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This work is aimed at showing the present capabilities and future potentialities of an imaging radar system that can be mounted onboard flexible aerial platforms, such as helicopters or small airplanes, and may operate in the UHF and VHF frequency bands as Sounder and as Synthetic Aperture Radar (SAR). More specifically, the Sounder operates at 165 MHz, whereas the SAR may operate either at 450 MHz or at 860 MHz. In the work, we present the first results relevant to a set of Sounder and SAR data collected by the radar during a helicopter-borne campaign conducted in 2018 over a desert area in Erfoud, Morocco, just after the conclusion of a system upgrading procedure. In particular, a first analysis of the focusing capabilities of the Sounder mode and of the polarimetric and interferometric capabilities of the SAR mode is conducted. The overall system, originally developed by CO.RI.S.T.A. according to a ASI funding set up in 2010, has been upgraded in the frame of a contract signed in 2015 between ASI and different private and public Italian Research Institutes and Universities, namely CO.RI.S.T.A., IREA-CNR, Politecnico di Milano and University of Trento.

This paper reports on a model developed for evaluating major system performance of a spaceborne bistatic synthetic aperture radar (SAR) for remote sensing applications. The procedure accounts for formation flying aspects. It is particularly aimed at comparison of monostatic and bistatic cases, and, as a test case, it is applied to study a novel configuration, based on a small satellite equipped with a receiving-only antenna orbiting in tandem with a large, noncooperative transmitting spacecraft, the Italian COSMO-SkyMed mission. Numerical results and plots show the effectiveness of the procedure as a mission design tool and put in evidence key issues and characteristics of the proposed spaceborne bistatic formation.

This letter deals with the design, realization, and validation of a multimode/multifrequency airborne radar designed for both surface and subsurface prospections. The system operates in the frequency band from very high frequency (VHF) to ultrahigh frequency (UHF) and works in two different modes: 1) a nadir-looking sounder in the VHF band (carrier frequency of 163 MHz); and 2) a side-looking imager (i.e., synthetic aperture radar) in the UHF band with two channels at 450 and 860 MHz, respectively. The system validation has been carried out for the “sounder” mode due to helicopter-borne surveys carried out over an area in the Campania region, Southern Italy. The surveys have provided a first proof of system capability in obtaining useful information about the surface and shallower subsurface layers over a large scale and in a relatively short time. In particular, the data collected by the sounder have been processed by means of a microwave tomographic reconstruction approach, and features consistent with tunnels buried at a depth of 15 m have been identified.

MINISAR is a compact airborne interferometric SAR potentially suitable for many applications but mainly finalized for the production of technical topographic maps and monitoring the evolution of landslides events and assessing their extension and risk area. The program is co-funded by the Italian Ministry for Education, Universities and Research (M.I.U.R.) The hardware consists in an airborne X-band radar, able to obtain a resolution less than a meter (because of a 280 MHz stepped chirp signal) and an altimetric accuracy less than 7 meters. Such an accuracy derives from an equivalent 1.5 meters baseline and the high gain antennas that let MINISAR to use a transmitted power of only 80 W. The system will be mounted on board of a small platform and it is thought to have future development for unmanned platform. Data will be processed using a chirp scaling algorithm in order to obtain the two Single Look Complex (SLC) images which can be then processed to obtain high accuracy Digital Elevation Model (DEM).

This paper describes scientific rationale and technical approach for a spaceborne bistatic synthetic aperture radar (SAR) mission (BISSAT). The studied configuration is based on a small satellite, equipped with a receiving-only microwave system that catches the echoes of an already existing, main orbiting SAR, without requiring its design modification or additional operating complexities. This experiment has been proposed to the Italian Space Agency as candidate for the third Italian Small Scientific and Technological Mission and preliminary founded for a competitive phase A study. BISSAT experiment offer unique features: (a) to conduct original scientific experiments and to exploit novel applications; (b) to perform a technology demonstration of an original space formation; (c) to keep cost within a small mission budget. Bistatic scattering has proven to be of fundamental importance to many branches of earth sciences and several investigations have been conducted, but considering one or both earth-based antennas and targets of limited dimensions because bistatic observation requires accurate time synchronization and antenna pointing. As an example, bistatic echoes allows innovative characterization of vegetated and urban surfaces for biomass evaluation, or sea surface waves and current to be mapped. Proposed bistatic experiment will allow original scientific activities to be carried out for the first time from space, such as: (i) evaluation of bistatic radar cross section of natural and man-made targets, by means of multi-angle bistatic SAR observations; (ii) acquisition of terrain elevation and slope by means of range and bistatic scattering measurements; (iii) acquisition of velocity measurements thanks to the simultaneous measurement of two Doppler frequencies; (iv) stereogrammetric applications thanks to the large antenna separation involved; (v) improvement of image classification and pattern recognition procedures; (vi) high-resolution measurements of components of sea wave spectra; (vii) signal processing of bistatic data; (viii) across-track and along-track interferometry. Technical feasibility of the mission has been demonstrated, in particular taking advantage from Italian COSMO/SkyMed X-band SAR2000 experience, which has been selected as main mission. Development of bistatic receiver chain can be carried out with wide reuse of components and instruments already qualified within COSMO project. Furthermore, BISSAT will add value and exploit further scientific applications of COSMO mission. Ground segment and bistatic SAR processing require novel, although limited, implementations, again founded on well-assessed expertise. Regarding the platform, BISSAT mission will allow novel experience and potentialities to be fulfilled, such as: propulsion for formation flying and orbit maintenance, and fine attitude and pointing control. It is worth noting that formation flying is an internationally recognized important scenario.