Chandrayaan-1

Did You Know?

• The idea of an Indian scientific mission to the Moon was first raised in 1999 during a meeting of the Indian Academy of Sciences.
• Former Prime Minister Atal Bihari Vajpayee announced the Chandrayaan-1 project.
• The American Institute of Aeronautics and Astronautics selected the Chandrayaan-1 mission as a recipient of its annual AIAA SPACE 2009 awards.

Specifications

The spacecraft was cuboid in shape, approximately 1.5 m. It had a mass of 1380 kg at launch, 675 kg at lunar orbit, and 523 kg after releasing the impactor. Communications used X band for payload data transmission via a 0.7 m diameter dual gimballed parabolic antenna, while Telemetry, Tracking & Command operated in S band. Power came from a solar array covering 2.15 m² generating 750 W peak, stored in a 36 Ah lithium-ion battery. Propulsion used a bipropellant system with one 440 N engine and eight 22 N thrusters, with fuel and oxidizer in two 390 L tanks. The craft was 3-axis stabilized with two star sensors, gyros, and four reaction wheels.

Payload

The scientific payload massed 90 kg and included five Indian instruments and six from other countries. The Terrain Mapping Camera (TMC) was a CMOS camera with 5 m resolution and a 40 km swath in the panchromatic band, used to produce a high-resolution map of the Moon. The Hyper Spectral Imager (HySI) performed mineralogical mapping in the 400–900 nm band with 15 nm spectral resolution and 80 m spatial resolution. The Lunar Laser Ranging Instrument (LLRI) determined surface topography by sending infrared laser pulses and detecting reflections, collecting 10 measurements per second. The High Energy X-ray Spectrometer (HEX) measured Uranium, Thorium, Lead-210, Radon-222 degassing, and other radioactive elements in the 30–200 keV range with 40 km ground resolution. The Moon Impact Probe (MIP) carried a C-band Radar altimeter, a video imaging system, and a mass spectrometer; it was ejected at 14:30 UTC on 14 November 2008 and impacted the lunar south pole at 15:01 UTC on the same day.

Mission timeline

Chandrayaan-1 was launched on 22 October 2008 at 00:52 UTC from Satish Dhawan Space Centre using the four-stage PSLV C11 launch vehicle. It was sent to the Moon via a series of orbit-increasing manoeuvres around Earth over 21 days, rather than a direct trajectory. At launch it entered a geostationary transfer orbit with an apogee of 22860 km and a perigee of 255 km. The first orbit burn on 23 October 2008 at 03:30 UTC raised the apogee to 37900 km and perigee to 305 km. The second burn on 25 October 2008 at 00:18 UTC raised apogee to 74715 km and perigee to 336 km, making it the first Indian spacecraft beyond geostationary orbit. The third burn on 26 October 2008 at 01:38 UTC raised apogee to 164600 km and perigee to 348 km. ISRO's telemetry, tracking and command network (ISTRAC) at Peenya in Bangalore tracked and controlled the spacecraft. A high-level review was conducted on 29 January 2009 after the first 100 days in space.

Results

The Moon Mineralogy Mapper confirmed the magma ocean hypothesis that the Moon was once completely molten. The Terrain Mapping Camera produced over 70,000 three-dimensional images and recorded images of the Apollo 15 landing site. TMC and HySI covered about 70% of the lunar surface, while M3 covered more than 95%. The Lunar Laser Ranging Instrument covered both lunar poles, and the High Energy X-ray Spectrometer made about 200 orbits over the poles. The Miniature Synthetic Aperture Radar provided complete coverage of both polar regions. The C1XS X-ray Spectrometer detected titanium, confirmed calcium, and gathered accurate measurements of magnesium, aluminium and iron on the lunar surface. The payload enabled study of the interaction between solar wind and a planetary body without a magnetic field.