An Assessment of CYGNSS Normalized Bistatic Radar Cross Section Calibration

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Abstract
A cyclone global navigation satellite system (CYGNSS)calibration analysis is presented using version 2.0 of the Level 1 dataset available on PO.DAAC. Three separate analyzes are conducted, namely, an examination of the specular bin location (in delay) andrelationship, an investigation of the impact of recently improved characterizations of the GPS effective isotropically radiated power on CYGNSS, and an intersatellitecalibration analysis. We first noted a correlation between the specular delay bin location and, where an increase in the specular delay bin resulted in an increase inregardless of the wind speed level; a specular delay bin location ranging from 4.75 to 5.00 and from 7.00 to 7.25 resulted in a 14.74 and 17.72 dB median, respectively. Noticeable improvements in the medianwere present in the version 2.0 dataset, when separating the data by GPS block type: for blocks IIR, IIF, and IIR-M, medianwere 15.39, 15.42, and 15.10 dB, respectively (compared to 19.38, 20.53, and 21.38 dB in version 1.1). Finally, an unexpected correlation between the instrument noise floor andwas observed for all eight observatories while conducting the intersatellitecalibration analysis. Approximately 0–1 dB absolutedifference biases (with up to1 dB standard deviation) between spacecrafts were observed. A report of this analysis was presented to CYGNSS scientists and engineers, who eventually found an issue with the D/A DDM scaling algorithm. We expect better statistical performances in future releases of the data.
Funding Information
  • NASA Cyclone Global Navigation Satellite System (NNL13AQ00C)

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