Calibration Measurements June - September 2004

During each RxH3 map calibration measurements are done at positions where amplitude and phase vary little with position (minimizing the influence of pointing errors). These positions are at offsets (307",0") at 80 GHz and (483",0") at 160 GHz. Calibrations normally are done every 20 rows and take 2 seconds, and consist of 4000 (80 GHz) or 14000 (160 GHz) data points. These data are currently not used to correct maps because amplitude and phase vary too irregularly (except maybe in perfect weather).

Below are the results of calibration measurerements for the period June - September 2004. Plotted are phase (left) and amplitude (right), derived from the real and imaginary signal: phase = atan(imag/real) and amplitude = sqrt(real**2+imag**2). No frequency deciphering was done, so the phase plotted is not necessarily for the same frequency, and all amplitude signals are shown. Phase data show a range of 0.4 radians containing data for 2 or 3 frequencies.

On 20030613 the weather was particularly bad and difference maps containing this map show strong striping effects. However calibration scans do not show much difference compared to maps made in good weather: