The GNSS receiver for occultation, reflectometry and scatterometry (GORS) has been designed and developed within the framework of the GITEWS project (German Indonesian Tsunami Early Warning System Project, 2006 bis 2009) by the Russian-American manufacturer JAVAD GNSS for the project partners GFZ and DLR. Initially, the instrument was based on the 72-channel GeNeSiS-112 receiver board; in 2008 TR-G3T modules based on the 216-channel Triumph chip set were introduced. Later development utilized the Duo-G2D and Quattro-G3D modules featuring two and four antenna input lines, respectively. These receivers support the GPS L1/L2/L2C as well as the Galileo-E1 signals.
For the GORS project the manufacturer JAVAD GNSS created customized firmware versions which provide positioning solutions as well as carrier phase and pseudorange data with high temporal resolution. In addition, these firmware version output of I/Q vectors with 200 Hz sampling rate and cloning of two or more detection channels (channel slaving). Control and monitoring of the individual receiver channels during an observation is accomplished with JPS commands sent via the RS232 interface. The high bandwidth of the USB interface allows to handle high-rate measurement data from several channels simultaneously. These JAVAD receivers with modified firmwares were successfully used in a number of ground-based, ship- and airborne measurement campaigns (e.g., Airship Zeppelin, Research Aircraft HALO, Research Vessels Fram and Polarstern).
References
Semmling, M., Wickert, J., Kreb, F., Hoque, M.M., Divine, D.V., Gerland, S., Spreen, G.: Sea-Ice Permittivity Derived from GNSS Reflection Profiles: Results of the MOSAiC Expedition, IEEE Transactions on Geoscience and Remote Sensing, 60, 36, doi: 10.1109/TGRS.2021.3121993, 2022.
Rajabi M., Hoseini M., Nahavandchi H., Semmling M., Ramatschi M., Goli M., Haas R., Wickert J., Polarimetric GNSS-R Sea Level Monitoring Using I/Q Interference Patterns at Different Antenna Configurations and Carrier Frequencies, IEEE Transactions on Geoscience and Remote Sensing, 60:1–13, https://doi.org/10.1109/TGRS.2021.3123146, 2022.
Semmling, M., Rösel, A., Divine, D. V., Gerland, S., Stienne, G., Reboul, S., Ludwig, M., Wickert, J., Schuh, H.: Sea-Ice Concentration Derived From GNSS Reflection Measurements in Fram Strait. - IEEE Transactions on Geoscience and Remote Sensing, 57, 12, 10350-10361, https://doi.org/10.1109/TGRS.2019.2933911, 2019.
Semmling, A. M., J. Wickert, S. Schön, R. Stosius, M. Markgraf, T. Gerber, M. Ge, and G. Beyerle, A zeppelin experiment to study airborne altimetry using specular Global Navigation Satellite System reflections, Radio Sci., 48, 427–440 (2013). doi:10.1002/rds.20049
Helm A., Montenbruck O., Ashjaee J., Yudanov S., Beyerle G., Stosius R., Rothacher M.; GORS - A GNSS Occultation, Reflectometry and Scatterometry Space Receiver; ION-GNSS-2007 Conference; 26-28 Sept. 2007; Fort Worth, Texas (2007).
