| Description: | A reflector telescope focuses the incident electromagnetic fields in the focal plane. This hypnotising movie shows the simulated power distribution in the focal plane of a Westerbork telescope at 21 cm. It has the typical pattern of a main lobe at the geometrical focus, surrounded by airy rings. The direction of the incoming plane wave is varied up to 1 degree from the on-axis direction. The red and blue dots represent the location of the array elements of DIGESTIF, which will measure 80 cm x 80 cm.
Conventional single pixel feeds have a fixed position and produce a single beam at the sky. Each element of a focal plane array has its own pattern on the sky. Due to the close spacing of the elements these element patterns will overlap. By combining these elements one can produce a number of optimised beams on the sky. The trick is to find an set of weighting coefficients that produces the desired beam shape with maximum sensitivity. This is one of the objectives of DIGESTIF. |
