Before India achieves the feat of soft landing on the Moon, let’s look at what the first mission attained and how the second will be different
GSLV MarkIII-M1 vehicle coming out of the vehicle assembly building in ISRO. Photo: ISRO When Vikram, Chandrayaan-2’s lander, touches down on the lunar surface on September 6-7, 2019, India will join an elite group of countries to have achieved this feat. The United States, Russia and China were the first three to make a soft landing on the Moon.
A soft landing does not destroy the object on impact while a hard landing does. Soft landing ensures that the object is able to carry out further experimentation on the target planet or satellite, mostly with the help of a rover.
This will not be the first time that any object launched by India will leave its imprint on the surface of the Earth’s only natural satellite. The country achieved hard landing on the lunar surface 11 years ago.
The first attempt
On November 14, 2008 the Moon Impact Probe (MIP) detached from the orbiting Chandrayaan-1 spacecraft and hard landed on a designated spot, close to the Moon’s South Pole.
Chandrayaan-1 was India’s first mission to the Moon and lasted for 312 days before the Indian Space Research Organisation (ISRO) lost contact with it. The National Aeronautical and Space Administration (NASA) found it in 2017 still orbiting the Moon.
During the descent, while stabilising its spin, the MIP conducted a series of experiments in the lunar atmosphere. One of these experiments led to the mission’s most important discovery — it detected traces of water vapour.
“This amazing discovery was confirmed by the JPL-Brown University payload Moon Mineralogy Mapper (M3). M3 detected spectral lines near the wavelengths in the range of 2.8-3 micrometres, a property attributed to water and Hydroxyl ions. It is believed that formation of Hydroxyl ions and water molecules on the lunar surface is an ongoing process,” according to ISRO.
The MIP later hard landed on the surface of the Moon and was destroyed on impact. Its impact released underground debris which was later analysed by instruments on Chandrayaan 1 for further evidence of existence of water molecules.
The presence of water on the Moon was later confirmed by missions conducted by NASA and many other space agencies.
How different?
Apart from the MIP, all the other experiments part of the Chandrayaan-1 mission were onboard the orbiting spacecraft. It carried instruments for chemical, mineralogical and photo-geologic mapping of the lunar atmosphere and surface but all of it was done from afar, except the MIP.
This is where Chandrayaan 2 fundamentally differs from Chandrayaan-1. Chandrayaan-2 aims to experience the Moon from much closer quarters and conduct experiments that will yield more significant results using Vikram and Pragyan, the lunar rover that will be released by the lander.
Vikram is going to land close to the south pole of the Moon, a region where the MIP had crash landed. This will be the first soft landing attempt on this part of the Moon ever. Then it will release Pragyan, which is a six-wheeled vehicle that weighs around 27 kg. It runs on around 50 W of power and can travel 500 m at a speed of 1cm/sec.
It will conduct experiments related to topography, mineralogy and chemistry of the lunar surface. Primarily, it will survey the surface and sub-surface for the presence of water and hydroxyl ions.
To do this, the rover will carry a lot of state-of-the-art instrumentation like cameras, an alpha proton X-ray spectrometer and a laser-induced ablation spectroscopy experiment.
The rover will be in constant contact with the lander, which will be in constant contact with the orbiter and also with the Indian Deep Space Network (IDSN).
The IDSN is a network of antennas and communication facilities established by ISRO to support interplanetary spacecraft missions. Such complicated communication will be made possible by NASA-developed laser retroreflector arrays which are part of Chandrayaan-2.
The transportation of the lander and the rover has been made possible by the latest Geosynchronous Satellite Launch Vehicle Mk III (GSLV Mk III) rocket which can carry a much greater payload than the Polar Satellite Launch Vehicle-C11, used for Chandrayaan-1.
The entire Chandrayaan mission weighs in at a whopping 2,379 kg and its solar arrays are capable of producing power of up to 1000 W. Vikram itself weighs around 1,471 kg and can generate 650 W of power.
GSLV Mk III is currently capable of placing a 4,000 kg satellite in the Geosynchronous Transfer Orbit, which is at a height of about 42,000 kilometres above the Earth’s surface.
If Chandrayaan 2 is successfully placed in the lunar orbit and its components fulfill the objectives then it would not only help us understand the Moon better but also create background knowledge to transform it into a staging area. From here, future human missions to explore far-off planetary bodies can be launched.
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