Russian Foundation for Basic Research

SSRT - Radio telescope's beam

The SSRT uses two identical linear antenna arrays with coincident symmetry centers that are oriented in the E-W and N-S directions. Such a crossed antenna array with an equidistant arrangement of identical antenna elements and a uniform distribution of the field in its aperture has a multibeam power directivity pattern:

l = cosa m = cosb - direction cosines; a, b - angles at which the source is observed relative to the array baselines; F0(l,m) - directivity pattern of a single antenna element, determining the SSRT field of view; N - number of antennas in the arrays, d - period of the array, and l - wavelength. The width of the power directivity pattern in the plane of the linear interferometer is determined by the projection of the array baseline onto the wave front, and in the adaptive mode it is:

In the other coordinate, the beam width equals that of the antenna element. The angular distance between adjacent lobes is:

It is at a minimum near a normal to the array baseline. To eliminate the superimposition of signals from different regions in full solar disk observations, g min is chosen to be equal to the solar ardio diameter at a minimum wavelength in the SSRT reception band. The value 94,4l (4,9 m) of the aray period corresponds to this condition. Array baselines at Nd = 622,3 m with the number of antennas N = 128 corresponds to a one-dimensional angular resolution at r = 15".

Solar images obtained on October 20, 1996, at Nobeyama Radioheliograph (left), SSRT (middle), and at the space-borne X-ray Yohkoh telescope (right)