Isro reveals details of the innovative approaches used for the record breaking PSLV-C37 launch

The unprecedented number of satellites on a single mission called for unique approaches in accommodating the satellites and designing the mission by Isro.


Isro has revealed the unusual steps it took for the record setting launch of 104 satellites in the PSLV-C37 launch. The mission used the "workhorse" rocket of Isro to its full capacity, and there were innovative approaches needed to pack all the satellites, release them in the correct orbit, and ensure that all the passenger satellites on board separated in a safe and timely manner, without colliding into each other. The unprecedented number of satellites on a single mission called for unique approaches in accommodating the satellites and designing the mission.

 Isro reveals details of the innovative approaches used for the record breaking PSLV-C37 launch

The majestic lift-off of the PSLV-C37. Image: Isro.

The mission was meticulously planned at the Sriharikota High Altitude Range (SHAR) at the Satish Dhawan Space Centre (SDSC). The assembly of the satellites, handling of the sub-systems and preparing the satellites for launch were all planned and executed at India's rocket launch facility. Including the satellites and the stages of the rocket, there were 114 separation events over the course of the launch. All the separation events were captured on video by an onboard imaging system.

A stream of satellites being injected into orbit by the PSLV-C37 mission, captured from on board cameras. Image: Isro.

A stream of satellites being injected into orbit by the PSLV-C37 mission, captured from on board cameras. Image: Isro.

To house the satellites, conventional adapters such as Multiple Satellite Adapter (MSA) and Payload Adapter (PLA) were used along with six custom made adapters to house the nanosatellites. The primary payload was mounted on the PLA. Some of the custom made adapters allowed multiple tier attachments of satellites. A few nanosatellites were even housed in the Vehicle Equipment Bay, which normally only contains the systems for ground communications, and functions as the "brain" of the launch vehicle. The configuration used optimally used the volume available, as well as the lift capacity of the launch vehicle.

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A dual launch adapter on the PSLV-C20 mission. Image: Isro.

There was a requirement for managing the separation events of the satellites. Most of the satellites would have to be released after the launch vehicle lost contact with the Isro Telemetry, Tracking and Command Network (ISTRAC) tracking station at Mauritius, and before establishing contact with the Troll station in Antartica. The stage to which the satellites were attached had a complex maneuvering program, along with a sequence and timing for the satellite separation events. Isro engineers conducted detailed studies to ensure that the 105 objects, including a PSLV stage, would not collide after separation.

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The primary payload sits on top of the Payload Adapter (PLA), in the middle of the image. Towards the bottom, eight satellites can be seen housed on the Multiple Satellite Adapter. This is the PSLV-C35 mission that launched multiple satellites in different orbits. Image: Isro.

Isro had to track 5460 pairs of objects, to make sure that they would not collide with each other. The command for separating from the launch vehicle had to reach the satellites at the right time and in the right predefined sequence. This was accomplished using a complex electrical wiring scheme. Any error in the wiring scheme would mean that the wrong satellite would be separated at the wrong time, potentially leading to collisions between the satellites.

The nanosatellites being injected into orbit as seen from a camera on board the PSLV-C37. Image: Isro.

The nanosatellites being injected into orbit as seen from a camera on board the PSLV-C37. Image: Isro.

The PSLV-C37 mission was the 39th flight of the PSLV, one of the world's most reliable launch vehicles. India's CartoSat-2 Series satellite was the primary payload, with 103 other satellites piggybacking on the ride as passengers. The nanosatellites weighed between one to ten kg each, with two nanosatellites being from India. 101 satellites on board were from foreign countries. All the satellites on board weighed a total of 1378 kg.

The PSLV-C37 mission in mid-flight. Image: isro.

The PSLV-C37 mission in mid-flight. Image: Isro.

The launch of 104 satellites has cemented the important presence of India in the international satellite launch market. Next, Isro plans to take two Google Lunar Xprize contenders to the moon on the same PSLV, go on missions to Mars and Venus, and is waiting from the Government for the go ahead and budget allocation for building its own space station.


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