The SRT-2 project is to test and operate a new instructional radio telescope. The SRT-2 is a replacement for the SRT telescope originally designed at Haystack Observatory and purchased from CASSI corporation. It is a complete redesign of the original SRT concept. The system is designed primarily to observe the 21-cm galactic HI line.
Students from the Radio Astronomy in Spring 2012 constructed the antenna and receiver and students for the 2012 course built and tested the antenna motion control system and the spectrometer. This year we will integrate a ‘software digital radio’ system for the spectrometer. The will complete the system.
The original SRT used a parabolic dish and 2-axis motorized mount originally designed for TV satellite reception. We found that the mount was not reliable, especially with the high wind loading of the 3 m diameter dish, and after 2 years of use,the mount weld broke and the dish surface lost several panels. The SRT-2 design uses an array of four 45-element Yagi antennas built by Directive Systems arranged in a 2x2 array. The antenna gain should be 26 dB, with a FWHM primary beam of 8 deg, similar to a 3 m dish. The mount is be a commercial 2-axis positioner (Yaesu G5500) with a serial interface, so that the telescope can be controlled and its position displayed on a sky map using an inexpensive planetarium program (Starry Night Pro 6).
Receiver and Spectrometer
The receiver is a conventional single-conversion heterodyne design. The first low noise amplifier (25 dB gain, 0.7 dB NF) and narrowband filter (10 MHz centered at 1420 MHz) will be located at the antenna. The down-converted IF frequency (30 MHz, 10 MHz BW) is sampled by a commercially available ‘software-define radio’ (NetSDR) which we use as a USB-based spectrum analyzer.
An excellent general online reference for radio astronomical instrumentation (antennas, receivers, and spectrometers) is the Haystack Observatory SRT site.