The Copernicus POD Service and beyond: Scientific ...€¦ · The Copernicus POD Service and...
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The Copernicus POD Service and beyond: Scientific exploitation of the orbit-related data and products H. Peter 1 , J. Fernández 2 , C. Fernández 2 , P. Féménias 3 1 PosiTim UG, Germany 2 GMV AD, Spain 3 ESA/ESRIN, Italy Poster compiled by H. Peter, April 2017 [email protected] Copernicus POD Quality Working Group The Copernicus POD (Precise Orbit Determination) Service is an operational service to provide accurate orbit and attitude products for the Sentinel-1, -2, and -3 missions. All these Sentinel satellites are equipped with two dual-frequency GPS receivers (nominal and redundant) delivering the observables for the precise orbit determination. Sentinel-3 is also equipped with a laser retro reflector for Satellite Laser Ranging and with a DORIS receiver. Both techniques allow for an independent validation of the GPS-derived orbit products. Summary Acknowledgements: The Copernicus POD Service is financed under ESA contract no. 4000108273/13/1- NB, which is gratefully acknowledged. The work performed in the frame of this contract is carried out with funding by the European Union. The views expressed herein can in no way be taken to reflect the official opinion of either the European Union or the European Space Agency. Copernicus POD Service The Copernicus POD Service is supported by the Copernicus POD Quality Working Group (QWG) which is built by POD experts from the following institutions: Astronomical Institute, University of Bern, Switzerland Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen, Germany European Space Operations Centre, Darmstadt, Germany Delft University of Technology, Delft, The Netherlands Technische Universität München, Munich, Germany CNES (Centre Nationale d‘Etudes Spatiales), Toulouse, France (only for S-3) Eumetsat (European Organisation for the Exploitation of Meteorological Satellites), Darmstadt, Germany (only for S-3) The QWG institutions provide independent Sentinel orbit solutions for validation. Different software packages and different orbit parametrization are used from the QWG. Orbit-related data The Sentinel orbit products (listed in Tab.1) are Level 2 products and are made available for the PDGS of the corresponding mission. Orbit-related input data (Level 1): GPS observation data is available in the well-known RINEX (Receiver INdependent Exchange,[1]) format: • Sentinel-1 and -2: 0.1 Hz • Sentinel-3: 1 Hz Attitude information is provided • as input files with quaternions for Sentinel-2 and -3 • as model for Sentinel-1 Navigation solutions from the satellites are provided in sp3 [2] format Auxiliary information such as GPS antenna reference point coordinates, antenna phase center offsets and variations, mass history and CoG position, maneuver information etc. are provided either in separate files or within a specific Technical Note describing the necessary information. The GNSS RINEX L1B files of the first three Sentinel missions are planned to be provided in the Copernicus Open Access Hub (https ://scihub.copernicus.eu/) in Q3 of this year. Beyond the scope of precise orbit determination the data is suitable for scientific exploitation covering among others geodetic and atmospheric applications. Anyone you is willing to become a POD S3VT (S-3 Validation Team) member is invited to apply @ http ://earth.esa.int/aos/S3VT EGU2017- 6731 EGU General Assembly 2017 April 23-29, 2017, Vienna, Austria Mission Category Orbit Accuracy (RMS) Latency Coverage S-1 NRT 10 cm (2D) 180 min 2 orbits NTC 5 cm (3D) 20 days 26 h S-2 NRT (pred.) 3 m (2D) 90 min before ANX 2 orbits NRT 1 m (3D) 30 min Received PVT span + 2 orbits backwards S-3 NRT 10 cm radial (target of 8 cm) 30 min Received PVT span + 5 OSV before and after STC 4 cm radial (target of 3 cm) 1.5 days 26 h NTC 3 cm radial (target of 2 cm) 25 days 26 h Table1: Orbit products, accuracy and latency requirements, and coverage The scientific exploitation of the orbit-related data and products is manifold. First of all the Sentinel‘s orbit validation within the Copernicus POD QWG is a scientific exploitation. Different approaches (e.g., purely mathematical or partly based on physical models) to combine the orbit solutions are studied for instance. One idea behind a combined orbit is, e.g., to generate a reference orbit to which all other solutions are compared. Mean RMS values of comparisons of all available orbit solutions to such a combined orbit are shown in the plots below for Sentinel-2A and Sentinel-3A from a 4-month period (Oct 2016-Jan 2017). Scientific Exploitation [1] IGS RINEX WG, RTCM-SC104 (2015) RINEX – The Receiver INdependent EXchange format, Version 3.03, 14 July 2015. ftp ://igs.org/pub/data/format/rinex303.pdf [2] Hilla, S. (2015) The Extended Standard Product 3 Orbit Format (sp3-c), https ://igscb.jpl.nasa.gov/igscb/data/format/sp3c.txt [3] Stolle, C. et al. (2016) Strong plasma density fluctuations and GPS and TEC performance, presentation at the 6th Swarm DQW, 24-27 Sep 2016, Edinburgh, U.K. [4] Arnold, D. et al. (2017) Combined Swarm/Sentinel Gravity Fields, poster at the 4th Swarm Science meeting, 20-24 Mar 2017, Banff, Canada References Orbit modelling Ionosphere Dual-frequency GPS observations provide information about the TEC (Total Electron Content) in the ionosphere. Data from LEOs are important for TEC studies due to the global coverage and continuous availability. [3] Stolle et al.(2016) For instance the slant TEC from different GPS satellite passes tracked on Swarm-C revealed fluctuations in TEC before GPS tracking failures occur (grey shaded). These problems could be minimized by modifications in the GPS receiver settings. The Sentinel GPS data will provide a large amount of additional data to study, e.g., short-time TEC fluctuations. Gravity field modelling Sophisticated satellite models (in terms of geometry and optical properties) are needed to provide best possible orbit products. The Sentinel-1 satellites have a complex structure where all parts of the satellite have to be considered correctly. In first satellite models the front of the SAR antenna and the mountings of the solar panels were missing. The left plot shows the corresponding areas, which had been added (green => v8, green+blue => v9). The plot on the right shows for the corresponding satellite models the estimated scale factor for the solar radiation pressure acting on the satellite (value of 1 is ideal). This shows the large impact of small changes in a satellite model on the orbit parameters. 2.46 m 2 3.46 m 2 Over the last decade the GRACE mission has been used for time-variable gravity field modelling. To bridge the gap between GRACE and the upcoming GRACE-FO mission kinematic orbit data from as many LEO missions as possible are used instead. The ESA Earth Explorer Swarm mission is already known to be important as gap filler for the time-variable gravity field modelling. The difference degree amplitudes (solid lines) in the plot show that the higher flying Sentinel satellites can contribute on the same level as the Swarm satellites at least to the very low terms of the gravity field. The low terms are the most important ones for time-variable gravity field modelling. [4] Arnold et al.(2017) Other opportunities for scientific exploitation are described in the boxes below. These are not the only ones but they exemplarily stand for a number of interesting research topics, which are or will be triggered by the availability of the orbit- related input data from the first three Sentinel missions.
Transcript of The Copernicus POD Service and beyond: Scientific ...€¦ · The Copernicus POD Service and...
The Copernicus POD Service and beyond: Scientific exploitation of the orbit-related data
and products H. Peter1, J. Fernández2, C. Fernández2, P. Féménias3
1 PosiTim UG, Germany2 GMV AD, Spain3 ESA/ESRIN, Italy
Poster compiled by H. Peter, April [email protected]
Copernicus POD Quality Working Group
The Copernicus POD (Precise Orbit Determination) Service is anoperational service to provide accurate orbit and attitudeproducts for the Sentinel-1, -2, and -3 missions.All these Sentinel satellites are equipped with two dual-frequencyGPS receivers (nominal and redundant) delivering the observablesfor the precise orbit determination. Sentinel-3 is also equippedwith a laser retro reflector for Satellite Laser Ranging and with aDORIS receiver. Both techniques allow for an independentvalidation of the GPS-derived orbit products.
Summary
Acknowledgements: The Copernicus POD Service is financed under ESA contract no. 4000108273/13/1-NB, which is gratefully acknowledged.The work performed in the frame of this contract is carried out with funding by the European Union. The views expressed herein can in no way be taken to reflect the official opinion of either the European Union or the European Space Agency.
Copernicus POD Service
The Copernicus POD Service is supported by the Copernicus PODQuality Working Group (QWG) which is built by POD experts fromthe following institutions: Astronomical Institute, University of Bern, Switzerland Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen, Germany European Space Operations Centre, Darmstadt, Germany Delft University of Technology, Delft, The Netherlands Technische Universität München, Munich, Germany CNES (Centre Nationale d‘Etudes Spatiales), Toulouse, France (only for S-3) Eumetsat (European Organisation for the Exploitation of Meteorological
Satellites), Darmstadt, Germany (only for S-3)
The QWG institutions provide independent Sentinel orbit solutionsfor validation. Different software packages and different orbitparametrization are used from the QWG.
Orbit-related data
The Sentinel orbit products (listed in Tab.1) are Level 2products and are made available for the PDGS of thecorresponding mission.
Orbit-related input data (Level 1):GPS observation data is available in the well-known RINEX(Receiver INdependent Exchange,[1]) format:• Sentinel-1 and -2: 0.1 Hz• Sentinel-3: 1 HzAttitude information is provided• as input files with quaternions for Sentinel-2 and -3• as model for Sentinel-1Navigation solutions from the satellites are provided in sp3[2] format
Auxiliary information such as GPS antenna reference pointcoordinates, antenna phase center offsets and variations,mass history and CoG position, maneuver information etc.are provided either in separate files or within a specificTechnical Note describing the necessary information.
The GNSS RINEX L1B files of the first threeSentinel missions are planned to be provided inthe Copernicus Open Access Hub(https://scihub.copernicus.eu/) in Q3 of this year.Beyond the scope of precise orbit determinationthe data is suitable for scientific exploitationcovering among others geodetic andatmospheric applications.
Anyone you is willing to become a POD S3VT (S-3Validation Team) member is invited to apply @http://earth.esa.int/aos/S3VT
EGU2017- 6731EGU General Assembly 2017April 23-29, 2017, Vienna, Austria
Mission CategoryOrbit Accuracy(RMS)
Latency Coverage
S-1NRT 10 cm (2D) 180 min 2 orbits
NTC 5 cm (3D) 20 days 26 h
S-2
NRT (pred.) 3 m (2D) 90 min before ANX 2 orbits
NRT 1 m (3D) 30 minReceived PVT span +2 orbits backwards
S-3
NRT10 cm radial(target of 8 cm)
30 minReceived PVT span +5 OSV before and after
STC4 cm radial(target of 3 cm)
1.5 days 26 h
NTC3 cm radial(target of 2 cm)
25 days 26 h
Table1: Orbit products, accuracy and latency requirements, and coverage The scientific exploitation of the orbit-related data andproducts is manifold.First of all the Sentinel‘s orbit validation within theCopernicus POD QWG is a scientific exploitation. Differentapproaches (e.g., purely mathematical or partly based onphysical models) to combine the orbit solutions are studiedfor instance. One idea behind a combined orbit is, e.g., togenerate a reference orbit to which all other solutions arecompared. Mean RMS values of comparisons of all availableorbit solutions to such a combined orbit are shown in theplots below for Sentinel-2A and Sentinel-3A from a 4-monthperiod (Oct 2016-Jan 2017).
Scientific Exploitation
[1] IGS RINEX WG, RTCM-SC104 (2015) RINEX – TheReceiver INdependent EXchange format, Version 3.03, 14July 2015. ftp://igs.org/pub/data/format/rinex303.pdf[2] Hilla, S. (2015) The Extended Standard Product 3 OrbitFormat (sp3-c),https://igscb.jpl.nasa.gov/igscb/data/format/sp3c.txt[3] Stolle, C. et al. (2016) Strong plasma densityfluctuations and GPS and TEC performance, presentationat the 6th Swarm DQW, 24-27 Sep 2016, Edinburgh, U.K.[4] Arnold, D. et al. (2017) Combined Swarm/SentinelGravity Fields, poster at the 4th Swarm Science meeting,20-24 Mar 2017, Banff, Canada
References
Orbit modelling
IonosphereDual-frequency GPS observations provide informationabout the TEC (Total Electron Content) in theionosphere. Data from LEOs are important for TECstudies due to the global coverage and continuousavailability.
[3] Stolle et al.(2016)
For instance the slant TEC from different GPS satellitepasses tracked on Swarm-C revealed fluctuations inTEC before GPS tracking failures occur (grey shaded).These problems could be minimized by modificationsin the GPS receiver settings.The Sentinel GPS data will provide a large amount ofadditional data to study, e.g., short-time TECfluctuations.
Gravity field modelling
Sophisticated satellite models (in terms of geometry and optical properties) are needed toprovide best possible orbit products. The Sentinel-1 satellites have a complex structure whereall parts of the satellite have to be considered correctly. In first satellite models the front of theSAR antenna and the mountings of the solar panels were missing. The left plot shows thecorresponding areas, which had been added (green => v8, green+blue => v9). The plot on theright shows for the corresponding satellite models the estimated scale factor for the solarradiation pressure acting on the satellite (value of 1 is ideal). This shows the large impact ofsmall changes in a satellite model on the orbit parameters.
2.46 m2
3.46 m2
Over the last decade the GRACE mission has been used fortime-variable gravity field modelling. To bridge the gapbetween GRACE and the upcoming GRACE-FO missionkinematic orbit data from as many LEO missions as possibleare used instead.
The ESA Earth Explorer Swarm mission is already known tobe important as gap filler for the time-variable gravity fieldmodelling. The difference degree amplitudes (solid lines)in the plot show that the higher flying Sentinel satellitescan contribute on the same level as the Swarm satellitesat least to the very low terms of the gravity field. The lowterms are the most important ones for time-variablegravity field modelling.
[4] Arnold et al.(2017)
Other opportunities for scientific exploitation are describedin the boxes below. These are not the only ones but theyexemplarily stand for a number of interesting research topics,which are or will be triggered by the availability of the orbit-related input data from the first three Sentinel missions.
