Satellites to get self-drive tech
While the country is celebrating the capability acquired by the Indian Space Research Organisation to launch a large number of satellites in a single mission, former Isro chairman Madhavan Nair has expressed worry over tiny satellites clogging space.
Dr Nair said recently that the nano-satellites, which have a life of one or two years, end up becoming space debris thereafter. Since they are small — nano-satellites are less than 10 kg — tracking them and locating their position af the end of their life is a very difficult task, dr Nair observed during a programme in Hyderabad recently.
Space debris has become an issue affecting the safety of space activities, including manned flight, and long term sustainability of the space environment.
According to data, least 25 per cent of the active low earth orbit objects are small satellites. The life of a spacecraft or satellite ends when it runs out of onboard propellant. Such non-functional objects undergo changes due to the environment while orbiting in space, and create a large amount of debris when they explode due to pressure and temperature changes.
The process of injecting a spacecraft into orbit involves the final stage of the rocket also reaching space to achieve orbital velocity. The rocket debris practically follow the satellites in the same orbit — but as a passive non-functional object.
According to Isro engineers, every space agency, spacecraft operator, launch operator, and insurance underwriter is worried about the safety of space objects due to possible collision with debris. Countries which operate manned missions in low earth orbit are much more worried about the implications of increasing debris.
Former director of Satish Dhawan Space Centre M.Y.S. Prasad, who represented Isro and India in the UN conference on peaceful uses of outer space from 1997 to 2006, said that approximately 60 per cent of While admitting that there are limitations in tracking the debris of small satellites, Dr K. Sivan, director of Vikram Sarabhai Space Centre at Thiruvananthapuram, said it was not a constraint because most of them are injected into lower orbits of around 500 km.
They start falling towards earth after they run out of propellants, and down up as they enter the atmosphere.
He said small satellite can be manoeuvred into lower orbits by orienting the large solar panels. He said that it was better to have more small satellites than a single large satellite, in terms of cost, coverage and utility.
For instance, one has to wait for data of a particular region for a full one day in case of a big satellite because it reaches the same spot once in 24 hours.
In the case of multiple satellites, the global the catalogued objects are generated from the fragmentation of spacecraft and rocket bodies, 18 per cent are the result of mission related debris and rocket bodies which remain in orbits, and 15 per cent of the debris are non-functional satellites.
The number of catalogued data will be available anywhere at any time.
He said future satellites will have advanced technology to enable them steer clear of space debris on their own and also indicate their location and health. This could be similar to the technology used in selfdrive cars.
The current density of the space debris in the two regions — low earth orbit and geostationary orbit — very significant for space operations.
Low earth orbit stretches to 400 km to 800 km above earth. Satellites in the geostationary are placed approximately 36,000 km above the Earth. They are orientated in such a way that they appear to be at the same spot above the Earth.
Most manned missions and space stations are 400 km to 500 km above the Earth. These missions have close encounters with debris, and have to plan collision avoidance manoeuvres. space objects at the end of September 2016 was around 17,800, including functional satellites and debris. The total pieces of debris is roughly around 13,600. Around 1,500 of these objects are in the Geosynchronous Orbit, and most of the remaining are in low earth orbit.