How ISRO plans to launch 103 satellites in one go

They will be injected into orbit at different locations at different angles, at different times and different orientations

The Indian Space Research Organisation (ISRO) will set a record when it launches 103 satellites in one go on a single rocket in the first week of February. Explaining how all the satellites will be placed in orbit, Dr. K. Sivan, Director of the Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram, says: “The satellites will be separated from the launch vehicle in different directions. The separation angle and time of separation will be such that one satellite will not collide with another.”

Different velocities

The satellite separated from the launch vehicle will have a relative velocity of one metre per second. So, after 1,000 seconds the distance between a satellite and the rocket will be 1,000 metres. “The satellite that gets launched first will move at a relatively faster velocity than the next satellite that is launched. Due to different relative velocities, the distance between the satellites will increase continuously but the orbit will be the same,” he says.

“When the vehicle reaches the orbital condition, we will wait for the disturbances to die down before the preparation for separation begins,” he says. At an orbital altitude of around 500 km, it would take the vehicle 90 minutes to complete one orbit. “So we have sufficient time to launch all the 103 satellites,” he says.

Even one degree difference in separation angle combined with relative velocity will ensure that no two satellites would collide with each other. “The satellites will be injected into orbit at different locations at different angles, at different times and different orientations,” Dr. Sivan says.

Single mission

In June last year, ISRO launched 20 satellites in one go. It took about 26 minutes to launch all the 20 satellites. In 2008, ISRO launched 10 satellites in a single mission. The highest number of satellites launched in a single mission so far has been 37 by Russia in 2014; NASA launched 29 satellites in one go in 2013.

ISRO’s workhorse PSLV-C37 with 103 satellites will be launched from the Satish Dhawan Space Centre in Sriharikota in Andhra Pradesh. Except for three satellites, the remaining are from other countries. The 100 satellites are micro-small satellites. The weight of the payload will be 1,350 kg, of which 500-600 kg will be the satellite’s weight.