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 .

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>

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>

scholarly journals MULTI-CHANNEL FRY COUNTER DESIGN USING OPTOCOUPLER SENSOR

2019 ◽  
Vol 4 (2) ◽  
pp. 97-104
Author(s):  
Lazuardi Umar ◽  
Yanuar Hamzah ◽  
Rahmondia N. Setiadi
Keyword(s):  
Counting Process ◽  
Production Capacity ◽  
High Accuracy ◽  
Limited Capacity ◽  
High Concentration ◽  
Counting System ◽  
Channel Detection ◽  
Accuracy Level ◽  
High Level ◽  
Almost All

This paper describes a design of a fry counter intended to be used by consuming fish farmer. Along this time, almost all the fry counting process is counted by manual, which is done by a human. It is requiring much energy and needs high concentration; thus, can cause a high level of exhaustion for the fry counting worker. Besides that, the human capability and capacity of counting are limited to a low level. A fry counter design in this study utilizes a multi-channel optocoupler sensor to increase the counting capacity. The multi-channel fry counter counting system is developed as a solution to a limited capacity of available fry counter. This design uses an input signal extender system on controller including the interrupt system. From the experiment, high accuracy level is obtained on the counting and channel detection, therefore, this design can be implemented and could help farmers to increase the production capacity of consuming fish.

An improved approach for testing gravitational redshift via spacecraft based three frequency links combination

2021 ◽  
Author(s):  
Ziyu Shen ◽  
Wen-Bin Shen ◽  
Lin He ◽  
Tengxu Zhang ◽  
Zhan Cai
Keyword(s):  
International Space Station ◽  
Gravitational Potential ◽  
Natural Science ◽  
Space Station ◽  
Gravitational Redshift ◽  
New Approach ◽  
International Space ◽  
Hardware Requirement ◽  
Ground Station ◽  
Gravity Probe

<p>We propose a new approach for testing the gravitational redshift based on frequency signals transmission between a spacecraft and a ground station. By a combination of one uplink signal and two downlink signals, the gravitational redshift can be tested at about 6.5×10<sup>-6</sup> level for a GNSS satellite (the signals’ frequencies are about 1.2~1.6 GHz), and about 2.2×10<sup>-6</sup> level for the International Space Station (the signals’ frequencies are up to 14.7 GHz), under the assumption that the clock accuracy is about 10<sup>-17</sup> level. For better desinged cases the accuracy of gravitational redshift test can be improved to several parts in 10<sup>-8</sup> level (the signals’ frequencies are about 8~12 GHz). Compared to the scheme of Gravity Probe-A (GP-A) experiment conducted in1976, the new approach does not require any onboard signal transponders, and the frequency values of the three links can be quite arbitrarily given. As the hardware requirement is reduced, a number of spacecrafts could be chosen as candidates for a gravitational redshift experiment. This approach could also be used in gravitational potential determination, which has prospective applications in geodesy. This study is supported by National Natural Science Foundation of China (NSFC) (grant Nos. 42030105, 41721003, 41631072, 41874023, 41804012), Space Station Project (2020)228, and Natural Science Foundation of Hubei Province(grant No. 2019CFB611).</p>

Optimized Space  Station CV Method and Its Differences from GNSS CV

2020 ◽  
Author(s):  
Yinhua Liu ◽  
Xiaohui Li
Keyword(s):  
Atomic Clock ◽  
Space Station ◽  
Satellite System ◽  
Comparison Method ◽  
Space System ◽  
Common View ◽  
Near Earth Space ◽  
Clock System ◽  
Blind Area ◽  
Global Navigation Satellite

Abstract There will be better atomic clock system and micro-wave time comparison link in the near earth space station, like Chinese Space Station and European ACES(Atomic Clock Ensemble in Space) system, than those in the GNSS(Global Navigation satellite System) satellites. Therefore, the space station common-view (CV) will realize more accurate time comparison than GNSS CV in theory. But due to the orbit characteristic of the space station, there are some limitations if traditional GNSS CV time comparison method is applied to the space station. In order to solve these problems, the GNSS CV method is optimized and the method that is appropriate for the space station is proposed. First, the basic CV principle is analyzed, and the delay items which are needed to be considered for GNSS and space station CV are compared and analyzed. Then, the differences between GNSS and space station CV are studied, and the influences of orbit error on these two CV methods are analyzed in detail. The GNSS CV method is optimized to be fit for the space station next. Finally, the performance of the optimized method is validated by simulated experiments. The simulation results show that the space station time comparison accuracy of several tens of picoseconds can be obtained by the optimized method. Furthermore, the problem of CV blind area is solved by the optimized method effectively.

scholarly journals EARLINET evaluation of the CATS L2 aerosol backscatter coefficient product

2019 ◽  
Author(s):  
Emmanouil Proestakis ◽  
Vassilis Amiridis ◽  
Eleni Marinou ◽  
Ioannis Binietoglou ◽  
Albert Ansmann ◽  
...  
Keyword(s):  
Space Station ◽  
Backscatter Coefficient ◽  
Backscatter Signal ◽  
Evaluation Activity ◽  
Ground Station ◽  
Free Relative ◽  
Climate Studies ◽  
Aerosol Backscatter ◽  
Level 2 ◽  
Good Agreement

Abstract. We present the evaluation activity of the European Aerosol Research Lidar Network (EARLINET) for the quantitative assessment of the Level 2 aerosol backscatter coefficient product derived by the Cloud-Aerosol Transport System (CATS) onboard the International Space Station (ISS). The study employs correlative CATS and EARLINET backscatter measurements within 50 km distance between the ground station and the ISS overpass and as close in time as possible, typically within 90 min, from February 2015 to September 2016. The results demonstrate the good agreement of CATS Level 2 backscatter coefficient and EARLINET. Three ISS overpasses close to the EARLINET stations of Leipzig-Germany, Évora-Portugal and Dushanbe-Tajikistan are analysed here to demonstrate the performance of CATS lidar system under different conditions. The results show that under cloud-free, relative homogeneous aerosol conditions CATS is in good agreement with EARLINET, independently of daytime/nighttime conditions. CATS low negative biases, partially attributed to the deficiency of lidar systems to detect tenuous aerosol layers of backscatter signal below the minimum detection thresholds, may lead to systematic deviations and slight underestimations of the total Aerosol Optical Depth (AOD) in climate studies. In addition, CATS misclassification of aerosol layers as clouds, and vice versa, in cases of coexistent and/or adjacent aerosol and cloud features, may lead to non-representative, unrealistic and cloud contaminated aerosol profiles. The distributions of backscatter coefficient biases show the relatively good agreement between the CATS and EARLINET measurements, although on average underestimations are observed, 22.3 % during daytime and 6.1 % during nighttime.

General relativity tests with space clocks in highly elliptic orbits

2017 ◽  
Vol 26 (05) ◽  
pp. 1741014 ◽  
Author(s):  
Philippe Jetzer
Keyword(s):  
Equivalence Principle ◽  
Atomic Clock ◽  
Space Mission ◽  
The Other ◽  
Crucial Importance ◽  
Hydrogen Maser ◽  
Elliptic Orbits ◽  
Satellite Experiment ◽  
Fundamental Forces ◽  
Microwave Link

The test of the Einstein Equivalence Principle (EEP) is of crucial importance as a deviation from it could hint to quantum effects in gravity or to unification with the other fundamental forces. One aspect of EEP is the local position invariance (LPI), which can be tested by measuring the gravitational red-shift. As an example of a possible space mission which could test the EEP, we will discuss a recently proposed satellite experiment, Einstein Gravitational RedShift Probe (E-GRIP), with the aim to test LPI using an hydrogen maser atomic clock on a highly elliptic orbit around Earth and compare the on-board clock to clocks located on Earth via a microwave link.

ATOMIC CLOCK ENSEMBLE IN SPACE: AN UPDATE

2007 ◽  
Vol 16 (12b) ◽  
pp. 2511-2523 ◽  
Author(s):  
C. SALOMON ◽  
L. CACCIAPUOTI ◽  
N. DIMARCQ
Keyword(s):  
Atomic Clock ◽  
Space Station ◽  
Microgravity Environment ◽  
Time Base ◽  
Standard Model Extension ◽  
Fundamental Physics ◽  
Frequency Standards ◽  
Stability And Accuracy ◽  
Microwave Link ◽  
New Generation

Atomic Clock Ensemble in Space (ACES) is a mission in fundamental physics that will operate a new generation of atomic clocks in the microgravity environment of the International Space Station. Fractional frequency stability and accuracy of a few parts in 1016 will be achieved. The on-board time base, distributed on the Earth via a microwave link, will be used to perform space-to-ground as well as ground-to-ground comparisons of atomic frequency standards. Based on these comparisons, ACES will perform fundamental physics tests (Einstein's theories of special and general relativity, the search for drift of fundamental constants, the Standard Model extension and tests of string theories) and develop applications in time and frequency metrology, time scales, geodesy, global positioning and navigation. After an overview of the mission concept and its scientific objectives, the present status of ACES instruments and subsystems will be discussed.

Making Space for Islam: Religion, Science, and Politics in Contemporary Malaysia

2010 ◽  
Vol 69 (4) ◽  
pp. 1143-1166 ◽  
Author(s):  
Darren C. Zook
Keyword(s):  
International Space Station ◽  
International Politics ◽  
Outer Space ◽  
Space Station ◽  
Religious Practice ◽  
Space Mission ◽  
International Space ◽  
Science And Politics ◽  
Cooperative Venture

In October 2007, Malaysia celebrated sending its first astronaut into space, as part of a cooperative venture on board a Russian space mission. As Malaysia's first astronaut was a Muslim, the Malaysian government commissioned, through its Department of Islamic Development, a project to create a definitive set of guidelines for the practice of Islam in outer space, specifically on board the International Space Station. What may on the surface appear to be a practical exercise in clarifying religious practice reveals upon closer examination to be a complex restructuring of Malaysia's domestic and international politics, with the role of Islam as the catalytic and somewhat controversial centerpiece.

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