The PO.DAAC is pleased to announce the public release of the CYGNSS Level 1 Full Delay Doppler Map (DDM) Version 3.0 dataset from the Delay Doppler Mapping Instrument (DDMI) aboard the CYGNSS satellite constellation. More information about the CYGNSS mission is available on the PO.DAAC CYGNSS mission page.
The primary CYGNSS instrument, DDMI, measures the incoming radio frequency (RF) streams from three input antenna channels (2 nadir oriented science antennas and one zenith oriented navigation antenna) and processes them in real time into DDMs, which are two-dimensional maps of the signal scattered from the Earth surface as a function of propagation time delay and Doppler frequency shift. The Full DDM data, provided in netCDF format, contains the raw sensor counts sampled over a wider range of measurements compared to the standard DDMs. Full DDM processing also retains the uncompressed (lossless) scattered signal strength, as opposed to the compressed DDMs used to produce the Level 1 SDR and CDR data. The Full DDM data records are typically 10-15 min in duration and are initiated by ground commands to coincide with an overpass by one of the spacecraft of a target area of interest. The ATBD provides greater detail on processing methodology, as well as the science applications for these data, which include but are not limited to land-based hydrology and air-sea interaction over the ocean.
This version supersedes the Full DDM Version 1.0 (https://doi.org/10.5067/CYGNS-L1FDD) for data retrieved during or after August 2018. For data retrieved prior to August 2018, users will need to continue using the Full DDM Version 1.0. This version links the Full DDMs to the CYGNSS SDR v3.0 L1 files (https://doi.org/10.5067/CYGNS-L1X30) whereas the version 1.0 Full DDM linked the Full DDMs to the CYGNSS SDR v2.1 L1 files (https://doi.org/10.5067/CYGNS-L1X21). The spatial resolution of Full DDM is comparable to standard L1 CYGNSS data products (i.e., SDR and CDR), yet it provides a higher area of spatial coverage; 25 km is the nominal Full DDM resolution. The calibration of the Full DDMs has not been modified for this release.
The time series of this dataset begins on 6 August 2018. The time interval and latency are irregular because the processing depends on ground-controlled spacecraft commands issued at specific time intervals for a target area of interest on the Earth’s surface. Once CYGNSS spacecraft are operating in Full DDM mode, the latency is comparable to SDR processing (1 to 6 days). More information and access to these data can be obtained directly through the Web Portal via the links in the DOI reference below.
Citation: CYGNSS. 2020. CYGNSS Level 1 Full Delay Doppler Map Data Record Version 3.0. Ver. 3.0. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at https://doi.org/10.5067/CYGNS-L1F30
Reference: Gleason, S., C. S. Ruf, A. O'Brien, D. S. McKague, "The CYGNSS Level 1 Calibration Algorithm and Error Analysis Based On On-Orbit Measurements", IEEE J. Sel. Topics Appl. Earth Obs. Remote Sens., DOI: 10.1109/JSTARS.2018.2832981, 2018.