Direct Signal Power Update

The focus for GNSS-Reflectometry with the SGR-ReSI is to measure geophysical parameters such as ocean wind-speed and mean-squared-slope. This is performed by receiving the GPS navigation signals reflected from the Earth, measuring the power and signal distortion caused by the reflection then inferring back the parameters of the surface.

One of the factors that affect the reflection power measurement is the power level transmitted by each of the GNSS satellites. There is variation between each GPS transmitter and over their antenna patterns.

The SGR-ReSI uses the signals directly from the GPS transmitters for navigation and for the steering of the DDM processing to the location of the reflection. The power of the direct signals is measured onboard with a similar setup to that used for the reflections.

With the last update to MERRByS the direct signal power measurements were exported to NetCDF file and released. These contain the time-series of our direct signal power measurments. The DirectSignalPower.nc files have now been replaced on MERRByS with version 0.3. Additional fields have been added and a number of corrections to the fields, so that now radiometric calibration can be performed on the data.

The Direct Signal Power file is in NetCDF format and contains self documenting headers that can be inspected from the file itself. There are some minor updates in a new version of the  MERRByS Product Manual V4.

Update of Level 2 data

The Level 2 FDI wind-speed data has been updated to include measurements at high and low latitudes.

The processing remains FDI V1.11.

Originally a filter of 55 degree latitude was used to be sure that sea ice was excluded from the retrieval. The new approach filters using a sea-ice map so that our measurements continue closer to the Arctic and Antarctic.

Below are the availability of L2 wind-speed product,

With new sea ice filter:

Original sea ice filter by latitude: