Feb 26, 2017
Space junk and ISRO
The Indian Space Research Organisation (ISRO) sent 104 satellites into orbit and the wild applause was soon followed by growing mutterings about India’s space agency adding to space junk. However, it’s irrational to blame the agency.
If anything, carrying multiple payloads lowers orbital debris as each rocket used to send satellites to space also adds to the space junk.
ISRO is also ideally located for launches because its proximity to the Equator gives the rockets an extra velocity kick into space so they use less fuel to launch heavier payloads.
And unlike space tourism, satellites serve a practical purpose, providing data that support communication, navigation, scientific research, weather observation, military support, earth imaging, among others.
ISRO has developed the models and software for statistical analysis of risk due to space debris and close approach of debris to the functional satellites and to prevent in-orbit break-up by designing spacecraft to be not susceptible to on-orbit explosion.
Space junk
Since the launch of the first artificial satellite Sputnik 1 by the former Soviet Union in 1957, dozens of countries have launched satellites, with close to 3,000 working satellites still orbiting the Earth. These functional satellites are just a fraction of the than 500,000 pieces of dead satellites ranging from the size of a marble to much bigger machines that continue to orbit the Earth.
There are many millions of smaller pieces of dead spacecraft, abandoned launch vehicle stages, mission-related debris and fragmentation debris that are too tiny to be tracked.
The greatest risk to space missions comes from non-trackable debris. Debris shields can withstand impacts of particles smaller than 1 cm.
Space junk travels at speeds up to 30,000 km an hour, which turns tiny pieces of orbital debris into deadly shrapnel that can damage satellites, space shuttles, space stations and spacecraft with humans aboard.
Kessler syndrome: it is a scenario in which the density of objects in space is high enough that collisions between objects could cause a cascade where each collision generates space debris that increases the likelihood of further collisions. One implication is that the distribution of debris in orbit could render space activities and the use of satellites in specific orbital ranges unfeasible for many generations.
Tracking debris
A multi-object tracking radar (MOTR) developed by the Satish Dhawan Space Centre allows ISRO to track 10 objects simultaneously. It tracks India’s space assets and space debris, for which India was solely dependent on data provide by the US space agency NASA till early 2016.
ISRO is a part of the Inter-Agency Space Debris Coordination Committee (IADC), an international governmental forum that coordinates global efforts to reduce man-made and natural space debris by sharing research and identifying debris mitigation options.
Global mitigation measures take many forms, including preventing the creation of new debris, designing satellites to withstand impacts by small debris, and improving operational procedures such as using orbital regimes with less debris, and predicting and avoiding collisions.
