Details about Chandrayaan-2

The Indian Space Research Organisation (ISRO) lost contact with the Chandrayaan-2 lander Vikram just moments before it was to land on near the south pole of the Moon. The Chandrayaan-2 mission, however, is far from being a failure.

ISRO Chairman K Sivan announced that communication had been lost with the lander. which Dr. Sivan called “15 minutes of terror”.

Isro lost contact with Chandrayaan-2 lander 2.1 km above the lunar surface

  • The Indian Space Research Organisation’s ’15 minutes of terror’ was about to come to a euphoric end. Or, so it seemed. The setting was Isro’s Mission Operations Complex in Bengaluru that is tracking the progress of Chandrayaan-2, India’s second mission to the Moon.
  • The landing was to make India the only country in the world to land a rover near the south pole of the Moon.
  • The landing began minutes before 1:40 am on Saturday. And for the next few minutes, everything went right according to plan. ISRO scientists at the Mission Operations Complex cheered and clapped as Vikram aced the various stages of descent on to the lunar surface.
  • And then suddenly, around 12 minutes after Vikram began it’s decent, things went away. That outside of Isro’s control center did not know what was wrong.
  • All anxious India waited for news from Isro. After some times Isro chief K Sivan was seen heading up to the control center’s viewing gallery, where Prime Minister Narendra Modi was sitting, watching the Chandrayaan-2 landing and announced that communication had been lost with the lander.

About Chandrayaan-2

After  Chandrayaan-1, Chandrayaan-2 is the second lunar exploration mission developed by the Indian Space Research Organisation (ISRO). It consists of a lunar orbiter, the Vikram lander, and the Pragyan lunar rover, all of which were developed in India. 

The main scientific objective is to map the location and abundance of lunar water via Pragyan, and ongoing analysis from the orbiter circling at a lunar polar orbit of 100 × 100 km.

The mission was launched to the Moon from the second launch pad at Satish Dhawan Space Centre on 22 July 2019 at 2.43 PM IST (09:13 UTC) by a Geosynchronous Satellite Launch Vehicle Mark III (GSLV Mk III). The craft reached the Moon’s orbit on 20 August 2019 and began orbital positioning maneuvers for the landing. Vikram and the rover were scheduled to land on the near side of the Moon, in the south polar region at a latitude of about 70° south at approximately 1:50 am on 7 September 2019.

However, at about 1:52 am IST, the lander deviated from its intended trajectory at around 2.1 kilometers from landing and the last location of the spacecraft showed it to be 1km from its landing site traveling vertically at 60m/s and horizontally at 48m/s.

The scientists and engineers of the Chandrayaan-2 project

Project Director –Muthayya Vanitha 

Project Director –Mylswamy Annadurai 

Mission Director –Ritu Karidhal 

Deputy Project Director (Radiofrequency systems)-Chandrakanta Kumar.

Deputy Project Director (Optical Payload Data Processing, SAC)-Amitabh Singh.

The objective of Chandrayaan-2:

The primary objectives of Chandrayaan-2 are to demonstrate the ability to soft-land on the lunar surface and operate a robotic rover on the surface and 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. The onboard 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.

The mission was launched on a Geosynchronous Satellite Launch Vehicle Mark III (GSLV Mk III) with an approximate lift-off mass of 3,850 kg (8,490 lb) from Satish Dhawan Space Centre on Sriharikota Island. As of June 2019, the mission has an allocated cost of ₹978 crore (approximately US$141 million) which includes ₹603 crore for space segment and ₹375 crore as launch costs on GSLV Mk III. Chandrayaan-2 stack was initially put in an Earth parking orbit of 170 km perigee and 40,400 km apogee by the launch vehicle.

Orbiter

The orbiter will orbit the Moon at an altitude of 100 km (62 mi). The orbiter carries eight scientific instruments. The approximate launch mass was 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. The orbiter’s structure was manufactured by Hindustan Aeronautics Limited and delivered to ISRO Satellite Centre on 22 June 2015.

At the time of launch, the Chandrayaan 2 Orbiter will be capable of communicating with Indian Deep Space Network (IDSN) at Byalalu as well as the Vikram Lander. The mission life of the Orbiter is one year and it will be placed in a 100X100 km lunar polar orbit.

Weight-2,379 kg

Electric power generation capacity-1,000 W

  • Dimensions: 3.2 × 5.8 × 2.2 m
  • 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)
  • Power generation capacity: 1000 W
  • Mission duration: 1 year in lunar orbit, which may be extended to 2 years.

The orbiter carries eight scientific instruments

  1. Large Area Soft X-ray Spectrometer (CLASS) from ISRO Satellite Centre (ISAC), Bangalore
  2. Solar X-ray Monitor (XSM) from Physical Research Laboratory (PRL), Ahmedabad for mapping major elements present on the lunar surface.
  3. Dual Frequency L and S-band Synthetic Aperture Radar (DFSAR) from Space Applications Centre (SAC), Ahmedabad for probing the first few tens of meters of the lunar surface for the presence of different constituents, including water ice. SAR is expected to provide further evidence confirming the presence of water ice below the shadowed regions of the Moon.
  4. Imaging IR Spectrometer (IIRS) from Space Applications Centre (SAC), Ahmedabad for mapping of lunar surface over a wide wavelength range for the study of minerals, water molecules, and hydroxyl present.
  5. Chandrayaan-2 Atmospheric Compositional Explorer 2 (ChACE-2)Quadrupole Mass Analyzer from Space Physics Laboratory (SPL), Thiruvananthapuram to carry out a detailed study of the lunar exosphere.
  6. Terrain Mapping Camera-2 (TMC-2) from Space Applications Centre (SAC), Ahmedabad for preparing a three-dimensional map essential for studying the lunar mineralogy and geology.
  7. Radio Anatomy of Moon Bound Hypersensitive Ionosphere and Atmosphere – Dual Frequency Radio Science experiment (RAMBHA-DFRS) by SPL
  8. Orbiter High-Resolution Camera (OHRC) by SAC for scouting a hazard-free spot for landing. Imagery from OHRC will help prepare digital elevation models of the lunar surface.

Lander Vikram 

Rover Pragyan mounted on the ramp of Vikram lander

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

Weight-1,471 kg

Electric power generation capacity-650 W

It is designed to function for one lunar day, which is equivalent to about 14 Earth days. Vikram has the capability to communicate with IDSN at Byalalu near Bangalore, as well as with the Orbiter and Rover. The Lander is designed to execute a soft landing on the lunar surface.

The Vikram lander will detach from the orbiter and descend to a low lunar orbit of 30 km × 100 km (19 mi × 62 mi) using its 800 N 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 14 days.

The approximate combined mass of the lander and rover is 1,471 kg (3,243 lb).

 Vikram can safely land on slopes up to 12°.

The payloads on the Vikram lander are

  • Instrument for Lunar Seismic Activity (ILSA) Seismometer by LEOS for studying Moon-quakes near the landing site.
  • Chandra’s Surface Thermophysical Experiment (ChaSTE) Thermal probe for estimating the thermal properties of the lunar surface.
  • RAMBHA-LP Langmuir probe for measuring the density and variation of lunar surface plasma
  • A laser retroreflector array (LRA) by NASA Goddard Space Flight Center for taking precise measurements of the distance between the reflector on the lunar surface and satellites in lunar orbit. The micro-reflector weighs about 22 grams and can not be used for taking observations from Earth-based lunar laser stations.

Rover  Pragyan

The mission’s rover is called Pragyan. The rover’s mass is about 27 kg (60 lb) and will operate on solar power. The rover will move on 6 wheels traversing 500 meters on the lunar surface at the rate of 1 cm per second and leverages solar energy for its functioning.  performing on-site chemical analysis and sending the data to the lander, which will relay it to the Mission Control on the Earth. 

It can only communicate with the Lander.

Weight-27 kg

Electric power generation capacity-50 W

Chandrayaan 2’s Rover is a 6-wheeled robotic vehicle named Pragyan, which translates to ‘wisdom’ in Sanskrit. It can travel up to 500 m (½-a-km).

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, and help in path-planning by generating a digital elevation model of the 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 driven by independent brushless DC electric motors. Steering is accomplished by the differential speed of the wheels or skid steering.

Pragyan rover carries two instruments to determine the abundance of elements near the landing site:

  • Laser-induced Breakdown Spectroscopy (LIBS) from Laboratory for Electro Optic Systems (LEOS), Bangalore.
  • Alpha Particle Induced X-ray Spectroscopy (APXS) from PRL, Ahmedabad.

The expected operating time of Pragyan rover is one lunar day or around 14 Earth days as its electronics are not expected to endure the frigid lunar night. However, its power system has a solar-powered sleep/wake-up cycle implemented, which could result in longer service time than planned. 

Landing  site

Two landing sites were selected, each with a landing ellipse of 32 km x 11 km.

  1. The prime landing site (PLS54) is at 70.90267 S 22.78110 E (350 km north of the South Pole-Aitken Basin rim),
  2. The alternate landing site (ALS01) is at 67.874064 S 18.46947 W. The prime site is on a high plain between the craters Manzinus C and Simpelius N, on the near side of the Moon.

Vikram separated from Chandrayaan-2 on 7 September 2019 and was scheduled to land on the Moon at around 1:50 a.m.and  communications with the craft were not able to regain signal. The craft may have made a crash landing and may not be functional.

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