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

Mertikas, Stelios P.; Donlon, Craig; Féménias, Pierre; Mavrocordatos, C.; Galanakis, Demitris; Tripolitsiotis, Achilles; Frantzis, X.; Tziavos, I. N.; Vergos, Georgios S.; Guinle, Thierry

doi:10.3390/rs10101557

Cited by 33 publications

(23 citation statements)

References 37 publications

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Section: Crossover Analysissupporting

confidence: 62%

“…An analysis of the sea-surface heights as estimated by the Sentinel-3A and Jason-3 altimeters at this crossover location indicates that Sentinel-3A measures heights higher than Jason-3 (i.e., S3A-JA3) by about +4 cm with a standard deviation for the estimated mean as ±8 cm. Results for this crossover analysis have also been reported in [35]. The data used for the sea-surface calibration of Sentinel-3A are SAR mode, Level 2 products, WAT data, Non-Time Critical orbits, and with Processing Baseline PB 2.2 and for its cycles 1-31 (June, 2018).…”

Section: Crossover Analysismentioning

confidence: 99%

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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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Section: Crossover Analysissupporting

confidence: 62%

Section: Crossover Analysismentioning

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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“…In general, the final uncertainty for the absolute knowledge of the geoid with respect to ellipsoid is no less than ±35 cm. Recent satellite observations with GOCE and GRACE gravity missions may enable us to claim that the final produced accuracy of the geoid height is about ±8 cm in absolute sense for the Gavdos Cal/Val site [12]. The absolute determination of the orthometric height at the Cal/Val site based on these models is not that clear and definitive, even today.…”

Section: Geoid and Mdt Models Around The Cal/val Sitementioning

confidence: 99%

“…Then the problem is to determine the procedure and finally a statistical quantity which purports objectively the measure of location for the sought parameter (e.g., central value of the satellite altimeter bias) and its degree of scatter (i.e., uncertainty) represented by the FRM measurements (Figures 4 and 5). Today, there exists four such absolute, permanent, and historic Cal/Val facilities in the world: One is operated by the CNES (the French Space Agency) in Corsica, France [9], one run by the Jet Propulsion Lab/NASA in California, USA [10], one managed by the University of Tasmania in Bass Strait, Tasmania, Australia [11] and one operated by the Technical University of Crete in west Crete and Gavdos in Greece [12]. Several other non-permanent sites have also been operated at various locations, as shown in Figure 3.…”

Section: The Frm Problem At Issuementioning

confidence: 99%

An Action Plan Towards Fiducial Reference Measurements for Satellite Altimetry

et al. 2019

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Satellite altimeters have been producing, as of 1992, an amazing and historic record of sea level changes. As Europe moves into full operational altimetry, it has become imperative that the quality of these monitoring signals with their uncertainties should be controlled, fully and properly descripted, but also traced and connected to undisputable standards and units. Excellent quality is the foundation of these operational services of Europe in altimetry. In line with the above, the strategy of the Fiducial Reference Measurements for Altimetry (FRM4ALT) has been introduced to address and to achieve reliable, long-term, consistent, and undisputable satellite altimetry products for Earth observation and for sea-level change monitoring. FRM4ALT has been introduced and implemented by the European Space Agency in an effort to reach a uniform and absolute standardization for calibrating satellite altimeters. This paper examines the problem and the need behind the FRM4ALT principle to achieve an objective Earth observation. Secondly, it describes the expected FRM products and services which are to come into being out of this new observational strategy. Thirdly, it outlines the technology and the services required for reaching this goal. And finally, it elaborates upon the necessary resources, skills, partnerships, and facilities for establishing FRM standardization for altimetry.

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“…Satellite altimetry supports absolute and undisputable sea level monitoring over regional to global scales, accurate to some [mm/yr] and with respect to the center of mass of the Earth (Mertikas et al 2018). Sea-level is a key indicator of the impact of climate change over oceans.…”

Section: Measurement Principles In Altimetrymentioning

confidence: 99%

Satellite Altimetry

Mertikas¹,

Kokolakis²

2020

Encyclopedia of Solid Earth Geophysics

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Altimetry is a technique for measuring heights. Satellite altimetry measures the time taken by an electromagnetic pulse to propagate from the satellite to the surface and back to the satellite Satellite Altimetry Satellite altimetry is a technique of measuring heights of the Earth's surface from a satellite flying approximately at an attitude of about 1000 km. The word "altimetry" originates from the Latin "altus," meaning "high" and the Greek suffix "metry" ("metrίa," as in Geometry , Trigonometry , etc.) denoting the science or scientific discipline related to measuring heights. At the beginning, the objective of altimetry has been to measure height principally of sea surface to an accuracy of about AE1 cm, continuously, objectively, and on a global scale. Altimeters measure distances, or ranges, from a satellite to the Earth's surface and principally onto the sea, inland water levels (lakes, rivers) and ice surfaces as well (Fig. 1). Measurements of altimetric heights are thus creating profiles of the Earth's surface along satellite orbits with respect to Earth's center of mass. Satellite observations coming from altimeters, like those of Sentinel-3, Jason-3, CryoSat-2, IceSat-2, HY-2, and others, address several applications in solid Earth geophysics. Gravity determination, natural resources exploration, ocean circulation and variability, ice topography, hydrology, geodesy, climate change, bathymetry, sea-floor topography, etc., are a few applications of satellite altimetry.

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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

Cited by 33 publications

References 37 publications

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

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

An Action Plan Towards Fiducial Reference Measurements for Satellite Altimetry

Satellite Altimetry

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