[ Expanding the scientific knowledge about the moon, upgrading India’s technological capability
and providing challenging opportunities for planetary research for the younger generation ]

Scientific Objectives:

High resolution remote sensing of the moon in the visible, near infrared, low energy X-ray and high-energy X-ray regions for: 

Preparing 3-dimensional atlas of regions of scientific interest with a high spatial and altitude resolution of 5-10 m

Chemical mapping of the entire lunar surface for elements such as Mg, Al, Si, Ca, Fe and Ti with a spatial resolution of 10 km and elements of high atomic numbers (Z), such as 222Rn, U, Th and Gd with a spatial resolution of 20 km

Mission Objectives:

To realise the mission goal of harnessing the science payloads, lunar craft and the launch vehicle with suitable ground support systems including DSN station.

To realise the integration and testing, launching and achieving lunar polar orbit of about 100 km, in-orbit operation of experiments, communication/ telecommand, telemetry data reception, quick look data and archival for scientific utilization by identified group of scientists.

Click to Enlarge

Physical: 1.5 m cuboid-shaped main body with a dry weight of 525 kg in lunar orbit

Control: 3-axis stabilized using reaction wheels and attitude control thrusters, star sensors, inertial reference unit and accelerometers for attitude determination.

Power: Single sided canted solar array to generate 750 W. Li-Ion batteries for eclipse operations

Propulsion: Bipropellant system for transferring from GTO to lunar orbit and for orbit and attitude maintenance

Communication: TTC in S-band and scientific payload data transmission in X-band
Mission Life: 2 years

New Technologies: Lithium-ion batteries, Gimballed antenna system, Miniaturized communication system, Miniaturized star sensor, Spacecraft bus management
Chandrayaan - I
Launch Vehicle: Polar Satellite Launch Vehicle (PSLV-XL)

Lift off Weight: 316 tonnes

Height: 44.4 m

Power: Single sided canted solar array to generate 750 W. Li-Ion batteries for eclipse operations

Payload Capability: 525 kg in 100 km lunar orbit 1050 kg into Geosynchronous Transfer Orbit (200 km x 36000 km) 100 kg to 1350 kg payloads to Sun Synchronous Orbit

Proven Vehicle and Demonstrated multiple satellite launch capability

Mission Sequence:

The spacecraft would be launched by PSLV-XL launch system in a highly elliptical transfer orbit with perigee of about 240 km and an apogee of about 24,000 km. Later, the spacecraft would be raised to moon rendezvous orbit by multiple in-plane perigee maneuvers. These maneuvers would help to achieve the required 3,86,000 km apogee of the Lunar Transfer Trajectory (LTT).

After a quick estimate of the achieved LTT a mid-course correction will be imparted at the earliest opportunity. The spacecraft coasts for about five and a half days in this trajectory prior to the lunar encounter. The major maneuver of the mission, called Lunar Orbit Insertion (LOI) that leads to lunar capture, would be carried out at the peri-selene (nearest point in lunar orbit) leading to successful lunar capture in a polar, near circular 1000 km-altitude orbit.

After successful capture and health checks, the altitude is planned to be lowered through a series of in-plane corrections to achieve the target altitude of 100 km circular polar orbit.

Ground Segment for the Mission

Ground Segment for Chandrayaan-1 comprises three major elements viz. Deep Space Station (DSN), Spacecraft Control Center (SCC) and Indian Space Science Data Center (ISSDC). This trio of ground facility ensures the success of the mission by providing to and fro conduit of communication, securing good health of the spacecraft, maintaining the orbit and attitude to the requirements of the mission and conducting payload operations.The ground segment is also responsible for making the science data available for the Technologists / Scientists along with auxiliary information, in addition to storage of payload and spacecraft data.

( Text & Photo Courtesy: ISRO - Indian Space Research Organization )