India's Moon mission pulled off another trick: an experimental orbital sequel

Swift software development effort saw Chandrayaan-3 propulsion module make an unexpected return to Earth

India has revealed an unexpected sequel to its Chandrayaan-3 Moon lander mission.

The triumphant lunar adventure started on July 14 with the launch of an LVM3 rocket carrying a propulsion module that brought the Vikram lander and Pragyan rover into orbit around the Moon.

That plan worked. Vikram and Pragyan performed as hoped, and the rover spent several days trundling around on Luna before shutting down for the lunar night. As expected, it did not recover from that exertion.

India's Space Research Organisation (ISRO) planned for the mission to continue, as the propulsion module carries an Earth observation instrument: the Spectro-polarimetry of HAbitable Planet Earth (SHAPE). The space org planned to run SHAPE for three months, from lunar orbit.

But the precision with which Chandrayaan-3 operated saw around 100kg of fuel remain in the propulsion module.

ISRO decided to use that fuel "to derive additional information for future lunar missions and demonstrate the mission operation strategies for a sample return mission."

On Monday the space agency revealed that its plan had succeeded.

After firing the propulsion module's engines on October 9 to raise its orbit, then again on the 13th to conduct a Trans-Earth injection maneuver, the module flew by the Moon four times before departing Earth's sole natural satellite on November 10.

The module reached Earth orbit on November 22 and is presently in an orbit with a 13-day period, 27-degree inclination, and a perigee of 115,000 kilometers.

SHAPE continues to operate.

ISRO hasn't said how long it thinks the instrument will work, but has given assurances the module's orbit poses no risk to other spacecraft.

The space org appears chuffed that its plan worked – noting that success depended on very speedy creation of plans for a gravity assisted flyby and a software module to make it possible.

Turns out India's good at rapid software development. Who knew?

Avoiding an uncontrolled crash of the propulsion module into the Moon is also a win, as ISRO hoped not to create debris. ®

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