The RT-32 radio telescope pointing system

Abstract

The new generation multiwave high precision radio telescope (RT) with a 32 m diameter mirror was developed and manufactured within the framework of the project of creating the national Quasar KVO radiointerferometric network [1][2][3][4]. To date, three RTs have been built and actively operate at the Svetloe (Leningrad oblast), Zelenchuk (North Caucasus), and Badary (near lake Baikal) observatories. The RT of the Badary observatory is shown in Fig. 1.The RT is intended for fundamental investigations of celestial objects of different natures within wave length ranges from 1.35 to 21.00 cm [5][6][7][8]. The main element of the RT is the reflector antenna system (AS). The AS was built according to the modified Cas segrain scheme with a quasi parabolic principal mir ror and quasi hyperbolic secondary mirror (conver gent mirror) 4 m in diameter. An important feature of the focusing system is a slight deflection of the focal axis of the secondary mirror from the rotation axis of the quasi paraboloid of the principal mirror. Such an orientation scheme of the axes allows placement of the primary feeds of the RT [9, 10] receivers on a circle with a diameter of ~3 m and provides prompt switch ing of the ranges of received signals via adjustment of the convergent mirror position [3].The rotary support of the AS provides azimuthal and elevation angle rotations. The electrical drive of the principal mirror provides azimuthal and elevation angle displacements of the AS within angles of ±270°a nd 0°-90°, respectively.The AS azimuthal movement is performed along a 40 m diameter circular rail track. The azimuthal drive consists of four paired carriages, each of which is equipped with two pairs of dc motors with different powers.The large weight of the RT 32 structure (>600 t) and the requirements imposed on the dynamic char acteristics of the RT movement determine the param eters of the AS electrical drive and control system.The electrical drive provides high speed displace ments along the azimuthal (up to 1.5 deg/s) and eleva tion angle (up to 1 deg/s) coordinates with accelera tions of up to 0.8 deg/s 2 at the speed up stage [3]. In this case, the AS control system must control the RT movement dynamics so as to ensure the required accu racy, absence of vibrations, and a dynamic but smooth acceleration and deceleration. Impact loads on the RT structure must be excluded. When nonstandard situa tions arise, the safe RT stoppage must be provided.The electrical drive of the AS operates in two modes. The AS is displaced to a specified region using more powerful high speed motors for a maximally rapid change in the orientation of the antenna princi pal mirror upon a change to the next object under observation. The source tracking mode is provided by low speed motors that are enabled after the AS reaches the rated vicinity of the radio source coordi APPLICATION OF COMPUTERS IN EXPERIMENTSAbstract-Quasar-KVO RT 32 radio telescopes of the radio interferometric complex of the Russian Acad emy of Sciences are equipped with unique 32 m diam...