GPS World

Tag: COSMIC-1

  • NASA releases GNSS radio occultation data in common CF compliant format

    NASA releases GNSS radio occultation data in common CF compliant format

    The NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) and principal investigator Stephen Leroy of JANUS Research Group have released GNSS Radio Occultation (GNSS-RO) datasets.

    The data release includes 72 different products from 15 different GNSS-RO receivers (or constellations of receivers) processed at four different GNSS-RO retrieval/processing centers. The data from different processing centers have been reformatted to have a common Climate and Forecast Metadata Conventions (CF) compliant format.

    The algorithm was developed with funding from the NASA ACCESS 2019 program and the NASA Supplements for Open Science Support. These are the version 2.0 GNSS-RO products; version 1.1 is available through the AWS Registry of Open Data. 

    GNSS-RO data undergoes processing that is radically different from that of most atmospheric sounders, but it can still be categorized by its processing step: 

    • uncalibrated data, as provided by the satellite instrument with communication information stripped, are Level 1a (not part of this release); 
    • calibrated data, wherein the clock biases of the transmitters and receivers are removed and precise orbits determined are Level 1b; 
    • extremely high vertical-resolution profiles of RO bending angle and microwave refractivity are Level 2a; and 
    • profiles of temperature, pressure, and specific humidity on a coarser vertical grid are Level 2b.

    Products are still being added to the archive. This initial release is complete for all processing levels of the COSMIC-1 data sets from four different processing centers. After all of the products in the initial release are complete for available data through July 2025, the project will bebegin forward processing for missions still actively producing data.

    For more information about these products please see the README document and the Algorithm Theoretical Basis Document (ATBD).

  • COSMIC-1 mission for GPS radio occultation comes to an end

    COSMIC-1 mission for GPS radio occultation comes to an end

    Image: NOAA
    Image: NOAA

    The COSMIC-1 program ended on May 1, when the last of six tiny satellites were decommissioned. The satellites were launched 14 years ago, and outlived their planned lifespan by 12 years.

    COSMIC — the Constellation Observing System for Meteorology, Ionosphere  and Climate (COSMIC) mission — uses GPS signals to provide a wealth of accurate atmospheric data and improve weather forecasts, according to Laura Snider, University Corporation for Atmospheric Research (UCAR), which ran the COSMIC program.

    Meanwhile, the COSMIC-2 program (FORMOSAT-7 in Taiwan) continues. Its six satellites were launched on June 25, 2019, into low-inclination orbits. The mission was launched by NOAA as the agency’s first operational GNSS radio occultation mission.

    COSMIC-1 demonstrated the value of GNSS radio occultation (GNSS-RO) to derive vertical atmospheric profiles of temperature, humidity and pressure by measuring the degree to which GPS signals bend as they travel through Earth’s atmosphere.

    Weather centers used the high-quality, accurate data to improve forecasts; the data was also used by researchers.

    “Throughout its lifetime, COSMIC-1 made an astounding 7 million vertical atmospheric profiles available to the operational forecast centers and research community,” writes Snider. “These data demonstrably boosted forecast accuracy and were referenced in more than 550 peer-reviewed scientific publications. In all, more than 5,000 users from over 100 countries have accessed COSMIC data.

    COSMIC-1 was primarily funded by the National Space Organization in Taiwan, where the mission is called FORMOSAT-3. The leading U.S. sponsor on the project was the National Science Foundation. Other U.S. partners included NASA, the National Oceanic and Atmospheric Administration (NOAA), the Air Force and the Office of Naval Research.

    UCAR also led the GPS/MET GPS radio occultation mission in the mid-1990s.