ISRO scientists will briefly lose contact with the PSLV C-25, carrying India’s first interplanetary orbiter to Mars, before the signals are picked up by communication ships in the South Pacific Ocean during its proposed launch on November 5.
The PSLV C-25 is set to take off from the Satish Dhawan Space Centre at Sriharikota and the silent period would occur around 30 minutes after the launch.
The duration of silence is likely to be closer to 20 minutes though the ISRO chairman estimated it be a more modest 10 minutes.
The Indian Space Research Organisation has ground stations at Sriharikota, Port Blair, Brunei and Biak (Indonesia) to keep track of the satellite. However, as the path of this spacecraft is well beyond anything ISRO has launched before. This is why they have deployed two ships to the Pacific to track the spaceship.
“This mission is beyond the range of the Biak station and we will be losing signal for about 10 minutes till it is picked up by the ships,” said ISRO chairman Dr K Radhakrishnan.
However, officials at the Mission Control Centre at SDSC let on that the ‘quiet’ period will be between 15-20 minutes. “We will not be able to see the pitch, yaw, roll, corrections that the PSLV is making for that time. We will extrapolate its trajectory and hope that the on-board computer makes the corrections as programmed,” said the official.
The data will be logged and downloaded to ISRO’s servers as soon as the ships’ receivers pick up the telemetry signals from the spaceship.
It may be recalled that the initial launch date was deferred from October 28 to November 5, because the communication vessels Nalanda and Yamuna had been delayed by choppy weather in the South Pacific seas. Leased from the Shipping Corporation of India, the ships left in September. “SCI Nalanda has a 4.6m antenna and is already at the required location (OP1 point) and SCI Yamuna with 1.8m antenna is now moving towards the OP2 point and will be there by November 3,” added Radhakrishnan.
The crucial stages of the fourth stage propulsion, the burnout, the separation of the satellite and the deployment of the solar panels will be observed by the ships’ observation systems and transmitted to ISRO. After the Mars orbiter separates from the launch vehicle, it will be tracked by deep space satellites and transmitted to international reception centres.