The eagerly anticipated Chandrayaan-3 mission to the Moon was launched by the Indian Space Research Organisation (ISRO) on July 14. On board the Launch Vehicle Mark-III (LVM3) at the Satish Dhawan Space Centre in Sriharikota, the spacecraft launched flawlessly.
India’s second attempt to set foot on the moon’s surface was made with Chandrayaan-3, the third mission in the Chandrayaan series. The mission, which is expected to have cost Rs 615 crore, aspires to make India a moon fairing country and join the privileged club.
By placing the Chandrayaan-3 mission in a precise orbit, the LVM3 was able to complete the mission successfully, demonstrating its capability once more. Following the launch from Sriharikota, the spacecraft detached from LVM3 after more than 900 seconds. All three stages operated as expected.
Now that the spacecraft is on its way to the Moon, ISRO will carry out the orbit-raising manoeuvres in the ensuing days. On August 5, Chandrayaan-3 is slated to enter lunar orbit, and by the end of the month, a soft-landing attempt is anticipated.
Till date, only three other nations have successfully landed a spacecraft on the Moon’s surface. These include the US, Russia (erstwhile USSR), and China. The goal of India is to enter the record books as the fourth nation.
With Chandrayaan-3, India has sent a lander, rover, and propulsion module to the Moon. The lander-rover configuration will attempt the perilous touchdown while the Propulsion Module will put the spacecraft into lunar orbit. The lander will make an attempt to land in the Moon’s Southern Polar Region after being separated.
The precise landing site has not yet been disclosed. Details suggest that it may be closer to the location of the 2019 Chandrayaan-2 crash landing. To connect with the ground stations on Earth, the Chandrayaan-2 orbiter, which is already in lunar orbit, will be used.
Here’s what transpired on Vikram’s landing in 2019
On September 6, 2019 — the day of landing, ISRO lost touch with Vikram when it was only 335 metres (0.335 km) from the Moon’s surface. The malfunction was thought to have happened during the ‘Fine braking phase’ of Vikram’s final flight (an altitude of 5 km to 400 m), which began when the lander was 5 km from the lunar surface, according to the first data from the space agency’s Telemetry Tracking and Command Centre.
The centre’s massive screens revealed that the lander’s green line started to veer off course when it was just over 2 km in altitude, continued to veer off course and finally stopped at a place that was obviously below 1 km in height and somewhere close or below 500m.
The module was still travelling at a speed of 48.1 m/sec (about 173 km/hr) horizontally and 59 metres per second (212 km/hr) vertically at that time. The distance between the lander and its intended Moon landing location at that time was 1.09 km.
Planned to conduct a gentle vertical fall at ‘walking pace’, Vikram was scheduled to lose the majority of its momentum by the time it was 400 metres from the lunar surface and should have been hovering above the designated landing place. But because of its great speed, it struck the Moon’s surface.
ISRO chief S Somanath, in a press conference detailed on Chandrayaan-3 and said, “…In a nutshell, if you tell what was the problem in Chandrayaan-2, it is simple to say that the ability to handle parameter variation or dispersion was very limited. So, what we did this time is simply expand it further. Look at what are the things that can go wrong. So, instead of success-based design in Chandrayaan-2, we are doing a failure-based design in Chandrayaan-3. What all can fail, and how to protect it — this is the approach that we have taken.”
Important distinctions between Chandrayaan 2 and 3
There are some changes between the two missions even though the mission design remains the same for both. What is carried aboard the GSLV-MkIII rocket is where the two missions diverge most. Chandrayaan-3 is launched with merely a lander and a rover as opposed to Chandrayaan-2’s combination of the Vikram lander, Pragyan rover, and an orbiter.
According to reports, Chandrayaan-3 would employ the Orbiter that was launched with Chandrayaan-2 and is currently circling the Moon to fulfil its communication and terrain imaging needs.
‘Lander hazard detection and avoidance cameras’ are a feature of the Chandrayaan-3 lander mission that allow for communication with the orbiter and mission control throughout the Moon landing procedure. Chandrayaan-3 features two of these cameras, compared to Chandrayaan-2’s single one.
The Vikram lander also has stronger legs than its predecessor. From 3 m/s to 2 m/s, the landing velocity has been increased. Accordingly, the lander won’t crash or shatter (its legs) even at 3 m/s, said ISRO director Somanath.
“Vikram has also undergone the installation of more fuel, which will increase its ability to travel or handle dispersion. Additionally, a new sensor has been included. The laser doppler velocity metre, a new sensor that will examine the lunar surface, has been installed. Additionally, we will be able to obtain the components of three velocity vectors using laser source sounding. Redundancy in measurement will be achieved by adding this to the currently available instruments,” he added.
The ISRO director had already discussed the specifics of what went wrong with the Vikram lander of Chandrayaan-2, which hurtled towards the designated landing location on the lunar surface that measured 500 m by 500 m while the engines intended to slow it down developed more thrust than anticipated. This time, the landing space has increased from 500m x 500m to four kilometres by 2.5 km.
The Vikram lander now has extra solar panels on different surfaces, according to the ISRO director, to ensure that it can generate power regardless of how it lands. While cranes were used to test the landing procedures, the spacecraft was also flown over various terrains to test its capacity to tolerate vibrations.
An astounding total of nine in-situ instruments, all of which are still in use in the Moon’s orbit, were aboard the Chandrayaan-2 Orbiter when it was launched. In contrast, the Chandrayaan-3 mission’s propulsion module only contains the Spectro-Polarimetry of Habitable Planetary Earth (SHAPE) instrument, which will be used to analyse the spectral and polarimetric measurements of Earth from the lunar orbit.
The Laser Retroreflector Array (LRA), a passive experiment to comprehend the dynamics of the Moon system, is being sent with the lander as an adjunct to the Chandrayaan-3 mission.
*The writer is Associate Editor, Science India.
