The spacecraft will also allow scientific instruments of other space agencies weighing up to about 10 kg that could supplement and complement the scientific data from the Indian instruments.

The spacecraft for Chandrayaan-1 will be a 1.5 m cuboid with a dry mass of 525 kg in its final lunar orbit.

It will be 3-axis stabilized using reaction wheels and attitude control thrusters. Star Sensors, Inertial Reference Unit and accelerometers will help in attitude determination. The spacecraft will be powered by a single-sided canted solar array generating 750 W of electrical power. It will have a Lithium-Ion battery back-up for operation during eclipse.

The spacecraft will use a bi-propellant propulsion system for transferring it from Geosynchronous Transfer Orbit (GTO) to lunar orbit and for orbit and attitude maintenance.

The telemetry, tracking and command system will operate in S-band and the scientific data will be transmitted in X-band.

India’s Polar Satellite Launch Vehicle (PSLV) will be used to launch the spacecraft. With seven successful launches so far, the PSLV has become a workhorse vehicle, placing Indian Remote Sensing Satellites as main payloads and four satellites of other space agencies as piggy-backs. With a lift-off weight of 295 tonne, the 44.4 m tall PSLV has also launched a meteorological satellite, KALPANA-1, to GTO. This is the orbit in which the spacecraft for Chandrayaan-1 will also be placed by PSLV.

In the Chandrayaan-1 mission, the spacecraft will be initially launched into a GTO with a perigee of about 240 km and an apogee of 36,000 km. Two consecutive in-plane perigee maneuvers, using the Liquid Apogee Motor(LAM) on board the spacecraft, will raise the apogee to 3,86,000 km, which is very close to the Moon (Lunar Transfer Trajectory - LTT). It will take 5½ days for the spacecraft to approach the moon. When the spacecraft is at peri-selene (nearest point around the moon), another maneuver by LAM firing will place the spacecraft in a near circular 1,000 km orbit of moon. In this orbit, the solar panel of the spacecraft will be deployed.

Subsequently, the orbit height will be reduced to 200 km and orbital plane corrections carried out to place the spacecraft in polar orbit. The spacecraft will be maintained in this orbit for 1-2 weeks that will help in studying the orbit perturbations. Finally, orbital altitude will be reduced to 100 km circular polar orbit of the moon for its two year scientific mission.