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April 25, 2017

Essay : Chandrayaan 1 - India's First Lunar Mission

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Chandrayaan-1 India's First Lunar Mission

  • Introduction of Chandrayaan-1. 
  • Major initiatives of Lunar Mission. 
  • Description of Lunar Mission. 
  • The primary objective of the mission. 
  • The journey of Chandrayaan-1. 
  • The major discovery of Chandrayaan-1.
  • The data obtained by this mission. 
  • The important findings of this mission and its significance of Indian Space Mission.
Chandrayaan-1 is India's first mission to the moon and was launched on 22nd October, 2008, from Satish Dhawan Space Centre (SDSC), Shriharikota. It was launched using a Polar Satellite Launch Vehicle (PSLV). The spacecraft orbited at a height of 100 km from the lunar surface for chemical, mineralogical and photo-geologic mapping of the moon. The scientific payloads from India included the Terrain Mapping Camera (TMC), Hyper Spectral Imager (HySI), Lunar Laser Ranging Instrument (LLRI) etc. It also carried scientific instruments built in the USA, the UK, Germany, Sweden, and Bulgaria.

The video imaging system was designed to take images of moon's surface, the radar measured the rate of descent of the probe, and mass spectrometer made a detailed study of the extremely thin lunar atmosphere. The idea of undertaking a scientific mission to the Moon was mooted by Indian Academy of Sciences. It was further discussed by the Astronomical Society of India. Based on the recommendations of the scientific community and as a first major initiative, a National Lunar Mission Task Mission was constituted by Indian Space Research Organisation (ISRO).

The mission had leading scientists and technologists from all over the country, for considering and making an assessment of the possible configuration and feasibility of taking up an Indian moon mission. The task team conducted a feasibility study. On the basis of the study, it detailed the Indian lunar mission's scientific objectives, instruments to be flown, launch and spacecraft technologies that are available and those to be developed, setting up of a Deep Space Network (DSN) station that supports the interplanetary spacecraft missions of India.

The study report was viewed by the team of hundred eminent scientists from the fields of geology, physics, astronomy, cosmology, planetary and space physics. After detailed discussions participants unanimously recommended that India should undertake the Moon Mission. Subsequently, the Government of India had approved ISRO's proposal for the first Indian moon mission, called Chandrayaan-1. The primary objective of the mission was to expand the scientific knowledge about the origin and evolution of the moon. It focused on chemical, mineralogical and photo-geologic mapping of the moon in the visible, near infrared low energy and high energy X-rays with high spatial resolution.

It intended to create a three-dimensional atlas of both the near and far sides of the moon. The mission aimed at the mapping of the distribution of metals such as Si, Al, Mg, Ca, and elemental chemical species including radioactive nuclides. These mappings have helped the scientists to unravel the mysteries about the origin and evolution of the planetary system in general and moon- earth in particular.

Chandrayaan-1 was first made to circle the Earth in its transfer orbit and then was put into elliptical extended transfer orbits by repeatedly firing its liquid engine in a pre-determined sequence. When it reached near the Moon and passed at a few hundred kilometres from it, its liquid engine was fired again so that the spacecraft slowed down sufficiently to enable the gravity of the Moon to capture it into an elliptical orbit.

After cautious and detailed observation of the orbit perturbations, the orbital height of Chandrayaan 1 was finally lowered to its intended 100 km height from the lunar surface.

The major discovery of the Chandrayaan-1 mission was the detection of water (H2O) and hydroxyl (OH) on the lunar surface. The data also revealed their enhanced abundance towards the polar region. (ChACE Chandra's Altitudinal Composition Explorer: Quadrupole Mass Spectrometer) onboard Moon Impact Probe (MIP) indicated the possible presence of water molecules along with other molecular species in the lunar environment.

The data obtained by certain instruments TMC and HySI confirmed the existence of huge exposures of crystalline feldspars in lunar highlands validating the global magma ocean hypothesis. According to the magma ocean hypothesis, the moon was once completely molten.

The data on lunar polar areas was provided by Lunar Laser Ranging Instrument (LLRI) and High Energy X-ray Spectrometer (HEX) of ISRO as well as Miniature Synthetic Aperture Radar (Mini-SAR) of the USA. The Terrain mapping camera on board Chandrayaan-1, besides producing more than 70000 three dimensional images, had recorded images of the landing site of US spacecraft Apollo 15.

Chandrayaan-1 X-ray Spectrometer (C1XS) detected characteristic X-ray signals from the lunar surface during weak solar flares, thus providing the first set of high resolution X-ray spectra indicating the presence of Mg, Al, Si, and Ca at several locations on the lunar surface.

SARA payload onboard Chandrayaan-1 had found that up to 20% of the solar wind protons impinging on the lunar surface are reflected back to space as neutral hydrogen atoms. This finding annuls the widely accepted assumption that the regolith almost completely absorbs the impinging solar wind. The Mini-Sar (miniature synthetic aperture radar), a NASA payload on board Chandrayaan-1 found more than forty craters with water ice, the size of the craters ranging between two and 15 kilometres in diameter. The eleven payloads of Chandrayaan-1 studied the moon from different perspectives and provided excellent quality of high resolution data.

The satellite made more than 3400 orbits around the Moon and the mission was concluded when the communication with the spacecraft was lost on 29th August, 2009. The successful realisation of this mission demonstrated India's capability and proficiency in carrying out highly complex space missions.

Chandrayaan-1 added another feat to the glory of Indian space mission. It would be followed by Chandrayan-2 with an orbiter, a lander and a rover which is planned for launch by 2017. This mission would play a major role in reinvigorating research in fundamental science, help in upgrading, technological capacities for future space programmes and become a meaningful contender in the international space arena for exploration resources in the immeadiate neighbourhood of our planet.

Difficult Words with Meanings :
  • Photo-geologic technique of interpreting geology from aerial photographs
  • Payloads part of a cargo expressed in weight
  • Terrain a tract of land, especially considered with reference to its natural features
  • Cosmology branch of astronomy that deals with the general structure and evolution of universe
  • Perturbations a disturbance of the regular and usually elliptical course of motion of a celestial body that is produced by force additional to that which causes its regular motion; 
  • Spectrometer an optical device for measuring wavelengths
  • Hypothesis a proportion assumed as a premire in an argument
  • Miniature greatly reduced or abridged form
  • Regolith mantle rock
  • Craters a circular or almost circular area having a depressed floor.
shared by Nisheeta Mirchandani
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