ISRO brings back Chandrayaan-3 propulsion module to Earth’s orbit

This experiment, which began with the first orbit-raising manoeuvre on October 9, helped Isro plan and execute a trajectory back to Earth. While the space agency has successfully taken spacecraft to an orbit around the moon three times, this is the first time it has brought anything back.

This, in addition to the hop experiment conducted at the end of life of the Chandrayaan-3 lander, gives glimpses of Isro’s preparedness for future missions that would require the spacecraft to not only land successfully on the moon but also take off from it and make its way back to Earth.

The current experiment is also the first time the space agency has demonstrated a gravity assist flyby not around Earth but another celestial body. Gravity assist flyby is a technique where gravity of a planet or celestial body is used to redirect, speed up, and slingshot a spacecraft towards Earth.

The experiment has also helped Isro test software that can plan such a manoeuvre.

Bringing the propulsion module back to Earth avoids it not only from crashing into the moon at the end of its life, but also from entering geostationary orbit and colliding with other satellites. “Considering the estimated fuel availability and the safety to GEO spacecrafts, the optimal Earth return trajectory was designed for October 2023,” the space agency said.

The first manoeuvre of the propulsion module was performed on October 9, increasing the orbit around the moon to 5,112 km from 150 km. This increased the time it takes the spacecraft to go around the moon from 2.1 hours to 7.2 hours. Another manoeuvre was performed on October 13 to increase the orbit to 1.8 lakhs x 3.8 lakhs km. The propulsion module went around the moon four times before exiting its sphere of influence on November 10.

At present, the propulsion module is orbiting the Earth at an altitude of about 1.54 lakh km, reaching the altitude of 1.15 llakh kilometres at its closest. The orbit is around 13 days. “As per current orbit prediction, there is no threat of close approach with any operational Earth orbiting satellites,” the space agency said.

The payload on-board the propulsion module, called SHAPE, will continue to conduct spectroscopic study of the Earth’s atmosphere from its new orbit. The payload was designed to try to pick up signals that will help scientists understand the markers of life on other planets outside our solar system.