On the stability of large antennas as calibration targets

Abstract

Large radar cross section (RCS) and high temporal stability are the typical requirements expressed nowadays to external calibration targets to be used for spaceborne SAR calibration. The use of ground-based large parabolic reflector antennas may be a good alternative to active radar calibrators or corner reflectors. Outstanding stability of the antennas RCS was demonstrated in a calibration series under AO3-343 in 1999-2000. Under the extension of the project in 2002 with a goal of preparation to ENVISAT mission we were able to demonstrate the repeatability of the series of observations made before as well as our ability to control polarisation of backscattered signal and to show phase stability of the backscatter, what is important for repeated orbits interferometry.

The Potential for Unifying Global‐Scale Satellite Measurements of Ground Displacements Using Radio Telescopes

“…The global geodetic network currently consists of~30 VLBI telescopes, with at least one located on each major landmass and over which Sentinel-1 acquires imagery at a frequency of between 1 and 12 days ( Figure 1). These telescopes act simultaneously as direct ties to the International Terrestrial Reference Frame (ITRF) (Altamimi et al, 2011(Altamimi et al, , 2016, while other radio telescopes (e.g., ground stations) have been identified as passive reflectors suited to radiometric calibration for SAR (Keen, 1983;Meadows, 2000;van't Klooster, 2011;Zakharov et al, 2003). Exploiting VLBI telescopes as persistent, high-amplitude scatterers in InSAR imagery therefore presents an immediate opportunity to unify ground displacement measurements from InSAR across continents, while avoiding the implicit assumptions, additional costs, and ongoing fieldwork required when connecting InSAR measurements to other geodetic infrastructures.…”