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  • 1
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    Scale Factors of the Thermospheric Density: A Comparison of Satellite Laser Ranging and Accelerometer Solutions (2021)
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    Publication Date: 2022-03-25
    Description: A major problem in the precise orbit determination (POD) of satellites at altitudes below 1,000 km is the modeling of the aerodynamic drag which mainly depends on the thermospheric density and causes the largest non‐gravitational acceleration. Typically, empirical thermosphere models are used to calculate density values at satellite positions but current thermosphere models cannot provide the required accuracy. Thus, unaccounted variations in the thermospheric density may lead to significantly incorrect satellite positions. For the first time, we bring together thermospheric density corrections for the NRLMSISE‐00 model in terms of scale factors with a temporal resolution of 12 hr derived from satellite laser ranging (SLR) and accelerometer measurements. Whereas, the latter are in situ information given along the satellite orbit, SLR results have to be interpreted as mean values along the orbit within the underlying time interval. From their comparison, we notice a rather similar behavior with correlations of up to 80% and more depending on altitude. During high solar activity, scale factors vary around 30% at low solar activity and up to 70% at high solar activity from the value one. In addition, we found the scaled thermospheric density decreasing stronger as the modeled density of NRLMSISE‐00. To check the reliability of the SLR‐derived scale factors, we compare the POD result of two different software packages, namely DOGS‐OC from DGFI‐TUM and GROOPS from IGG Bonn. Furthermore, a validation of our estimated scale factors with respect to an external data set proofs the high quality of the obtained results.
    Description: Plain Language Summary: Variations in the density of the thermosphere must be taken into account when modeling and predicting the motion of satellites in the near‐Earth environment. Typically, thermospheric densities at the position of satellites are provided by models, but their accuracy is limited. Due to the sensitivity of satellites orbiting the Earth in the altitude range of the thermosphere, they can be used to derive information about the thermospheric density. In this study, we compare for the first time thermospheric density corrections in terms of scale factors for the NRLMSISE‐00 model with a temporal resolution of 12 hr derived from two geodetic measurement techniques, namely satellite laser ranging (SLR) and accelerometry. Our results demonstrate that both measurement techniques can be used to derive comparable scale factors of the thermospheric density, which vary around the desired value one. This indicates to which extent the NRLMSISE‐00 model differs from the observed thermospheric density. On average, during high solar activity, the model underestimates the thermospheric density and can be scaled up using the estimated scale factors. We additionally discuss our estimated scale factors with respect to an external data set. Furthermore, we validate the approach of deriving scale factors from SLR measurements by using two independent software packages.
    Description: Key Points: For the first time, we compare scale factors of the thermospheric density derived from satellite laser ranging (SLR) and accelerometer measurements. The estimated scale factors vary by up to 30% at low solar activity and up to 70% at high solar activity from the desired value 1. Correlations of 0.7–0.8 are obtained between the estimated scale factors from SLR and accelerometer measurements depending on the height.
    Description: German Research Foundation (DFG)
    Description: Technical University of Munich (TUM)
    Keywords: ddc:551.5 ; ddc:526.1
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 2
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    GFZ VER11 SLCCI precise orbits of altimetry satellites ERS-1, ERS-2, Envisat, TOPEX/Poseidon, Jason-1 and Jason-2 in the ITRF2008 (2016)
    GFZ Data Services
    Details
    Publication Date: 2022-01-17
    Description: Abstract
    Description: The data set provides GFZ VER11 orbits of altimetry satellitesERS-1 (August 1, 1991 - July 5, 1996),ERS-2 (May 13, 1995 - February 27, 2006),Envisat (April 12, 2002 - April 8, 2012),Jason-1 (January 13, 2002 - July 5, 2013) andJason-2 (July 5, 2008 - April 5, 2015)TOPEX/Poseidon (September 23, 1992 - October 8, 2005),derived at the time spans given at Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences within the Sea Level phase 2 project of the European Space Agency (ESA) Climate Change Initiative using "Earth Parameter and Orbit System - Orbit Computation (EPOS-OC)" software and the Altimeter Database and processing System (ADS, http://adsc.gfz-potsdam.de/ads/) developed at GFZ. The orbits were computed in the same (ITRF2008) terrestrial reference frame for all satellites using common, most precise models and standards available and described below.The ERS-1 orbit is computed using satellite laser ranging (SLR) and altimeter crossover data, while the ERS-2 orbit is derived using additionally Precise Range And Range-rate Equipment (PRARE) measurements. The Envisat, TOPEX/Poseidon, Jason-1 and Jason-2 orbits are based on Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) and SLR observations.The orbit files are available in the Extended Standard Product 3 Orbit Format (SP3-c, ftp://igscb.jpl.nasa.gov/igscb/data/format/sp3c.txt) Files are gzip-compressed. File names are given as sate_YYYYMMDD_SP3C.gz, where "sate" is the abbreviation (ENVI, ERS1, ERS2, JAS1, JAS2, TOPX) of the satellite name, YYYY stands for 4-digit year, MM stands for month and DD stands for day of the beginning of the file.More details on these orbits are provided in Rudenko et al. (2017)
    Keywords: Jason-1 ; Jason-2 ; ERS-1 ; ERS-2 ; Envisat ; ESA CCI Sea Level ; Altimetry satellite ; Low Earth Orbit satellites ; sea level ; TOPEX/POSEIDON ; ITRF2008 ; Earth Remote Sensing Instruments 〉 Active Remote Sensing 〉 Altimeters 〉 Radar Altimeters ; equipment 〉 artificial satellite 〉 observation satellite ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 SATELLITE ORBITS/REVOLUTION 〉 ORBITAL POSITION ; EARTH SCIENCE 〉 OCEANS 〉 SEA SURFACE TOPOGRAPHY 〉 SEA SURFACE HEIGHT
    Language: English
    Type: Dataset
    Format: 6 Files
    Format: application/octet-stream
    Format: application/octet-stream
    Format: application/octet-stream
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    DATA GFZ
  • 3
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    GFZ VER13 SLCCI precise orbits of altimetry satellites ERS-1, ERS-2, Envisat, TOPEX/Poseidon, Jason-1, and Jason-2 in the ITRF2014 reference frame (2018)
    GFZ Data Services
    Details
    Publication Date: 2022-01-17
    Description: Abstract
    Description: The data set provides GFZ VER13 orbits of altimetry satellites:ERS-1 (August 1, 1991 - July 5, 1996),ERS-2 (May 13, 1995 - February 27, 2006),Envisat (April 12, 2002 - April 8, 2012),TOPEX/Poseidon (September 23, 1992 - October 8, 2005),Jason-1 (January 13, 2002 - July 5, 2013) andJason-2 (July 5, 2008 - April 5, 2015)derived at the time spans given at the GFZ German Research Centre for Geosciences (Potsdam, Germany) within the Sea Level phase 2 project of the European Space Agency (ESA) Climate Change Initiative using "Earth Parameter and Orbit System - Orbit Computation (EPOS-OC)" software (Zhu et al., 2004) and the Altimeter Database and processing System (ADS, http://adsc.gfz-potsdam.de/ads/) developed at GFZ. The orbits were computed in the ITRF2014 terrestrial reference frame for all satellites using common, most precise models and standards available and described below.The ERS-1 orbit is computed using satellite laser ranging (SLR) and altimeter crossover data, while the ERS-2 orbit is derived using additionally Precise Range And Range-rate Equipment (PRARE) measurements. The Envisat, TOPEX/Poseidon, Jason-1, and Jason-2 orbits are based on Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) and SLR observations. For Envisat, altimeter crossover data were used additionally at 44 of 764 orbital arcs with gaps in SLR and DORIS data.The orbit files are available in the Extended Standard Product 3 Orbit Format (SP3-c). Files are gzip-compressed. File names are given as sate_YYYYMMDD_SP3C.gz, where "sate" is the abbreviation (ENVI, ERS1, ERS2, JAS1, JAS2, TOPX) of the satellite name, YYYY stands for 4-digit year, MM for month and DD for day of the beginning of the file. More details on these orbits are provided in Rudenko et al. (2018) to which these orbits are supplementary material.
    Keywords: Altimetry satellite ; Low Earth Orbit satellites ; ESA CCI Sea Level ; sea level ; ITRF2014 ; ERS-1 ; ERS-2 ; Envisat ; TOPEX/Poseidon ; Jason-1 ; Jason-2 ; Orbit ; Earth Observation Satellites 〉 ENVISAT ; Earth Observation Satellites 〉 OSTM/JASON-2 ; Earth Observation Satellites 〉 TOPEX/POSEIDON ; Earth Observation Satellites 〉 JASON-1 ; Earth Observation Satellites 〉 ERS Earth Resource Satellite 〉 ERS-2 ; Earth Observation Satellites 〉 ERS Earth Resource Satellite 〉 ERS-1 ; Earth Remote Sensing Instruments 〉 Active Remote Sensing 〉 Altimeters 〉 Radar Altimeters ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 SATELLITE ORBITS/REVOLUTION 〉 ORBITAL POSITION ; EARTH SCIENCE 〉 OCEANS 〉 SEA SURFACE TOPOGRAPHY 〉 SEA SURFACE HEIGHT
    Language: English
    Type: Dataset
    Format: 1 Files
    Format: application/octet-stream
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    DATA GFZ
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