Why ISRO's new SpaDeX mission is crucial for India

The Indian Space Research Organisation (ISRO) will launch its PSLV-C60/SpaDeX Mission from Sriharikota in Andhra Pradesh at 9:58 pm on December 30, 2024. The SpaDeX mission will launch on a PSLV-C60 rocket.

Why SpaDeX mission is important for ISRO and India

The mission is expected to be a game-changer for Indian space technology. It will demonstrate in-space docking using two small spacecraft.

"This groundbreaking technology is key to future lunar missions, building Bharatiya Antariksh Station (BAS), and more," ISRO said.

With this mission, India aims to join the elite club of nations with space-docking capabilities. If successful, India will march towards becoming the fourth country in the world to have space-docking technology.

Importance of in-space docking

"Docking" happens when a spacecraft can manoeuvre and attach to a space station by itself. For many years, there has been a lot of interest in automated spaceship docking and rendezvous.

Meanwhile, NASA defined docking as “mating operations where an active vehicle flies into the mating interface under its own power”.

Science Direct explained that Spacecraft docking has significant applications such as ferrying supplies to manned space stations, refueling space vehicles, and recovering daughter spacecraft separated from mother spacecraft.

It stated, “Starting from manned missions represented by Gemini 8, Apollo, and Soyuz, interest in and demand for space docking have been shifting to unmanned, automated operations.”

Similarly, ISRO explained that this technology is essential for India’s space ambitions, such as "Indian on Moon", sample return from the Moon [Chandrayaan 4 mission], and the building and operation of Bharatiya Antariksh Station (BAS)."

"In-space docking technology is essential when multiple rocket launches are required to achieve common mission objectives," the Indian space agency said.

India's space ambition

The Centre announced its Space Vision 2047 earlier this year, which targets establishing Bharatiya Antariksh Station (BAS) by 2035 and sending an Indian to the Moon by 2040. The ISRO also aims to launch the Chandrayaan-4 mission to bring back lunar samples by 2027.

What to expect from SpaDex mission?

According to ISRO, the primary objective of the SpaDeX mission is to develop and demonstrate the technology needed for rendezvous, docking, and undocking of two small spacecraft in a low-Earth circular orbit.

One of the two spacecraft is SDX01, which is the Chaser, and the other one is SDX02, the Target. They weigh 220 kg each.

SpaDeX mission will also perform microgravity experiments using PSLV's spent fourth stage, called POEM-4 (PSLV Orbital Experimental Module). It will carry 24 payloads -- of which 14 payloads are from ISRO/DOS centres and 10 payloads are from various Non-Government Entities (NGEs).

What will happen during SpaDex mission?

Here's what ISRO explained:

The two small spacecraft part of the mission will be launched by PSLV-C60, independently and simultaneously, into a 470 km circular orbit at 55° inclination. The local time cycle will be about 66 days.

A small relative velocity will be given between the Target and Chaser spacecraft at the time of separation from the launch vehicle.

This incremental velocity will allow the Target spacecraft to build a 10-20 km inter-satellite separation with respect to the Chaser within a day.

At the end of this "drift arrest manoeuvre", the Target and Chaser will be in the same orbit with identical velocity but separated by about 20 km, known as "Far Rendezvous".

The Chaser will then approach the Target with progressively reduced inter-satellite distances of 5 km, 1.5 km, 500 m, 225 m, 15 m, and 3 m, ultimately leading to the docking of the two spacecraft.

After successful docking and rigidization, electrical power transfer between the two satellites will be demonstrated before undocking and separation of the two satellites to start the operation of their respective payloads.

The expected mission life is up to two years.