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Description

This CYGNSS Level 1 (L1) science data record dataset contains the version 3.2 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 3.1: https://doi.org/10.5067/CYGNS-L1X31. 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 correction for coarse quantization effects that was implemented in v3.1 for the signal portion of the DDM has been updated to include a correction to the noise floor portion of the DDM. This update is found to improve the sensitivity to soil moisture over land and to have a minimal effect on the sensitivity to wind speed over ocean. An update is made to the correction for the temperature dependence of the receiver electronics. This update reduces slow variations in calibration bias associated with a ~60 day oscillation in the mean temperature of the satellites. L1 variables over land and ocean are now combined in common netcdf data files, with additional details added regarding the specular point calculation over land. Nadir (science) antenna pattern and NBRCS rescaling has been updated to improve the inter-satellite consistency of the L1 calibration.

The CYGNSS is a NASA Earth System Science Pathfinder Mission that is intended to 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 micro-satellites, the observatories 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 approximately 38° N and 38° S latitude. This range includes the critical latitude band for tropical cyclone formation and movement.

Product Summary

Platforms
CYGNSS
Instruments
DDMI
Spatial Extent

N: 40 S: -40 E: 180 W: -180

Spatial Resolution
25000 Meters x 25000 Meters
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
2018-08-01
Data Partner
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC) ,
Cyclone Global Navigation Satellite System Mission, NASA Earth Science System Pathfinder, University of Michigan (NASA/ESSP/UMICH/CYGNSS)
Concept ID
C2832195379-POCLOUD
Data State
ACTIVE
Number of Files/Granules
21374
Processing Level
1
Published
Science Keywords
Radar Cross-Section ,
Radar Reflectivity

Citation

Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.

Copy Citation

CYGNSS. (2024). CYGNSS Level 1 Science Data Record Version 3.2 [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/CYGNS-L1X32 Date Accessed: 2026-05-28

Documents

USER'S GUIDE

DATA PRODUCT SPECIFICATION

ANOMALIES

DATA CITATION GUIDELINES

PUBLICATIONS

GENERAL DOCUMENTATION

Variables

The table below lists the variables contained within a single granule for this dataset. Variables often contain observed or derived geophysical measurements collected from a variety of sources, including remote sensing instruments on satellite and airborne platforms, field campaigns, in situ measurements, and model outputs. The terms variable, parameter, scientific data set, layer, and band have been used across NASA’s Earth science disciplines; however, variable is the designated nomenclature in NASA’s Common Metadata Repository (CMR). Variable metadata attributes such as Name, Description, Units, Data Type, Fill Value, Valid Range, and Scale Factor allow users to efficiently process and analyze the data. The full range of attributes may not be applicable to all variables. Additional information on variable attributes is typically available in the data, user guide, and/or other product documentation.

For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor Offset
sc_pos_z_pvt The Z component of the spacecraft WGS84 reference frame ECEF position, in meters, at pvt_timestamp_utc meter int -99999999 N/A 1 N/A
sc_roll Spacecraft roll angle relative to the orbit frame, in radians at ddm_timestamp_utc radian float -9999 N/A 1 N/A
sc_roll_att Spacecraft roll angle relative to the orbit frame, in radians at att_timestamp_utc radian float -9999 N/A 1 N/A
sc_vel_x The X component of the spacecraft WGS84 reference frame ECEF velocity, in m/s, at ddm_timestamp_utc meter s-1 int -9999 N/A 1 N/A
sc_vel_x_pvt The X component of the spacecraft WGS84 reference frame ECEF velocity, in m/s, at pvt_timestamp_utc meter s-1 int -9999 N/A 1 N/A
sc_vel_y The Y component of the spacecraft WGS84 reference frame ECEF velocity, in m/s, at ddm_timestamp_utc meter s-1 int -9999 N/A 1 N/A
sc_vel_y_pvt The Y component of the spacecraft WGS84 reference frame ECEF velocity, in m/s, at pvt_timestamp_utc meter s-1 int -9999 N/A 1 N/A
sc_vel_z The Z component of the spacecraft WGS84 reference frame ECEF velocity, in m/s, at ddm_timestamp_utc meter s-1 int -9999 N/A 1 N/A
sc_vel_z_pvt The Z component of the spacecraft WGS84 reference frame ECEF velocity, in m/s, at pvt_timestamp_utc meter s-1 int -9999 N/A 1 N/A
sc_yaw Spacecraft yaw angle relative to the orbit frame, in radians at ddm_timestamp_utc radian float -9999 N/A 1 N/A
sc_yaw_att Spacecraft yaw angle relative to the orbit frame, in radians at att_timestamp_utc radian float -9999 N/A 1 N/A
spacecraft_id The CCSDS spacecraft identifier: 0xF7 (247): CYGNSS 1 0xF9 (249): CYGNSS 2 0x2B ( 43): CYGNSS 3 0x2C ( 44): CYGNSS 4 0x2F ( 47): CYGNSS 5 0x36 ( 54): CYGNSS 6 0x37 ( 55): CYGNSS 7 0x49 ( 73): CYGNSS 8 0x00 ( 0): end to end simulator 0x0E ( 14): engineering model 0x0D ( 15): default 0xFF (255): unknown 1 short N/A N/A 1 N/A
spacecraft_num The CYGNSS spacecraft number: Ranges from 1 through 8 and 99. 1 through 8 are on-orbit spacecraft. 99 is the CYGNSS end-to-end simulator 1 byte N/A 1 to 99 1 N/A
sp_alt Altitude of the specular point relative to the WGS 84 datum in meters, at ddm_timestamp_utc, as calculated on the ground. Note that an approximated DTU10 mean sea surface height model is used to calculate the specular point altitude. meter float -9999 N/A 1 N/A
sp_az_body Let line A be the line that extends from the spacecraft to the specular point, at ddm_timestamp_utc. Let line B be the projection of line A onto the spacecraft body frame XY plane. sp_az_body is the angle between the spacecraft body frame +X axis and line B, in degrees, at ddm_timestamp_utc. See UM Doc. 148-0336, CYGNSS Science Data Processing Coordinate Systems Definitions. degree float -9999 N/A 1 N/A
sp_az_orbit Let line A be the line that extends from the spacecraft to the specular point at ddm_timestamp_utc. Let line B be the projection of line A onto the orbit frame XY plane. sp_az_orbit is the angle between the orbit frame +X axis (the velocity vector) and line B, in degrees, at ddm_timestamp_utc. See UM Doc. 148-0336, CYGNSS Science Data Processing Coordinate Systems Definitions. degree float -9999 N/A 1 N/A
sp_calc_method Method used for Specular Point Calcualtion: 0 = Ocean, uses DTU10 for altitude 1 = Land, uses SRTM for altitude N/A byte -99 N/A 1 N/A
sp_ddmi_delay_correction For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. 1 float -9999 N/A 1 N/A
sp_ddmi_dopp For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. s-1 float -9999 N/A 1 N/A
sp_ddmi_dopp_correction For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. s-1 float -9999 N/A 1 N/A
sp_delay_error For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. 1 float -9999 N/A 1 N/A
sp_dopp_error For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. s-1 float -9999 N/A 1 N/A
sp_fsw_delay For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. 1 float -9999 N/A 1 N/A
sp_inc_angle The specular point incidence angle, in degrees, at ddm_timestamp_utc. This is the angle between the line normal to the Earth's surface at the specular point and the line extending from the specular point to the spacecraft. See UM Doc. 148-0336, CYGNSS Science Data Processing Coordinate Systems Definitions. degree float -9999 N/A 1 N/A
sp_land_confidence Meaning of each confidence value: 0 = Lowest confidence, land SP wrong 1 = Land SP probably wrong, but low SNR is the cause 2 = Land SP probably OK, despite low SNR 3 = Highest confidence, land SP OK N/A byte -99 N/A 1 N/A
sp_land_valid Land specular point location estimate is valid with reasonable confidence, as per the calculation algorithm described in [4]. This flag is set to 1 (valid) if the sp_land_confidence value is either 3 or 4, and set to 0 (invalid) otherwise. N/A byte -99 N/A 1 N/A
sp_lat Specular point latitude, in degrees North, at ddm_timestamp_utc degrees_north float -9999 N/A 1 N/A
sp_lon Specular point longitude, in degrees East, at ddm_timestamp_utc degrees_east float -9999 N/A 1 N/A
sp_pos_x The X component of the specular point position in the ECEF coordinate system, in meters, at ddm_timestamp_utc, as calculated on the ground. meter int -99999999 N/A 1 N/A
sp_pos_y The Y component of the specular point position in the ECEF coordinate system, in meters, at ddm_timestamp_utc, as calculated on the ground. meter int -99999999 N/A 1 N/A
sp_pos_z The Z component of the specular point position in the ECEF coordinate system, in meters, at ddm_timestamp_utc, as calculated on the ground. meter int -99999999 N/A 1 N/A
sp_rx_gain The receive antenna gain in the direction of the specular point, in dBi, at ddm_timestamp_utc. dBi float -9999 N/A 1 N/A
sp_theta_body The angle between the spacecraft body frame +Z axis and the line extending from the spacecraft to the specular point, in degrees, at ddm_timestamp_utc. See UM Doc. 148-0336, CYGNSS Science Data Processing Coordinate Systems Definitions. degree float -9999 N/A 1 N/A
sp_theta_orbit The angle between the orbit frame +Z axis and the line extending from the spacecraft to the specular point, in degrees, at ddm_timestamp_utc. See UM Doc. 148-0336, CYGNSS Science Data Processing Coordinate Systems Definitions. degree float -9999 N/A 1 N/A
sp_vel_x The X component of the specular point velocity in the ECEF coordinate system, in m/s, at ddm_timestamp_utc, as calculated on the ground. meter s-1 int -9999 N/A 1 N/A
sp_vel_y The Y component of the specular point velocity in the ECEF coordinate system, in m/s, at ddm_timestamp_utc, as calculated on the ground. meter s-1 int -9999 N/A 1 N/A
sp_vel_z The Z component of the specular point velocity in the ECEF coordinate system, in m/s, at ddm_timestamp_utc, as calculated on the ground. meter s-1 int -9999 N/A 1 N/A
srtm_dem_alt Altitude at the specular point calculated using the 1km resolution SRTM DEM. Land observations only. meter float -9999 N/A 1 N/A
srtm_slope Surface slope at the specular point calculated using the 1km resolution SRTM DEM. Land observations only. degree float -9999 N/A 1 N/A
starboard_gain_setting The Nadir-Starboard Gain Setting (dB, 0=Automatic) dB int -9999 N/A 1 N/A
static_gps_eirp Heritage version of gps_eirp (v2.1 and earlier) that assumed a static value for the power level of the L1 signal transmitted by the GPS satellite, prior to implementation of dynamic gps_eirp monitoring in August 2018. watt float -9999 N/A 1 N/A
status_flags_one_hz One Hz status flags. These flags apply to all four DDMs. 1 indicates presence of condition. Flag masks: 1 = Milky way in zenith antenna field of view 2 = Sun in zenith antenna field of view 4 = Sub-satellite point over open ocean 8 = Sub-satellite point latitude ascending, i.e. sc_lat has increased since the previous DDM sample N/A int -9999 N/A 1 N/A
sv_num The GPS unique space vehicle number that transmitted prn_code. 1 int -9999 N/A 1 N/A
track_id A track is a temporally contiguous series of DDMs that have the same prn_code. Each track in the file is assigned a unique track_id starting with one. track_id ranges from 1 to N, where N is the total number of tracks in the file. 1 int -9999 N/A 1 N/A
tx_clk_bias The GPS spacecraft (sv_num) clock time minus GPS constellation time (in seconds) times the speed of light, in meters. meter float -9999 N/A 1 N/A
tx_pos_x The X component of the GPS spacecraft WGS84 reference frame ECEF position, in meters, at ddm_timestamp_utc meter int -99999999 N/A 1 N/A
tx_pos_y The Y component of the GPS spacecraft WGS84 reference frame ECEF position, in meters, at ddm_timestamp_utc meter int -99999999 N/A 1 N/A
tx_pos_z The Z component of the GPS spacecraft WGS84 reference frame ECEF position, in meters, at ddm_timestamp_utc meter int -99999999 N/A 1 N/A
tx_to_sp_range The distance between the GPS satellite and the specular point, in meters, at ddm_timestamp_utc. meter int -9999 N/A 1 N/A
tx_vel_x The X component of the GPS spacecraft WGS84 reference frame ECEF velocity in meters, at ddm_timestamp_utc meter s-1 int -9999 N/A 1 N/A
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