After a long 11 years, India made the giant leap of launching its second Moon mission, Chandrayaan-2, on the 22nd of July, that will boldly go where no country has ever gone before — the south polar region of the Moon. The lunar mission, which had only a few minutes window to set on its 384,400 km journey to the Moon, successfully took off at 2:43 pm IST from the second launch pad at Satish Dhawan Space Centre in Sriharikota, which is in Nellore district of Andhra Pradesh.
This is India’s second lunar exploration mission after Chandrayaan-1, which was launched in 2008. Developed by the Indian Space Research Organization (ISRO), Chandrayaan-2 was launched by the indigenously developed Geosynchronous Satellite Launch Vehicle Mark III (GSLV Mk III).
Chandrayaan-2 lifts off atop a GSLV Mk III rocket
Getting a bit more technical, the primary objectives of Chandrayaan-2 are to demonstrate the ability to soft-land on the lunar surface and operate a robotic rover on the surface. Scientific goals include studies of lunar topography, mineralogy, elemental abundance, the lunar exosphere, and signatures of hydroxyl and water ice. The orbiter will map the lunar surface and help to prepare 3D maps of it. The onboard radar will also map the surface while studying the water ice in the south polar region and thickness of the lunar regolith on the surface. Chandrayaan-2 will also inform the location and abundance of lunar water for exploitation by the future lunar base proposed by the Artemis program.
Weighing around 3850 Kg, Chandrayaan-2 has three modules: The orbiter, the lander named Vikram, Rover named Pragyan (which is a small, 20-kilogram, six-wheeled rover). The orbiter will circle the moon and provide information about its surface. This orbiter has a variety of instruments in it, such as Terrain Mapping Camera 2, Collimated Large Array Soft X-ray Spectrometer, Solar X-ray Monitor, etc. Once in lunar orbit, Chandrayaan-2 will deploy Vikram, which will make a precise, safe and soft landing on the moon at 1:55 IST on 7th September, 2019. Vikram is also equipped with the following instruments; Instrument for Lunar Seismic Activity, Chandra’s Surface Thermophysical Experiment, and the RAMBHA-Langmuir Probe, which perform various functions such as look for moonquakes, examine the surface’s thermal properties, look at plasma density on the surface, respectively. Once Vikram lands, the rover Pragyan will deploy to perform mobility and scientific experiments on the lunar surface. The rover will carry two science instruments to look at the composition of the surface: The Laser-Induced Breakdown Spectroscope (LIBS) and the Alpha Particle X-Ray Spectrometer (APXS). The rover will move semi-autonomously, examining the lunar regolith’s composition. The payload in Vikram and Pragyan will then be turned on and thus help in collecting information on lunar topography, mineralogy, elemental abundance, lunar exosphere and signatures of hydroxyl ions and water-ice.
The mission life of the orbiter is one year and that of Vikram and Pragyan is one lunar day which approximately corresponds to 14 earth days. While NASA is not directly participating in this mission, the measurements taken by Chandrayaan-2 could be a help for future lunar missions.
Hoisting of Vikram lander during Chandrayaan2 spacecraft integration at launch centre
The launch of Chandrayaan-2 was originally scheduled for 15 July 2019 but was called off due to a technical snag noticed around 56 minutes before launch. ISRO engineers noticed a sudden drop in pressure of a helium gas bottle that pressurised the fuel and oxidiser for use in the GSLV-Mk III cryogenic engine, suggesting a leak. The problem, however, was fixed and just a week later the mighty Indian rocket powered Chandrayaan-2 into space. In fact, owing to the cryogenic upper stage of the rocket burning to depletion, the rocket was put into an initial orbit of 169 km perigee (closest point to Earth) and 45,475 km apogee (farthest point from Earth), 6000 km higher than intended. This meant that about 40kgs more fuel was available for the rest of the mission than expected.
Chandrayaan-2 orbit profile
This was followed by a series of orbit raising manoeuvres, the 5th and final one of which, carried out on 14th August and lasting over 20 minutes, put the Chandrayaan-2 spacecraft stack into a successful Lunar Transfer Trajectory, awaiting an encounter with the Moon. After being intercepted by the Moon’s gravity, a Lunar Orbit Insertion (LOI) manoeuvre lasting just under 29 minutes was performed on 20th August, enabling the spacecraft stack to be captured into a high eccentricity elliptical orbit around the moon with a periselene (closest point to the Moon) of 114 km and an aposelene (farthest point from the Moon) of 18,072 km . This was followed by a series of 4 orbit lowering manoeuvres until the orbit was more or less circular, having a periselene and aposelene of 127 km and 119 km respectively. It was at this stage when the Vikram lander separated from the orbiter on 2nd September, followed by lander health checks and two orbit lowering manoeuvres performed in subsequent days on the Vikram lander until an elliptical orbit of 35 km x 101 km was attained by 4th September.
Images of Lunar Surface captured by Terrain Mapping Camera -2 (TMC-2) of Chandrayaan 2
It is now that we have reached the final, most tense stage of the mission for ISRO, as well as for every Indian and space enthusiast all over the world: a 15 minute powered descent phase that will drop the lander out of its current orbit and hurtle it towards the lunar surface, where it will attempt to make a soft landing on its primary landing site, about 350 km north of the South Pole–Aitken basin, and make history by making India the first nation to ever attempt a landing near the lunar south pole.
“Special moments that will be etched in the annals of our glorious history! The launch of #Chandrayaan2 illustrates the prowess of our scientists and the determination of 130 crore Indians to scale new frontiers of science. Every Indian is immensely proud today!” – tweeted Indian Prime Minister, Narendra Modi. Chandrayaan-2 will attempt to answer questions on unexpected lunar surface and open up possibilities of using the Moon as a platform for the exploration of the solar system and beyond. With this, India reiterates its excellence in space technology and its commitment in humanity.
Devan Rajendran & Kiran Nandanan
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