Low-Cost L-Band Receiving System Front-End for Irbene RT-32 Cassegrain Radio Telescope

Abstract

Irbene RT-32 radio telescope is one of the main instruments operated by Ventspils International Radio Astronomy Center (VIRAC), which is used for participation in VLBI and single-dish mode observations, including European VLBI Network (EVN) and other astronomy projects such as recently started research on small bodies of solar system, which involves weak spectral line detection at L-band. Since start of the operation as a radio telescope, single C-X band receiver has been available at RT-32, but regular demand for L-band frequencies has been received due to its importance in spectral line science. In case of RT-32 geometry, optimum dimensions of L-band feed antenna system are inconveniently large and its installation without significant feed cone rebuilding is complicated. While work is currently ongoing to redesign the feed cone for multiple receiver support and to develop high performance L-band feed system, temporal, compact and low-cost receiver has been built and installed laterally to secondary focus, which in sense of performance and functionality has been proven to be appropriate for most of the current needs. Receiver is based on small parabolic reflector allowing one to use a compact dual circular polarized horn antenna, which together with a Cassegrain antenna forms a three-mirror system. Front-end is uncooled that allows reducing operational and maintenance costs, while still providing acceptable noise performance. Practical tests show average overall sensitivity of 750 Jy at 1650 MHz in terms of system effective flux density (SEFD). The paper describes the development of the receiver and presents the main results of performance characterization obtained at Irbene RT-32.

Observations of Weak Galactic OH Masers in 1.6 GHz Frequency Band Using Irbene RT-32 Radio Telescope

“…A suitable receiver developed by VIRAC team consists of a compact feed horn with dual circular polarized channels and parabolic reflector, which together with exist-ing Cassegrain antenna forms a triple mirror system. Room temperature low noise amplifiers are used for both channels (right and left circular polarization), which allows us to achieve system noise temperatures of less than 60 K. Estimated aperture efficiency at 1.65 GHz is between 30 and 50 %, which translates to RT-32 radio telescope gains of at least 0.1 K/Jy [7]. The overall estimated sensitivity SEFD is between 650 and 900 Jy depending on the elevation of the antenna, and the weak object detection could be a challenging task.…”