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Chandrayaan 3

Chandrayaan 3


Chandrayaan 3 represents a mission conducted by the Indian Space Research Organization (ISRO) with the principal objective of deploying a lander and rover within the highlands adjacent to the southern pole of the Moon. This mission, scheduled for August 23, 2023, aims to showcase comprehensive capabilities in both landing and roving. Additionally, it is designed to conduct various scientific measurements from both the lunar surface and orbit. The mission comprises two main components: a lander/rover unit and a propulsion module. The lander/rover unit draws inspiration from the Vikram rover utilized in the Chandrayaan 2 mission, featuring enhancements to ensure a secure landing. This unit will be transported to lunar orbit by the propulsion module, which will remain in lunar orbit serving as a satellite for communication purposes.


Spacecraft and Subsystems:

The propulsion module takes the form of a box-like structure with an altered I-3K design. It boasts a sizable solar panel affixed to one side, along with a prominent cylinder at its apex—the Intermodule Adapter Cone—intended for mounting the lander. The main thruster nozzle is positioned at the module’s base. With a total mass of 2145.01 kg, a substantial portion, namely 1696.39 kg, is allocated for propellant used in the MMH + MON3 bi-propellant propulsion system. The module is capable of generating 738 W of power. Communication is established via the S-Band, while attitude sensing is facilitated by a star sensor, Sun sensor, Inertial Reference unit, and an Accelerometer Package (IRAP).


The Vikram lander, named in honor of Indian space program pioneer Vikram Sarabhai, adopts a generally box-shaped configuration measuring 200 x 200 x 116.6 cm. It is equipped with four landing legs and four landing thrusters. The lander weighs 1749.86 kg, inclusive of a 26 kg rover component, and can generate 738 W through side-mounted solar panels. Various sensors are integrated into the lander to ensure a safe touchdown, including an accelerometer, altimeters (both Ka-band and laser-based), Doppler velocimeter, star sensors, inclinometer, touchdown sensor, and a suite of cameras for hazard avoidance and positional awareness. Attitude control is achieved using reaction wheels, while propulsion relies on a MMH and MON3 bipropellant system featuring four 800 N throttleable engines and eight 58 N throttleable engines. Communications are facilitated by an X-band antenna. The lander accommodates the rover within a compartment, complete with a deployment ramp for surface release.


The Pragyan rover, bearing the Sanskrit name for “wisdom,” is constructed with a rectangular chassis measuring 91.7 x 75.0 x 39.7 cm. It employs a six-wheel rocker-bogie wheel drive assembly and is equipped with navigation cameras and a solar panel generating 50 W of power. Communication with the lander is established through Rx/Tx antennas.


The Vikram lander incorporates several instruments for scientific investigations, including Chandra’s Surface Thermophysical Experiment (ChaSTE) to measure surface thermal properties, the Instrument for Lunar Seismic Activity (ILSA) for seismicity assessment around the landing site, the Radio Anatomy of Moon Bound Hypersensitive ionosphere and Atmosphere (RAMBHA) for studying the gas and plasma environment, and a passive laser retroreflector array from NASA for lunar ranging studies. The Pragyan rover is equipped with two instruments for analyzing local surface elemental composition: an Alpha Particle X-ray Spectrometer (APXS) and a Laser Induced Breakdown Spectroscope (LIBS). The Propulsion Module / Orbiter carries an experiment known as the Spectropolarimetry of HAbitable Planet Earth (SHAPE) to study Earth from lunar orbit.


Mission Profile:

Chandrayaan 3 was launched on July 14, 2023, at 9:05:17 UT (2:35 p.m. India standard time) using a GSLV Mark 3 (LVM 3) heavy lift launch vehicle from the Satish Dhawan Space Center in Sriharikota, India. The launch propelled it into an elliptical Earth parking orbit of approximately 170 x 36,500 km. Over the course of around 40 days, a series of maneuvers were executed to position the spacecraft toward the Moon. On August 5, a 30-minute engine firing positioned the spacecraft into a lunar orbit measuring 164 x 18,074 km. Through subsequent firings by the propulsion module, the lander/rover was inserted into a circular polar lunar orbit at an altitude of 100 km by August 17. The Vikram lander then separated and initiated its powered descent toward the lunar surface on August 23 at 12:14 UT. After 19 minutes, at 12:33 UT (6:03 p.m. India Standard Time), the lander successfully touched down in the Moon’s south polar region, near coordinates 69.37 S, 32.35 E. The propulsion module / communications relay satellite will continue to operate in lunar orbit, facilitating communication with Earth, while Chandrayaan 2 remains on standby as a backup relay. The lander and rover are designed to function throughout one lunar daylight period, equivalent to about 14 Earth days.


Image credit: ISRO


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