13 October 2006 Altimeter range determination and applications using a transponder
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Abstract
Within the Gavdos Project (Establishment of a European radar altimeter calibration and sea level monitoring site for Jason, Envisat and Euro-Gloss), a transponder has been used for an experimental work package. The instrument has been deployed on the island of Gavdos beneath the ascending pass of Envisat and was receiving the altimeter pulses, amplifying and retransmitting them back to the altimeter. The transponder could thus be easily identified in the altimeter data stream in the characteristic variation of the waveform power. Acting as a point target for the satellite radar altimeter, the range measurements from the satellite to the transponder are not subject of "speckle" effects, as it happens in the case of the sea surface when the multitude of scatters cause interference effects to the radar echo. The distance measurement has a resolution of < 1 cm [1]; provided that the atmospheric delays are properly modeled, the accuracy of a range measurement is estimated to 2 cm. The applications deriving from the use of the transponder in the altimetry context are based on the accurate determination of the transponder-satellite distance. These include the altimeter bias calibration, the measurement of the orbit radial errors especially in places where positioning systems are unavailable, determination of ice thickness, and height transfer between land and ocean or land and land.
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Elena Cristea, Elena Cristea, Philip Moore, Philip Moore, } "Altimeter range determination and applications using a transponder", Proc. SPIE 6360, Remote Sensing of the Ocean, Sea Ice, and Large Water Regions 2006, 63600F (13 October 2006); doi: 10.1117/12.691041; https://doi.org/10.1117/12.691041
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