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Chandrayaan-2 in Moon’s orbit

In a 29-minute operation that started at 9.02am Tuesday, the Indian Space Research Organisation (Isro) successfully guided Chandrayaan-2 into an elliptical orbit around Moon

Isro chairman K Sivan, said: “We’ve crossed another milestone. A precise LOI put chandrayaan-2 in the desired orbit perfectly”

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BENGALURU: In a 29-minute operation that started at 9.02am Tuesday, the Indian Space Research Organisation (Isro) successfully guided Chandrayaan-2 into an elliptical orbit around Moon. After a few more manoeuvres, Vikram, the lander, is expected to touch down on the lunar surface at 1.55am on September 7.

Right now, Chandrayaan-2 is an integrated spacecraft comprising the orbiter on which Vikram, the lander, is attached. Vikram, in turn, has inside it Pragyan, the rover, which is expected to roll out about four hours after the lunar landing.

Speaking after the ‘lunar orbit insertion’ (LOI) that put Chandrayaan-2 in a 114km x 18,072km orbit around Moon, Isro chairman K Sivan, said: “We’ve crossed another milestone. A precise LOI put chandrayaan-2 in the desired orbit perfectly.”

He said in order to achieve the soft-landing on September 7, the spacecraft should achieve an inclination of 90°; as of Tuesday, Chandrayaan-2 has an inclination of 88°. The space agency will now perform four more manoeuvres – on August 21, 28, 30 and September 1 – to take the spacecraft to lower orbits.

After the last set of manoeuvres on September 1, the composite body is likely to be in a 114km x 128km orbit. On September 2, Vikram will be separated from the composite body and preparations for Moon landing will begin. While the oribter will spend the rest of its life in the orbit Isro manages to achieve after the September 1 manoeuvres, Vikram will be further lowered to a height of 30km to 35km from the lunar surface, in the four days between its separation and landing.

Sivan, stating that Isro has learnt from all the mistakes made by other countries, including Israel, said that the availability of new technology and a lot of simulation has helped Isro.

Moon Landing

On September 3, a day after lander separation, a short three-second health check will be performed on Vikram. After that, on September 4, the de-orbit manoeuvre will be done for 6.5 seconds.

“The lander will be in a 35kmX97km orbit when various parameters will be checked. At 1.40am on September 7, the powered descent will start, and at about 1.55am, the lander will make the touchdown. Four hours after this, the rover will reach the lunar surface,” Sivan said.

Two hours after Vikram’s landing, the ramp will roll out completely and touch the lunar surface. “And, 3 hours and 10 minutes after landing, the solar panels of the rover will be turned on and five minutes later, Pragyan will start moving, and it will make a touchdown four hours after Vikram’s landing,” Sivan added.

Although only 37% of all attempts to land on Moon have been successful, he said Isro was confident of achieving it in the first try as it has learnt from others’ failures. “Specifically from the Israeli mission, we learnt that there needs to be more and more autonomy of the lander. Sensor characterisation was key. We’ve done everything we can humanly do and are confident of a successful landing,” Sivan said.

While Isro has already spoken about Moon dust and other challenges earlier, Sivan pointed one specific challenge on Tuesday. “If we land in a slope that is more than 12°, or if even one of the lander legs is on a boulder, we will topple. We’ve chosen the site very carefully, and have tested everything through simulations very thoroughly,” Sivan said.

Further, India, which has used data from previous NASA missions, to prepare for Chandrayaan-2, will be returning the favour by sharing data with the US agency, which has announced that it will send humans again to Moon, Sivan said on Tuesday.

Chandrayaan-2 is carrying 14 payloads—including one passive instrument from Nasa that will measure the distance between Moon and Earth—with special focus of the orbiter on mapping craters in the polar region, besides checking for water again.

While that’s for the orbiter, the rover payloads will check on mineralogical compositions on the Moon and determine the composition (what elements it contains) of lunar rocks and soil and instruments on the lander will focus on measuring thermal properties and seismicity among other things.

According to Sivan, Isro will be sharing scientific data obtained from payloads other than that of NASA’s too. “Moon’s South Pole is a unique region where no country has landed payloads before, and the US, which has already announced a programme to land humans in this region will be getting data from us. While I can say we will be sharing information, I cannot say what exactly this will be at this moment,” Sivan said.

The US had applauded India’s accomplishments, determination, and dedication to space exploration and innovation soon after the launch of Chandrayaan. And, Kathleen Hosie, spokesperson, US Consulate General in India told TOI by email: “We wish India great success with the Chandrayaan-2 mission, which would be India’s first lunar landing and make India the first nation to land on the lunar South Pole, helping to inform the United States’ Artemis Mission to send the first American woman and the next American man to the Moon by 2024.”

“…The United States looks forward to expanding cooperation with India in space as part of our commitment to strengthening our strategic partnership,” she added.

Reiterating the importance Chandrayaan-2, Sivan, on Tuesday said that not only will the mission put India in an elite club of nations to land a probe on Moon, but that going to South Pole gives it an added advantage.

“We are going where nobody has gone, and that will provide a big advantage for future projects,” Sivan said. Answering a specific question on China’s Chang’e 4 landing on Moon earlier this year, Sivan said that while the Chinese have managed to go the far side, they did not land near the polar region.

“They have gone to the far side, we will be on the other side. But China landed near the equator which is quite easy to achieve compared to landing near the South Pole, which we will be doing,” he said.

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