Vikram lander breaks away: What next in Chandrayaan-3 mission?

India’s Moon mission is a step closer to achieving its goal of a soft landing on the lunar surface. The Vikram lander of the Chandrayaan-3 spacecraft has successfully split up from the propulsion module, Indian Space Research Organisation (ISRO) announced today (17 August). The lander module, comprising the Vikram lander and Pragyaan rover, is expected to touchdown on the Moon’s south pole on 23 August, while the propulsion module will continue with its journey in the same orbit. What is next for the Vikram lander? What are Chandrayaan-3’s objectives after landing on the Moon? Let’s take a closer look. What next for the lander module? With a successful separation, the lander module will now continue its lunar journey independently. A series of deboost manoeuvres have been planned for the lander. As per ISRO, the first deboosting manoeuvre will take on 18 August evening. “Thanks for the ride, mate!’ said the Lander Module (LM). LM is successfully separated from the Propulsion Module (PM). LM is set to descend to a slightly lower orbit upon a deboosting planned for tomorrow around 1600 Hrs, IST,” ISRO wrote on X, formerly Twitter.

Chandrayaan-3 Mission:

‘Thanks for the ride, mate! 👋’
said the Lander Module (LM).

LM is successfully separated from the Propulsion Module (PM)

LM is set to descend to a slightly lower orbit upon a deboosting planned for tomorrow around 1600 Hrs., IST.

Now, 🇮🇳 has3⃣ 🛰️🛰️🛰️… pic.twitter.com/rJKkPSr6Ct

— ISRO (@isro) August 17, 2023

Vikram lander’s first orbit-reduction manoeuvre will put it in the circular 100×100 km orbit; the second will position it further closer to the lunar surface in the 100×30 km orbit, farthest and closest point from the Moon respectively. It is from this orbit that the lander will attempt the soft landing on the south polar region of the Moon possibly on 23 August. How is Chandrayaan-3’s Vikram lander different? After Chandrayaan-2, this is India’s second attempt to create history by landing on the Moon’s south pole, a feat yet to be accomplished by any country. However, Russia’s lunar mission, Luna-25, is on its way to change this just like Chandrayaan-3 and it may do so before India’s lunar probe. Chandrayaan-2 had failed to soft-land on the lunar surface due to flaws in the algorithm aboard the navigation software, as per Indian Express. This time, ISRO has ensured that the Vikram lander will have a soft landing even if it encounters problems on its lunar journey. According to Times of India (TOI), Vikram has stronger legs so that it can withstand higher velocity on landing. “We have enhanced the landing velocity to 3m/second from 2m/second. That means even at 3m/sec, the lander will not crash or break (its legs),” ISRO chief S Somanath told the newspaper. The two-metre tall robotic moon lander has more fuel to tackle disruptions and has the “ability to come back”, the report added. A new lander sensor called the Laser Doppler Velocimetery (LDV) has been added to the craft. Somanath told TOI that Chandrayaan-3 has additional solar panels and more panel area to generate power. This will assist the Vikram lander in producing power in case it lands in a different position, where it is not facing the Sun. What about the propulsion module? The main purpose of the module was to accompany the lander and the rover to the 100 km lunar orbit. It will now proceed on its path in the current orbit for months or even years, noted ISRO. The propulsion module is equipped with a Spectro-polarimetry of Habitable Planet Earth (SHAPE) payload that will examine spectral and polarimetric measurements of Earth from the lunar orbit, according to India’s space agency. “The SHAPE payload onboard would perform spectroscopic study of the Earth’s atmosphere and measure the variations in polarisation from the clouds on Earth to accumulate signatures of exoplanets that would qualify for our habitability!” ISRO wrote on X.

Chandrayaan-3 Mission:

Meanwhile, the Propulsion Module continues its journey in the current orbit for months/years.

The SHAPE payload onboard it would
☑️ perform spectroscopic study of the Earth’s atmosphere and
☑️ measure the variations in polarization from the clouds on…

— ISRO (@isro) August 17, 2023

What happens after the landing? If everything goes as per ISRO’s plans, then the lander module should be able to successfully mark a soft landing on the lunar surface. As per The Hindu, this power descent – when the lander has to burn engines at correct times and altitudes, make precise scans of hills and craters on the lunar surface, and use the accurate amount of fuel – was described as “fifteen minutes of terror” by the then ISRO chief K Sivan in 2020. The lander will have to be steered in a vertical position for a safe landing on the Moon. Once the landing is complete, the payloads on the lander module will carry out in-situ scientific experiments. There are four payloads on the lander. The first, Radio Anatomy of Moon Bound Hypersensitive ionosphere and Atmosphere (RAMBHA), will measure “near-surface plasma (ions and electrons) density and its changes with time”, as per ISRO. Chandra’s Surface Thermo-physical Experiment (ChaSTE) will obtain an assessment of the thermal properties of the lunar surface near the polar region. [caption id=“attachment_13008952” align=“alignnone” width=“640”] Chandrayaan-3 is expected to reach Moon’s south pole on 23 August. AP File Photo[/caption] Instrument for Lunar Seismic Activity (ILSA) will compute seismicity around the landing site as well as map out the structure of the Moon’s crust and mantle. As per India Today, LASER Retroreflector Array (LRA) is developed to “facilitate real-time distance measurements between the Moon and Earth”. It can help in understanding the orbital behaviour of the Earth’s only natural satellite and its impact on the planet. After the landing, the Pragyaan rover will exit the lander module to conduct its own lunar exploration. The rover has two scientific payloads. Alpha Particle X-ray Spectrometer (APXS) is designed to ascertain the elemental composition of lunar soil and rocks around the landing site on the Moon. The other payload, LASER Induced Breakdown Spectroscope (LIBS), will study the chemical composition and infer mineralogical composition for a better understanding of the lunar surface. This lander and rover will carry out their Moon mission for one lunar day or 14 Earth days. With inputs from agencies