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AIUB IGSWS2018 – PS13 International GNSS Service Workshop 2018 29 Oct.-02 Nov. 2018, Wuhan, China D. Arnold 1 , S. Schaer 1,2 , A. Villiger 1 , R. Dach 1 , A. Jäggi 1 1 Astronomical Institute, University of Bern, Bern, Switzerland 2 Swiss Federal Office of Topography, Wabern, Switzerland Poster compiled by Daniel Arnold, October 2018 Astronomical Institute, University of Bern, Bern [email protected] Undifference ambiguity resolution for GPS- based precise orbit determination of low Earth orbiters using the new CODE clock and phase bias products Introduction • GNSS-based Precise Orbit Determination (POD) of Low Earth Orbiters (LEOs) has nowadays become a standard ap- plication for high-quality GNSS products as provided by the IGS, or its individual analysis centers. For many LEOs, e.g., for altimetry missions, the centimeter absolute orbit preci- sion and accuracy achieved by carrier phase-based GNSS positioning is mandatory and could hardly be obtained by other tracking data. • Resolving carrier phase ambiguities to their integer values has been known to inherently stabilize solutions for param- eters since a long time and has been confirmed in many ap- plications. • E.g., double-difference (DD) processing of space or space- ground baselines for relative LEO POD allows for ambiguity resolution (AR) without any dedicated GNSS products in ad- dition and is known to significantly enhance relative POD. • In case of Precise Point Positioning, undifferenced or zero- difference ambiguity resolution (ZD AR) requires the knowledge of GNSS satellite phase biases which cancel out in forming baselines. Recently, the Center for Orbit Determi- nation in Europe (CODE) IGS analysis center has established the generation of a high-quality signal-specific phase bias product and a fully consistent ambiguity-fixed clock prod- uct within its rapid and final IGS-related processing (more details in presentation Schaer et al. in session PY01). • Using this new product, we demonstrate the benefit of ZD AR on the quality of LEO POD and compare its performance to results obtained in double-difference processing (includ- ing AR). Methods Reduced-dynamic and kinematic single-satellite orbits and base- line solutions are computed using the development version of the Bernese GNSS Software (Dach et al., 2015). The following param- eters are estimated in a batch least-square adjustment: • Reduced-dynamic POD: 6 initial conditions, 3 constant em- pirical accelerations in radial (R), along-track (T), and cross- track (N) direction, constrained 6-min. piecewise constant accelerations (PCAs) in R,T,N direction, epoch-wise receiver clock correction, carrier phase ambiguities. • Kinematic POD: 3-dimensional position and receiver clock correction at every observation epoch, carrier phase ambi- guities. • For both the reduced-dynamic and kinematic baseline de- termination, the reduced-dynamic orbit of LEO A serves as reference orbit and relative parameters for LEO B are esti- mated. For the reduced-dynamic baseline determination the differential accelerations are relatively loosely constrained (1 · 10 -8 m/s 2 ). Satellite-specific phase center variation (PCV) maps are intro- duced (i.e., no relative PCV corrections). For the reduced-dynamic POD GOCO03S up to degree and order 120 is used for the Earth gravity field model and non-gravitational forces are not explicitly modeled. AR strategy: For both ZD AR and DD AR in a first step, the Melbourne-Wuebbena linear combination of pseudo-range and carrier phase observations is processed to resolve the widelane ambiguities. In a second step, the ionosphere-free linear combi- nation is processed to resolve the narrowlane ambiguities using the sigma strategy (Dach et al., 2015) and to solve for the parame- ters of the reduced-dynamic orbit. The same resolved ambiguities are then introduced in the subsequent kinematic POD. Data used: For GRACE, GPS and attitude data of April 2007 are processed. Sentinel-3A and -B are in formation with nearly iden- tical orbits and 30s separation since June 2018, thus allowing for double difference processing of baselines. Furthermore, the gen- eration of Sentinel-3 carrier phase data has recently been refined to avoid half-cycle ambiguities (Montenbruck et al., 2018), allowing for proper integer AR. For this study, Sentinel-3 orbits and base- lines are computed for the month September 2018. In all cases, data sampling is 10 s. How to use CODE’s new clock and phase bias products Since GPS week 2009 (July 2018) CODE produces a high-quality signal-specific phase bias product (the products for April 2007 have been generated for this study), see Fig. 1. The corresponding OSB files can straightforwardly be introduced into GPSEST, the main parameter estimation program of the Bernese GNSS Software, which has been extended to allow for zero-difference ambiguity resolution, see Fig. 2. The new CODE rapid, final, and MGEX clock corrections are based on a fully consistent ambiguity fixing processing. Bias SVN PRN Station name Obs yyyy mm dd hh mm ss yyyy mm dd hh mm ss Value (ns) RMS (ns) *** **** *** ************* *** ******************* ******************* *********** *********** OSB G032 G01 C1C 2007 04 01 00 00 00 2007 04 02 00 00 00 0.52254 0.00610 OSB G032 G01 C1W 2007 04 01 00 00 00 2007 04 02 00 00 00 -0.00000 0.00025 OSB G032 G01 C2W 2007 04 01 00 00 00 2007 04 02 00 00 00 -0.00000 0.00025 ... OSB G032 G01 L1C 2007 04 01 00 00 00 2007 04 02 00 00 00 0.16431 0.00000 OSB G032 G01 L1W 2007 04 01 00 00 00 2007 04 02 00 00 00 0.16431 0.00000 OSB G032 G01 L2C 2007 04 01 00 00 00 2007 04 02 00 00 00 0.24524 0.00000 OSB G032 G01 L2W 2007 04 01 00 00 00 2007 04 02 00 00 00 0.24524 0.00000 OSB G032 G01 L2X 2007 04 01 00 00 00 2007 04 02 00 00 00 0.24524 0.00000 ... Figure 1: Observation-specific bias (OSB) files generated by CODE, containing pseudo-range and phase biases for Integer-PPP (IPPP). Figure 2: GPSEST, the main parameter estimation program of the Bernese GNSS Software, now allows for zero-difference ambiguity resolution. Ambiguity resolution Figure 3 shows the percentage of successfully resolved narrowlane ambiguities for both the ZD AR and DD AR in the GRACE and Sentinel-3 processing. For GRACE, slightly less ambiguities are resolved in the DD processing compared to the ZD processing. In ZD AR more ambiguities are resolved for GRACE-B (99.1%) than for GRACE-A (97.1%). The AR success rate for Sentinel-3 is in all cases close to 100%. 84.0 86.0 88.0 90.0 92.0 94.0 96.0 98.0 100.0 01 April 04 April 07 April 10 April 13 April 16 April 19 April 22 April 25 April 28 April NL AR success rate [%] Date in 2007 GRACE Average: 97.1 % 99.1 % 92.2 % GRACE-A ZD GRACE-B ZD GRACE-A/B DD 97.0 97.5 98.0 98.5 99.0 99.5 100.0 01 Sep 04 Sep 07 Sep 10 Sep 13 Sep 16 Sep 19 Sep 22 Sep 25 Sep 28 Sep NL AR success rate [%] Date in 2018 Sentinel-3 Average: 99.0 % 99.2 % 98.8 % Sentinel-3A ZD Sentinel-3B ZD Sentinel-3A/B DD Figure 3: Percentage of resolved narrowlane ambiguities for GRACE (top) and Sentinel-3 (bottom). Red: ZD AR for LEO A. Green: ZD AR for LEO B. Blue: DD AR for baseline. K-Band validation GRACE offers the possibility to validate computed orbits, in par- ticular the along-track component, with the ultra-precise inter- satellite K-band measurements. Figure 4 shows the K-band range (KBR) residuals of reduced-dynamic ambiguity-float and ambiguity-fixed GRACE orbits for one day, as well as the spec- tral analysis of the residuals. Both the ZD and the DD AR lead to a significant reduction of KBR residuals, especially regarding longer periods. Figure 5 shows the daily RMS values of K-band residu- als for the entire month for both reduced-dynamic and kinematic orbit and baseline solutions. For the reduced-dynamic and kine- matic solutions ZD AR and DD AR implies a reduction of the KBR residuals by about a factor of 3-4 and 3-5, respectively. -8 -6 -4 -2 0 2 4 6 8 10 12 0 5 10 15 20 KBR residuals [mm] Hour of day 07/091 GRACE-A/B red.-dyn. KBR residuals Float ZD AR DD AR Figure 4: K-band range residuals for reduced-dynamic orbits and baseline solu- tions, as well as their spectral analysis for April 1, 2007. 0 1 2 3 4 5 6 7 8 01 April 04 April 07 April 10 April 13 April 16 April 19 April 22 April 25 April 28 April KBR residauls [mm] Date in 2007 GRACE-A/B red.-dyn. KBR residuals Average: 5.54 mm 1.82 mm 1.32 mm Float ZD AR DD AR 0 2 4 6 8 10 12 14 16 18 20 22 01 April 04 April 07 April 10 April 13 April 16 April 19 April 22 April 25 April 28 April KBR residauls [mm] Date in 2007 GRACE-A/B kin. KBR residuals Average: 14.32 mm 4.74 mm 2.70 mm Float ZD AR DD AR Figure 5: Daily RMS values of K-band residuals for reduced-dynamic (left) and kinematic (right) orbit and baseline solutions. For the kinematic solution statistics an outlier threshold of 10 cm was applied. Reduced-dynamic vs. kinematic solutions Figure 6 shows for GRACE-A the differences between the reduced-dynamic and kinematic single-satellite solutions for one day. It can be observed that especially in along-track and cross- track direction the long-periodic differences are significantly re- duced by the ZD AR. Figure 7 shows the daily RMS values of orbit differences for April 2007. Figure 8 shows the correspond- ing statistics for Sentinel-3 for September 2018. In all cases a pro- nounced reduction can be observed in the ambiguity-fixed orbits. -40 -20 0 20 40 0 5 10 15 20 Orbit differences [mm] Hour of day 07/091 GRACE-A RD-KN (float vs fixed), radial Float Fixed -40 -20 0 20 40 0 5 10 15 20 Orbit differences [mm] Hour of day 07/091 GRACE-A RD-KN (float vs fixed), along-track Float Fixed -40 -20 0 20 40 0 5 10 15 20 Orbit differences [mm] Hour of day 07/091 GRACE-A RD-KN (float vs fixed), cross-track Float Fixed Figure 6: Differences between reduced- dynamic and kinematic GRACE-A or- bit for April 1, 2007 in radial (top left), along-track (top right), and cross-track (bottom) direction for the ambiguity-float (red) and the ZD ambiguity-fixed (green) solution. 6 8 10 12 14 16 18 20 22 24 26 01 April 04 April 07 April 10 April 13 April 16 April 19 April 22 April 25 April 28 April RMS of orb. diff. [mm] Date in 2007 GRACE RD-KN (float vs fixed), radial Average: 13.7 mm 18.6 mm 8.5 mm 11.3 mm GRACE-A float GRACE-B float GRACE-A ZD GRACE-B ZD 2 4 6 8 10 12 14 16 18 20 22 24 01 April 04 April 07 April 10 April 13 April 16 April 19 April 22 April 25 April 28 April RMS of orb. diff. [mm] Date in 2007 GRACE RD-KN (float vs fixed), along-track Average: 10.8 mm 15.6 mm 4.2 mm 4.8 mm GRACE-A float GRACE-B float GRACE-A ZD GRACE-B ZD 0 5 10 15 20 25 30 01 April 04 April 07 April 10 April 13 April 16 April 19 April 22 April 25 April 28 April RMS of orb. diff. [mm] Date in 2007 GRACE RD-KN (float vs fixed), cross-track Average: 8.9 mm 14.3 mm 2.3 mm 2.9 mm GRACE-A float GRACE-B float GRACE-A ZD GRACE-B ZD Figure 7: Daily RMS values of dif- ferences between reduced-dynamic and kinematic orbit solutions for April 2007 in radial (top left), along-track (top right), and cross-track (bottom) direction for GRACE-A and -B. 6 8 10 12 14 16 18 20 22 24 01 Sep 04 Sep 07 Sep 10 Sep 13 Sep 16 Sep 19 Sep 22 Sep 25 Sep 28 Sep RMS of orb. diff. [mm] Date in 2018 Sentinel-3 RD-KN (float vs fixed), radial Average: 15.1 mm 15.6 mm 8.9 mm 9.3 mm Sentinel-3A float Sentinel-3B float Sentinel-3A ZD Sentinel-3B ZD 2 4 6 8 10 12 14 16 18 20 22 01 Sep 04 Sep 07 Sep 10 Sep 13 Sep 16 Sep 19 Sep 22 Sep 25 Sep 28 Sep RMS of orb. diff. [mm] Date in 2018 Sentinel-3 RD-KN (float vs fixed), along-track Average: 11.6 mm 12.1 mm 4.1 mm 4.3 mm Sentinel-3A float Sentinel-3B float Sentinel-3A ZD Sentinel-3B ZD 2 4 6 8 10 12 14 16 01 Sep 04 Sep 07 Sep 10 Sep 13 Sep 16 Sep 19 Sep 22 Sep 25 Sep 28 Sep RMS of orb. diff. [mm] Date in 2018 Sentinel-3 RD-KN (float vs fixed), cross-track Average: 8.7 mm 8.7 mm 2.5 mm 2.6 mm Sentinel-3A float Sentinel-3B float Sentinel-3A ZD Sentinel-3B ZD Figure 8: Daily RMS values of dif- ferences between reduced-dynamic and kinematic orbit solutions for September 2018 in radial (top left), along-track (top right), and cross-track (bottom) direction for Sentinel-3A and -3B. SLR validation Satellite Laser Ranging (SLR) normal points from 12 laser stations were used for orbit validation, residuals larger than 20 cm have been rejected and an elevation cutoff of 10 ◦ applied. No parame- ters were estimated. Table 1 shows the mean values and standard deviations of SLR residuals, confirming the positive impact of ZD AR on the orbit quality. Float ZD AR Orbits red.-dyn. kin. red.-dyn. kin. GRACE-A +0.5/15.5 +1.5/16.6 +2.5/12.4 +2.6/12.0 GRACE-B +0.9/12.1 -0.5/16.9 +3.8/8.5 +3.7/9.6 Sentinel-3A -6.0/11.5 -6.5/14.7 -5.7/10.7 -5.4/11.9 Sentinel-3B -2.9/12.4 -4.3/15.2 -3.5/10.4 -3.3/11.1 Table 1: Mean values and standard deviations in mm of SLR residuals over April 2007 (GRACE) and September 2018 (Sentinel-3), respectively. Conclusions Using CODE’s new observation-specific phase bias product, a consistent ambiguity-fixed clock product and extensions of the Bernese GNSS Software, zero-difference ambiguity resolution was applied to the GPS-based POD of the GRACE and Sentinel-3 satel- lites. Ambiguity fixing is shown to significantly improve the orbit quality in terms of the independent validation measures K-band and SLR, as well as in terms of the internal consistency between the reduced-dynamic and kinematic orbit solutions. The achiev- able relative orbit quality is comparable to what can be obtained from a double-difference processing of space baselines employing ambiguity fixing. All results confirm a high quality of the CODE clock and phase bias product. References R. Dach, S. Lutz, P. Walser, and P. Fridez, editors. Bernese GNSS Software, Version 5.2. Astronomical Institute, University of Bern, Bern, Switzerland, November 2015. ISBN 978-3-906813-05-9. doi: 10.7892/boris.72297. User manual. O. Montenbruck, S. Hackel, and A. Jäggi. Precise orbit determination of the Sentinel-3A altimetry satellite using ambiguity-fixed GPS carrier phase obser- vations. Journal of geodesy, 92(7):711–726, 2018. Contact address Daniel Arnold Astronomical Institute, University of Bern Sidlerstrasse 5 3012 Bern (Switzerland) [email protected]
Transcript of Astronomical Institute, University of Bern, Bern 3012 Bern … · 2019. 1. 2. · AIUB...
AIUB
IGSWS2018 – PS13International GNSS ServiceWorkshop 2018 29 Oct.-02 Nov. 2018, Wuhan, China
D. Arnold1, S. Schaer1,2, A. Villiger1, R. Dach1, A. Jäggi1
1Astronomical Institute, University of Bern, Bern, Switzerland2Swiss Federal Office of Topography, Wabern, Switzerland
Poster compiled by Daniel Arnold, October 2018Astronomical Institute, University of Bern, [email protected]
Undifference ambiguity resolution for GPS-based precise orbit determination of low Earth orbiters
using the new CODE clock andphase bias products
Introduction• GNSS-based Precise Orbit Determination (POD) of Low
Earth Orbiters (LEOs) has nowadays become a standard ap-plication for high-quality GNSS products as provided by theIGS, or its individual analysis centers. For many LEOs, e.g.,for altimetry missions, the centimeter absolute orbit preci-sion and accuracy achieved by carrier phase-based GNSSpositioning is mandatory and could hardly be obtained byother tracking data.
• Resolving carrier phase ambiguities to their integer valueshas been known to inherently stabilize solutions for param-eters since a long time and has been confirmed in many ap-plications.
• E.g., double-difference (DD) processing of space or space-ground baselines for relative LEO POD allows for ambiguityresolution (AR) without any dedicated GNSS products in ad-dition and is known to significantly enhance relative POD.
• In case of Precise Point Positioning, undifferenced or zero-difference ambiguity resolution (ZD AR) requires theknowledge of GNSS satellite phase biases which cancel outin forming baselines. Recently, the Center for Orbit Determi-nation in Europe (CODE) IGS analysis center has establishedthe generation of a high-quality signal-specific phase biasproduct and a fully consistent ambiguity-fixed clock prod-uct within its rapid and final IGS-related processing (moredetails in presentation Schaer et al. in session PY01).
• Using this new product, we demonstrate the benefit of ZDAR on the quality of LEO POD and compare its performanceto results obtained in double-difference processing (includ-ing AR).
MethodsReduced-dynamic and kinematic single-satellite orbits and base-line solutions are computed using the development version of theBernese GNSS Software (Dach et al., 2015). The following param-eters are estimated in a batch least-square adjustment:
• Reduced-dynamic POD: 6 initial conditions, 3 constant em-pirical accelerations in radial (R), along-track (T), and cross-track (N) direction, constrained 6-min. piecewise constantaccelerations (PCAs) in R,T,N direction, epoch-wise receiverclock correction, carrier phase ambiguities.
• Kinematic POD: 3-dimensional position and receiver clockcorrection at every observation epoch, carrier phase ambi-guities.
• For both the reduced-dynamic and kinematic baseline de-termination, the reduced-dynamic orbit of LEO A serves asreference orbit and relative parameters for LEO B are esti-mated. For the reduced-dynamic baseline determination thedifferential accelerations are relatively loosely constrained(1 · 10−8m/s2).
Satellite-specific phase center variation (PCV) maps are intro-duced (i.e., no relative PCV corrections). For the reduced-dynamicPOD GOCO03S up to degree and order 120 is used for the Earthgravity field model and non-gravitational forces are not explicitlymodeled.
AR strategy: For both ZD AR and DD AR in a first step, theMelbourne-Wuebbena linear combination of pseudo-range andcarrier phase observations is processed to resolve the widelaneambiguities. In a second step, the ionosphere-free linear combi-nation is processed to resolve the narrowlane ambiguities usingthe sigma strategy (Dach et al., 2015) and to solve for the parame-ters of the reduced-dynamic orbit. The same resolved ambiguitiesare then introduced in the subsequent kinematic POD.Data used: For GRACE, GPS and attitude data of April 2007 areprocessed. Sentinel-3A and -B are in formation with nearly iden-tical orbits and 30s separation since June 2018, thus allowing fordouble difference processing of baselines. Furthermore, the gen-eration of Sentinel-3 carrier phase data has recently been refined toavoid half-cycle ambiguities (Montenbruck et al., 2018), allowingfor proper integer AR. For this study, Sentinel-3 orbits and base-lines are computed for the month September 2018. In all cases,data sampling is 10 s.
How to use CODE’s new clock and phase bias productsSince GPS week 2009 (July 2018) CODE produces a high-quality signal-specific phase bias product (the products for April 2007 have beengenerated for this study), see Fig. 1 . The corresponding OSB files can straightforwardly be introduced into GPSEST, the main parameterestimation program of the Bernese GNSS Software, which has been extended to allow for zero-difference ambiguity resolution, see Fig. 2.The new CODE rapid, final, and MGEX clock corrections are based on a fully consistent ambiguity fixing processing.
Bias SVN PRN Station name Obs yyyy mm dd hh mm ss yyyy mm dd hh mm ss Value (ns) RMS (ns)
*** **** *** ************* *** ******************* ******************* *********** ***********OSB G032 G01 C1C 2007 04 01 00 00 00 2007 04 02 00 00 00 0.52254 0.00610OSB G032 G01 C1W 2007 04 01 00 00 00 2007 04 02 00 00 00 -0.00000 0.00025OSB G032 G01 C2W 2007 04 01 00 00 00 2007 04 02 00 00 00 -0.00000 0.00025...OSB G032 G01 L1C 2007 04 01 00 00 00 2007 04 02 00 00 00 0.16431 0.00000OSB G032 G01 L1W 2007 04 01 00 00 00 2007 04 02 00 00 00 0.16431 0.00000OSB G032 G01 L2C 2007 04 01 00 00 00 2007 04 02 00 00 00 0.24524 0.00000OSB G032 G01 L2W 2007 04 01 00 00 00 2007 04 02 00 00 00 0.24524 0.00000OSB G032 G01 L2X 2007 04 01 00 00 00 2007 04 02 00 00 00 0.24524 0.00000...
Figure 1: Observation-specific bias (OSB) files generated by CODE, containingpseudo-range and phase biases for Integer-PPP (IPPP).
Figure 2: GPSEST, the main parameter estimation program of the BerneseGNSS Software, now allows for zero-difference ambiguity resolution.
Ambiguity resolutionFigure 3 shows the percentage of successfully resolved narrowlaneambiguities for both the ZD AR and DD AR in the GRACE andSentinel-3 processing. For GRACE, slightly less ambiguities areresolved in the DD processing compared to the ZD processing. InZD AR more ambiguities are resolved for GRACE-B (99.1%) thanfor GRACE-A (97.1%). The AR success rate for Sentinel-3 is in allcases close to 100%.
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Figure 3: Percentage of resolved narrowlane ambiguities for GRACE (top) andSentinel-3 (bottom). Red: ZD AR for LEO A. Green: ZD AR for LEO B. Blue: DDAR for baseline.
K-Band validationGRACE offers the possibility to validate computed orbits, in par-ticular the along-track component, with the ultra-precise inter-satellite K-band measurements. Figure 4 shows the K-bandrange (KBR) residuals of reduced-dynamic ambiguity-float andambiguity-fixed GRACE orbits for one day, as well as the spec-tral analysis of the residuals. Both the ZD and the DD AR lead to asignificant reduction of KBR residuals, especially regarding longerperiods. Figure 5 shows the daily RMS values of K-band residu-als for the entire month for both reduced-dynamic and kinematicorbit and baseline solutions. For the reduced-dynamic and kine-matic solutions ZD AR and DD AR implies a reduction of the KBRresiduals by about a factor of 3-4 and 3-5, respectively.
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Figure 5: Daily RMS values of K-band residuals for reduced-dynamic (left) andkinematic (right) orbit and baseline solutions. For the kinematic solution statisticsan outlier threshold of 10 cm was applied.
Reduced-dynamic vs. kinematic solutionsFigure 6 shows for GRACE-A the differences between thereduced-dynamic and kinematic single-satellite solutions for oneday. It can be observed that especially in along-track and cross-track direction the long-periodic differences are significantly re-duced by the ZD AR. Figure 7 shows the daily RMS values oforbit differences for April 2007. Figure 8 shows the correspond-ing statistics for Sentinel-3 for September 2018. In all cases a pro-nounced reduction can be observed in the ambiguity-fixed orbits.
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ferences between reduced-dynamic andkinematic orbit solutions for April 2007in radial (top left), along-track (top right),and cross-track (bottom) direction forGRACE-A and -B.
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Sentinel-3A ZDSentinel-3B ZD Figure 8: Daily RMS values of dif-
ferences between reduced-dynamic andkinematic orbit solutions for September2018 in radial (top left), along-track (topright), and cross-track (bottom) directionfor Sentinel-3A and -3B.
SLR validationSatellite Laser Ranging (SLR) normal points from 12 laser stationswere used for orbit validation, residuals larger than 20 cm havebeen rejected and an elevation cutoff of 10◦ applied. No parame-ters were estimated. Table 1 shows the mean values and standarddeviations of SLR residuals, confirming the positive impact of ZDAR on the orbit quality.
Float ZD AROrbits red.-dyn. kin. red.-dyn. kin.GRACE-A +0.5/15.5 +1.5/16.6 +2.5/12.4 +2.6/12.0GRACE-B +0.9/12.1 -0.5/16.9 +3.8/8.5 +3.7/9.6Sentinel-3A -6.0/11.5 -6.5/14.7 -5.7/10.7 -5.4/11.9Sentinel-3B -2.9/12.4 -4.3/15.2 -3.5/10.4 -3.3/11.1
Table 1: Mean values and standard deviations in mm of SLR residuals over April2007 (GRACE) and September 2018 (Sentinel-3), respectively.
ConclusionsUsing CODE’s new observation-specific phase bias product, aconsistent ambiguity-fixed clock product and extensions of theBernese GNSS Software, zero-difference ambiguity resolution wasapplied to the GPS-based POD of the GRACE and Sentinel-3 satel-lites. Ambiguity fixing is shown to significantly improve the orbitquality in terms of the independent validation measures K-bandand SLR, as well as in terms of the internal consistency betweenthe reduced-dynamic and kinematic orbit solutions. The achiev-able relative orbit quality is comparable to what can be obtainedfrom a double-difference processing of space baselines employingambiguity fixing. All results confirm a high quality of the CODEclock and phase bias product.
ReferencesR. Dach, S. Lutz, P. Walser, and P. Fridez, editors. Bernese GNSS Software, Version
5.2. Astronomical Institute, University of Bern, Bern, Switzerland, November2015. ISBN 978-3-906813-05-9. doi: 10.7892/boris.72297. User manual.
O. Montenbruck, S. Hackel, and A. Jäggi. Precise orbit determination of theSentinel-3A altimetry satellite using ambiguity-fixed GPS carrier phase obser-vations. Journal of geodesy, 92(7):711–726, 2018.
Contact addressDaniel ArnoldAstronomical Institute, University of BernSidlerstrasse 53012 Bern (Switzerland)[email protected]
