By 
September 3rd, 2023
Image credit: ISRO
India’s Chandrayaan-3 Moon lander/rover mission is busily gathering science data since its touchdown on August 23 with the country chalking up a first by landing in a region of the Moon’s south pole.
According to the Indian Space Research Organization (ISRO), the mooncraft mission activated a number of experiments:
Image credit: ISRO
Image credit: ISRO
Image credit: ISRO
The Instrument for Lunar Seismic Activity (ILSA) payload on the Chandrayaan-3 Lander is the first instance of a Micro Electro Mechanical Systems (MEMS) technology-based instrument on the Moon. It has recorded the vibrations occurring due to the movements of India’s on-the-prowl rover and other payloads.
ILSA is a cluster of six high-sensitivity accelerometers, with a primary objective to measure ground vibrations generated by natural quakes, impacts, and artificial events.
The vibrations recorded during the rover’s navigation on August 25, 2023, are depicted in the figure. Additionally, an event, seemingly natural, recorded on August 26, 2023, is also shown. The source of this event is currently under investigation.
Image credit: ISRO
Lunar plasma
The Radio Anatomy of Moon Bound Hypersensitive ionosphere and Atmosphere – Langmuir Probe (RAMBHA-LP) payload onboard the Chandrayaan-3 Lander has made the first on-the-spot measurements of the surface-bound lunar plasma environment over the south polar region.
Image credit: ISRO
The Langmuir probe is a device used for characterizing a plasma. It features a metallic spherical probe mounted on a one-meter boom attached to the Chandrayaan-3 Lander’s upper deck. The extended boom length ensures that the spherical probe operates within the undisturbed lunar plasma environment, isolated from the lander’s body.
The initial assessment indicates that the plasma encompassing the lunar surface is relatively sparse, characterized by a number density ranging from approximately 5 to 30 million electrons per cubic meter. This evaluation specifically pertains to the early stages of the lunar daytime.
“These ongoing observations hold significant implications for comprehending the process of charging within the lunar near-surface region,” ISRO explains, “particularly in response to the fluctuations in solar space weather conditions.”
India’s Moon rover operates its Alpha Particle X-ray Spectrometer (APXS).
Image credit: ISRO
Soil and rock analysis
Toted by the lunar rover is an Alpha Particle X-ray Spectrometer (APXS) for in-situ analysis of the elemental composition of soil and rocks on the surface of planetary bodies having little atmosphere, such as the Moon.
APXS carries radioactive sources that emit alpha particles and X-rays onto the surface sample. The atoms present in the sample in turn emit characteristic X-ray lines corresponding to the elements present. By measuring the energies and intensities of these characteristic X-rays, researchers can find the elements present and their abundances.
“APXS observations have discovered the presence of interesting minor elements, including sulfur, apart from the major expected elements such as aluminum, silicon, calcium, and iron,” an ISRO website explains.
In addition, the LASER Induced Breakdown Spectroscope (LIBS) instrument onboard the rover also confirmed the presence of sulfur. LIBS can derive the chemical composition and infer mineralogical composition of the lunar topside.
Detailed scientific appraisal of these observations is in progress.
India Moon lander makes use of Surface Thermo physical Experiment (ChaSTE) and Instrument for Lunar Seismic Activity (ILSA)
Image credit: ISRO
Rover re-activation?
In a statement from ISRO, the Chandrayaan-3 rover has completed its assignments.
“It is now safely parked and set into sleep mode. APXS and LIBS payloads are turned off. Data from these payloads is transmitted to the Earth via the Lander. Currently, the battery is fully charged. The solar panel is oriented to receive the light at the next sunrise expected on September 22, 2023. The receiver is kept on,” ISRO states.
“Hoping for a successful awakening for another set of assignments! Else, it will forever stay there as India’s lunar ambassador,” the ISRO X tweet concludes.
Image credit: ISRO
Image credit: ISRO
Retro-reflector array
Now on the Moon, mounted atop the Chandrayaan-3 Moon lander is a NASA laser retro-reflector array. In NASA acronym-land, the device is better known as an LRA, supplied by the LRA project based at NASA’s Goddard Space Flight Center.
Image credit: ISRO/NASA
The ultra-small, compact LRA is designed to use reflected laser light from a laser altimeter or lidar on a spacecraft orbiting the Moon or landing on the Moon. They are too small to be radiated by laser light shot from the Earth.
An LRA consists of eight tiny retro-reflectors mounted on a small, high hemispherical platform. Total mass of the LRA is 20 grams, and requires no power.
“Since LRA is a passive payload, there are no milestones for the LRA unit itself beyond a safe landing,” said Daniel Cremons of Goddard’s Planetary Geology, Geophysics, and Geochemistry Laboratory.
Image credit: ISRO/NASA
Cremons told Inside Outer Space that the Lunar Orbiter Laser Altimeter (LOLA) on NASA’s Lunar Reconnaissance Orbiter (LRO) is the only NASA laser altimeter capable of ranging to LRA in lunar orbit right now.
The LOLA team will be attempting to range to LRA using LOLA once the Chandrayaan-3 lander and rover missions are complete, Cremons said. “Since LOLA was not designed for precision targeting, this may not be successful on the first attempt but that is our plan right now,” he said.
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