Determination of the Geopotential Difference between Atomic Clock Ensemble in Space (ACES) and Ground Station using the Tri-Frequency Combination (TFC) Method

2021 ◽  
Author(s):  
Mostafa Ashry ◽  
Wenbin Shen ◽  
Ziyu Shen ◽  
Hussein A. Abd-Elmotaal ◽  
Abdelrahim ruby ◽  
...  
Keyword(s):  
Natural Science ◽  
Doppler Effect ◽  
High Performance ◽  
Atomic Clock ◽  
Space Station ◽  
Earth Tide ◽  
Relativity Theory ◽  
Atomic Clocks ◽  
Clock Signal ◽  
Ku Band

<p>According to general relativity theory, a precise clock runs at different rates at positions with different geopotentials. Atomic Clock Ensemble in Space (ACES) is a mission using high-performance clocks and links to test fundamental laws of physics in space. The ACES microwave link (MWL) will make the ACES clock signal available to ground laboratories equipped with atomic clocks. The ACES-MWL will allow space-to-ground and ground-to-ground comparisons of atomic frequency standards. This study aims to apply the tri-frequency combination (TFC) method to determine the geopotential difference between the ACES and a first order triangulation station in Egypt. The TFC uses the uplink of carrier frequency 13.475 GHz (Ku band) and downlinks of carrier frequencies 14.70333 GHz (Ku band) and 2248 MHz (S-band) to transfer time and frequency. Here we present a simulation experiment. In this experiment, we use the international space station (ISS) orbit data, ionosphere and troposphere models, regional gravitational potential and geoid for Africa, solid Earth tide model, and simulated clock data by a conventionally accepted stochastic noises model. The scientific object requires stabilities of atomic clocks at least 3 × 10 <sup>−16</sup> /day, so we must consider various effects, including the Doppler effect, second-order Doppler effect, atmospheric frequency shift, tidal effects, refraction caused by the atmosphere, and Shapiro effect, with accuracy levels of decimetres. This study is supported by the National Natural Science Foundations of China (NSFC) under Grants 42030105, 41721003, 41804012, 41631072, 41874023, Space Station Project (2020)228, and the Natural Science Foundation of Hubei Province of China under Grant 2019CFB611.</p>

Test of gravitational redshift based on tri-frequency combination of frequency links between Atomic Clock Ensemble in Space and a ground station

2020 ◽  
Author(s):  
Xiao Sun ◽  
Wen-Bin Shen ◽  
Ziyu Shen ◽  
Chenghui Cai ◽  
Wei Xu ◽  
...  
Keyword(s):  
Natural Science ◽  
Doppler Effect ◽  
High Performance ◽  
Atomic Clock ◽  
Gravitational Redshift ◽  
Tidal Effects ◽  
Frequency Shifts ◽  
Ground Station ◽  
Shapiro Effect ◽  
Accuracy Level

<p>Atomic Clock Ensemble in Space (ACES) is an ESA mission designed mainly to test gravitational redshift with high-performance atomic clocks in space and on the ground. Here we develop tri-frequency combination (TFC) method based on the measurements of frequency shifts of three independent microwave links between ACES and a ground station. The potential scientific object requires an accuracy of at least 3×10<sup>-16</sup>, thus we need to consider various effects including Doppler effect, second-order Doppler effect, atmospheric frequency shift, tidal effects, refraction caused by atmosphere, Shapiro effect, with accuracy level of tens of centimeters. The ACES payload will be launched in middle of 2021, and the formulation proposed in this study will enable us to test gravitational redshift at an accuracy level at least 2×10<sup>-6</sup> level, one order more higher than the present accuracy level. This study is supported by NSFCs (grant Nos. 41721003, 41631072, 41874023, 41804012, 41429401, 41574007) and Natural Science Foundation of Hubei Province of China (grant No. 2019CFB611).</p>

The effect of the GNSS time transfer performance for geopotential difference determination

2021 ◽  
Author(s):  
Chenghui Cai ◽  
Wen-Bin Shen ◽  
Ziyu Shen ◽  
Wei Xu ◽  
Lei Wang
Keyword(s):  
Natural Science ◽  
Space Station ◽  
Satellite System ◽  
Relativity Theory ◽  
Time Transfer ◽  
Simulation Experiments ◽  
Good Opportunity ◽  
Free Running ◽  
Global Navigation Satellite ◽  
The Relationship

<p>The quick development of the global navigation satellite system (GNSS) time transfer technique provides a good opportunity to determine the geopotential difference based on the general relativity theory (GRT). In this study, we propose an approach that uses the precise point positioning (PPP) technique to directly compute clock offsets between two clocks at two arbitrary positions for the purpose of determining the geopotential difference and the accuracy of this approach depends not only on both the accuracies and stabilities of clocks, but also the time transfer technique itself. To validate the relationship between the performance of GNSS time transfer and the accuracy of this approach, simulation experiments are conducted.<strong> </strong>We evaluated the performances of GNSS time transfer in different cases using different type of free-running clocks, and results show that the proposed approach could be applied to testing GRT. This study was supported by the National Natural Science Foundations of China (grant Nos. 41721003, 42030105, 41804012, 41631072, 41874023, 41574007), Natural Science Foundation of Hubei Province of China (grant Nos. 2019CFB611), and Space Station Project (2020)228.</p>

FUNDAMENTAL PHYSICS ACTIVITIES IN THE HME DIRECTORATE OF THE EUROPEAN SPACE AGENCY

2007 ◽  
Vol 16 (12a) ◽  
pp. 1957-1966
Author(s):  
LUIGI CACCIAPUOTI ◽  
OLIVIER MINSTER
Keyword(s):  
Inertial Sensors ◽  
European Space Agency ◽  
Atomic Clock ◽  
Space Station ◽  
Matter Wave ◽  
Microgravity Environment ◽  
Atomic Clocks ◽  
Space Applications ◽  
Fundamental Physics ◽  
Space Agency

The Human Spaceflight, Microgravity, and Exploration (HME) Directorate of the European Space Agency is strongly involved in fundamental physics research. One of the major activities in this field is represented by the ACES (Atomic Clock Ensemble in Space) mission. ACES will demonstrate the high performances of a new generation of atomic clocks in the microgravity environment of the International Space Station (ISS). Following ACES, a vigorous research program has been recently approved to develop a second generation of atomic quantum sensors for space applications: atomic clocks in the optical domain, aiming at fractional frequency stability and accuracy in the low 10-18 regime; inertial sensors based on matter-wave interferometry for the detection of tiny accelerations and rotations; a facility to study degenerate Bose gases in space. Tests of quantum physics on large distance scales represent another important issue addressed in the HME program. A quantum communication optical terminal has been proposed to perform a test of Bell's inequalities on pairs of entangled photons emitted by a source located on the ISS and detected by two ground stations. In this paper, present activities and future plans will be described and discussed.

scholarly journals Test of gravitational red-shift based on tri-frequency combination of microwave frequency links

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Xiao Sun ◽  
Wen-Bin Shen ◽  
Ziyu Shen ◽  
Chenghui Cai ◽  
Wei Xu ◽  
...  
Keyword(s):  
Doppler Effect ◽  
Atomic Clock ◽  
Space Station ◽  
Microwave Frequency ◽  
Space Mission ◽  
Red Shift ◽  
Combination Method ◽  
Ground Station ◽  
Accuracy Level ◽  
Almost All

AbstractOver the decades, testing gravitational red-shift (GRS) based on microwave links has made great process, including the GPA experiment, the planned Atomic Clock Ensemble in Space mission, and the China Space Station (CSS). Until now, the formulations of microwave links are almost all based on the time comparison. However, there are advantages of using frequency comparison instead of time comparison to test GRS. Here we develop a tri-frequency combination method based on the measurements of the frequency shifts of three independent microwave links between a space station and a ground station. Aiming at the frequency links’ accuracy of $$3\times 10^{-16}$$ 3 × 10 - 16 , we should consider various effects, including the Doppler effect, second-order Doppler effect, atmospheric frequency shift, tidal effects, refraction caused by the atmosphere, and Shapiro effect, with accuracy levels of tens of centimeters. The CSS will complete construction in 2022, and the formulation proposed in this study will enable us to test GRS at an accuracy level of at least $$2\times 10^{-6}$$ 2 × 10 - 6 , which is one order higher than the present accuracy level of $$7\times 10^{-5}$$ 7 × 10 - 5 .

Geopotential Determination Between Ultra-Stable Distant Clocks Based on Two-Way Space Laser Time Transfer Links

2021 ◽  
Author(s):  
Abdelrahim Ruby ◽  
Wen-Bin Shen ◽  
Ahmed Shaker ◽  
Mostafa Ashry ◽  
Zhang Pengfei ◽  
...  
Keyword(s):  
Natural Science ◽  
Atomic Clock ◽  
Space Station ◽  
Signal Propagation ◽  
Gravity Potential ◽  
Time Transfer ◽  
Main Challenge ◽  
Satellite Links ◽  
Potential Applications ◽  
Beidou Satellites

<p>The Earth’s gravity potential (geopotential) field plays an important role in geodesy, for instance, it is the basis for defining the geoid and the International Height Reference System (IHRS). In chronometric geodesy, the main challenge for directly measuring geopotential differences between two stations lies in that a reliable link for time comparison is needed. Currently, most satellite links for time comparison are dealt with in the microwave domain, for which the ionospheric and tropospheric effects are major error sources that greatly influence the signal propagation compared to optical space links. Recently, accurate laser time transfer links between satellite and ground stations have already been planned and confirmed, such as Laser Time Transfer (LTT, China) on BeiDou satellites and Tiangong II / China's space station (CSS), Time Transfer by Laser Link (T2L2, French) on Jason-2 mission and European Laser Timing (ELT, Europe) on Atomic Clock Ensemble in Space (ACES). Therefore, in this study, we propose an approach for determining the geopotential difference between two ground atomic clocks based on the Two-way Laser Time Transfer (TWLTT) technique via a space station as a bridge, which could have potential applications in geoscience. This study is supported by the National Natural Science Foundations of China (NSFC) under Grants 42030105, 41721003, 41804012, 41631072, 41874023, Space Station Project (2020)228, and the Natural Science Foundation of Hubei Province of China under Grant 2019CFB611.</p>

Design of X-Ku band broadband high-performance and high-integration T / R module

2021 ◽  
Author(s):  
Yong-feng Gui ◽  
Lai-fu Jin ◽  
De-zhi Ding ◽  
Qi-lin Xie ◽  
Shi-wei Wu ◽  
...  
Keyword(s):  
High Performance ◽  
Ku Band

Magnetic carbon nanofibers containing uniformly dispersed Fe/Co/Ni nanoparticles as stable and high-performance electromagnetic wave absorbers

2014 ◽  
Vol 2 (40) ◽  
pp. 16905-16914 ◽  
Author(s):  
Jun Xiang ◽  
Jiale Li ◽  
Xionghui Zhang ◽  
Qin Ye ◽  
Jiahuan Xu ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Carbon Nanofibers ◽  
High Performance ◽  
Ni Nanoparticles ◽  
Absorption Properties ◽  
Electromagnetic Wave Absorption ◽  
Wave Absorption ◽  
Magnetic Carbon ◽  
Ku Band

Magnetic carbon nanofibers containing uniformly dispersed Fe/Co/Ni nanoparticles (CNF–M) exhibit excellent electromagnetic wave absorption properties from the C-band to the Ku-band.

Ku-band interferences for the Space Station multiple access link

2003 ◽  
Author(s):  
Y.C. Loh ◽  
K.P. Land ◽  
D. Arndt ◽  
S.W. Novosad
Keyword(s):  
Multiple Access ◽  
Space Station ◽  
Access Link ◽  
Ku Band

Determining gravity potential difference via VLBI time comparisons

2021 ◽  
Author(s):  
Yifan Wu ◽  
Wen-Bin Shen
Keyword(s):  
High Reliability ◽  
Space Station ◽  
Potential Difference ◽  
Gravity Potential ◽  
Atomic Clocks ◽  
Height System ◽  
Celestial Bodies ◽  
Excellent Work ◽  
Present Simulation ◽  
Comparison Technique

<p>VLBI technique plays important role in both astronomy and geodesy due its fantastic ability to determine the position of celestial bodies and the length of baseline on Earth. Moreover it also presents excellent work on time comparisons between atomic clocks located in remote positions where optical fiber links are not accessible. Due to its high reliability and stability, the information of Earth’s gravity field can be extracted from VLBI time comparisons in the framework of general relativity. In this study, we provide a formulation to determine the gravity potential difference by VLBI time comparisons. In fact the precision of the estimated gravity potential depends on the performance of participated clocks and the accuracy of time comparison technique. Thus we present simulation experiments using clocks with 10<sup>-16</sup>@1d stability and broadband VLBI observation and determine gravity potential difference within a VLBI network around world with 10 m<sup>2</sup>/s<sup>2 </sup>precision which is equivalent to 1 m in height. The results could be greatly improved using optical atomic clocks with much higher stabilities. Furthermore it can be applied to height transfer across oceans and unifying the height system. This study is supported by the National Natural Science Foundations of China (NSFC) under Grants 42030105, 41721003, 41804012, 41631072, 41874023, and Space Station Project (2020)228.</p>

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