, a six-foot high cylindrical object, perhaps the fuel tank of an Indian rocket, had washed ashore at Green Head Beach, 250 km north of Perth, Australia. The artificial lighting, the loud explosion, and the large fuel tank found there reignited one question: How to vacuum-clean the graveyard in the deep, dark heavens to safeguard assets worth billions of dollars?
Such assets include satellites circling the Earth at 300 km to 36,000 km, in support of telecommunications, broadcasting, meteorology, civil aviation, telemedicine, distance education, and even espionage (by military satellites launched without fanfare).
Space junk
Outer space contains hundreds of dead satellites, millions of fragments of old satellites and rockets, and even paint flakes; each is hurtling through space at an incredible speed of 10 km a second, with a lethal punch of a 550-pound object. NASA estimates there are around 23,000 pieces of debris larger than a softball, half a million pieces the size of a marble or up to a centimeter, 100 million pieces one millimeter and larger.
Example of space junk include a glove lost by Edward Higgins White during America’s first spacewalk, Michael Collins’ camera lost near Gemini 10, a thermal blanket lost during STS-88, the first space shuttle mission, garbage bags jettisoned by cosmonauts during Mir’s 15-year life, a wrench, and a toothbrush.
Indian-American astronaut Sunita Williams lost her camera during her spacewalk from the space shuttle in 2007, and astronaut Heidemarie Stefanyshyn-Piper lost a briefcase-sized tool bag during her spacewalk the following year.
And if you think the Hollywood film ‘Gravity’, where a spacecraft is hit by a cloud of space debris (killing George Clooney’s character, and nearly marooning Sandra Bullock) was fiction, then consider that in 1996, a French satellite was hit and damaged by a French rocket that had exploded a decade earlier. Or that on February 10, 2009, a defunct Russian spacecraft collided with and destroyed a USA Iridium commercial spacecraft. The collision over northern Siberia added 2,300 pieces of large trackable debris and a bigger quantity of smaller trash to the existing space junk.
China did not help matters when in 2007 it used a missile to destroy an old weather satellite, creating 3,500 pieces of large debris. In 2016, a tiny piece of debris punched a hole in the solar panel of the European Space Agency (ESA) observation satellite, Copernicus Sentinel 1A. Even the Hubble Telescope’s solar array shows hundreds of tiny holes caused by dust-sized debris.
The risk of trash colliding with satellites could spiral higher in the future, K R Sridhara Murthy, Honorary Director and former vice president of Paris-based International Institute of Space Law (IISL), and a former senior scientist of the Indian Space Research Organisation (ISRO), told RT.
This is because a large number of private companies – SpaceX, OneWeb, Amazon Kuiper, Guo Wang (China), Samsung (Korea), and Astrome Tech (India) plan to add a whopping 75,000 satellites within a decade to provide global communication networks (superfast internet services), and Automatic Identification Systems (AIS) to track ships (including those of pirates) among other benefits.
Though smaller than conventional satellites, they will crowd the low earth orbit (LEO), about 400 km from the ground, and multiply the number already in this sphere. "More companies are joining the race to position their satellites in orbit because the economics of satellite launch are changing drastically owing to reduction in the cost of putting a satellite into orbit and the deployment of reusable rockets," Murthy added.
Need for self-discipline
Nations have not been unmindful of the hazards of space junk. The USA and the former USSR tracked objects measuring four inches or more from the Cold War era using a string of radars. NASA and the US Defense Department's Space Surveillance Network (SSN) have cataloged more than 27,000 pieces of debris, and track each piece’s trajectory.
Not surprisingly, nations with ambitions in space, including India, are setting up facilities to track the burgeoning amount of trash.
The importance of tracking can be gauged when even the voyage of a rocket into space is delayed by a couple of minutes to prevent debris from causing a disastrous impact on missions, Dr. Mylswami Annadurai, the "Moon man of India" and former director of ISRO's Prof. U R Rao Satellite Centre in Bengaluru, told RT. He said that ISRO delayed the launch of its rockets three times to avoid a piece of space junk: a one-minute delay in the blast-offs in 2011 and 2016 and a three-minute hold in 2014.
All space agencies realize the need for self-discipline in outer space and try not to disturb the operations of other satellites when decommissioning an old and defunct one. "For example, we (ISRO) brought down Megha-Tropiques (a satellite designed jointly and launched by ISRO and CNES of France in 2011 to study tropical atmosphere in the context of climate change) last year with the help of fuel available onboard without causing damage to any other satellite," Rao said.
Last month, Indian space scientists reduced the altitude of the last stage of the Polar Satellite Launch Vehicle (PSLV) rocket as part of its initiative to avoid creating more space junk. "Left alone at a 536 km circular orbit, the PSLV4 stage would orbit the Earth for over 25 years. As the number of satellites in LEO (low earth orbit) is growing and the space around this orbit is of particular interest, the orbit of the spent PSLV4 was reduced to 300 km," said the ISRO's spokesperson.
"Everybody wants to clear outer Space of debris, but how to do it is a billion-dollar question,” K Sivan, former Chairman of ISRO, explained to RT. “We are part of the Inter-Agency Space Debris Coordination Committee (IADC). This international governmental forum coordinates global efforts to reduce debris by sharing research and identifying debris mitigation options.”
When Sivan was at the helm, ISRO established a radar at the Deep Space Network Station on the outskirts of Bengaluru as part of a project, called ‘Nethra’, to track junk in outer space and to share the data with other space agencies. Earlier, ISRO established the Multi-Object Tracking Radar at Satish Dhawan Space Centre, Sriharikota, the country's spaceport just off the eastern coast in Odisha, to track the trajectory of 10 pieces of space junk and share the data with IADC.
According to Sivan’s predecessor, Gopalan Madhavan Nair, options include preventing new debris, designing satellites to withstand the impact of minor pieces, and improving procedures such as using orbits with less trash.
"Earlier, we used to allow the last stage of our PSLV rocket, along with some fuel, to drift away after launching the satellite, but now we make sure that the fuel (propellant) is exhausted to prevent an explosion of the last stage, or it is used to push the last stage closer to the Earth. Eventually, the last stage will drift further down and burn on re-entering the Earth's atmosphere," he said, alluding to the recent manoeuver.
Clearing efforts
In 2018, the United Nations Institute for Disarmament Research (UNDIR) proposed three A-SAT (anti-satellite) test guidelines for preventing junk in outer space. No consensus, however, has been reached among space-faring nations on the policies.
To mitigate the hazards of vast amounts of junk in outer space, the Japanese Space Agency, JAXA, has launched a project to develop a sprawling net akin to the one used by fishermen, to trap and drag down the trash. Many private companies are working on similar methods to cart away the garbage through operations that could fetch them millions of dollars.
ESA has teamed up with a consortium led by Swedish start-up, ClearSpace, to remove all ESA-owned, defunct satellites in the LEO. Their mission, ClearSpace1, will be launched in 2025 to capture a 100-kg upper-stage left orbit after the second flight of ESA's Vega launcher in 2013. During follow-up missions, ESA will attempt multi-object captures.
Other space agencies and private enterprises could follow suit, each with unique techniques to reduce the trash in outer space by 2050. Space scientists, however, feel new satellite observation methods, too, ought to be developed to forecast the trajectory of orbiting satellites and debris to avoid collisions.