• → European Space Agency

      • Space for Europe
      • Space News
      • Space in Images
      • Space in Videos
    • About Us

      • Welcome to ESA
      • DG's news and views
      • For Member State Delegations
      • Business with ESA
      • Law at ESA
      • ESA Exhibitions
      • ESA Publications
      • Careers at ESA
      • ESAshop
    • Our Activities

      • Space News
      • Observing the Earth
      • Human Spaceflight
      • Space Transportation
      • Navigation
      • Space Science
      • Space Engineering & Technology
      • Operations
      • Telecommunications & Integrated Applications
      • Preparing for the Future
    • Careers at ESA

    • For Media

      • Media
      • ESA TV
      • Videos for professionals
      • Photos
    • For Educators

    • For Kids

    • ESA

    • Observing the Earth

    • Living Planet

    • Meteorological missions

    • MetOp

    • MetOp at a glance
    • Overview
    • Why we need MetOp
    • Facts & figures
    • History
    • Satellite

      • About the satellite
      • Payload Module
      • Service Module
    • Instruments

      • Overview
      • Technical summary
    • Launch

      • Launch sequence
      • Launcher
    • Mission operations

      • Operations
      • Orbit
    • Resources

      • Publications
      • General links
      • Glossary
      • Acronym list
    • Multimedia
    • MetOp images
    • MetOp videos
    • MetOp animations
    • Help
    • Services
    • Subscribe

    ESA > Our Activities > Observing the Earth > The Living Planet Programme > Meteorological missions > MetOp

    ASCAT calibration

    Prototype of an ASCAT transponder

    The Advanced Scatterometer (ASCAT) will make use of external calibration targets to allow the generation of radiometrically calibrated scattering coefficient data. These external targets will take the form of well-calibrated and stable transponders located at various points on the ground.

    Ground reflections (clutter) can interfere with the return signal from the transponder. To overcome this, the transponder has a time delay. This means that the transponder echo is only present after the ground clutter has decayed. A special calibration mode is used in the instrument in which echo data is collected in the second pulse repetition interval after pulse transmission, instead of the usual first. Like the real target, the transponders will need to appear as large radar targets, this means that their internal electronics need to have a high gain, which may be temperature sensitive. An internal calibration loop is used to stabilise this gain. The transponders will track the satellite during its overflight and will allow the fore, mid and aft beams to be calibrated in sequence.

    MetOp's orbit results in a large number of closely spaced ground tracks. Calibration of the instrument can therefore be made at closely spaced intervals across the instrument swaths. This means that the complete external calibration process can be accomplished in about one month.

    Last update: 28 June 2006

    Rate this

    Views

    Share

    • Currently 0 out of 5 Stars.
    • 1
    • 2
    • 3
    • 4
    • 5
    Rating: 0/5 (0 votes cast)

    Thank you for rating!

    You have already rated this page, you can only rate it once!

    Your rating has been changed, thanks for rating!

    319
    Tweet
    • In depth
      • About ASCAT
      • Scanning principle
      • Instrument design drivers
      • Calculation wind speed and direction
        • Description
        • Functional elements
        • Performance
        • Products
        • Calibration
        • Ground Processor Prototype
        • Related articles
          • Measuring wind over the oceans with ASCAT
          • MetOp's instruments
          • A/DCS
          • AMSU-A1
          • AMSU-A2
          • ASCAT
          • AVHRR
          • GOME-2
          • GRAS
          • HIRS
          • IASI
          • MHS
          • SARP-3
          • SARR
          • SEM
    • App Store
    • Subscribe
    • mobile version
    • LATEST ARTICLES
    • · Walking on the Moon – underwater
    • · Storm hunter in position
    • · Mars impact crater or supervolcano?
    • · Top tomatoes thanks to Mars missio…
    • · Mars Express v2.0
    • FAQ

    • Site Map

    • Contacts

    • Terms and conditions