Data Processing

The major processing steps are :

1. Correlate the two tapes in the Mk4 correlator. This produces a file of time-stamped correlation coefficients normalised to unit system temperature.

2. Apply the VanVleck corrections; scale to the observed system temperature; use the time-stamped telescope data to attach to each visibility the azimuth and elevation offsets from the satellite position. Fourier transform each visibility to the spectral domain; extract the two spectral channels with the beacon signal.

3. Calibrate the data (using the boresight observations)

4. Grid the visibilities in the 2-D (az/el) grid. Fourier transform to the aperture plane.

5. Split the complex aperture plane distribution into an amplitude map (the illumination function), and phase (the surface error map).

6. Process the surface error map: correct for pointing, feed offsets; transform from the aperture plane to the reflector surface.

The software details are discussed in the document "Effelsberg_Holography_software", available on request.