The PO.DAAC is pleased to announce the public release of the Cyclone Global Navigation Satellite System (CYGNSS) Version 2.0 Science Data Record, which includes datasets from processing levels 1, 2, and 3. CYGNSS is a NASA Earth System Science Pathfinder Mission that will collect the first frequent space‐based measurements of surface wind speeds in the inner core of tropical cyclones. Made up of a constellation of eight microsatellites, the observatories will provide nearly gap-free Earth coverage using an orbital inclination of approximately 35° from the equator, with a mean (i.e., average) revisit time of seven hours and a median revisit time of three hours. This inclination allows CYGNSS to measure ocean surface winds between 38° N and 38° S latitude. This range includes the critical latitude band for tropical cyclone formation and movement.
Version 2.0 represents the first “post-provisional” release of the CYGNSS Science Data Record generated using calibrated and validated level 1 calibration algorithms which were trained and assessed using engineering and science data collected during Phase E operations. Version 2.0 supersedes the previous provisional data versions 1.1 and 1.0, and all data users moving forward are advised to use this latest version for fundamental science and applied research activities.
The Level 1 (L1) Science Data Record contains both Level 1A (L1A) and Level 1B (L1B) measurement parameters and quality indicators. The primary measurement parameters are the Delay Doppler Map (DDM) of Bistatic Radar Cross Section (BRCS), the Delay Doppler Map Average (DDMA) of Normalized Bistatic Radar Cross Section (NBRCS), and the Leading Edge Slope (LES) of the integrated delay waveform. The Level 2 (L2) Science Data Record contains the following measurement parameters: wind speed (from DDM and LES), mean square slope (MSS), various quality flags/indicators, and other measurements and ancillary parameters; the L2 wind speed retrieval is also provided from two different geophysical model functions (GMF) that deliver wind speed into two unique data variables: one provides wind speed using a traditional “Fully Developed Seas” GMF (i.e., the legacy approach) while the other is derived from a “Young Seas/Limited Fetch” GMF that is tailored for tropical cyclone conditions. The Level 3 (L3) Science Data Record primarily delivers hourly averaged wind speed and MSS provided on a 0.2x0.2 degree latitude by longitude equirectangular grid.
Each L1, L2, and L3 data file is provided in netCDF-4 format using internal compression. All data files provide data covering up to a full 24-hour UTC day. The L1 data files are specific to one of the eight CYGNSS observatories. The L2 and L3 data files consist of an aggregation of data provided from all operating observatories for a given day.
The time series for all datasets starts on 18 March 2017 and continues to the near present day with a maximum mission-specified latency of 6 days. Actual data latency may oscillate between 1 to 6 days from the last retrieved observation with lowest possible latency for the L1 data.
All interested data users may now gain access to the data and learn more about the updates and improvements made from Version 1.1 to Version 2.0 by visiting the following dataset information pages (specific to each processing level):
- L1: https://podaac.jpl.nasa.gov/dataset/CYGNSS_L1_V2.0
- L2: https://podaac.jpl.nasa.gov/dataset/CYGNSS_L2_V2.0
- L3: https://podaac.jpl.nasa.gov/dataset/CYGNSS_L3_V2.0
The CYGNSS Handbook and ATBD will soon be updated to include details regarding the Version 2.0 calibration, algorithm improvements, and updates to the data model. The Handbook, ATBD, and other reference materials may be accessed here: https://podaac.jpl.nasa.gov/CYGNSS
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