The Indian Space Research Organisation (ISRO) said its Polar Satellite Launch Vehicle (PSLV) has accomplished zero orbital debris mission.
This was achieved on March 21, when the PSLV Orbital Experimental Module-3 (POEM-3) met its fiery end through a re-entry into the Earth’s atmosphere.
The PSLV-C58 mission was launched on January 1. The PSLV-C58 rocket, in its 60th mission, carried the primary payload X-Ray Polarimeter Satellite (XPoSat).
After completing the primary mission of injecting all satellites into their desired orbits, the terminal stage of PSLV was transformed into a 3-axis stabilised platform, the POEM-3.
POEM-3 was configured with a total of nine different experimental payloads to carry out technology demonstrations and scientific experiments on the newly developed indigenous systems.
The mission objectives of these payloads were met in a month.
The stage was deorbited from 650 km to 350 km, which facilitated its early re-entry, and was passivated to remove residual propellants to minimise any accidental break-up risks.
The PSLV-C58/XPoSat mission has practically left zero debris in orbit.
ISRO’s System for Safe and Sustainable Spacecraft Operations Management (IS4OM) has been monitoring and analysing the orbital decay throughout the mission.
What is space debris?
• Space debris consists of discarded launch vehicles or parts of a spacecraft that float around in space hundreds of kilometres above the Earth, risking collision with a satellites or a space station.
• Debris can also be caused by an explosion in space or when countries conduct missile tests to destroy their own satellites.
• Ever since the start of the space age there has been more space debris in orbit than operational satellites.
• The amount of objects, combined mass and combined area has been steadily rising since the beginning of the space age, leading to the appearance of involuntary collisions between operational payloads and space debris.
• Space debris encompasses both natural meteoroid and artificial (human-made) orbital debris. Meteoroids are in orbit about the Sun, while most artificial debris is in orbit about the Earth (hence the term “orbital” debris).
• Orbital debris is any human-made object in orbit about the Earth that no longer serves a useful function. Such debris includes non-functional spacecraft, abandoned launch vehicle stages, mission-related debris, and fragmentation debris.
• There are approximately 23,000 pieces of debris larger than a softball orbiting the Earth. They travel at speeds up to 28,000 kmph, fast enough for a relatively small piece of orbital debris to damage a satellite or a spacecraft.
• There are half a million pieces of debris the size of a marble or larger (up to 0.4 inches, or 1 centimeter) or larger, and approximately 100 million pieces of debris about .04 inches (or one millimeter) and larger. There is even smaller micrometer-sized (0.000039 of an inch in diameter) debris.
• Even tiny paint flecks can damage a spacecraft when traveling at these velocities. A number of space shuttle windows were replaced because of damage caused by material that was analysed and shown to be paint flecks. In fact, millimeter-sized orbital debris represents the highest mission-ending risk to most robotic spacecraft operating in low Earth orbit.
• The International Space Station (ISS) orbits Earth at an altitude of just over 400 km. In the two decades since its launch, about 30 ‘collision avoidance manoeuvres’ have been performed in order to dodge space debris, with three taking place in 2020 alone. If a potential collision appears imminent, and there is no time to move the Station, they can take emergency shelter.
• In 1996, a French satellite was hit and damaged by debris from a French rocket that had exploded a decade earlier.
• China’s 2007 anti-satellite test, which used a missile to destroy an old weather satellite, added more than 3,500 pieces of large, trackable debris and many more smaller debris to the debris problem.
• In February 2009, at 776 km altitude above Siberia, a privately owned American communication satellite — Iridium-33 — and a Russian military satellite — Cosmos 2251 — collided. The collision added more than 2,300 pieces of large, trackable debris and many more smaller debris to the inventory of space junk.
• Not only a hazard, space debris increases the cost for satellite operators. Satellite operators in the geostationary orbit have estimated protective and mitigation measures account for about 5-10 per cent of mission costs and for lower-Earth orbits the cost is higher.
• As a consequence of the rising debris object count, the probability for catastrophic collisions will also grow progressively, doubling the number of objects will increase the collision risk by approximately four times. As the debris population grows, more collisions will occur.
• The most important action currently is to prevent the unnecessary creation of additional orbital debris. This can be done through prudent vehicle design and operations. Cleaning up the environment remains a technical and economic challenge.
• As space debris poses a problem for the near Earth environment on a global scale, only a globally supported solution can be the answer.
• The United Nations Committee on the Peaceful Uses of Outer Space by the United Nations Office for Outer Space Affairs (UNOOSA) has paid particular attention to the issue of preventing and minimising the creation of space debris.
ISRO System for Safe and Sustainable Operations Management (IS4OM)
• In July 2022, ISRO System for Safe and Sustainable Operations Management (IS4OM) was established.
• IS4OM is ISRO’s holistic approach to ensure the safety of India's space assets and thus, sustains the utilisation of outer space for national development.
• In response to ever-growing space object population and the risk of collisions in space, it undertakes observation and monitoring of space objects and space environment, processing the observations for orbit determination, object characterisation and cataloging, analysis of space environment evolution, risk assessment and mitigation, and data exchange and collaboration.
• The system safeguards all Indian Space assets by mitigating the collisional threats from space objects through specific orbit maneuvers and complying to international guidelines on post mission disposal and satellite’s end-of-life operations.