Mission Impossible? Chandrayaan-3 Landing Journey Revealed!

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Chandrayaan-3 Landing Date & Time

After successful completion of second deboosting of the lander module today (20^th August 2023), Chandrayaan-3 is now reached far more closer to the moon. The first deboosting took place on Friday, ISRO tweeted. The separation of Lander Module from the Propulsion Module took place one day prior to this first deboosting operation, on Thursday.

Chandrayaan-3 Mission:

The second and final deboosting operation has successfully reduced the LM orbit to 25 km x 134 km.

The module would undergo internal checks and await the sun-rise at the designated landing site.

The powered descent is expected to commence on August… pic.twitter.com/7ygrlW8GQ5

— ISRO (@isro) August 19, 2023

First deboosting operation reduced Lander’s orbit to 113 km x 157 km, whereas with second and final deboosting it further reduced to 25 km x 134 km. “Chandrayaan-3 is set to land on the moon on August 23, 2023, around 1804 Hrs. IST” ISRO tweeted. The health of the lander module, comprising the lander (Vikram) and the rover (Pragyan), is normal even after deboosting, the Indian space agency added.

Chandrayaan-3 Mission:

🇮🇳Chandrayaan-3 is set to land on the moon 🌖on August 23, 2023, around 18:04 Hrs. IST.

Thanks for the wishes and positivity!

Let’s continue experiencing the journey together
as the action unfolds LIVE at:
ISRO Website https://t.co/osrHMk7MZL
YouTube… pic.twitter.com/zyu1sdVpoE

— ISRO (@isro) August 20, 2023

How soft landing of Lander will be achieved?

Biggest challenge! Awaiting !!

The velocity at the start of the landing process is almost 1.68 km per second, but this speed is horizontal to the surface of the moon. To land on the moon, it has to be tilted by 90 degrees and become vertical, this is the most trickiest part of the landing.

Secondly, reducing the speed from 1.68 km /sec (i.e. almost 6000 kmph) to zero, where there no atmosphere is another challenge waiting for lander to land successfully. (We have already discussed difficulties in landing in South Polar Region of the Moon in our previous article: Chandrayaan-3 Vs Luna-25, Who will win the race?

As final deboosting has already been done, now its time for Vikram lander to reorient itself to 90 degrees for safe landing on Moon’s surface. At around 100 meter altitude, the lander will scan the complications, if everything found normal, it would gradually descend, controlling its speed using thrusters until touchdown.

Recently ISRO has released a short video of the Moon, captured by Chandrayaan-3’s Lander Position Detection Camera onboard spacecraft on 15 August 2023.

You can be part of this proud moment by watching live telecast of Chandrayaan-3 landing on the link below: ISRO Official Website 

Chandrayaan-3 Mission:

🌖 as captured by the
Lander Position Detection Camera (LPDC)
on August 15, 2023#Chandrayaan_3#Ch3 pic.twitter.com/nGgayU1QUS

— ISRO (@isro) August 18, 2023

What after soft landing?

As we have already discussed in our previous article, soft landing on the surface of the moon is most critical part of the mission and is one of the objective of the mission after failure of Chandrayaan-2. You can read detailed article on the Chandrayaan-3 on the link below: Chandrayaan-3: Complete info, Update, Landing, Images

After successful landing on the South Polar Region of the moon, ‘In-situ scientific experiments’ is another objective of the mission. ISRO has designed and boarded different payloads with Lander Module (LM) and Rover for these scientific experiments.

After successful detachment of lander and rover configuration from Propulsion Module (PM) at 100km lunar orbit,  the Propulsion module will study the spectral and polarimetric measurements of Earth from the lunar orbit using its payload namely Spectro-polarimetry of HAbitable Planet Earth (SHAPE).

Vikram Lander is equipped with payloads to measure the thermal conductivity and temperature, seismicity around the landing site, plasma density and its variations, a passive Laser Retroreflector Array from NASA is accommodated for lunar laser ranging studies. Details of these payloads are as follows:

Sr.No.	Payload	Significance
1	Chandra’s Surface Thermophysical Experiment (ChaSTE)	To measure the thermal conductivity and temperature.
2	Instrument for Lunar Seismic Activity (ILSA)	For measuring the seismicity around the landing site.
3	Langmuir Probe (LP)	For estimating the plasma density and its variations.

Pragyan Rover is equipped with payloads such as Alpha Particle X-ray Spectrometer (APXS) and Laser Induced Breakdown Spectroscope (LIBS) for deriving the elemental composition in the vicinity of landing site.

Changes incorporated in Chandrayaan-3 after failure of Chandrayaan-2

In our previous article we have discussed key differences between Chandrayaan-3 and Russia’s Luna-25. Here, to study improvement in design of Chandrayaan-3, we have to compare it with Chandrayaan-2. How we have improved our design learning from failures of Chandrayaan-2, lets discuss:

Launch vehicle

Launch vehicle used by Chandrayaan-3 is GSLV-Mk III-LVM3 M4, which is more advanced and powerful than Chandrayaan-2 GSLV-Mk III – M1.

Chandrayaan-2 spacecraft consisted of an orbiter, a lander called as Vikram and a rover called Pragyan. Unfortunately, Vikram lander was not successful in landing on the moon surface, but other aspects of the mission were successful. Chandrayaan-3 is also consisted of the Vikram lander & Pragyan Rover, but no orbiter this time.

Sensors

The sensors used in Chandrayaan-3 are more advance and precise, which will be helpful for soft landing this time. These sensors are capable of providing real time data to lander, so that lander can take decisions based on the situation.  ‘Laser Doppler Velocimeter’ newly added by ISRO for measuring velocity of lunar air while autonomous landing. The sensors are designed to detect any potential hazard at the time landing.

The Vikram lander is designed to land autonomously even after failure of all sensors & engines. This is achieved by adding redundancy.

Engines

Chandrayaan-3 provided with four throttleable engines as compared to five 800 Newton engines of Chandrayaan-2. Throttleable engines has advantage of variation of thrust. Though number of engines are reduced due to advance technology as compared to previous version, it gave extra space for fuel storage.

Solar Power Supply

The Solar array’s size has been increased this time to ensure consistent power supply while performing operations on the moon.

Lander Legs

The legs of Vikram lander are designed in such a way to withstand impact of landing.

To counter software glitch

Learning from previous failure, this time algorithms and software are advanced to avoid any software glitch.

Increased landing area

One of the mistake of Chandrayaan-2 landing was a small landing site – within a 500mx500m area. ISRO this time increased the landing area of Chandrayaan-3 spacecraft to 4km x 2.5 km to provide additional flexibility in landing.

You can see this animated video released by ISRO Official YouTube channel depicting complete landing process of Chandrayaan-2:

Crash Landing of Luna-25

It is very unfortunate that Luna-25 crash-landed on Moon’s surface, after reaching so close. This tells us that space exploration is journey of challenges and is full of complexities.

Still reasons for Luna-25 failure are unknown, in our next article we will discuss about the most probable reasons and how it happened.

Thank you very much for reading the article, have a nice day!!!