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Frm4alt International Review Workshop

“International Review Workshop On Satellite Altimetry Cal/Val Activities and Applications"

23-26 April 2018,
Chania, Crete, Greece.

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Transponder calibration

Transponder calibration at the CDN1 ESA Altimeter Calibration Site:

  • CryoSat-2 on 5-Feb-2018 18:41:47 UTC (Previous Cal/Val 5-Jan-2018 at 8:04:26 UTC),
  • Tandem mission of Jason-2 and Jason-3, March-October 2016,
  • Jason-3 continuously every 10 days after its launch,
  • Sentinel-3A every 27 days at 20:00:12 UTC continuously after its launch.


Within this FRM4ALT project, to derive the instrument measurement uncertainty for altimetry calibration, the following tasks will be implemented at the Permanent Altimeter Calibration Facility (PFAC), located on the island of Gavdos and mainland West Crete, Greece, towards absolute direct (sea surface & transponder) and indirect calibration (cross-over at sea and on land) of altimeters:

  • Modernisation of the PFAC infrastructure and field instrumentation for attaining the utmost quality for satellite calibration values;
  • Periodic instrument characterization and calibration that will provide and update instrument's measurement coefficients. This instrument characterization/calibration program will be established taking into account the need for continuous PACF operation, in SI-traceable standards;
  • Establishment of procedures for relative validation of instrument's performance under the same real-life conditions. For example, the performance of different types of tide gauges (i.e., radar, acoustic, pressure) installed at the same location will be monitored, evaluated and compared to conclude on reliable and robust measurement for satellite altimeter calibration;
  • Establishment of documentation to report critical instrument parameters;
  • Establishment of a standardised procedure for automated and in-situ data retrieval and archival.


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frm4alt logo 6 Dec 2017


SeRAC: Sentinel-3 Radar Altimeter Calibration Site in Crete

Serac crete eu


FRM4ALT is continued in the Sentinel-3 Radar Altimeter Calibration in Crete (SeRAC) activity with Operational Support, now in place. The objective of this SeRAC project is to ensure the routine operations and maintenance of the CDN1 transponder Cal/Val site for Sentinel-3A but also for Sentinel-3B Commissioning and Routine Operational Phase. The transponder Cal/Val operations shall be further supported by the sea-surface Cal/val sites established at the Permanent Facility for Altimetry Calibration in west Crete, Greece.

url: www.serac-crete.eu