scholarly journals Development and Prospect of Chinese Lunar Relay Communication Satellite

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Lihua Zhang
Keyword(s):  
Libration Point ◽  
Satellite System ◽  
Polar Regions ◽  
South Pole ◽  
Soft Landing ◽  
Communication Support ◽  
Communication Satellite ◽  
Relay Communication ◽  
Exploration Mission ◽  
Operation Status

Relay communication satellites play a very important role on the lunar far side and pole areas exploration missions. Queqiao relay communication satellite was developed to provide relay communication support for the lander and the rover of Chang’e-4 mission landing on the far side of the Moon. From entering into the halo mission orbit around Earth-Moon libration point 2 on June 14, 2018, it has operated on the orbit more than thirty months. It worked very well and provided reliable, continuous relay communication support for the lander and the rover to accomplish the goals of Chang’e-4 lunar far side soft landing and patrol exploration mission. Exploration of the lunar south polar regions is of high scientific interest. A new relay communication satellite for Chinese south pole exploration mission is also under study. The system design and on-orbit operation status of Queqiao relay communication satellite were summarized in this paper. The system concept of the relay communication satellite for lunar south pole exploration missions is proposed. Finally, the future development and prospect of the lunar relay communication satellite system are given.

scholarly journals Technical characteristics of the relay communication satellite “Queqiao” for Chang’e-4 lunar farside exploration mission

2019 ◽  
Vol 49 (2) ◽  
pp. 138-146 ◽  
Author(s):  
LiHua ZHANG ◽  
Liang XIONG ◽  
Ji SUN ◽  
Shan GAO ◽  
XiaoLei WANG ◽  
...  
Keyword(s):  
Communication Satellite ◽  
Lunar Farside ◽  
Relay Communication ◽  
Exploration Mission

scholarly journals Spatial and Temporal Sampling of Polar Regions from Two-Satellite System on Molniya Orbit

2011 ◽  
Vol 28 (8) ◽  
pp. 977-992 ◽  
Author(s):  
Alexander P. Trishchenko ◽  
Louis Garand
Keyword(s):  
Temporal Resolution ◽  
Arctic Region ◽  
Satellite System ◽  
Elliptical Orbit ◽  
High Temporal Resolution ◽  
Polar Regions ◽  
Temporal Sampling ◽  
Continuous Coverage ◽  
Depth Analysis

Abstract There has been a significant increase of interest in the building of a comprehensive Arctic observing system in recent years to properly and timely track the environmental and climate processes in this vast region. In this regard, a satellite observing system on highly elliptical orbit (HEO) with 12-h period (Molniya type) is of particular interest, because it enables continuous coverage of the entire Arctic region (58°–90°N) from a constellation of two satellites. Canada is currently proposing to operate such a constellation by 2017. Extending the pioneering study of S. Q. Kidder and T. H. Vonder Haar, this paper presents in-depth analysis of spatiotemporal sampling properties of the imagery from this system. This paper also discusses challenges and advantages of this orbit for various applications that require high temporal resolution and angular sampling.

Comparison of Tropospheric Zenith Wet Delay from VLBI and GNSS Estimations

2021 ◽  
Author(s):  
Vicky Jia Liu ◽  
Maaria Nordman ◽  
Nataliya Zubko
Keyword(s):  
Time Series ◽  
Seasonal Variations ◽  
Elevation Angle ◽  
Correlation Coefficients ◽  
Satellite System ◽  
Tropospheric Delay ◽  
Polar Regions ◽  
Long Baseline ◽  
Zenith Wet Delay ◽  
Space Geodetic Techniques

<p>Tropospheric delay is one of the major error sources for space geodetic techniques such as Very Long Baseline Interferometry (VLBI) and Global Navigation Satellite System (GNSS). In this study, we compared the agreement of tropospheric zenith wet delay (ZWD) seasonal variations derived from VLBI and GNSS observations at 8 stations that are located at all around the globe. We have analysed time series of 8 years, starting in 2012 until end of 2019. Results show that VLBI_ZWD present clear seasonal variations which depend on the location of each station, in the tropics the variability is more pronounced than in mid-latitudes or polar regions. Furthermore, the VLBI_ZWD also shows a reasonably good agreement with seasonal fit model. When comparing zenith wet delays derived from co-located GNSS and VLBI stations at  cut-off elevation angle, they agree quite well, which is proved by the high correlation coefficients, varying from 0.6 up to 0.95. The biases between the techniques are in mm level and standard errors of the whole time series are in few centimetres.</p>

scholarly journals Research on Absolute Calibration of GNSS Receiver Delay through Clock-Steering Characterization

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6063
Author(s):  
Feng Zhu ◽  
Huijun Zhang ◽  
Luxi Huang ◽  
Xiaohui Li ◽  
Ping Feng
Keyword(s):  
Measurement Errors ◽  
Periodic Variation ◽  
Satellite System ◽  
Absolute Calibration ◽  
Universal Method ◽  
Gnss Receiver ◽  
Combined Uncertainty ◽  
Zero Baseline ◽  
Global Navigation Satellite ◽  
Operation Status

The receiver delay has a significant impact on global navigation satellite system (GNSS) time measurement. This article comprehensively analyzes the difficulty, composition, principle, and calculation of GNSS receiver delay. A universal method, based on clock-steering characterization, is proposed to absolutely calibrate all types of receivers. We use a hardware simulator to design several experiments to test the performance of GNSS receiver delay for different receiver types, radio frequency (RF) signals, operation status and time-to-phase (TtP). At first, through the receivers of Novatel and Septentrio, the channel delay of Septentrio is 2 ns far lower than 65 ns for Novatel, and for the inter-frequency bias of GLONASS L1, Septentrio tends to increase within 10 ns compared with decreasing of Novatel within 5 ns. Secondly, a representative receiver of UniNav-BDS (BeiDou) is chosen to test the influence of Ttp which may be ignored by users. Under continuous operation, the receiver delay shows a monotone reduction of 10 ns as TtP increased by 10 ns. However, under on-off operation, the receiver delay represents periodic variation. Through a zero-baseline comparison, we verifies the relation between receiver delay and TtP. At last, the article analyzes instrument errors and measurement errors in the experiment, and the combined uncertainty of absolute calibration is calculated with 1.36 ns.

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