Accurately measuring Earth's long-wavelength gravity field
"The satellite missions Grace, Grace Follow-on, and GOCE have been instrumental in capturing the Earth's gravity field. Yet, these missions fall short in resolving long-wavelength gravitational components that span continental scales," said Sandro Krauss from the Institute of Geodesy at TU Graz. In contrast, SLR measurements are exceptionally precise in capturing these larger-scale wavelengths.
SLR technology utilizes a global network of laser stations targeting satellites equipped with retro-reflectors. By tracking the return time of the laser, satellites' positions can be pinpointed to centimeter-level precision, and repeated measurements allow researchers to detect shifts in satellite orbits caused by mass changes on Earth's surface.
Krauss explained, "Combining SLR with other satellite data significantly improves gravity field resolution, enabling detailed mapping of water mass distributions on Earth. Furthermore, this data improves the prediction and mapping of satellite and debris positions, enhancing orbital safety."
Over 40,000 space debris objects larger than ten centimeters orbit Earth, and about 1 million fragments one centimeter or larger are also in motion, traveling at 30,000 km/h. Due to their varied trajectories, collisions with these objects pose significant threats to satellites and crewed space missions. Therefore, accurately predicting their orbits is essential for space safety.
Precision improvements: from kilometers to centimeters
Radar is the current standard for tracking space debris, but its precision is limited to several kilometers, which complicates exact location tracking. TU Graz, in collaboration with the Austrian Academy of Sciences' Space Research Institute's Satellite Laser Ranging Station, has achieved breakthroughs in accuracy.
TU Graz's team developed force models that enable satellite and debris tracking within 100-meter accuracy, facilitating precise laser tracking. Additional measurements during subsequent passes refined these estimates, further enhancing orbital predictions.
Torsten Mayer-Gurr from TU Graz's Institute of Geodesy stated, "To predict orbits, we need to model all forces acting on satellites, including gravitational influences from mass distributions like water. By merging these models with SLR data, our GROOPS software achieves highly accurate results. To our knowledge, GROOPS is the only open-source tool available for gravity field, orbit determination, and SLR analysis, and user feedback enables continuous improvement."
Research Report:Bridging the gap between GRACE and GRACE Follow-On by combining high - low satellite-to-satellite tracking data and satellite laser ranging
Related Links
Graz University of Technology
Space Technology News - Applications and Research
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