Design and simulations of a phased array feed for the biralet radar

Abstract

The number of space debris in orbit around the Earth is continuously growing and represents a potential problem for the development and growth of the Space Economy. For this reason, there are worldwide many different programs aiming at monitoring and mitigating the proliferation of space debris. For this purpose, a Space Surveillance and Tracking (SST) Support Framework was established by the European Commission in 2014 and a SST Consortium of five EU Member States (France, Germany, Italy, Spain and UK) was formed in 2015. INAF (Italian National Institute for Astrophysics) participates to the EUSST Consortium by offering different sensors and capabilities, including optical and radio telescopes. One of the tracking radars we are proposing in the framework of the EUSST is the so-called BIRALET, a bi-static radar composed by a transmitting antenna and by the SRT (Sardinia Radio Telescope) as a receiver. The transmitting antenna is a parabolic dish with a diameter of 7 m managed by the Italian Air Force, whereas the SRT is a fully steerable wheel-and-track 64 m dish radio telescope, with a Gregorian optical configuration, managed by INAF. Both sensors are located in Sardinia, Italy, with a baseline of about 20 km. BIRALET is a Doppler radar, which transmits a CW (Continuous Wave) signal with a maximum power of 10 kW in P-band at 410 MHz and receives the echo radar with a cryogenically cooled P-band single beam receiver installed on the primary focus of its receiver system, the SRT. The BIRALET system can generate a set of data for every observed space debris (both beam-parking and tracking mode), i.e. Doppler shift, pointing coordinates and measured power intensity. One of the limitations, for particular observation scenarios, of the current BIRALET system is the relatively low pointing speed of SRT and the availability of only one beam, resulting in a limited Field of View. (FoV). In this paper, the authors present a study for the upgrade of the BIRALET, based on the development of a new receiver for the SRT, a C-band Phased Array Feed, which can guarantee some improvements respect to the original system, like sensitivity, antenna gain, and the tracking of the observed object, allowed by the multiple beams with a consequent improvement of the orbit determination of known and unknown debris.