Antenna beam pointing accuracy and stability are key issues for obtaining reliable and high quality remote sensing data in space-borne SAR sensors. A wide set of causes, related to technological aspects and environmental conditions acting at both Bus and Payload level, contribute to misalign the actual antenna bore sight from the theoretical direction. Even very small error angles on the yaw, pitch and roll axes directly reflect on antenna pointing, impacting on key image quality parameters such as resolution, swath width, signal to ambiguity ratio. Particularly, two major types of errors can be considered: time invariant (static) errors and time-variant (dynamic) errors. The different SAR image quality parameters show different sensitivity to mispointing and therefore are affected in different ways by satellite attitude. In this paper we analyze the effects of static and dynamic errors and we predict their impact of the most relevant SAR image quality parameters, by assuming as reference a generic X-band SAR mission.

COSMO-SkyMed is the Italian Remote Sensing programme which foresees the utilization of a constellation of four SAR Satellites in Low Earth Orbit, dedicated to the management, control and exploitation of Earth resources for civil and defence applications. The program is completely funded by the Italian Government, mainly through the Italian Ministry of Research (MIUR) and the Ministry of Defence (I-AD). Thales Alenia Space Italia is responsible for the design, development and verification of the complete constellation. Satellites will take SAR images of the Earth in the X-band for a variety of government, commercial and scientific users, providing data with unprecedented quality in terms of numbers of images, resolution and accuracy. Following the canonical space qualification and acceptance processes customers and Thales Alenia Space Italia decided to pursue an end-to-end experimental verification of the SAR instrument in order to provide evidence of its capabilities. With respect to the classical approach for the on-ground verification of space-borne SAR which is done through the verification by parts and the final analytical compilation, it was decided to set-up an outdoor verification Test able to exploit all radar functionalities and performance in an integrated approach i.e. radar electronics, antenna and calibrated targets all together. In this paper they are described the test-set-up and the results of the experimental verification campaign made through the qualification hardware of the SAR.

According to the Mars Express mission, the MARSIS primary scientific objectives are to map the distribution of water, both liquid and solid, in the upper portions of the crust of Mars. Three secondary objectives are also defined subsurface geologic probing, surface characterization, and ionosphere sounding. In order to obtain the primary objectives the Radar Sounder design was based on the Ice/water interface and Dry/ice interface scenario: defining the material composition of the first layers and porosity and the pore filling materials. Concerning the surface, we have characterized the geometric structure in terms of a large-scale morphology, on which a small-scale geometric structure, due to rocks, is superimposed, taking into account also that recently the structure of the planets surface was described by means of fractals and in particular the new MARS surface models obtained by processing of the MOLA data. According to these models, this paper provides a description of the operational planning approach and expected performances of MARSIS.