Altimetry, bathymetry and geoid variations at the Gavdos permanent Cal/Val facility

Mertikas, Stelios P.; Daskalakis, A.; Tziavos, I. N.; Andersen, Ole; Vergos, Georgios S.; Tripolitsiotis, Achilles; Zervakis, Vassilis; Frantzis, X.; Partsinevelos, Panagiotis

doi:10.1016/j.asr.2012.10.021

Cited by 12 publications

(7 citation statements)

References 21 publications

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“…109 and the descending orbit No. 18 for Jason satellites [24,40,[46][47][48][49]. It is not the purpose of this paper to provide details on calibration procedures over the sea surface.…”

Section: Sea-surface Calibration Resultsmentioning

confidence: 99%

“…In the past (circa 2010), the relative accuracy of the applied geoid and MDT models and calibrating techniques has been verified by boat, ship, and buoy campaigns, as bathymetry is deep and changes abruptly around Gavdos and western Crete [40,41]. These campaigns were made predominately along the satellite groundtracks at sea.…”

Section: Regional Models and Reference Surfacesmentioning

confidence: 98%

“…The data collected were integrated with previous gravity campaigns using airborne [43], shipborne, and terrestrial resources to generate, through optimal combinations, several regional geoid models [44]. Details of those reference surfaces currently used to perform sea-surface calibration at the Gavdos/Crete PFAC are presented in Reference [40]. Bias results for all these altimeters (i.e., Jason-1, Jason-2, Jason-3, SARAL, HY-2A, and Sentinel-3A) have been obtained with sea-surface measurements, but also with crossover comparisons at sea.…”

Section: Regional Models and Reference Surfacesmentioning

confidence: 99%

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Fifteen Years of Cal/Val Service to Reference Altimetry Missions: Calibration of Satellite Altimetry at the Permanent Facilities in Gavdos and Crete, Greece

et al. 2018

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Satellite altimetry provides exceptional means for absolute and undisputable monitoring of changes in sea level and inland waters (rivers and lakes), over regional to global scales, with accuracy and with respect to the center of mass of the Earth. Altimetry system’s responses have to be continuously monitored for their quality, biases, errors, drifts, etc. with calibration. Absolute calibration of altimeters is achieved by external and independent to satellite facilities on the ground. This is the mainstay for a continuous, homogenous, and reliable monitoring of the earth and its oceans. This paper describes the development of the Permanent Facility for Altimetry Calibration in Gavdos/Crete, Greece, as of 2001 along with its infrastructure and instrumentation. Calibration results are presented for the reference missions of Jason-1, Jason-2, and Jason-3. Then, this work continues with the determination of relative calibrations with respect to reference missions for Sentinel-3A, HY-2A, and SARAL/AltiKa. Calibration results are also given for Jason-2 and Jason-3 altimeters using the transponder at the CDN1 Cal/Val site on the mountains of Crete, with simultaneous comparisons against sea-surface calibration and during their tandem mission. Finally, the paper presents procedures for estimating uncertainties for altimeter calibration to meet the Fiducial Reference Measurement standards.

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“…109 and the descending orbit No. 18 for Jason satellites [24,40,[46][47][48][49]. It is not the purpose of this paper to provide details on calibration procedures over the sea surface.…”

Section: Sea-surface Calibration Resultsmentioning

confidence: 99%

Section: Regional Models and Reference Surfacesmentioning

confidence: 98%

Section: Regional Models and Reference Surfacesmentioning

confidence: 99%

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Fifteen Years of Cal/Val Service to Reference Altimetry Missions: Calibration of Satellite Altimetry at the Permanent Facilities in Gavdos and Crete, Greece

et al. 2018

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“…Models are often being validated as a matter of usual practice by means of dedicated boat campaigns. They are used to transfer SSH from the Gavdos reference Cal/Val site to open seas [29,30], by first establishing its sea level anomaly (SLA):…”

Section: Sea-surface Calibrationmentioning

confidence: 99%

Absolute Calibration of the European Sentinel-3A Surface Topography Mission over the Permanent Facility for Altimetry Calibration in west Crete, Greece

et al. 2018

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This work presents calibration results for the altimeter of Sentinel-3A Surface Topography Mission as determined at the Permanent Facility for Altimetry Calibration in west Crete, Greece. The facility has been providing calibration services for more than 15 years for all past (i.e., Envisat, Jason-1, Jason-2, SARAL/AltiKa, HY-2A) and current (i.e., Sentinel-3A, Sentinel-3B, Jason-3) satellite altimeters. The groundtrack of the Pass No.14 of Sentinel-3A ascends west of the Gavdos island and continues north to the transponder site on the mountains of west Crete. This pass has been calibrated using three independent techniques activated at various sites in the region: (1) the transponder approach for its range bias, (2) the sea-surface method for the estimation of altimeter bias for its sea-surface heights, and (c) the cross-over analysis for inspecting height observations with respect to Jason-3. The other Pass No.335 of Sentinel-3A descends from southwest of Crete to south and intersects the Gavdos calibration site. Additionally, calibration values for this descending pass are presented, applying sea-surface calibration and crossover analysis. An uncertainty analysis for the altimeter biases derived by the transponder and by sea-surface calibrations is also introduced following the new standard of Fiducial Reference Measurements.

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“…A transponder facility has been established at Gavdos, south of Crete and used to determine the biases of Envisat, Jason-1 and Jason-2 5 ; it has now been further developed for calibration of Sentinel-3 6 . It is in a well-surveyed location on an open hillside, and the facility also includes instrumentation for measuring the atmospheric delay terms through radiometry.…”

Section: Analysis Of Transponder Data From Gavdosmentioning

confidence: 99%

Ensuring that the Sentinel-3A altimeter provides climate-quality data

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Remote Sensing of the Ocean, Sea Ice, Coastal Waters, and Large Water Regions 2017

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Sentinel-3A, launched in February 2016, is part of ESA's long-term commitment to climate monitoring from space. Its suite of instruments for measuring surface topography includes a Microwave Radiometer (MWR) and SRAL, the first delay-Doppler instrument to provide global coverage. SRAL promises fine spatial resolution and reduced noise levels that should together lead to improved performance over all Earth surfaces. The Sentinel-3 Mission Performance Centre (S3MPC) has been developing the methodology to evaluate the accuracy of retrievals, monitor any changes and develop solutions to known problems.The S3MPC monitors internal temperatures, path delays and the shape of the generated pulses to assess the instruments health. The MWR records over known reference surfaces are compared with those from other spaceborne instruments. Over the ocean the SRAL's return pulses are analysed to give range to the sea surface, wave height and signal strength (which can be interpreted as wind speed). The metocean data are regularly contrasted with records from in situ measurements and the output from meteorological models, which rapidly highlights the effects of any changes in processing.Range information is used to give surface elevation, which is assessed in three ways. First, flights over a dedicated radar transponder provide an estimate of path delay to within ~10 mm (r.m.s.). Second, measurements are compared to GPSlevelled surfaces near Corsica and over Lake Issyk-kul. Third, there are consistency checks between ascending and descending passes and with other missions. Further waveform analysis techniques are being developed to improve the retrieval of information over sea-ice, land-ice and inland waters.

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Altimetry, bathymetry and geoid variations at the Gavdos permanent Cal/Val facility

Cited by 12 publications

References 21 publications

Fifteen Years of Cal/Val Service to Reference Altimetry Missions: Calibration of Satellite Altimetry at the Permanent Facilities in Gavdos and Crete, Greece

Fifteen Years of Cal/Val Service to Reference Altimetry Missions: Calibration of Satellite Altimetry at the Permanent Facilities in Gavdos and Crete, Greece

Absolute Calibration of the European Sentinel-3A Surface Topography Mission over the Permanent Facility for Altimetry Calibration in west Crete, Greece

Ensuring that the Sentinel-3A altimeter provides climate-quality data

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