Thursday, February 14, 2019

DOI: 10.5067/QSNON-L1CA2

The PO.DAAC is pleased to announce the public release of the QuikSCAT Level 1C Averaged Sigma-0 and Winds from Non-spinning Antenna Version 2.0 dataset. More information about QuikSCAT is available from the mission page. This dataset contains a number of significant enhancements over Version 1.0 (see: DOI 10.5067/QSNON-L1CA1) as follows:

  • The Geophysical Model Function (GMF) has been updated (QNS2016a) to make use of ECMWF nowcast 1x1 degree resolution wind direction information for the entire historical data record;
  • The new QNS2016a GMF leverages a calibration adjustment from Remote Sensing Systems (RSS) resulting in a consistently lower Normalized Radar Cross Section (NRCS or Sigma-0) measurements that establishes a Sigma-0 bias of -0.25 dB (-5.9% linear scale) compared to the L1C Version 1 data;
  • The new QNS2016a GMF applies an azimuthal modulation that is decreased by several tenths of a dB (for Sigma-0) in variation with wind speed; this results in a more consistent wind speed retrieval comparison between "non-spinning" and "spinning" modes of the QuikSCAT instrument;
  • Spacecraft attitude was re-estimated using slice data over multiple orbits as a replacement for lost echo-tracking capability during the "non-spinning" mode of the instrument; this new attitude estimation follows an unpublished manual technique that leverages the echo power of individual slice observations; since only a small subset of slice observations are analyzed, rapid variations in attitude are not captured;
  • Continues data production beyond October 2016 through the end of mission on 30 August 2018.

Retrieved wind directions are only slightly different from ECMWF values and should not be considered an independent measurement of wind direction.

This dataset provides global coverage from 16 July 2010 through 30 August 2018 and is provided in flat-binary format with sample data file readers provided in MATLAB and Python. Each data file is unique to a specific 5-digit orbital revolution (i.e., “rev”) number, which can be cross-referenced with the data start/stop dates and times at this text file.

This dataset is described, accessible and discoverable via the PO.DAAC data portal. The data files can be accessed directly via PO.DAAC’s public FTP site, but preferentially via PO.DAAC Drive.

Comments/Questions? Please contact podaac@podaac.jpl.nasa.gov or visit the PO.DAAC Forum.


Important Information for Users:

NASA is in the process of deprecating the use of the FTP protocol for data and information access. PO.DAAC is pleased to offer PO.DAAC Drive as a robust FTP alternative for browsing and retrieving data at PO.DAAC (https://podaac-tools.jpl.nasa.gov/drive/). It offers file navigation and download through an interface served directly through your browser, and with a familiar look and feel. It also allows users to access data via a command line so that interactions can be easily scripted. The entire PO.DAAC archive can also be mounted to a local computer as a virtual data store.

After 3 June 2019, FTP service will no longer be available at PO.DAAC. We recommend an earlier transition to maximize familiarity with PO.DAAC’s operational HTTPS data distribution services and minimize data disruption when FTP service is no longer available. To ensure a successful transition for all FTP users, our User Services Team is standing by to address all technical issues and concerns.