S V Krishna Chaitanya By

Express News Service

Come this April, Indian Space Research Organisation (ISRO) will be scripting a new chapter and join the elite league of moon landers with Chandrayaan-2 mission. The mission is entering the critical phase, with integration of the Orbiter, the Lander and Rover nearing completion.

The Chandrayaan-2, which is a totally indigenous mission costing about Rs 800 crore, would orbit round the moon and perform the objective of remote sensing the natural satellite. The payloads will collect scientific information on topography, mineralogy, elemental abundance, lunar exosphere and signatures of hydroxyl and water-ice.

In the run-up to the most challenging space exploration programme undertaken ever by India, ISRO chairman K Sivan told Express that integration of all the three components of the spacecraft is nearing completion at ISRO Satellite Centre in Bengaluru. “The next 45-60 days will be crucial as the composite pack, comprising Orbiter, Lander and Rover will go through a series of rigorous tests in disassembled and assembled mode. The outcome of these test results will determine the launch date. If we succeed to achieve the desired results in the first attempt, then the launch would take place in April, but in case any technical problems are encountered, there would be a delay. Since this is the first such attempt being made, there is always an uncertainty,” he said.

The chairman said the launch window is fixed between April and October, within which the space agency hopes to accomplish the mission. “The launch date depends on multiple factors like the moon’s relative position with respect to Earth. After the lift-off from Sriharikota, it would take approximately two months to reach the designated moon’s orbit. Another important factor is that when the Lander makes the touchdown on the pre-determined site near south pole of lunar surface, there should be sunlight. In a month, moon sees sunlight for only 14 days,” Sivan said.

Decoding the mission

Explaining how the mission proceeds, Sivan said once the GSLV-F10 puts the spacecraft in the 170 km x 20,000 km elliptical orbit, the orbiter will be maneuvered towards the 100-km lunar orbit by firing thrusters and then the Lander housing the Rover will separate from the Orbiter. After a controlled descent, the Lander will soft land on the lunar surface at a specified site and deploy the six-wheeled robotic Rover which will move around the landing site in semi-autonomous mode as decided by ground commands. The instruments on the rover will observe lunar surface and send back data, which will be useful for analysis of its soil.

Scientists and engineers in several centres of ISRO are working tirelessly and leaving no stone unturned to accomplish the mission.

Vikram Sarabhai Space Centre (VSSC) director S Somnath, who till recently was heading the ISRO Liquid Propulsion Systems Centre (LPSC), said VSSC was playing a key role supplying all the composite and structural items. “Solar panels, antenna dishes, sensors, support in software, machine design reviews and special materials are supplied by VSSC. The on-board cameras like hazard avoidance and navigation cameras are supplied by Space Application Centre (SAC) in Ahmedabad and the propulsion systems are delivered by LPSC and the entire assembly and integration is done at ISAC Bengaluru. So, it’s a collective effort and will be a path-breaking launch, which will serve the scientific community across the world,” he said.

He said the initial lifespan of the mission will be for 14 days. “The rover will be carrying out its functions using solar power. So, we look to achieve our mission objectives in these first 14 days and the rover will go into passive mode during night phase which is about 15 days. We hope the solar panels in the rover will get recharged once the sunlight is back, but we are not sure about it since this is our first attempt to land on lunar surface. We are hopeful and conducting relevant tests to extend the life of the mission.”

Challenging but achievable

The most complex part of the entire mission is soft landing on the lunar surface of the moon. Only USA, Russia and China have been able to soft-land spacecraft on the lunar surface. ISRO Propulsion Centre (IPRC) at Mahendragiri in Tamil Nadu will be the cynosure of all eyes for next few weeks.

IPRC director S Pandian told Express that soft landing tests will be underway at Mahendragiri in the next two weeks. “There was slight delay in realisation of engines and software associated validation. Now, everything is almost ready and the tests will commence. We are striving for an April launch. If all the parameters are met, the tests will be completed by the end of March.”

A 100-metre tall crane has been specially built for the purpose of conducting tests. “We have to ensure that the spacecraft lands smoothly without crashing onto moon’s surface. The craft, weighing about half-a-tonne, will be lowered from 100 metres high and ignited in lower gravity conditions like that of moon. It has to move vertical and horizontal, maneuvering its way to find a suitable place to land. If there is a rock or some obstacle, the craft on its own should detect and find a ideal location to land. These tests will be conducted in Mahendragiri,” he said.

It has been 10 years ever since the Union Cabinet, chaired by the then Prime Minister Manmohan Singh, approved Chandrayaan-2 mission (September 18, 2008). Initially, it was decided that Russian Federal Space Agency (Roscosmos) and ISRO will together work on the project. An agreement was signed according to which ISRO would build the Orbiter, while Roscosmos was to provide the Lander/Rover. The entire mission fell apart after Roscosmos withdrew in the wake of failure of the Fobos-Grunt mission to Mars, the reason being that technical aspects connected with the mission were also used in the lunar projects, which need to be reviewed.

In this backdrop, India had decided to develop the lunar mission independently. When asked about this, Sivan said there was a plan to launch two rovers, one developed by Russia and the other by ISRO. “Anyway, it’s all history and holds no relevance today. It gave Indian scientists an opportunity to build an indigenous mission and we are very close to it.”

Chandrayaan-2 will carry 13 scientific payload instruments and will study the Earth’s natural satellite in a totally different perspective. This will pave the way for fascinating possibilities of future habitation of the moon. Already, Chandrayaan-1 mission has made history detecting water on a moon crater. It has completed 3,000 orbits acquiring 70,000 images of the lunar surface, which ISRO believes is quite a record compared to the lunar flights of other nations.

Manned landings

Totally, 12 men have landed on the Moon. This was accomplished with two US pilot-astronauts flying a Lunar Module on each of six NASA missions across a 41-month period starting on July 20, 1969, with Neil Armstrong and Buzz Aldrin on Apollo 11, and ending on December 14, 1972 with Gene Cernan and Jack Schmitt on Apollo 17. Cernan was the last to step off the lunar surface.

Important payloads on board Chandrayaan-2 spacecraft

Large Area Soft X-ray Spectrometer (CLASS) from ISRO Satellite Centre (ISAC), Bengaluru and Solar X-ray Monitor (XSM) from Physical Research Laboratory (PRL), Ahmedabad for mapping the major elements present on the lunar surface

L and S band Synthetic Aperture Radar (SAR) from Space Applications Centre (SAC), Ahmedabad, for probing the first few tens of metres of the lunar surface for the presence of different constituents including water-ice. SAR is expected to provide further evidence confirming the presence of water ice below the shadowed regions of the moon

Imaging IR Spectrometer (IIRS) from SAC, Ahmedabad, for mapping of lunar surface over a wide wavelength range for the study of minerals, water molecules and hydroxyl present

Neutral Mass Spectrometer from Space Physics Laboratory (SPL), Thiruvananthapuram, to carry out a detailed study of the lunar exosphere

Terrain Mapping Camera-2 (TMC-2) from SAC, Ahmedabad, for preparing a three-dimensional map essential for studying the lunar mineralogy and geology

Laser Induced Breakdown Spectroscope (LIBS) from Laboratory for Electro Optic Systems (LEOS), Bengaluru

Alpha Particle Induced X -ray Spectroscope (APIXS) from PRL, Ahmedabad

Moon Profile

3,475 km Diameter

384,400 km Orbit Distance

27.3 days Orbit Period (-)233 to 123°C Surface Temperature

Unmanned landings