scholarly journals Centimeter-Level Orbit Determination for TG02 Spacelab Using Onboard GNSS Data

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2671 ◽  
Author(s):  
Kai Li ◽  
Xuhua Zhou ◽  
Wenbin Wang ◽  
Yang Gao ◽  
Gang Zhao ◽  
...  
Keyword(s):  
Orbit Determination ◽  
Dynamic Method ◽  
Precise Orbit Determination ◽  
Low Earth Orbit ◽  
Dual Frequency ◽  
Phase Measurements ◽  
Gnss Data ◽  
Cross Track ◽  
Along Track ◽  
Reduced Dynamic

Tiangong-2, the second Chinese manned spacecraft, was launched into low Earth orbit on 15 September 2016. The dual-frequency geodetic GNSS receiver equipped on it is supporting a number of scientific experiments in orbit. This paper uses the onboard GNSS data from 3–31 December 2016 (in the attitude mode of three-axis Earth-pointing stabilization) to analyze the data quantity, as well as the code multipath error. Then, the dynamic and reduced-dynamic methods are adopted to perform the post Precise Orbit Determination (POD) based on the carrier phase measurements, respectively. After that, the orbit accuracy is evaluated using a number of tests, which include the analysis of observation residuals, Overlapping Orbit Differences (OODs), orbit comparison between dynamic and reduced-dynamic and Satellite Laser Ranging (SLR) validation. The results show that: (1) the average Root Mean Square (RMS) of the on-board GNSS phase fitting residuals is 8.8 mm; (2) regarding the OODs determined by the reduced-dynamic method, the average RMS in radial (R), along-track (T) and cross-track (N) directions is 0.43 cm, 1.34 cm and 0.39 cm, respectively, and there are no obvious system errors; (3) the orbit accuracy of TG02 determined by the reduced-dynamic method is comparable to that of the dynamic method, and the average RMS of their differences in R, T, N and 3D directions is 3.05 cm, 3.60 cm, 2.52 cm and 5.40 cm, respectively; (4) SLR data are used to validate the reduced-dynamic orbits, and the average RMS along the station-satellite direction is 1.94 cm. It can be seen that both of these two methods can meet the demands of 3D centimeter-level orbit determination for TG02.

Comparison of precise orbit determination methods of zero-difference kinematic, dynamic and reduced-dynamic of GRACE-A satellite using SHORDE software

2017 ◽  
Vol 11 (3) ◽  
Author(s):  
Kai Li ◽  
Xuhua Zhou ◽  
Nannan Guo ◽  
Gang Zhao ◽  
Kexin Xu ◽  
...  
Keyword(s):  
Orbit Determination ◽  
Precise Orbit Determination ◽  
Low Earth Orbit ◽  
Phase Measurements ◽  
Perturbation Model ◽  
Precise Orbit ◽  
Average Accuracy ◽  
Low Earth Orbit Satellites ◽  
Gps Observations ◽  
Reduced Dynamic

AbstractZero-difference kinematic, dynamic and reduced-dynamic precise orbit determination (POD) are three methods to obtain the precise orbits of Low Earth Orbit satellites (LEOs) by using the on-board GPS observations. Comparing the differences between those methods have great significance to establish the mathematical model and is usefull for us to select a suitable method to determine the orbit of the satellite. Based on the zero-difference GPS carrier-phase measurements, Shanghai Astronomical Observatory (SHAO) has improved the early version of SHORDE and then developed it as an integrated software system, which can perform the POD of LEOs by using the above three methods. In order to introduce the function of the software, we take the Gravity Recovery And Climate Experiment (GRACE) on-board GPS observations in January 2008 as example, then we compute the corresponding orbits of GRACE by using the SHORDE software. In order to evaluate the accuracy, we compare the orbits with the precise orbits provided by Jet Propulsion Laboratory (JPL). The results show that: (1) If we use the dynamic POD method, and the force models are used to represent the non-conservative forces, the average accuracy of the GRACE orbit is 2.40cm, 3.91cm, 2.34cm and 5.17cm in radial (R), along-track (T), cross-track (N) and 3D directions respectively; If we use the accelerometer observation instead of non-conservative perturbation model, the average accuracy of the orbit is 1.82cm, 2.51cm, 3.48cm and 4.68cm in R, T, N and 3D directions respectively. The result shows that if we use accelerometer observation instead of the non-conservative perturbation model, the accuracy of orbit is better. (2) When we use the reduced-dynamic POD method to get the orbits, the average accuracy of the orbit is 0.80cm, 1.36cm, 2.38cm and 2.87cm in R, T, N and 3D directions respectively. This method is carried out by setting up the pseudo-stochastic pulses to absorb the errors of atmospheric drag and other perturbations. (3) If we use the kinematic POD method, the accuracy of the GRACE orbit is 2.92cm, 2.48cm, 2.76cm and 4.75cm in R, T, N and 3D directions respectively. In conclusion, it can be seen that the POD of GRACE satellite is practicable by using different strategies and methods. The orbit solution is well and stable, they all can obtain the GRACE orbits with centimeter-level precision.

scholarly journals Integrity monitoring for precise orbit determination of LEO satellites

GPS Solutions ◽  
2021 ◽  
Vol 26 (1) ◽  
Author(s):  
Kan Wang ◽  
Ahmed El-Mowafy ◽  
Chris Rizos
Keyword(s):  
Real Time ◽  
Orbit Determination ◽  
Precise Orbit Determination ◽  
High Accuracy ◽  
Dynamic Mode ◽  
Average Case ◽  
Leo Satellites ◽  
Cross Track ◽  
Along Track ◽  
Reduced Dynamic

AbstractDue to an increasing requirement for high accuracy orbital information for low Earth orbit (LEO) satellites, precise orbit determination (POD) of LEO satellites is a topic of growing interest. To assure the safety and reliability of the applications requiring high accuracy LEO orbits in near-real-time, integrity monitoring (IM) is an essential operation of the POD process. In this contribution, the IM strategy for LEO POD in both the kinematic and reduced-dynamic modes is investigated. The overbounding parameters of the signal-in-space range error are investigated for the GPS products provided by the International GNSS Service’s Real-Time Service and the Multi-GNSS Advanced Demonstration of Orbit and Clock Analysis service. Benefiting from the dynamic models used and the improved model strength, the test results based on the data of the LEO satellite GRACE FO-1 show that the average-case mean protection levels (PLs) can be reduced from about 3–4 m in the kinematic mode to about 1 m in the reduced-dynamic mode in the radial, along-track and cross-track directions. The overbounding mean values of the SISRE play the dominant role in the final PLs. In the reduced-dynamic mode and average-case projection, the IM availabilities reach above 99% in the radial, along-track and cross-track directions with the alert limit (AL) set to 2 m. The values are still above 98% with the AL set to 4 m, when the duty cycle of tracking is reduced to 40%, e.g., in the case of power limits for miniature satellites such as CubeSats.

scholarly journals Precise Orbit Determination for GNSS Maneuvering Satellite with the Constraint of a Predicted Clock

2019 ◽  
Vol 11 (16) ◽  
pp. 1949 ◽  
Author(s):  
Xiaolei Dai ◽  
Yidong Lou ◽  
Zhiqiang Dai ◽  
Caibo Hu ◽  
Yaquan Peng ◽  
...  
Keyword(s):  
Orbit Determination ◽  
Precise Orbit Determination ◽  
Satellite System ◽  
Navigation Satellite ◽  
Precise Orbit ◽  
Gps Satellites ◽  
Global Navigation Satellite ◽  
Cross Track ◽  
Along Track ◽  
Backward Integration

Precise orbit products are essential and a prerequisite for global navigation satellite system (GNSS) applications, which, however, are unavailable or unusable when satellites are undertaking maneuvers. We propose a clock-constrained reverse precise point positioning (RPPP) method to generate the rather precise orbits for GNSS maneuvering satellites. In this method, the precise clock estimates generated by the dynamic precise orbit determination (POD) processing before maneuvering are modeled and predicted to the maneuvering periods and they constrain the RPPP POD during maneuvering. The prediction model is developed according to different clock types, of which the 2-h prediction error is 0.31 ns and 1.07 ns for global positioning system (GPS) Rubidium (Rb) and Cesium (Cs) clocks, and 0.45 ns and 0.60 ns for the Beidou navigation satellite system (BDS) geostationary orbit (GEO) and inclined geosynchronous orbit (IGSO)/Median Earth orbit (MEO) satellite clocks, respectively. The performance of this proposed method is first evaluated using the normal observations without maneuvers. Experiment results show that, without clock-constraint, the average root mean square (RMS) of RPPP orbit solutions in the radial, cross-track and along-track directions is 69.3 cm, 5.4 cm and 5.7 cm for GPS satellites and 153.9 cm, 12.8 cm and 10.0 cm for BDS satellites. When the constraint of predicted satellite clocks is introduced, the average RMS is dramatically reduced in the radial direction by a factor of 7–11, with the value of 9.7 cm and 13.4 cm for GPS and BDS satellites. At last, the proposed method is further tested on the actual GPS and BDS maneuver events. The clock-constrained RPPP POD solution is compared to the forward and backward integration orbits of the dynamic POD solution. The resulting orbit differences are less than 20 cm in all three directions for GPS satellite, and less than 30 cm in the radial and cross-track directions and up to 100 cm in the along-track direction for BDS satellites. From the orbit differences, the maneuver start and end time is detected, which reveals that the maneuver duration of GPS satellites is less than 2 min, and the maneuver events last from 22.5 min to 107 min for different BDS satellites.

Data pre-processing for ionosphere TEC retrieval based on DORIS observations

2020 ◽  
Author(s):  
Shaocheng Zhang ◽  
Wei Li ◽  
Fei Yin ◽  
Hongfei Gou
Keyword(s):  
Precise Orbit Determination ◽  
Low Earth Orbit ◽  
Cycle Slip ◽  
Dual Frequency ◽  
Phase Measurements ◽  
Cycle Slip Detection ◽  
Low Earth Orbit Satellites ◽  
Signal Path ◽  
Leo Satellite

<p><strong> </strong>DORIS system aims to provide precise orbit determination of low earth orbit satellites, and the dual-frequencies on S1=2036.25 MHz and U2=401.25 MHz were used on DORIS signals. The ionosphere TEC retrieval on the signal path is possible based on DORIS dual-frequency observations.</p><p>Analysis results show that DORIS pseudo-ranges had noise with several kilometers level, hence only the carrier-phase observations could be utilized on TEC retrieval. Moreover, as the DORIS ground stations were thousands kilometers separated with each other, station differential cannot be guaranteed and the data preprocessing can only be done base on the un-difference observations before the TEC could be precisely determined.</p><p>In this research, a polynomial function was applied to model the DORIS phase observations, and minimal detectable biases (MDB) of less than one cycle wavelength was used as the index on the cycle-slip detection. And then the geometry free combination of S1 and U2 phase measurements were calculated for each DORIS LEO satellite passing arc. Finally, the unknown ambiguities bias on S1 and U2 geometry free observables were shifted to coincide with STEC calculated from the IGS GIM products.</p><p>Both the Jason-2 & 3 based DORIS observations were used for the validation, several simulated +5 and -1 cycle-slip events on both DORIS observation could be clearly detected and correctly repaired. And the calculated STEC on one satellite passing arc from the LEO satellite to station show well agreement with IGS STEC on continent area, and the differences on ocean areas could be used to prove that the IGS GIM products were less precise on those areas.</p>

scholarly journals Real-Time Precise Orbit Determination for LEO between Kinematic and Reduced-Dynamic with Ambiguity Resolution

Aerospace ◽  
2022 ◽  
Vol 9 (1) ◽  
pp. 25
Author(s):  
Zhiyu Wang ◽  
Zishen Li ◽  
Ningbo Wang ◽  
Mainul Hoque ◽  
Liang Wang ◽  
...  
Keyword(s):  
Real Time ◽  
Ambiguity Resolution ◽  
Orbit Determination ◽  
Fixed Ratio ◽  
Precise Orbit Determination ◽  
Low Earth Orbit ◽  
Integer Ambiguity ◽  
The Real ◽  
Precise Orbit ◽  
Reduced Dynamic

The real-time integer-ambiguity resolution of the carrier-phase observation is one of the most effective approaches to enhance the accuracy of real-time precise point positioning (PPP), kinematic precise orbit determination (KPOD), and reduced-dynamic precise orbit determination (RPOD) for low earth orbit (LEO) satellites. In this study, the integer phase clock (IPC) and wide-lane satellite bias (WSB) products from CNES (Centre National d’Etudes Spatiales) are used to fix ambiguity in real time. Meanwhile, the three models of real-time PPP, KPOD, and RPOD are applied to validate the contribution of ambiguity resolution. Experimental results show that (1) the average positioning accuracy of IGS stations for ambiguity-fixed solutions is improved from about 7.14 to 5.91 cm, with an improvement of around 17% compared to the real-time float PPP solutions, with enhancement in the east-west direction particularly significant, with an improvement of about 29%; (2) the average accuracy of the estimated LEO orbit with ambiguity-fixed solutions in the real-time KPOD and RPOD mode is improved by about 16% and 10%, respectively, with respect to the corresponding mode with the ambiguity-float solutions; (3) the performance of real-time LEO RPOD is better than that of the corresponding KPOD, regardless of fixed- or float-ambiguity solutions. Moreover, the average ambiguity-fixed ratio can reach more than 90% in real-time PPP, KPOD, and RPOD.

scholarly journals Sentinel-6A precise orbit determination using a combined GPS/Galileo receiver

2021 ◽  
Vol 95 (9) ◽  
Author(s):  
Oliver Montenbruck ◽  
Stefan Hackel ◽  
Martin Wermuth ◽  
Franz Zangerl
Keyword(s):  
Orbit Determination ◽  
High Performance ◽  
Center Of Mass ◽  
Precise Orbit Determination ◽  
Altimeter Data ◽  
Dual Frequency ◽  
Gnss Receiver ◽  
Precise Orbit ◽  
Radial Orbit ◽  
Reduced Dynamic

AbstractThe Sentinel-6 (or Jason-CS) altimetry mission provides a long-term extension of the Topex and Jason-1/2/3 missions for ocean surface topography monitoring. Analysis of altimeter data relies on highly-accurate knowledge of the orbital position and requires radial RMS orbit errors of less than 1.5 cm. For precise orbit determination (POD), the Sentinel-6A spacecraft is equipped with a dual-constellation GNSS receiver. We present the results of Sentinel-6A POD solutions for the first 6 months since launch and demonstrate a 1-cm consistency of ambiguity-fixed GPS-only and Galileo-only solutions with the dual-constellation product. A similar performance (1.3 cm 3D RMS) is achieved in the comparison of kinematic and reduced-dynamic orbits. While Galileo measurements exhibit 30–50% smaller RMS errors than those of GPS, the POD benefits most from the availability of an increased number of satellites in the combined dual-frequency solution. Considering obvious uncertainties in the pre-mission calibration of the GNSS receiver antenna, an independent inflight calibration of the phase centers for GPS and Galileo signal frequencies is required. As such, Galileo observations cannot provide independent scale information and the estimated orbital height is ultimately driven by the employed forces models and knowledge of the center-of-mass location within the spacecraft. Using satellite laser ranging (SLR) from selected high-performance stations, a better than 1 cm RMS consistency of SLR normal points with the GNSS-based orbits is obtained, which further improves to 6 mm RMS when adjusting site-specific corrections to station positions and ranging biases. For the radial orbit component, a bias of less than 1 mm is found from the SLR analysis relative to the mean height of 13 high-performance SLR stations. Overall, the reduced-dynamic orbit determination based on GPS and Galileo tracking is considered to readily meet the altimetry-related Sentinel-6 mission needs for RMS height errors of less than 1.5 cm.

scholarly journals Exploring LEO cube satellite technology for space geodesy: SLR-VLBI POD in the GGOS era

2021 ◽  
Author(s):  
Grzegorz Kłopotek ◽  
Matthias Schartner ◽  
Markus Rothacher ◽  
Benedikt Soja
Keyword(s):  
Orbit Determination ◽  
Low Cost ◽  
Precise Orbit Determination ◽  
Simulated Data ◽  
Low Earth Orbit ◽  
Space Geodesy ◽  
Satellite Orbits ◽  
Dual Frequency ◽  
Satellite Technology ◽  
The Impact

<p>With test satellites already in space, the Swiss company Astrocast is currently in the process of establishing a constellation of about 80 nanosatellites for commercial purposes that are operating in a low Earth orbit (LEO). As a result of the collaboration with ETH Zürich, such satellites will be equipped with both low-cost multi-GNSS dual-frequency receivers and a small array of laser retroreflectors for satellite laser ranging (SLR). In the future, this set of geodetic instruments could be also extended with a simple, compact and low-power transmitter compliant with the next-generation very long baseline interferometry (VLBI) system, known as the VLBI Global Observing System (VGOS). Therefore, apart from scientific studies based on such state-of-the-art multi-GNSS receivers in space, the Astrocast nanosatellite network could also be examined in terms of satellite co-locations. In this case, the new geometrical connections in space could be realized together with all ground-based instruments that can observe the co-location satellites. Assuming sufficient precision of such observations and good knowledge of the spacecraft environment, this approach could result in an enhanced quantity of tie measurements at a high spatio-temporal resolution, potentially leading also to an enhanced quality of common geodetic parameters. However, accurate orbit determination is of high importance, whenever considering potential co-location in space or, in general, estimating various global parameters of geophysical interest.<br>In this contribution, we focus on precise orbit determination (POD) of LEO Astrocast-type nanosatellites based on global SLR-only, VGOS-only as well as combined SLR-VGOS observations. The impact of this concept on various geodetic parameters and the derived orbits is studied on the basis of Monte-Carlo simulations carried out with the c5++ analysis software. All simulated data are combined on the observation level and used to derive satellite orbits and to estimate both, station-based and global geodetic parameters. Our study is based on VGOS-type schedules created in VieSched++ and consisting of both quasar and satellite observations. In addition to the simulated laser measurements to Astrocast satellites, the SLR-related solutions include also global observations to LAGEOS-1/2 satellites. Our considerations involve solutions with different time intervals, satellite observation precision levels and quantity of the considered cube satellites, providing thus initial insights concerning prospective utilization of LEO cube satellite technology for space geodesy in the era of the Global Geodetic Observing System.</p>

scholarly journals Kinematic and reduced-dynamic precise orbit determination of low earth orbiters

2003 ◽  
Vol 1 ◽  
pp. 47-56 ◽  
Author(s):  
D. Švehla ◽  
M. Rothacher
Keyword(s):  
Ambiguity Resolution ◽  
Orbit Determination ◽  
Precise Orbit Determination ◽  
Double Difference ◽  
Phase Measurements ◽  
Precise Orbit ◽  
First Results ◽  
Orbit Dynamic ◽  
Reduced Dynamic

Abstract. Various methods for kinematic and reduced-dynamic precise orbit determination (POD) of Low Earth Orbiters (LEO) were developed based on zero- and double-differencing of GPS carrier-phase measurements with and without ambiguity resolution. In this paper we present the following approaches in LEO precise orbit determination: – zero-difference kinematic POD, – zero-difference dynamic POD, – double-difference kinematic POD with and without ambiguity resolution, – double-difference dynamic POD with and without ambiguity resolution, – combined GPS/SLR reduced-dynamic POD. All developed POD approaches except the combination of GPS/SLR were tested using real CHAMP data (May 20-30, 2001) and independently validated with Satellite Laser Ranging (SLR) data over the same 11 days. With SLR measurements, additional combinations are possible and in that case one can speak of combined kinematic or combined reduced-dynamic POD. First results of such a combined GPS/SLR POD will be presented, too. This paper shows what LEO orbit accuracy may be achieved with GPS using different strategies including zerodifference and double-difference approaches. Kinematic versus dynamic orbit determination is presently an interesting issue that will also be discussed in this article.Key words. POD, kinematic orbit, dynamic orbit, LEO, CHAMP, ambiguity resolution, GPS, SLR

scholarly journals A Second-Order Time-Difference Position Constrained Reduced-Dynamic Technique for the Precise Orbit Determination of LEOs Using GPS

2021 ◽  
Vol 13 (15) ◽  
pp. 3033
Author(s):  
Hui Wei ◽  
Jiancheng Li ◽  
Xinyu Xu ◽  
Shoujian Zhang ◽  
Kaifa Kuang
Keyword(s):  
Orbit Determination ◽  
Dynamic Models ◽  
Precise Orbit Determination ◽  
Second Order ◽  
Time Difference ◽  
Error Sources ◽  
Precise Orbit ◽  
Unmodeled Dynamic ◽  
Reduced Dynamic

In this paper, we propose a new reduced-dynamic (RD) method by introducing the second-order time-difference position (STP) as additional pseudo-observations (named the RD_STP method) for the precise orbit determination (POD) of low Earth orbiters (LEOs) from GPS observations. Theoretical and numerical analyses show that the accuracies of integrating the STPs of LEOs at 30 s intervals are better than 0.01 m when the forces (<10−5 ms−2) acting on the LEOs are ignored. Therefore, only using the Earth’s gravity model is good enough for the proposed RD_STP method. All unmodeled dynamic models (e.g., luni-solar gravitation, tide forces) are treated as the error sources of the STP pseudo-observation. In addition, there are no pseudo-stochastic orbit parameters to be estimated in the RD_STP method. Finally, we use the RD_STP method to process 15 days of GPS data from the GOCE mission. The results show that the accuracy of the RD_STP solution is more accurate and smoother than the kinematic solution in nearly polar and equatorial regions, and consistent with the RD solution. The 3D RMS of the differences between the RD_STP and RD solutions is 1.93 cm for 1 s sampling. This indicates that the proposed method has a performance comparable to the RD method, and could be an alternative for the POD of LEOs.

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