Chandrayaan 2 arrives in lunar orbit, targets moon landing next month

Artist’s illustration of the Chandrayaan 2 spacecraft, including the lander and orbiter, at the moon. Credit: ISRO

India’s Chandrayaan 2 spacecraft braked into orbit around the moon Tuesday, positioning the robotic science mission for a landing in the moon’s south pole region Sept. 6.

The spacecraft ignited its main engine at 0332 GMT Tuesday (11:32 p.m. EDT Monday) and fired for 29 minutes to reduce the the probe’s velocity by more than 600 mph (300 meters per second), allowing the moon’s gravity to capture Chandrayaan 2 into orbit.

The make-or-break rocket burn sets up Chandrayaan 2 for a series of burns to adjust its orbit over the next two weeks before the separation of the mission’s orbiter and lander elements Sept. 2, ahead of the lander’s final descent maneuver.

“Today, the Chandrayaan 2 mission crossed a major milestone,” said K. Sivan, chairman of the Indian Space Research Organization, India’s space agency.

Sivan said the 29-minute engine firing Tuesday “precisely injected” the Chandrayaan 2 spacecraft into the planned orbit around the moon.

Chandrayaan 2 became the second Indian spacecraft to orbit the moon after India’s Chandrayaan 1 orbiter, which arrived in 2008 and made history by detecting water-bearing molecules at the lunar poles, with the highest concentrations inside permanently-shadowed craters at the south pole.

Tuesday’s lunar orbit insertion maneuver placed the Chandrayaan 2 spacecraft in an elliptical orbit around the moon, with an altitude ranging from 70 miles (114 kilometers) at its lowest point, to a high point of 11,229 miles (18,072 kilometers), according to ISRO.

If Tuesday’s burn was unsuccessful, Chandrayaan 2 would have missed the moon and the mission would have been lost, Sivan said.

Less than half of the attempts to land on the moon since the dawn of the Space Age have been successful, and Chandrayaan 2 will be India’s first try.

“Even though we got a successful lunar orbit insertion today, still the landing is a terrifying moment,” Sivan said. “Until now, (many of) our lunar lander systems have not operated, especially the propulsion system. That will come only after the 2nd (of September). Only then we will know.

“That is a phase we are doing for the first time,” Sivan said. “Whereas today’s lunar orbit insertion … we’ve already done that once.”

“We have the confidence in this landing mission,” Sivan said. “We are confident because we have enough testing, enough simulations. All the subsystem- and system-level, sensor-level, thruster-level, all the simulations here are done. We are confident that anything humanly possible, we did.”

K. Sivan, ISRO’s chairman, displays a model of the Chandrayaan 2 spacecraft during a press conference Tuesday. Credit: ISRO

Chandrayaan 2 launched July 22 aboard India’s largest rocket, the GSLV Mk.3, into an egg-shaped orbit around Earth.

The spacecraft gradually boosted its orbit to higher latitudes with a series of five engine burns, culminating with a trans-lunar injection maneuver Aug. 13 (GMT) to place Chandrayaan 2 on a trajectory to intercept the moon.

With Chandrayaan 2 now in a stable orbit around the moon, ISRO ground teams will oversee a further sequence of burns using the orbiter’s propulsion system to guide the spacecraft into a circular 62-mile-high (100-kilometer) orbit. The lunar orbit maneuvers will begin with an engine firing Wednesday, followed by additional firings Aug. 28, Aug. 30 and Sept. 1.

“The next major event happens on the 2nd of September, when the lander will be separated from the orbiter,” Sivan said. “Until now, the entire operations are carried out by the propulsion systems from the orbiter. From Sept. 2 onwards, the entire attention will be on the lander.”

The landing module is named Vikram for Vikram Sarabhai, the father of India’s space program, and after touchdown will deploy the Pragyan rover, named for the Sanskrit word for “wisdom.”

After separating from the orbiter, the Vikram lander will conduct a test burn of its propulsion system Sept. 3.

The final 15-minute landing sequence will set up for touchdown in an ancient polar highlands region between two craters at approximately 70.9 degrees south latitude, and 22.8 degrees east longitude, closer to the moon’s south pole than any previous mission.

“After confirming the normalcy of the system, then on the 4th of September, we will be doing the real deorbit maneuver for the lander for about 6.5 seconds,” Sivan said. “In that maneuver, the lander will be put into an orbit with 35 kilometers (21 miles) perilune and about 97 kilometers (60 miles) apolune.”

“For the next (few) days, we’ll be checking the various parameters of the lander to ensure everything is right,” Sivan said.

The final 15-minute powered descent sequence will set up for touchdown in an ancient polar highlands region between two craters at approximately 70.9 degrees south latitude, and 22.8 degrees east longitude, closer to the moon’s south pole than any previous mission.

Landing is scheduled for around 2125 GMT (5:25 p.m. EDT) on Sept. 6, according to Sivan.

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