India Launches Lunar Probe Chandrayaan-2

India Launches Lunar Probe Chandrayaan-2

India launched a three-part probe to the Moon today.  Chandrayaan-2 will be captured into lunar orbit four weeks from now and on September 6 EDT, a lander/rover will separate from the orbiter and descend to the Moon’s South Pole.  Indian Space Research Organization (ISRO) Chairman K. Sivan referred to it as “15 minutes of terror” that, if all goes well, will make India the fourth country to successfully land on the Moon.

After a launch scrub last week, India’s GSLV MkIII/M1 rocket lifted off at 5:13 am EDT (2:43 pm Indian Standard Time).  During a post-launch speech, Sivan praised the launch team for “bouncing back with flying colors” after “a serious technical snag.”  He did not explain what the snag entailed.

India’s GSLV MkIII/M1 rocket lifts off from Sriharikota, India on July 22, 2019 with Chandrayaan-2 lunar probe. Screengrab.

Sivan adapted NASA’s description of the “7 minutes of terror” for the 2012 landing of the Curiosity rover on Mars to describe Chandrayaan 2’s landing sequence.  Landing on the Moon is quite different since it does not have an atmosphere and Chandrayaan-2 does not need anything like NASA’s Skycrane system to reach the surface, but that does not mean it is easy.  As Israel’s SpaceIL discovered in April with Beresheet, everything must go just right to make a survivable soft landing instead of crashing.

India’s first lunar spacecraft, Chandrayaan-1, was an orbiter.  It successfully entered lunar orbit in November 2008 and was intended to operate for 2 years, but ISRO lost contact with it after 10 months.  Nonetheless, it obtained valuable data with its 11 instruments from India, the United States, the United Kingdom, Germany, Sweden, and Bulgaria.  The U.S. Moon Mineralogy Mapper (M3) in particular is credited with confirming the existence of water on the Moon.

The 2,379 kilogram Chandrayaan-2 orbiter carries eight instruments including two cameras, a synthetic aperture radar, and an imaging infrared spectrometer.  The 1,471 kilogram lander, named Vikram after the founder of India’s space program Vikram Sarabhai, has three, and the 27 kilogram 6-wheeled rover, Pragyan (wisdom), has two.

Chandrayaan-2 is now in a highly elliptical geostationary transfer orbit around Earth.  Sivan said the rocket’s performance was better than expected and the apogee is 6,000 kilometers higher than planned.  Between now and August 20, onboard systems will raise the apogee (highest point away from Earth) until the spacecraft is captured into lunar orbit.  Then a series of engine burns will nudge it into the correct lunar polar orbit to enable the lander/rover to reach the Moon’s South Pole.  Landing is at 2:50 am September 7 Indian Standard Time (September 6, 5:20 pm EDT).

Illustration of Chandrayaan-2’s path to the Moon. Credit: ISRO

The United States, Russia, and China are the only countries so far to have successfully soft-landed spacecraft on the Moon.  All three landed robotic spacecraft, but the United States is the only country to put astronauts on the lunar surface.  The 50th anniversary of the first human lunar landing, Apollo 11, is being celebrated right now.

NASA’s Lunar Reconnaissance Orbiter (LRO) entered lunar orbit in 2009 and continues to send back high resolution images of the surface.  NASA is getting ready to land instruments on the Moon beginning next year through its Commercial Lunar Payload Services (CLPS) public-private partnership in preparation for returning astronauts to the lunar surface in 2024.

At the moment, China’s Chang’e-4 lander and Yutu rover are the only operational spacecraft on the lunar surface.  They are on the farside, which always faces away from Earth, also in the South Pole region, an area of great scientific interest.  They are the first spacecraft on that side of the Moon because a relay satellite (Quequio) is needed to communicate with ground controllers on Earth.   Chandrayaan-2 will be landing on the near side, which has a direct line-of-sight back to Earth.



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