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India returns Chandrayaan-3 propulsion module to Earth orbit

WASHINGTON — The spacecraft that transported the Chandrayaan-3 lander to the moon has returned to Earth orbit, a demonstration of technologies to support a future Indian lunar sample return mission.

The Indian space agency ISRO announced Dec. 4 that the propulsion module for the Chandrayaan-3 mission is now in a high orbit around the Earth after a series of maneuvers since October that returned the spacecraft from a low lunar orbit. ISRO had not previously disclosed any efforts to return the propulsion module to Earth orbit.

The main purpose of the 2,145-kilogram propulsion module was to transport the Chandrayaan-3 lander from an initial elliptical Earth orbit to low lunar orbit. The module, a modified version of ISRO’s I-3K satellite bus, performed several maneuvers starting a day after its July 14 launch to raise the apogee of the orbit, followed by a translunar injection burn and lunar orbit insertion burn. The module than moved into a nearly circular orbit about 150 kilometers above the moon before the lander separated Aug. 17.

The lander successfully touched down on the moon Aug. 23. The propulsion module remained in orbit, operating a single instrument called Spectro-polarimetry of Habitable Planet Earth, or SHAPE, to observe the Earth. ISRO provided little information about the propulsion module after the lander separated.

In a statement, ISRO said that it decided to attempt to bring the propulsion module back to Earth orbit after determining that the precision of the launch and earlier maneuvers left more than 100 kilograms of propellant on the spacecraft. The first maneuver in that plan took place Oct. 9, raising the apolune, or high point in its orbit around the moon, from 150 to 5,112 kilometers.

The module performed a transearth injection maneuver Oct. 13, placing it on a trajectory where it performed four close approaches to the moon before leaving its sphere of influence on Nov. 10. The spacecraft entered a high orbit around the Earth, making its first perigee Nov. 22 at an altitude of 154,000 kilometers.

ISRO said the maneuver allowed SHAPE to continue observations closer to Earth. It added, though, that the maneuvers were designed “to derive additional information for future lunar missions and demonstrate the mission operation strategies for a sample return mission.”

ISRO has not formally announced plans for a lunar sample return mission. Its next mission to the moon is the Lunar Polar Exploration Mission, or LUPEX, a joint effort with the Japanese space agency JAXA. That mission, sometimes called Chandrayaan-4, would feature a Japanese rover on an Indian lander to explore the south polar region of the moon. It is expected to launch no earlier than 2026.

However, ISRO officials have discussed the potential of a near-term sample return mission. “The government of India has given us a very tight timetable for exploration in space. We need to have a sample return from the moon within about four years,” said Shri M. Sankaran, director of ISRO’s U R Rao Satellite Center, during a panel discussion at the AIAA’s ASCEND conference Oct. 24 in Las Vegas.

He appeared to be referring to a meeting of ISRO leadership chaired by Indian Prime Minister Narendra Modi Oct. 17. A release by the prime minister’s office mentioned goals that included an Indian space station by 2035 and Indian crewed lunar landing by 2040, but did not discuss lunar sample return.

In a later presentation at the conference, he said that ISRO had developed a concept for a sample return mission, but did not go into details about it. “Maybe this sample return and LUPEX mission with JAXA may happen more or less concurrently,” he said.

The return of the propulsion module to Earth orbit was not the first demonstration of technologies needed for lunar sample return on Chandrayaan-3. In its final days of operations on the lunar surface in September, the lander reignited its engines, rising about 40 centimeters off the surface before touching down 30 to 40 centimeters away from its original landing location. “This ‘kick-start’ enthuses future sample return and human missions!” ISRO posted on social media.