Hectic activity is on at Sriharikota for the lift-off of the Polar Satellite Launch Vehicle (PSLV-C22) at 11.41 p.m. on July 1, which will put the Indian Regional Navigation Satellite System, IRNSS-1A into orbit. A PSLV-XL version, which uses six powerful strap-on booster motors, will put the 1,425-kg IRNSS-1A into orbit.
“Everything is going well for the launch and the satellite has been integrated with the PSLV,” ISRO Chairman K. Radhakrishnan told The Hindu on Monday from New Delhi. “Today, the phase 3, level 2 of the checks have started with the launch vehicle and the satellite together. There will be a final Mission Readiness Review [MRR] meeting on June 27 and clearance will be given for the countdown, which will begin on June 29 morning,” he said. It would be a 69-hour countdown.
The IRNSS will have a constellation of seven satellites and the IRNSS-1A is the first of the seven regional, satellite-aided navigation systems built by ISRO. The PSLV-C22 would put the IRNSS-1A into an elliptical orbit with an apogee of 20,600 km and a perigee of 280 km. “From there, it will be taken to a geosynchronous circular orbit of 36,000 km with an inclination of 29 degrees to the equator,” Dr. Radhakrishnan said.
Longer countdown
Asked why this launch had a longer countdown time of 69 hours, he said, “Since the launch is to take place at night, we would like to keep some cushion so that people can take some rest.”
The IRNSS-1A will provide accurate information on the position of cars/trucks, ships and aircraft vis-à-vis their destination, with the help of a receiver. It could be an independent receiver, or built into a mobile phone, a car or a ship. The satellite can provide precise information when the aircraft is about to land on the runway. The pilot will know how far he is from the runway or at what height he is above the runway, with an accuracy of 20 metres. Unlike the Global Positioning System (GPS) which can be used anywhere, this is called a regional navigation system because it is available to users in India and the surrounding region. A highly accurate atomic clock is part of the navigation payload of the satellite. Thus, the IRNSS applications include terrestrial, aerial and marine navigation, disaster management, tracking of vehicles, guiding hikers and travellers, and visual and voice navigation for drivers.
The PSLV-C22 launch was to have taken place on June 12, with its four stages fully integrated and undergoing electrical checks. Regarding the postponement, Dr. Radhakrishnan said: “When we were doing electrical checks of the vehicle, we found an anomaly in its second stage. The problem was identified to be with the electrohydraulic actuator. We have done the necessary replacement of the actuator.”
“Small disturbance”
M.Y.S. Prasad, Director, Satish Dhawan Space Centre, Sriharikota, said the control system in the PSLV’s second stage required the nozzle to be moved to control the vehicle’s flight.
An actuator pushed or pulled the nozzle to give “a correcting force” to the rocket if there was any deviation in the flight path. But ISRO engineers detected “a small disturbance” in the correcting force.
When they removed the actuator and investigated the issue, they found a problem with a valve in the actuator. So the entire actuator was removed and replaced with a new one. This necessitated the dismantling of the second, third and fourth stages after they had been assembled.
“After the new actuator was put in the second stage, we had to restack the vehicle,” Dr. Prasad said.
Hectic schedule
Dr. Radhakrishnan said ISRO was gearing up for a tough schedule in 2013 with the launch of INSAT-3D slated for July 26 by Ariane-5 vehicle of the Arianespace from Kourou, French Guiana; the lift-off of the Geosynchronous Satellite Launch Vehicle (GSLV-D5) with an indigenous cryogenic engine in August to put a communication satellite, GSAT-14, in orbit; the launch of GSAT-7 from Kourou in August; and the orbiter mission to Mars in October/November. INSAT-3D had already reached French Guiana.
