The Indian Space Research Organisation (ISRO) is gearing up for Chandrayaan-2, the country’s first moon lander and rover mission. Chandrayaan-2 is only a month away. The mission will be carried out by the Geosynchronous Satellite Launch Vehicle Mark III (GSLV MK III) rocket, which is designed to launch satellites into geostationary orbit. The ISRO’s takeoff has been scheduled for July 15 while the launch window has been kept open between July 9 and July 16.
Chandrayaan-2 is India’s second lunar mission after Chandrayaan-1 and it is divided into three modules namely Orbiter, Lander (Vikram) & Rover (Pragyan). The Orbiter and Lander modules accommodated inside the GSLV MK-III launch vehicle, interfaced mechanically and stacked together as an integrated module. The Rover is housed inside the Lander.
After launching into earthbound orbit by GSLV MK-III, the integrated module of the Orbiter and Lander will reach Moon orbit using Orbiter propulsion module. Afterwards, the Lander will part ways with the Orbiter and soft land at the proposed site close to the lunar South Pole, which is scheduled for September 6. Further, the Rover will perform certain scientific experiments on the lunar surface.
Meanwhile, the ISRO has outlined the challenges of a Moon landing, as follows:
The distance to the Moon is approximately 3.844 lakh km. Ensuring trajectory accuracy while navigating such a large distance poses many challenges as the trajectory is influenced by the non-uniform gravity of the Earth and Moon, the gravitational pull of other astronomical bodies, solar radiation pressure and the Moon’s true orbital motion.
Owing to the large distance from Earth and limited onboard power, radio signals used for communication are weak with heavy background noise, which needs to be picked by large antennas.
Trans Lunar Injection and Lunar Capture
Chandrayaan 2 will perform a series of TLI burns for raising its apogee successively to reach the vicinity of the Moon’s orbit. As the Moon’s location is continually changing due to orbital motion, the intersection of Chandrayaan 2 and the Moon’s path has to be predicted sufficiently in advance with a high level of accuracy.
Orbiting around the Moon
Lunar gravity is ‘lumpy’ due to uneven mass distribution under its surface. This influences the orbit of the spacecraft. Precise knowledge of the thermal environment at orbital altitude is essential for keeping onboard electronics safe.
Soft landing on the Moon
Variation in local gravity has to be factored into the lunar descent trajectory. The onboard NGC and Propulsion System have to work in unison, autonomously for a successful landing. Then landing site landscape features should not result in a communication shadow area.
Firing of onboard engines close to the lunar surface results in backward flow of hot gases along with dust. Lunar dust is minuscule and is hard barbed and jagged. Its negative charge makes it stick to most surfaces causing a disruption in deployment mechanisms, solar panel performance and NGC sensor performance.
Extreme temperatures and vacuum
A lunar day or night lasts 14 Earth days. This results in extreme surface variations. The ambient pressure of the lunar surface is a hard vacuum. This makes the lunar surface an extremely hostile environment for lander and rover operations.