CYGNSS Level 1 Science Data Record Version 2.1

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DOI	10.5067/CYGNS-L1X21
Short Name	CYGNSS_L1_V2.1
Description	This Level 1 (L1) dataset contains the Version 2.1 geo-located Delay Doppler Maps (DDMs) calibrated into Power Received (Watts) and Bistatic Radar Cross Section (BRCS) expressed in units of m2 from the Delay Doppler Mapping Instrument aboard the CYGNSS satellite constellation. This version supersedes Version 2.0. Other useful scientific and engineering measurement parameters include the DDM of Normalized Bistatic Radar Cross Section (NBRCS), the Delay Doppler Map Average (DDMA) of the NBRCS near the specular reflection point, and the Leading Edge Slope (LES) of the integrated delay waveform. The L1 dataset contains a number of other engineering and science measurement parameters, including sets of quality flags/indicators, error estimates, and bias estimates as well as a variety of orbital, spacecraft/sensor health, timekeeping, and geolocation parameters. At most, 8 netCDF data files (each file corresponding to a unique spacecraft in the CYGNSS constellation) are provided each day; under nominal conditions, there are typically 6-8 spacecraft retrieving data each day, but this can be maximized to 8 spacecraft under special circumstances in which higher than normal retrieval frequency is needed (i.e., during tropical storms and or hurricanes). Latency is approximately 6 days (or better) from the last recorded measurement time. The Version 2.1 release represents the second science-quality release. Here is a summary of improvements that reflect the quality of the Version 2.1 data release: 1) data is now available when the CYGNSS satellites are rolled away from nadir during orbital high beta-angle periods, resulting in a significant amount of additional data; 2) correction to coordinate frames result in more accurate estimates of receiver antenna gain at the specular point; 3) improved calibration for analog-to-digital conversion results in better consistency between CYGNSS satellites measurements at nearly the same location and time; 4) improved GPS EIRP and transmit antenna pattern calibration results in significantly reduced PRN-dependence in the observables; 5) improved estimation of the location of the specular point within the DDM; 6) an altitude-dependent scattering area is used to normalize the scattering cross section (v2.0 used a simpler scattering area model that varied with incidence and azimuth angles but not altitude); 7) corrections added for noise floor-dependent biases in scattering cross section and leading edge slope of delay waveform observed in the v2.0 data. Users should also note that the receiver antenna pattern calibration is not applied per-DDM-bin in this v2.1 release.
Version	2.1
Dataset Type	OPEN
Measurement	SPECTRAL/ENGINEERING > RADAR > RADAR REFLECTIVITY > ZENITH SIGNAL POWER SPECTRAL/ENGINEERING > RADAR > RADAR CROSS-SECTION > BISTATIC RADAR CROSS-SECTION
Processing Level	1
Coverage	Region: Global Northernmost Latitude: 40 degrees Southernmost Latitude: 40 degrees Westernmost Longitude: 0 degrees Easternmost Longitude: 360 degrees Time Span: 2017-Mar-18 to Present
Resolution	Spatial Resolution: 25 km (Along) x 25 km (Across)
Projection	Type: Detail: Ellipsoid: WGS 84
Latency	144 hours
Swath Width	2 m
Sample Frequency	4
Temporal Repeat (Nominal)	7.2 Hour
Temporal Repeat (Min)	2.8 Hour
Temporal Repeat (Max)	24 Hour
Platform/Sensor	CYGNSS Platform Name: Cyclone Global Navigation Satellite System (CYGNSS) Orbit Period: 94 minutes Inclination Angle: 35 degrees Ascending Node: 1970-Jan-01 00:00:00 / DDMI SENSOR Name: Delay Doppler Mapping Instrument (DDMI) Swath Width: 25 km Description: Delay Doppler Mapping Instrument (DDMI)
Project	Cyclone Global Navigation Satellite System (CYGNSS)
Data Provider	Creator: CYGNSS Release Place: PO.DAAC Release Date: 2018-Sep-21 Resource: http://clasp-research.engin.umich.edu/missions/cygnss/
Keyword(s)	cygnss, ddm, ddmi, ddma, doppler, delay doppler, delay, specular point, waveform, les, leading edge slope, bistatic, bi-static, radar, brcs, sigma0, sigma-0, sigma naught, sigma-naught, nbrcs, wind, winds, wind speed, version 2.1, v2.1
Persistent ID	PODAAC-CYGNS-L1X21

Questions related to this dataset? Contact podaac@podaac.jpl.nasa.gov

PO.DAAC DRIVE	https://podaac-tools.jpl.nasa.gov/drive/files/allData/cygnss/L1/v2.1
OPENDAP	https://podaac-opendap.jpl.nasa.gov/opendap/allData/cygnss/L1/v2.1/
Format (Compression)	NETCDF (NONE)
Read Software
IDL	https://podaac-tools.jpl.nasa.gov/drive/files/common/sw/generic_nc_readers/idl Generic IDL netCDF Reader
MATLAB	https://podaac-tools.jpl.nasa.gov/drive/files/common/sw/generic_nc_readers/matlab/ Generic MATLAB netCDF Reader
R	https://podaac-tools.jpl.nasa.gov/drive/files/common/sw/generic_nc_readers/R/ Generic R netCDF Reader
Python	https://podaac-tools.jpl.nasa.gov/drive/files/common/sw/generic_nc_readers/python/ Generic Python netCDF Reader

User's Guide
Level 1 Data Dictionary	https://podaac-tools.jpl.nasa.gov/drive/files/allData/cygnss/L1/docs/148-0346-6_L1_v2.1_netCDF_Data_Dictionary.xlsx
Project Materials
NASA CYGNSS Handbook	http://clasp-research.engin.umich.edu/missions/cygnss/reference/cygnss-mission/CYGNSS_Handbook_April2016.pdf Deriving Surface Winds from Tropical Cyclones
CYGNSS Mission Page	http://clasp-research.engin.umich.edu/missions/cygnss/
CYGNSS Algorithm Theoretical Basis Document Level 1B DDM Calibration	http://clasp-research.engin.umich.edu/missions/cygnss/reference/148-0137_ATBD_L1B_DDMCalibration_Rev2_Aug2018_release.pdf Level 1B DDM Calibration Algorithm Theoretical Basis Document, S. Gleason, CYGNSS Project Document 148-0137, Rev 2, 20 Aug. 2018.
CYGNSS Algorithm Theoretical Basis Document Level 1A DDM Calibration	http://clasp-research.engin.umich.edu/missions/cygnss/reference/148-0136_ATBD_L1A_DDMCalibration_Rev2_Aug2018_release.pdf Level 1A DDM Calibration Algorithm Theoretical Basis Document, S. Gleason, CYGNSS Project Document 148-0136, Rev 2, 20 Aug. 2018.
Journal References
Gleason et al. 2016 (TGRS)	https://doi.org/10.1109/TGRS.2015.2502245 Gleason, S., C. Ruf, M. P. Clarizia, A. O'Brien, 'Calibration and Unwrapping of the Normalized Scattering Cross Section for the Cyclone Global Navigation Satellite System (CYGNSS)', IEEE Trans. Geosci. Remote Sens., doi:10.1109/TGRS.2015.2502245, 2016.
n-Orbit Performance of the Constellation of CYGNSS Hurricane Satellites.	https://doi.org/10.1175/BAMS-D-18-0337.1 Ruf, C., S. Asharaf, R. Balasubramaniam, S. Gleason, T. Lang, D. McKague, D. Twigg, and D. Waliser. (2019). In-Orbit Performance of the Constellation of CYGNSS Hurricane Satellites. Bull. Amer. Meteor. Soc., 100, 2009 - 2023, https://doi.org/10.1175/BAMS-D-18-0337.1.
A CYGNSS-based algorithm for the detection of inland waterbodies	https://doi.org/10.1029/2019GL085134
Ruf et al. 2015 (BAMS)	https://journals.ametsoc.org/doi/10.1175/BAMS-D-14-00218.1 Ruf, C., R. Atlas, P. Chang, M. Clarizia, J. Garrison, S. Gleason, S. Katzberg, Z. Jelenak, J. Johnson, S. Majumdar, A. O'Brien, D. Posselt, A. Ridley, R. Rose, V. Zavorotny (2015). New Ocean Winds Satellite Mission to Probe Hurricanes and Tropical Convection. Bull. Amer. Meteor. Soc., doi:10.1175/BAMS-D-14-00218.1.
Known Issues
Spacecraft Attitude Tables	https://podaac-tools.jpl.nasa.gov/drive/files/allData/cygnss/L1/docs/att_tables/ Updated Monthly

Citation

CYGNSS. 2018. CYGNSS Level 1 Science Data Record Version 2.1. Ver. 2.1. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at https://doi.org/10.5067/CYGNS-L1X21.

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For more information see Data Citations and Acknowledgments.

Journal Reference

Ruf, C., S. Asharaf, R. Balasubramaniam, S. Gleason, T. Lang, D. McKague, D. Twigg, and D. Waliser. (2019). In-Orbit Performance of the Constellation of CYGNSS Hurricane Satellites. Bull. Amer. Meteor. Soc., 100, 2009 - 2023, https://doi.org/10.1175/BAMS-D-18-0337.1.