In April this year, a spacecraft weighing 1,330 kg will be sent hurling across to the moon. Covering this distance of over 3 lakh km in nine days, it will then become a satellite of the moon for a year and two, after which it will be crashed onto the lunar surface.
Chandrayaan-1, as it is called, will be launched from Sriharikota aboard the PSLV launch vehicle this April. All later manoeuvres will be executed by the control centre at ISRO's telemetry, tracking and command network campus in Bangalore. The tracking will be done by ground stations of ISRO and also space agencies of US, Russia and Brazil.
But in addition to this, a two-way radio communication link between the craft and earth will be established through the Deep Space Network (DSN) set up at Byalalu village, 30-odd km from Bangalore.
Comprising a huge parabolic dish 32 metre wide and made of 180 panels of aluminum and weighing over 60 tonnes, it can receive and send radio signals from/to objects beyond 1 lakh km. It can perform telemetry, tracking and command operations in the S-band and receive science data in the X-band.
The DSN stands tall in the prestigious list of few other antennas. NASA operates one with 70 m width and China a 34 m antenna. The rest are of smaller dimensions.
A beam wave guide which works like a periscope with seven mirrors directs the radiation (signal) from space into the computer system at the base from where it can be accessed at Istrac centres in Bangalore. Cryo cooled low noise amplifiers make it possible to have low system noise temperatures and very high power uplinking capability in S-band allows it to send commands to the lunar orbit and beyond.
High performance processors and the large size of the dish enable it to receive and decode low faint signals from deep space. Situated in a natural valley also helps to block out unwanted signals from the city.
The antenna can be manoeuvred for both horizontal and vertical movement to track any craft or moving object. A precise beam pointing accuracy of 15 x .0001 degrees and a reflector surface accuracy of 0.3 mm along with atomic clock measurements allow for precision.
Except for a few electronic equipments, the DSN has been totally indigenously manufactured with ECIL, Hyderabad being the prime contractor. Istrac, Isac, BARC, Godrej, L&T, HAL, Balajee Tanks and Vessels (that did the installing), and many other industries got into the act in Oct 2004.
The DSN installation has been completed. Tracking of a deep space probe is the next step to ensure its readiness for the moon mission. “We have been able to receive signals from satellites in orbits which are not exactly deep space but still, it can be called the first level of tracking though not characterisation,” said S K Shivakumar, director, Istrac. Tracking the sun has also been successful, he said but in the next week more objects will be tracked, he added.
While it will be handy for the moon mission, the DSN represents the nation's ambitious deep space missions to Mars and beyond. Even as Chandrayaan-1 is being seen as the precursor to Chandrayaan-2, which will land the craft on moon, drill into the surface and send back data, from the poles. The hope is to find helium, a potential fuel for mankind!
