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Queqiao

NSSDCA ID: QUEQIAO
COSPAR ID: 2018-045A

Description

Queqiao (or Queqaio 1) is the communications relay satellite for the Chang'e 4 lunar farside mission. It launched on 21 May 2018 and travelled to a halo orbit about the Earth-Moon L2 Lagrange point. From that position, it enabled communications between the Chang'e 4 lander on the lunar farside and the Earth. Launching with Queqiao were two scientific microsatellites, Longjiang-1 and Longjiang-2.

Spacecraft and Subsystems

The spacecraft is based on the CAST 100 small satellite platform, a rectilinear shaped, 1.4 x 1.4 x 0.85 meter bus. Total mass is 448.7 kg. The spacecraft is equipped with a 4.2 m diameter dish antenna for X-band communication, and a spiral S-band antenna. data rates to Earth can be up to 10 Mbits/s. Power of greater than 780 W is provided by a set of solar array wings composed of triple-junction GaAs solar cells and a 45 Ahr Li-ion storage battery with a 28 V power bus. Propulsion is a monopropellant hydrazine blow-down system, with four 20 N thrusters and twelve 5 N thrusters. 105 kg of propellant is held in two 70 liter tanks. The spacecraft is three-axis stabilized using four reaction wheels that can be desaturated by the thrusters, two star sensors, and two inertial measurement units.

In addition to its communication relay equipment, Queqiao will also carry the Netherlands-China Low Frequency Explorer (NCLE), a radio-astronomy experiment designed to measure radio emissions back to the early universe, study space weather, and observe the radio environment in the vicinity of the Earth and Moon. NLCE is described as a pathfinder experiment, experience with its operation and data is planned to be used to aid in the development of future radio astronomy instruments.

Mission Profile

Queqaio launched on 21 May 2018 at 5:28 a.m. local time (20 May 21:28 UT, 20 May 5:28 p.m. EDT) from Xichang Satellite Launch Center in China, on a Long March 4. After separation 1530 seconds after launch, and deployment of its solar arrays and antennas, Queqiao went into a lunar swingby transfer orbit to reach the L2 point. A braking maneuver at 100 km altitude from the Moon (203 m/s impulse for 912 s) put it into the correct trajectory for the L2 orbit insertion. It entered a halo orbit of roughly 35,000 km radius about the Earth-Moon L2 Lagrange point, a distance of 65,000 km from the Moon, with a 66 m/s delta-v burn on 14 June 2018. After entering orbit, Queqaio performed a number of on-orbit tests with Earth stations, and began communication with Chang'e 4 durign and after its landing on 3 January 2019. Communications continued throughout the Chang'e 4 mission, with X-band data rates of 125 bits/sec from Queqiao to Chang'e 4, and 555 kbits/s from the lander, and 285 kbits/s from the rover, to Queqaio.

Longjiang-1 and -2

The Longjiang-1 and -2 microsatellites each have a mass of 47 kg and carry radio astronomy instrumentation. Longjiang-2 also carried a Saudi Arabian built camera. The plan was to fly the satellites in close 300 x 3000 km orbits to permit astronomical interferometry, but Longjiang-1 failed to enter lunar orbit. Longjiang-2 entered a 350 x 13700 km altitude lunar orbit on 25 May. The microsatellites were developed by the Harbin Institute of Technology.

Queqiao means "Bridge of Magpies" referring to a Chinese folktale about magpies forming a bridge with their wings to allow Zhi Nu, the seventh daughter of the Goddess of Heaven, to reach her husband. Longjiang means "dragon river".

Alternate Names

  • 43470

Facts in Brief

Launch Date: 2018-05-20
Launch Vehicle: Long March 4
Launch Site: Xichang, Peoples Republic of China
Mass: 448.7 kg
Nominal Power: 780 W

Funding Agency

  • China National Space Administration (Peoples Republic of China)

Discipline

  • Planetary Science

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
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