Chandrayaan-3, ISRO's third lunar exploration mission, is all set to create history by landing on the uncharted south pole of the moon. The LM comprising the lander (Vikram) and the rover (Pragyan), is scheduled to make a touchdown near the south polar region of the Moon at 6:04 pm today.
Fourteen-day Moon mission
The lander and rover have a mission life of one lunar day, which is about 14 Earth days. Temperatures dip to as much as -1800C during lunar nights. However, there is an outside possibility of the lander and the rover coming back to life for another lunar day, claim scientists.
The powered braking of Vikram lander will begin at 5.45 pm with the retro firing of four thruster engines to reduce speed. Scientists call it 17 minutes of terror as the whole process will be automated. Complete instructions will be fed to Vikram by 3.45 pm.
The challenge is to reduce Vikram’s horizontal velocity from 1.68 km/sec at a height of 30 km to almost zero for a soft landing. At an altitude of 6.8 km, two engines will shut down. The other two will give reverse thrust to further slow down Vikram as it descends.
Landing is scheduled at 6.04 pm. If all goes well, after Vikram settles on the lunar surface, it will release a rover on board to take pictures of the surface and conduct experiments with two onboard instruments.
At an altitude of 150-100 metres, Vikram’s sensors will scan the surface to check for obstacles before final descent. If the sensors spot a hill or a boulder at the landing spot it can move laterally up to 150 m to a better landing spot.
Quick-fire experiments
“After powered descent onto the landing site, there will be deployment of ramp and rover coming out. After this, all the experiments will take place one after the other — all of which have to be completed in just one day on the Moon, which is 14 (Earth) days,” ISRO chief Somnath said.
"This whole process of turning from horizontal to vertical is a very interesting calculation mathematically. We have done a lot of simulations. It is here where we had the problem last time (Chandrayaan-2)," the ISRO chief added.
The Chandrayaan-3 is a follow-on mission to Chandrayaan-2 and its objectives are to demonstrate safe and soft-landing on the lunar surface, roving on the Moon, and to conduct in-situ scientific experiments.
Following are the major specifications of the lander and rover.
The lander has a mission life of one Lunar day, which is equivalent to 14 Earth days. It has a mass of 1749.86 kg including Rover.
There are four scientific payloads in it — Radio Anatomy of Moon Bound Hypersensitive Ionosphere and Atmosphere (RAMBHA) will measure the near-surface plasma (ions and electrons) density and its changes with time.
Chandra's Surface Thermophysical Experiment (ChaSTE) will carry out the measurements of thermal properties of the lunar surface near the polar region.
Instrument for Lunar Seismic Activity (ILSA) will measure seismicity around the landing site and delineate the structure of the lunar crust and mantle.
Laser Retroreflector Array (LRA) from NASA is a passive experiment to understand the dynamics of the Moon system. LRA will have seven sensors including Lander Hazard Detection & Avoidance Camera.
Lander has six mechanisms, which are Lander leg, Rover Ramp (Primary and Secondary), Rover, ILSA, Rambha & Chaste Payloads, Umbilical connector Protection Mechanism, and X- Band Antenna Rover: Laser Induced Breakdown Spectroscope (LIBS) Propulsion Module for qualitative and quantitative elemental analysis.
LIBS will help derive the chemical composition and infer mineralogical composition to further our understanding of the lunar surface.
Alpha Particle X-ray Spectrometer (APXS) will determine the elemental composition such as magnesium, Aluminium, Silicon, Potassium, Calcium, Titanium and Iron) of lunar soil and rocks around the lunar landing site.
(With additional inputs from PTI)