Chang’e 1 was the first Chinese-made spacecraft to fly beyond the Earth orbit. The spacecraft was required to be able to operate in both Earth and lunar orbital environments, with the capabilities of long-distance communications and telemetry, multiple orbital manoeuvres, high-precision stabilisation, and thermal controls to withstand extreme temperatures.
Objectives of the Chang’e 1 mission included:
- To obtain three-dimensional images of lunar surface and making outline graphs of lunar geology and structures;
- To search for useful elements on the lunar surface and analyse the elements and materials;
- To survey the lunar surface terrain and the depth of the lunar soil;
- To explore the space environment between 40,000 km and 400,000 km from the Earth;
Chang’e 1 was based on the DFH-3 satellite bus developed by China Academy of Space Technology (CAST). The 2,350 kg cube-shaped spacecraft consisted of 9 sub-systems: mission payload, space frame, thermal control, GNC (guidance, navigation and control), propulsions, power supply and management, data management, telemetry, and steerable antenna. Power was generated by a pair of solar panel wings, with a span of 18.1m when fully expanded.
The spacecraft was powered by a single 490 N orbit manoeuvre thruster and several 10 N thrusters for altitude control and translation. As China’s deep space network had not been completed at the time of the mission, the spacecraft utilised a combined Unified S-Band (USB) and Very-Long-Baseline Interferometry (VLBI) telemetry system to achieve telemetry, control and data transmission over long distance (400,000 km).
The 130 kg onboard mission payload package, developed by the Centre for Space Science and Applied Research (CSSAR) of the China Academy of Sciences (CAS), contained 8 pieces of equipment, including:
- Stereo camera with an optical resolution of 120m and spectrometer imager operating at wavelengths of 0.48 µm to 0.96 µm;
- Laser altimeter with 1,064 nm, 150 mJ laser, a range resolution of 1m and a spot size of 300m;
- Imaging spectrometer;
- Gamma and X-ray spectrometer working in an energy range of 0.5 to 50 keV for X-rays and 300 keV to 9 MeV for gamma rays;
- Microwave radiometer detecting 3, 7.8, 19.35 and 37 GHz with a maximal penetration depth of 30, 20, 10, 1 m and a thermal resolution of 0.5 K;
- High energy particle detector and two solar wind detectors capable of the detection of electrons and heavy ions up to 730 MeV;
Chang’e 1 was launched from the Xichang Satellite Launch Centre (XLSC) atop a Chang Zheng-3A (CZ-3A) launcher at 18:05 CST (10:05 GMT) on 24 October 2007. The spacecraft entered the Super-Synchronous Transfer Orbit (SSTO) at 10:29 GMT and its solar panel was expanded at 10:59 GMT.
After circling around the Earth in the SSTO for 1.5 times, the spacecraft fired its solid rocket motor for the first orbit changing manoeuvre at 09:55 GMT on 25 October. This was followed by another three orbit changing manoeuvres, which eventually placed the spacecraft in the lunar transfer orbit at 09:28 GMT on 31 October. The spacecraft left the lunar transfer orbit and entered the lunar orbit on 5 November.
Upon its arrival at the lunar orbit, Chang’e 1 fired its thrusters to slow down. After three retrofires, the spacecraft’s velocity was reduced to 5,724km/h. This settled Chang’e 1 into its final orbiting pattern, circling at 200km above the Moon’s surface once every 127 minutes.
The China National Space Administration (CNSA) revealed the first image of the Moon surface captured by the CCD camera (120m resolution) onboard the Chang’e 1 on 26 November 2007. On 11 December, the CNSA published more images from the Chang’e 1, showing the far side of the Moon.
Between November 2007 and October 2008, Chang’e 1 carried out various exploration missions in the lunar orbit, obtaining 1.37 TBytes of data. The data have been used to produce a 120 m/pixel resolution image covering the entire lunar surface. Its laser altimeter obtained 9.16 million of terrain measurements, allowing the production of the entire lunar terrain model with 3,000 m accuracy. The Gamma and X-ray spectrometer mapped out the distribution of Uranium, Potassium and Thorium in lunar soils for the entire lunar surface.
The Chang’e 1 mission officially ended in October 2008, but the spacecraft continued flying for another four months to conduct further tests in order to gain experience for future probe missions. On 6th December, the Mission Control Centre in Beijing commanded the spacecraft to lower its orbit to 100 km above the lunar surface. On 19 December, the spacecraft was lowered again to a 15—17 km orbit. On 1 March 2009, Chang’e 1 carried out a controlled crash into the Moon surface under the command of the Mission Control at GMT 08:13:10, ending its 16-month mission. The impact spot was located at 1.5°S 52.36°E.
- Mission Type: Lunar orbiting
- Launch Mass: 2,350 kg
- Launch Date: 2007-10-24
- Launch Time: 18:05 Beijing Time
- Launch Vehicle: Chang Zheng-3A
- Launch Site: Launch Complex 3, Xichang Satellite Launch Centre
- Decay Date: 2009-03-01
- Decay Time: 16:13:10 Beijing Time