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Description

The CYGNSS Level 1 Calibrated Raw IF Version 1.0 dataset is produced by the CYGNSS Science Team of the University of Michigan, and it contains the first release, Version 1.0, of the CYGNSS Calibrated Raw Intermediate Frequency (IF) based L1 Product. CYGNSS was launched on 15 December 2016, it is a NASA Earth System Science Pathfinder Mission that was launched with the purpose of collecting the first frequent space‐based measurements of surface wind speeds in the inner core of tropical cyclones. Originally made up of a constellation of eight micro-satellites, the observatories provide nearly gap-free Earth coverage using an orbital inclination of approximately 35°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.
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This product includes several established signal coherence detectors, including the power-ratio P<sub>ratio</sub>, complex zero-Doppler delay waveform and full entropy E<sub>full</sub>, and a novel fast entropy detector E<sub>fast</sub>. Both entropy detectors are provided with two temporal resolutions: 2 ms and 50 ms. Several scattered signal strength products are included: Signal-to-Noise Ratio SNR, reflected power P<sub>g</sub>, reflectivity Γ, and Normalized Bistatic Radar Cross-Section NBRCS. Each of these products is derived using a coherent integration time of T<sub>c </sub>= 1 ms and incoherent integration times of N<sub>inc</sub> = 1000, 500, 250, 100, 50, and 2 ms. Signal strength time series at the shorter (2 and 50 ms) times provides excellent detection of land-water transitions in heterogeneous scenes. Delay Doppler Maps (DDMs) are also generated with high delay (∆τ = 1/16 chip) and Doppler (∆f= 50 Hz) resolution. This suite of coherence detection methods can be used to detect the presence of small inland water bodies.

Product Summary

Platforms
CYGNSS
Instruments
DDMI
Spatial Extent

N: 38.15 S: -38.15 E: 180 W: -180

Spatial Resolution
1000 Meters x 1000 Meters
Geographic Region
GLOBAL ,
TROPICS
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
2018-08-01
Data Partner
Cyclone Global Navigation Satellite System Mission, NASA Earth Science System Pathfinder, University of Michigan (NASA/ESSP/UMICH/CYGNSS) ,
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC)
Concept ID
C2927929087-POCLOUD
Data State
ACTIVE
Number of Files/Granules
1463
Processing Level
1
Published
Updated
Science Keywords
SENSOR COUNTS

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 Calibrated Raw IF Version 1.0 [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/CYGNS-L1R10 Date Accessed: 2026-01-08

Documents

USER'S GUIDE

ANOMALIES

DATA CITATION GUIDELINES

GENERAL DOCUMENTATION

PUBLICATIONS

Variables

Variables are a set of physical properties whose values determine the characteristics or behavior of something. For example, temperature and pressure are variables of the atmosphere. Parameters and variables can be used interchangeably. Variable level attributes provide individual information for each variable.

The Name in this table is the variable name. Fill value indicates missing or undefined data points in a variable. Valid range is the range of values the variable can store. Scale factor is used to increase or decrease the size of an object and can be used to correct for distortion. For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor
add_range_to_sp For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. 1 float -9999 N/A 1
add_range_to_sp_pvt For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. 1 float -9999 N/A 1
att_timestamp_gps_sec The GPS second of week of att_timestamp_utc, with nanosecond resolution second double N/A N/A 1
att_timestamp_gps_week The GPS week number of att_timestamp_utc week int N/A N/A 1
att_timestamp_utc The spacecraft attitude epoch. The number of seconds since time_coverage_start with nanosecond resolution. This is the timestamp of the spacecraft attitude reported by the spacecraft attitude determinination system. seconds since 2024-01-03 19:09:46.699996840 double N/A N/A 1
bb_nearest The time between ddm_timestamp_utc and the ddm_timestamp_utc associated with the closest (in time) black body reading, in signed seconds. A positive value indicates that the black body reading occurred after ddm_timestamp_utc. A negative value indicates that the block body reading occurred before ddm_timestamp_utc. second float -9999 N/A 1
bb_power_temperature_density Raw counts of detected power radiated by the blackbody calibration target, divided by receiver gain and blackbody physical temperature in Kelvins, gives the detected power per unit absolute temperature. Counts/Kelvin float -9999 N/A 1
bit_null_offset_port For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. 1 float -9999 N/A 1
bit_null_offset_starboard For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. 1 float -9999 N/A 1
bit_null_offset_zenith For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. 1 float -9999 N/A 1
bit_ratio_lo_hi_port Bin ratio of the of the port antenna defined as (plus_1_cnts + minus_1_cnts) / (plus_3_cnts + minus_3_cnts). 1 float -9999 N/A 1
bit_ratio_lo_hi_starboard Bin ratio of the of the starboard antenna defined as (plus_1_cnts + minus_1_cnts) / (plus_3_cnts + minus_3_cnts). 1 float -9999 N/A 1
bit_ratio_lo_hi_zenith Bin ratio of the of the zenith antenna defined as (plus_1_cnts + minus_1_cnts) / (plus_3_cnts + minus_3_cnts). 1 float -9999 N/A 1
brcs 69 x 111 array of DDM bin bistatic radar cross section, m^2. The specular point is located in DDM bin round(brcs_ddm_sp_bin_delay_row), round(brcs_ddm_sp_bin_dopp_col). meter2 float -9999 N/A 1
brcs_ddm_peak_bin_delay_row The zero-based delay row of the peak value in the bistatic radar cross section DDM (brcs). Ranges from 0 to 16. 1 byte -99 N/A 1
brcs_ddm_peak_bin_dopp_col The zero-based Doppler column of the peak value in the bistatic radar cross section DDM (brcs). Ranges from 0 to 10. 1 byte -99 N/A 1
brcs_ddm_sp_bin_delay_row The zero-based delay row of the specular point delay in the bistatic radar cross section DDM (brcs). Note that this is a floating point value. 1 float -9999 N/A 1
brcs_ddm_sp_bin_dopp_col The zero-based Doppler column of the specular point Doppler in the bistatic radar cross section DDM (brcs). Note that this is a floating point value. 1 float -9999 N/A 1
code_phase_comp_ddm_center_row TBD N/A float -9999 N/A 1
coherency_ratio Ratio of the raw counts of the 3x5 grid surrounding the peak delay and Doppler values over sum of the rest of the values. 1 float -9999 N/A 1
commanded_sc_roll Commanded spacecraft attitude roll angle, in radians at ddm_timestamp_utc. This value is updated every 10 seconds from the ENG_HI packet radian float -9999 N/A 1
comp_ddm_sp_delay_row TBD 1 float -9999 N/A 1
comp_ddm_sp_doppler_col TBD 1 float -9999 N/A 1
ddm The netCDF coordinate variable associated with variables that are dimensioned by the 4 DDMI reflectometry channels. It enumerates the zero-justified index range of DDM reflectometry channels. Ranges from 0 to 3. 1 byte N/A N/A 1
ddmi_tracker_delay_center TBD N/A float -9999 N/A 1
ddm_ant The antenna that received the reflected GPS signal associated with the DDM. 0 = none 1 = zenith (never used) 2 = nadir_starboard 3 = nadir_port N/A byte -99 N/A 1
ddm_brcs_uncert Uncertainty of the BRCS 1 float -9999 N/A 1
ddm_end_time_offset For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. 1e-9 s int -9999 N/A 1
ddm_kurtosis The kurtosis of the DDM noise floor. For diagnostic use only. See UM document 148-0347 DDM RFI Algorithm for more information. 1 float -9999 N/A 1
ddm_les Leading edge slope of a 3 delay x 5 Doppler bin box that include the specular point bin. The specular point bin is in the top (least delay) row and the center Doppler column of the 3 x 5 box. 1 float -9999 N/A 1
ddm_nbrcs_center Approximation of the DDM NBRCS calculated by dividing a sum of the 3x5 grid centered around delay bin 35 and Doppler bin 55 (using zero based indexing) of the BRCS by the effective scatter area. This can be computed for all points instead of the limits of the normal NBRCS calculation. 1 float -9999 N/A 1
ddm_noise_floor For non-black-body DDMs: Is equal to the average bin raw counts in the first 45 delay rows of the uncompressed 20 x 128 DDM, in counts, at ddm_timestamp_utc. For black body DDMs: Is equal to the average bin raw counts in all 128 delay rows of the uncompressed 20 x 128 DDM, in counts, at ddm_timestamp_utc. 1 float -9999 N/A 1
ddm_noise_floor_corrected The ddm_noise_floor after a correction factor, based on the nadir antenna bin ratio, has been applied. 1 float -9999 N/A 1
ddm_snr 10log(Smax/Navg), where Smax is the maximum value (in raw counts) in a single DDM bin and Navg is the the average per-bin raw noise counts. ddm_snr is in dB, at ddm_timestamp_utc. dB float -9999 N/A 1
ddm_source The source of the Level 0 DDM raw counts and metadata. 0 = End-End Simulator (E2ES) 1 = GPS signal simulator 2 = CYGNSS spacecraft 3 = Source unknown N/A byte N/A N/A 1
ddm_timestamp_gps_sec The GPS second of week of ddm_timestamp_utc, with nanosecond resolution second double N/A N/A 1
ddm_timestamp_gps_sec_one_ms The GPS second of week of ddm_timestamp_utc, with nanosecond resolution second double N/A N/A 1
ddm_timestamp_gps_week The GPS week number of ddm_timestamp_utc week int N/A N/A 1
ddm_timestamp_gps_week_one_ms The GPS week number of ddm_timestamp_utc week int N/A N/A 1
ddm_timestamp_utc DDM sample time. The number of seconds since time_coverage_start with nanosecond resolution. Its position relative to the DDM sampling period is determined by ddm_time_type_selector. Some metadata required for DDM calibration are generated relative to pvt_timestamp_utc or att_timestamp_utc. These metadata are interpolated to ddm_timestamp_utc before being used for DDM calibration. Note that the DDM sampling period is not synchronized with the UTC change of second and can occur at any time relative to the UTC change of second. seconds since 2024-01-03 19:09:46.699996840 double N/A N/A 1
ddm_time_type_selector Determines the position of ddm_timestamp_utc relative to the DDM sampling period. Set to &lt;Middle of DDM sampling period&gt; for nominal science operations. Other settings are used for pre-launch testing only. 0 = Start of DDM sampling period (used for pre-launch testing only) 1 = Middle of DDM sampling period 2 = End of DDM sampling period (used for testing pre-launch only) 3 = pvt_timestamp_utc (used for testing pre-launch only) N/A byte N/A N/A 1
delay_resolution DDM delay bin resolution in chips. One chip is equal to 1/1,023,000 seconds. 1 float N/A N/A 1
doppler_comp_ddm_center_col TBD N/A float -9999 N/A 1
dopp_resolution DDM Doppler bin resolution in Hz s-1 float N/A N/A 1
eff_scatter 69 x 111 array of DDM bin effective scattering area, m^2. This is an estimate of the true surface scattering area that contributes power to each DDM bin, after accounting for the GPS signal spreading function. It is calculated by convolving the GPS ambiguity function with the surface area that contributes power to a given DDM bin as determined by its delay and Doppler values and the measurement geometry. The specular point bin location matches the specular point bin location in brcs. meter2 float -9999 N/A 1
fast_entropy It is a fast and approximate calculation of the full entropy metric. The eigendecomposition of the whitened data is not computed. 1 float -9999 N/A 1
fresnel_coeff The SQUARE of the left hand circularly polarized Fresnel electromagnetic voltage reflection coefficient at 1575 MHz for a smooth ocean surface at the specular point location and incidence angle. See UM document 148-0361 Fresnel Coefficient Calculation for more information. 1 float -9999 N/A 1
fsw_comp_delay_shift For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. 1 float -9999 N/A 1
fsw_comp_dopp_shift For diagnostic use only. See UM document 148-0372 CYGNSS L1 netCDF Diagnostic Variables for more information. s-1 float -9999 N/A 1
full_entropy It applies the Von Neumann information entropy metric for density matrices, a powerful indicator of the degree of mixing between states, coherent and incoherent, of the scene under investigation. 1 float -9999 N/A 1
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