Chandrayaan-2: India’s Lunar Mission

Chandrayaan-2
Chandrayaan-2

Chandrayaan-2 is India’s second lunar exploration mission after Chandrayaan-1. Developed by the Indian Space Research Organisation (ISRO) , the mission is planned to be launched to the Moon by a Geosynchronous Satellite Launch Vehicle Mark III. It includes a lunar orbiter, lander, and rover, all developed domestically. The main scientific objective is to map the location and abundance of lunar water.

Chandrayaan-2 will attempt a soft landing of a lander and rover in a high plain between two craters , at a latitude of about 70° south. The wheeled rover will move on the lunar surface and will perform on-site chemical analysis. It can relay data to Earth through the Chandrayaan-2 orbiter and lander .

Launch of Chandrayaan-2 was originally scheduled for 15 July 2019 2:51 IST but due to a technical glitch on the launcher. It was canceled 56 minutes before launch and postponed to July 22, 2019 at 14:43 UTC.

A successful landing would make India the 4th country to achieve a soft landing on the Moon , after the space agencies of the USSR , USA , and China. If successful, Chandrayaan-2 will be the second mission to soft-land near the lunar south pole after the Chinese Chang’e 4 mission , which landed in that region on 3 January 2019.

Chandrayaan-2: History

On 12 November 2007, representatives of the Russian Federal Space Agency and ISRO signed an agreement for the two agencies to work together on the Chandrayaan-2 project. ISRO would have the prime responsibility for the orbiter and rover . The design of the spacecraft was completed in August 2009, with scientists of both countries conducting a joint review.

Although ISRO finalized the payload for Chandrayaan-2 per schedule the mission was postponed in January 2013 and rescheduled to 2016 because Russia was unable to develop the lander on time. When Russia cited its inability to provide the lander even by 2015, India decided to develop the lunar mission independently.

The spacecraft’s launch had been scheduled for March 2018, but was first delayed to April and then to October to conduct further tests on the vehicle. On 19 June 2018, after the program’s fourth Comprehensive Technical Review meeting, a number of changes in configuration and landing sequence were planned for implementation. This pushed the launch to the first half of 2019. Two of the lander’s legs got minor damage during one of the tests in February 2019 the launch was scheduled for 15 July 2019 at 02:51 IST local time, with the landing expected on 6 September 2019. However, the launch was aborted due to a technical glitch. On 18th July, ISRO announced a new date of launch as 22nd July 2019 at 2:43 PM IST.

Chandrayaan-2: Objectives

The primary objectives are to demonstrate the ability to soft-land on the lunar surface and operate a robotic rover on the surface. Scientific goals include studies of lunar topography, mineralogy, elemental abundance, the lunar exosphere, and signatures of hydroxyl and water ice. The orbiter will map the lunar surface and help to prepare 3D maps of it. On board radar will also map the surface while studying the water ice in the south polar region and thickness of the lunar regolith on the surface. Chandrayaan-2 will inform the location and abundance of lunar water for exploitation by the future lunar base proposed by the Artemis program.

Chandrayaan-2: Design

Chandrayaan-2
Chandrayaan-2

The mission is planned to fly on a Geosynchronous Satellite Launch Vehicle Mark III (GSLV Mk III) with an approximate lift-off mass of 3,850 kg from Satish Dhawan Space Centre on Sriharikota Island. As of June 2019, the mission has an allocated cost of ₹978 crore which includes ₹603 crore for space segment and ₹375 crore as launch costs on GSLV Mk III. Chandrayaan-2 stack would be initially put in an Earth parking orbit of 170 km perigee and 40,400 km apogee by the launch vehicle. It will then perform orbit-raising operations followed by trans-lunar injection using its own power.

Chandrayaan-2: Orbiter

The orbiter will orbit the Moon at an altitude of 100 km (62 mi). The orbiter carries five scientific instruments. Three of them are new, while two others are improved versions of those flown on Chandrayaan-1. The approximate launch mass will be 2,379 kg (5,245 lb). The Orbiter High-Resolution Camera (OHRC) will conduct high-resolution observations of the landing site prior to the separation of the lander from the orbiter. Orbiter’s structure was manufactured by Hindustan Aeronautics Limited and delivered to ISRO Satellite Centre on 22 June 2015.

  • Gross lift-off mass: 2,379 kg (5,245 lb)
  • Propellant mass: 1,697 kg (3,741 lb)
  • Dry mass: 682 kg (1,504 lb)

Vikram lander

Vikram lander
Vikram lander

The mission’s lander is called Vikram named after Vikram Sarabhai (1919-1971), who is widely regarded as the father of the Indian space program.

The Vikram lander will detach from the orbiter and descend to a lunar orbit of 30 km × 100 km liquid main engines . It will then perform a comprehensive check of all its on-board systems before attempting a soft landing, deploy the rover, and perform scientific activities for approximately 15 days. The approximate combined mass of the lander and rover is 1,471 kg.

The preliminary configuration study of the lander was completed in 2013 by the Space Applications Centre (SAC) in Ahmadabad . The lander’s propulsion system consists of eight 50 N thrusters for attitude control and five 800 N liquid main engines derived from ISRO’s 440 N Liquid Apogee Motor. Initially , the lander design employed four main liquid engines, but a centrally mounted engine was added to handle new requirements of having to orbit the Moon before landing. An additional engine is expected to mitigate upward draft of lunar dust during the soft landing. Vikram can safely land on slopes up to 12°.

Pragyan rover

Pragyan rover
Pragyan rover

The mission’s rover is called Pragyaan. The rover’s mass is about 27 kg (60 lb) and will operate on solar power. Rover will move on 6 wheels traversing 500 meters on the lunar surface at the rate of 1 cm per second. It will perform on-site chemical analysis and send the data to the lander, which will relay it to the Earth station. For navigation, the rover uses:

  • Stereoscopic camera-based 3D vision: two 1 megapixel, monochromatic NAVCAMs in front of the rover will provide the ground control team a 3D view of the surrounding terrain.  IIT Kanpur contributed to the development of the subsystems for light-based map generation and motion planning for the rover.
  • Control and motor dynamics: the rover has a rocker-bogie suspension system and six wheels. Each is driven by independent brushless DC electric motors. Steering is accomplished by the differential speed of the wheels or skid steering.[

The expected operating time of Pragyaan rover is one lunar day or around 14 Earth days. But its power system has a solar-powered sleep/wake-up cycle implemented, which could result in longer service time than planned.

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