Chang’e 5-T1

Change 5-T1 3

Other name: CE-5-T1. Type: Technology demonstration. Programme: CLEPAgency: CNSA/SASTIND. Spacecraft family: Chang’e 5. Orbit: Lunar. Mass (gross): 2,215 kg. Launch site: Xichang. Launch complex: LC2. Launch vehicle: CZ-3CLaunch date: 2014-10-24. Lift-off time: 02:00 CST. Landing: 2014-11-01 06:42 CST. Duration: 8 days 4 hours 42 minutes.

Chang’e 5-T1 is a precursor mission to Chang’e 5, China’s robotic lunar sample return mission scheduled for 2017. The primary objective of the mission is to validate the design of Chang’e 5’s return capsule and to demonstrate high-speed atmospheric re-entry from the translunar flight.

The Spacecraft

The Chang’e 5-T1 spacecraft, designed and built by the China Academy of Space Technology (CAST), consists of a Service Module that was based on the Chang’e 2 lunar orbiter design, and a Chang’e 5 return capsule.

The Service Module, based on the CAST DFH-3A satellite bus, accommodates the power, thermal control, communications, telemetry, NGC (navigation, guidance and control), and propulsion sub-systems. The module had an empty mass of 1,150 kg and carried 1,065 kg of propellant. Each of its two solar panel wings consists of three panels with a total power of up to 1.7 kW. The satellite bus is fully three-axis stabilised through various sensors including star trackers, sun sensors and inertial navigation platform.

The return capsule is a scaled-down version of the Shenzhou re-entry module, about one-eighth the size of the latter. It is 2.50 metres in height and 2.52 metres in diameter, and weighs about 600 kg. The capsule has a spherical aerodynamic design, with its blunt end protected by a heat shield. It is equipped with a thruster system to actively control the its orientation and adjust its re-entry trajectory. Other onboard systems include telemetry/communication systems and radio beacons to allow the tracking and locating of the capsule throughout re-entry and landing.

Carried on the piggyback of Chang’e 5-T1 was the 4M experimental radio beacon developed by LuxSpace in Luxembourg and PS86X1 from the virtual organisation Pocket Spacecraft. The two small probes were carried in the launch vehicle’s third-stage and were to be released on the way to the Moon to conduct separate flyby experiments.

The spacecraft was to be launched by an improved variant of the Chang Zheng-3C (CZ-3C) launch vehicle, designated CZ-3C-GII. The rocket features an upgraded navigation package with dual-laser inertial platform coupled with GPS input. It also allows space-based telemetry and tracking through China’s Tianlian 1 satellites. The overall length of the rocket was extended by 1.5 metres and the two liquid boosters were also stretched by 0.8 metre to allow extra propellants. This increased the launcher’s GTO payload capacity from 3,800 kg to 3,900 kg, and its lunar transfer orbit payload capacity from 3,750 kg to 3,780 kg.

Mission Profile

The Chang’e 5-T1 spacecraft was delivered from its fabrication facilities in Beijing to the Xichang Satellite Launch Centre (XSLC) on 10 August 2014. The fuelling of the Chang Zheng-3C launch vehicle stack began on 22 October. At 02:00 local time on 24 October (18:00 GMT on 23 October), the launch vehicle carrying the spacecraft lifted off from Launch Complex 2.

Change 5-T1 launch vehicle at Xichang

CZ-3B / Chang’e 5-T1 on launch pad at Xichang

The spacecraft was placed directly into a lunar transfer orbit (perigee: 413,000 km; apogee: 209 km). By 11:30 CST on 27 October, it had reached 60,000 km from the Moon. Flying along a circumlunar free-return trajectory around the Moon, the spacecraft reached the 12,000 km perilune point at around 03:00 on 28 October. Under the control of the Beijing Aerospace Command and Control Centre (BACC), the spacecraft captured images of the Moon and Earth.

‘Blue marble’ image of Earth captured by Chang’e 5-T1

After passing behind the Moon once, the spacecraft began its flight to Earth. The journey back to Earth took roughly four days, during which a series of course correction manoeuvres were conducted to precise targeting of the re-entry trajectory corridor chosen for the mission.

At 05:53 CST on 1 November, the return capsule was separated from the Service Module at about 5,000 from Earth. The Service Module performed a main engine burn to adjust its flight path. The return capsule continued flying for 20 minutes before beginning its atmospheric re-entry at a speed and trajectory that mimics that of a real lunar sample return mission —the primary objective of this mission.

The Chang’e 5-T1 return capsule performed a skip re-entry, where the craft made an initial entry to slow itself down and then climbed to atmospheric exit for a ballistic exospheric segment (‘skip’), before performing a second re-entry. Such a technique helped create greater entry range and slow the craft down before final entry, but require precision guidance due to its more complex trajectory compared with a conventional ballistic entry. The same technique was used by the Soviet Zond 6, 7 and 8 lunar probes. The Apollo Command Module also made similar pull-up segments (though not leaving the atmosphere) during its re-entry.

The craft made its initial entry at 06:11 CST and exited from communication blackout at 06:17. The second entry occurred at 06:22 and the craft exited from communication blackout at 06:26. The main parachute was deployed at 06:32. The total travel distance during the entire re-entry was 6,000 km.

At 06:42 CST (22:42 GMT on 31 October), the Chang’e 5-T1 return capsule safely landed in its targeted landing zone in the Siziwang  Banner Landing Site in Inner Mongolia.

Change 5-T1 capsule landing

Chang’e 5-T1 re-entry capsule after landing

Expanded Mission

After separating from the return capsule, the Chang’e 5-T1 Service Module returned to a highly elliptic orbit (perigee: 540,000 km; apogee: 600 km). Under the command of the ground control, on 23 November 2014 the spacecraft flew towards the Earth-Moon Second Lagrange Point (L2) and entered the parking orbit circling around L2 on 27 November. During its stay at L2, the spacecraft performed three orbit maintenance burns on 28 November, 12 December and 26 December.

After circling L2 three times, the spacecraft left L2 at 23:00 CST on 4 January 2015 and flew towards the Moon for the second-phase of the expanded mission. At 03:00 CST on 11 January, the spacecraft fired its thrusters to slow down and entered into a 5,300 km by 200 km lunar orbit. After three retrofire burns the spacecraft eventually settled in a 200 km circular lunar orbit — a manoeuvre to simulate the flight of the future Chang’e 5 Orbiter Module.

The third phase of the expanded mission began on 3 March. Under the command of the ground control, the Chang’e 5-T1 Service Module performed three retrofire burns to lower itself to an altitude of 18 km from the lunar surface, and then simulated the flight of the Chang’e 5 Lunar Sample Module taking off from the lunar surface to rendezvous and dock with the Orbiter Module in the lunar orbit. This phase of the expanded mission was completed on 7 March.

The follow-up expanded mission of the Chang’e 5-T1 Service Module was to include surveying the proposed landing spot of the future Chang’e 5 mission.

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