Queqiao-2 relay satellite

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Queqiao 2
Rendering of Queqiao 2 satellite
Mission typeCommunication relay
Radio astronomy
OperatorCNSA
COSPAR ID2024-051A (QUEQIAO-2)
SATCAT no.59274
Mission durationPlanned: 8-10 years
1 month, 7 days (in progress)
Spacecraft properties
BusCAST-2000[1]
ManufacturerDFH Satellite Company LTD
Dry mass1,200 kilograms (2,600 lb)
DimensionsAntenna: 4.2 metres (14 ft) in diameter[1]
Power1350W[1]
Start of mission
Launch date20 March 2024, 00:31:28 UTC[2]
RocketLong March 8[2]
Launch siteWenchang Space Launch Site LC-2[2]
Orbital parameters
Reference system
Selenocentric frozen orbit
Periselene altitude200 km (120 mi)[3]
Aposelene altitude16,000 km (9,900 mi)[3]
Inclination62.4°[4]
Period24 hours[3]
Lunar orbiter
Orbital insertion24 March 2024, 17:05 UTC[5]
Instruments
  • Grid-based Energetic Neutral Atom imager (GENA)
  • Extreme
    Queqiao

Queqiao-2 relay satellite (Chinese: 鹊桥二号中继卫星; pinyin: Quèqiáo èr hào zhōngjì wèixīng; lit. 'Magpie Bridge 2 relay satellite'), is a second of the two communications relay and radio astronomy satellites designed to support the fourth phase the Chinese Lunar Exploration Program.[6][7][8] The China National Space Administration (CNSA) launched the Queqiao-2 relay satellite on 20 March 2024 to a elliptical frozen orbit around the Moon to support communications from the far side of the Moon and the Lunar south pole.[9][10][11][12]

The name Queqiao ("Magpie Bridge") was inspired by and came from the Chinese tale The Cowherd and the Weaver Girl.[9][8][13]

Background and mission planning

The initial phase of the

Queqiao so far only had to connect with two probes on the far side of the Moon (Chang'e 4 lander and Yutu-2 rover), future mission would include more workload, with up to ten robots being active on the moon for the ILRS project, which requires a complex and sophisticated communication network.[15]

The

Apollo crater on the far side of the Moon.[15]

Although the first Queqiao can provide the unique function of relaying constant communications to and from the far side of the Moon, aided by Chinese Deep Space Network, its halo orbits around the Earth-Moon L1 and L2 were inherently unstable[18] and requires the satellite to consumes 80 g (2.8 oz) of fuel for a small orbit correction maneuver approximately every 9 days. Therefore, a frozen elliptic orbit around the Moon itself was chosen for Queqiao 2 due to its more stable nature. The frozen elliptic orbit can provide visual contact with the Moon for eight hours, i.e., two-thirds of its 12-hour orbit, since the point of its periselene lies above the side of the southern polar region facing away from the Earth.[19]

When Queqiao-2 reaches a position about 200 km from the lunar surface, it will perform capture braking and enter a lunar parking orbit of 200 × 100,000 km with a period of about 10 days. Eventually, Queqiao-2 will enter a large elliptical frozen orbit of 200 × 16,000 km with a period of 24 hours, which is inclined at 62.4° to the equator, no further orbit correction maneuvers are necessary for a period of a good 10 years, i.e., in principle the assumed lifespan of the satellite.[3]

Design

Orbital regime of Queqiao-2 satellite

Queqiao 2 relay satellite and radio observatory is based on the CAST 2000 bus from

solar arrays, deliver a total output of 1350 W, the operating voltage is 30.5 V. During blackoutor eclipse period, it has accumulators with a charge storage capacity of 135 Ah. The manufacturing company assumes that Queqiao 2 will work properly for at least 8 to 10 years.[21][22]

Adopted from the first Queqiao, a

upper stage of the rocket and unfolding the solar modules, the antenna is also unfolded at the beginning of the transfer orbit to the Moon.[9][23][24][21][25][1]

Communication with the lunar surface is accomplished in the X band, using a high-gain 4.2 metres (14 ft) deployable parabolic antenna, the largest antenna used for a deep space exploration satellite.[26]

The large

Mbit/s when using a parabolic antenna. The signals are then demodulated and decoded in the satellite.[6]

The

data transfer rate is on average 100 Mbit/s. The antenna used is a small parabolic antenna with a diameter of 0.6 m in a gimbal suspension, which is mounted on the nadir side of the satellite bus on a fold-out arm that allows it to protrude above the large parabolic antenna.[9][22]

angular position.[22]

The systems are alternately redundant. In the event of a failure of the S-band system, the telemetry and control signals can also be transmitted via the Ka band, and if the Ka band signals are subject to strong

surface of the Moon with high accuracy.[8]

Scientific payloads

There are three scientific payloads on the spacecraft:[27][28]

  • Grid-based Energetic Neutral Atom imager (GENA):
    magnetotail.[27][28]
  • Extreme Ultraviolet Camera (EUC).[27][28]
  • Lunar Orbit
    transit time difference between the satellite and the terrestrial radio telescope for a given signal and thus calculate the position of the radio source or the spacecraft (the position of the satellite itself can be determined with an accuracy of 30 m), the satellite has an atomic clock with a maximum deviation of 10 −12 per second or 10 −14 per day. The receiver and clock together have a mass of 45 kg (99 lb) and have an average power consumption of 220 W.[27][28]

Mission

UTC,[33] where it is expected to operate for 8–10 years and by using a elliptical frozen orbit of 200 km × 16,000 km with an inclination of 62.4°,[3] instead of the L2 halo orbit.[34][35]

The initial mission of Queqiao-2 is to provide relay communication support for Chang'e 6. After Chang'e 6 completes its mission, it will adjust its orbit to provide services for Chang'e-7, Chang'e-8 and subsequent lunar exploration missions. In the future, Queqiao-2 will also work with Chang'e 7 and Chang'e 8 to build the International Lunar Research Station.[8]

Queqiao-2 also carries two smaller

laser ranging are inter-satellite microwave ranging are to be carried out by these satellites via high-precision lunar orbit determination technology.[38][8][39]

On 12 April 2024, CNSA announced that Queqiao-2 had successfully completed in-orbit communication tests with Chang'e 4 on the far side of the moon and the Chang'e 6 probe while still on the ground. The satellite entered its targeted elliptical orbit on 2 April after a correction midway, near-moon braking and orbital manoeuvre around the moon. It facilitates communication between Earth and lunar probes signaling China's commitment to space exploration and international cooperation.[40]

Comparison of relay satellites

Here is a comparison of some of the key differences of the two lunar relay satellites:[1][9][10][11][12][3][4]

Queqiao Queqiao 2
Bus CAST 100 CAST 2000
Mass 449 kg (990 lb) 1,200 kg (2,600 lb)
Power Supply 4 solar panels, total 800 W 4 solar panels, total 1350 W
Accumulator 45 Ah 135 Ah
Orbit Earth-Moon L2 Halo orbit
at 65,000 km from Moon		 Elliptical orbit around moon of
200 × 16,000 km at 62.4°
orbital period 14 days 24 hours
Line of sight of surface
probes		 always every 20 in 24 hours
No. of surface probes
monitored		 2 10
Antenna X-band parabolic antenna 4.2 m
S-band spiral antenna		 X-band parabolic antenna 4.2 m
4 S-band omni-directional antennas
UHF omni-directional antenna
Ka-band parabolic antenna 0.6 m
Satellite to lunar surface
probes communication		 X-Band 125 bit/s X-Band 1 kbit/s
Satellite to lunar surface
probes communication		 X-Band 555 kbit/s X-Band 5 Mbit/s
Satellite to and fro
Earth communication		 S-Band 4 Mbit/s Ka-Band 100 Mbit/s
Start of operation 2018 2024
End of operation 2026 (expected) 2034 (expected)

References

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  3. ^ a b c d e f Lihua Zhang (2024-03-20). "月亮之上"梦想绽放" 增强现实+AI生成技术揭秘鹊桥二号发射全程" (in Simplified Chinese). 央视网. Retrieved 2024-03-23.
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