Chandrayaan-1 is an unmanned lunar exploration mission by the Indian Space Research Organisation (ISRO). The mission includes a lunar orbiter as well as an impactor. The spacecraft will be launched by a modified version of the Polar Satellite Launch Vehicle.
The remote sensing satellite will weigh 1304 kg (590 kg initial orbit mass and 504 kg dry mass) and carry high resolution remote-sensing equipment for visible, near-infrared, soft and hard X-ray frequencies.
Over a two-year period, it is intended to survey the lunar surface to produce a complete map of its chemical characteristics and 3-dimensional topography. The polar regions are of special interest, as they might contain water ice.
The ISRO has identified Mylswamy Annadurai as the project chief.
Cost of the project is estimated at Rs 3.8 billion ($ 83 million).
The mission includes five ISRO payloads and six payloads from other international space agencies such as NASA and ESA, and the Bulgarian Aerospace Agency.
The spacecraft has state-of-the-art subsystems to facilitate the safe and efficient functioning of the 11 scientific instruments.
The spacecraft structure has been mainly built using composites and aluminum honeycomb material.
KEY SYSTEMS
The Thermal subsystem, consisting of paints, tapes, multi-layer insulation blanket, optical solar reflectors, heat pipes, heaters and temperature controllers, ensures the proper functioning of the spacecraft by keeping its temperature within acceptable limits.
The Mechanisms subsystem of Chandrayaan-1 spacecraft takes care of the deployment of its solar panel and the steering of the antenna.
The power generation would be through a canted single-sided solar array, which will provide required power during all phases of the mission. This deployable solar array, consisting of a single panel, generates 700W of peak power. The solar array, along with yoke, would be stowed on the south deck of the spacecraft in the launch phase. During eclipse, i.e., when the Sun's light will not reach the spacecraft, the spacecraft will be powered by Lithium ion (Li-Ion) batteries
The Telemetry, Tracking and Command subsystems of Chandrayaan-1 take care of radioing detailed information about the spacecraft's health, facilitating the knowledge about the spacecraft's position in space and reception and execution of commands coming from Earth.
Sun- and star-sensors as well as gyroscopes provide orientation reference for the spacecraft. The Attitude and Orbit Control subsystem, essentially the brain of Chandrayaan-1, consisting of a Bus Management Unit (BMU), reaction wheels and thrusters, ensures the proper orientation and stability of the spacecraft as well as in changing its orbit during different phases of its flight.
A liquid apogee motor (LAM) is used to make Chandrayaan-1 escape from Earth and travel towards the Moon. Liquid propellants needed for LAM as well as thrusters are stored onboard the spacecraft.
Chandrayaan-1's Communications subsystem transmits the precious information gathered by its eleven scientific instruments to Earth in 'X-band' through its dual-gimbaled antenna.
The spacecraft has been built at the ISRO Satellite Centre in Bangalore with contributions from ISRO and Department of Space (DOS) establishments like Vikram Sarabhai Space Centre (VSSC), Liquid Propulsion Systems Centre (LPSC), ISRO Inertial Systems Unit (IISU) of Tiruvananthapuram, Space Applications Centre (SAC) and Physical Research Laboratory (PRL) of Ahmedabad and Laboratory for Electro-optic Systems (LEOS) of Bangalore.
SPECIFICATIONS IN DETAIL
Cuboid in shape with each side approximately 1.50 m. Weighing 1304 kg at launch and 590 kg at lunar orbit. Accommodates eleven science payloads. 3-axis stabilised spacecraft using two star sensors, gyros and four reaction wheels. - After deployment, the solar panel plane is canted by 30º to the spacecraft pitch axis.
The spacecraft employs an X-band, 0.7m diameter parabolic antenna for payload data transmission. The antenna employs a dual-gimbaled mechanism to track the Earth station when the spacecraft is in lunar orbit. The spacecraft uses a bi-propellant integrated propulsion system to reach lunar orbit as well as orbit and attitude maintenance while orbiting the moon. The propulsion system carries required propellant for a mission life of two years, with adequate margin. The Telemetry, Tracking & Command (TTC) communication is in S-band frequency. The scientific payload data transmission is in X-band frequency. The spacecraft has three Solid State Recorders (SSRs) on board to record data from various payloads. SSR-1 will store science payload data and has capability of storing 32 GB data. SSR-2 will store science payload data along with spacecraft attitude information (gyro and star sensor), satellite house keeping and other auxiliary data. The storing capacity of SSR-2 is 8 GB. M3 (Moon Mineralogy Mapper) payload has an independent SSR with 10 GB capacity.
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