Systematic errors in SLR data and their impact on the ILRS products

Luceri, V.; Pirri, Mauro; Rodríguez, José; Appleby, G. M.; Pavlis, E. C.; Müller, Hendrik

doi:10.1007/s00190-019-01319-w

Cited by 38 publications

(28 citation statements)

References 11 publications

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“…Moreover, these two solutions also agree with the VLBI-based scale (+ 0.77 ppb) better than the SLR-based scale (-0.77) does. Compared with the updated SLR-based scale without systematic errors (Luceri et al 2019), the scales determined by GNSS in this study, by VLBI, and by SLR agree with each other with differences smaller than 1 ppb.…”

Section: Discussionsupporting

confidence: 61%

“…Therefore, the GNSS-based scale derived by both methods agree with each other well and agree with the VLBI-based scale better than the SLR-based scale does. After removing the systematic errors in SLR data by Luceri et al (2019), the scale derived by SLR is about + 1 ppb toward ITRF 2014 scale. Therefore, the scales determined by GNSS in this study, by VLBI, and by SLR have an agreement within differences smaller than 1 ppb.…”

Section: Estimated Z-1pco Gps and Terrestrial Scalementioning

confidence: 98%

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Two methods to determine scale-independent GPS PCOs and GNSS-based terrestrial scale: comparison and cross-check

et al. 2020

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The GPS satellite transmitter antenna phase center offsets (PCOs) can be estimated in a global adjustment by constraining the ground station coordinates to the current International Terrestrial Reference Frame (ITRF). Therefore, the derived PCO values rest on the terrestrial scale parameter of the frame. Consequently, the PCO values transfer this scale to any subsequent GNSS solution. A method to derive scale-independent PCOs without introducing the terrestrial scale of the frame is the prerequisite to derive an independent GNSS scale factor that can contribute to the datum definition of the next ITRF realization. By fixing the Galileo satellite transmitter antenna PCOs to the ground calibrated values from the released metadata, the GPS satellite PCOs in the z-direction (z-PCO) and a GNSS-based terrestrial scale parameter can be determined in GPS + Galileo processing. An alternative method is based on the gravitational constraint on low earth orbiters (LEOs) in the integrated processing of GPS and LEOs. We determine the GPS z-PCO and the GNSS-based scale using both methods by including the current constellation of Galileo and the three LEOs of the Swarm mission. For the first time, direct comparison and cross-check of the two methods are performed. They provide mean GPS z-PCO corrections of $$- 186 \pm 25$$ - 186 ± 25 mm and $$- 221 \pm 37$$ - 221 ± 37 mm with respect to the IGS values and $$+ 1.55 \pm 0.22$$ + 1.55 ± 0.22 ppb (parts per billion) and $$+ 1.72 \pm 0.31$$ + 1.72 ± 0.31 in the terrestrial scale with respect to the IGS14 reference frame. The results of both methods agree with each other with only small differences. Due to the larger number of Galileo observations, the Galileo-PCO-fixed method leads to more precise and stable results. In the joint processing of GPS + Galileo + Swarm in which both methods are applied, the constraint on Galileo dominates the results. We discuss and analyze how fixing either the Galileo transmitter antenna z-PCO or the Swarm receiver antenna z-PCO in the combined GPS + Galileo + Swarm processing propagates to the respective freely estimated z-PCO of Swarm and Galileo.

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Section: Discussionsupporting

confidence: 61%

Section: Estimated Z-1pco Gps and Terrestrial Scalementioning

confidence: 98%

Two methods to determine scale-independent GPS PCOs and GNSS-based terrestrial scale: comparison and cross-check

et al. 2020

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“…This result corroborates the statistically identical result that was seen in the standard QC processing of the two data sets that identified a bias of the same magnitude. Quantifying such errors at each site is very important because it helps explain and rationalize the observed variations in the systematic error characterization of these systems as they are estimated from long-term data analysis of the network (Appleby et al 2016;Luceri et al 2019).…”

Section: Direct Np Range Comparisonsmentioning

confidence: 99%

Transitioning the NASA SLR network to Event Timing Mode for reduced systematics, improved stability and data precision

Varghese¹,

Ricklefs²,

Pavlis

et al. 2019

J Geod

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NASA's legacy Satellite Laser Ranging (SLR) network produces about one-third of the global SLR data to support space geodesy. This network of globally distributed stations has been using Time Interval Units (TIU) for range measurements for the last 25 + years. To improve the reliability of the SLR network and satisfy the need for stable millimeter precision data, a phased replacement of the TIUs in the network with picosecond-precise Event Timer Modules was initiated in 2015. This scheme allowed the time of flight and laser transmit epoch measurement to one picosecond resolution. For a network with global scientific impact, transitioning to a new data generation metrological scheme requires significant data scrutiny and long-term science data validation. Any long-term testing/measurement has the potential to interrupt the station's daily operational data flow to the International Laser Ranging Service (ILRS) as the station under test will have to put its test data into quarantine. We have demonstrated a very effective way to test and implement the new device without removing the old hardware and without the need for the orbit analysis. This operationally noninvasive scheme performed concurrent test measurements enabling uninterrupted operational data flow to the users, while allowing simultaneous test data capture for short-and long-term systematics and stability analysis. Extensive analysis of the test data was performed by the NASA SLR engineering team and the ILRS Analysis Standing Committee, to uncover biases and any dependencies on the satellite ranges (for nonlinear scale issues). Multi-ETM comparison was also performed at two of the SLR stations through the interchange of hardware to establish the inter-device range biases and stability. Such benchmarked hardware was subsequently sent to the remaining stations to allow traceability and normalize the network performance. The range bias intercomparison performed using the multiyear SLR data analysis agreed well with the engineering changes, thus validating the approach to flush out station-specific ranging systematics affecting precise orbit determination. Such an improvement and rebalancing of the current network will allow an orderly transition of the current NASA SLR network operating at a maximum rate of 10 Hz to the NASA next generation

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“…The difficulty of this observation techniques combination is the treatment of the systematic errors of both systems. As SLR is not a standardized system, it has a complex error budget due to systematic biases of the different tracking stations (Schreiber and Kodet 2018;Luceri et al 2019;Zajdel et al 2019). For this reason, the potential of GNSS Precise Orbit Determination (POD) using a combination of GNSS and optical two-way ground-space measurements is still limited using SLR.…”

Section: Introductionmentioning

confidence: 99%

Galileo precise orbit determination with optical two-way links (OTWL): a continuous wave laser ranging and time transfer concept

Marz

Schlicht

Hugentobler

2021

J Geod

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In this simulation study we analyze the benefit of ground-space optical two-way links (OTWL) for Galileo precise orbit determination (POD). OTWL is a concept based on continuous wave laser ranging and time transfer with modulated signals from and to ground stations. The measurements are in addition to Global Navigation Satellite System (GNSS) observations. We simulate the measurements with regard to 16 Galileo Sensor Stations. In the simulation study we assume that the whole Galileo satellite constellation is equipped with terminals for OTWL. Using OTWL together with Galileo L-band, in comparison with an orbit solution calculated with L-band-only, demonstrates the advantage of combining two ranging techniques with different influences of systematic errors. The two-way link allows a station and satellite clock synchronization. Furthermore, we compare the ground-space concept with the satellite-to-satellite counterpart known as optical two-way inter-satellite links (OISL). The advantage of OTWL is the connection between the satellite system and the solid Earth as well as the possibility to synchronize the satellite clocks and the ground station clocks. The full network, using all three observation types in combination is simulated as well. The possibility to estimate additional solar radiation pressure (SRP) parameters within these combinations is a clear benefit of these additional links. We paid great attention to simulate systematic effects of all observation techniques as realistically as possible. For L-band these are measurement noise, tropospheric delays, phase center variation of receiver and transmitter antennas, constant and variable biases as well as multipath. For optical links we simulated colored and distance-dependent noise, offsets due to the link repeatability and offsets related to the equipment calibration quality. In addition, we added a troposphere error for the OTWL measurements. We discuss the influence on the formal orbit uncertainties and the effects of the systematic errors. Restrictions due to weather conditions are addressed as well. OTWL is synergetic with the other measurement techniques like OISL and can be used for data transfer and communication, respectively.

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Systematic errors in SLR data and their impact on the ILRS products

Cited by 38 publications

References 11 publications

Two methods to determine scale-independent GPS PCOs and GNSS-based terrestrial scale: comparison and cross-check

Two methods to determine scale-independent GPS PCOs and GNSS-based terrestrial scale: comparison and cross-check

Transitioning the NASA SLR network to Event Timing Mode for reduced systematics, improved stability and data precision

Galileo precise orbit determination with optical two-way links (OTWL): a continuous wave laser ranging and time transfer concept

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