Adjusting Azimuth Positioner Direction

The host software includes the possibility of precisely adjusting the azimuth positioner’s zero index position to North. This is useful for oreographic measurements or when different instruments shall be aligned to the same scanning directions. The described method assumes that the stand is horizontally aligned in a proper way as described in the operating manual, section 1.3.
In the Adjusting Azimuth menu, the host software calculates the sun position in elevation and azimuth from the GPS position and UTC time, both available from the GPS clock. The radiometer stand should be pre-adjusted so that the azimuth positioner’s zero position is pointing to North with an accuracy of better than 30°. This can be easily achieved with a standard low cost compass.
The user should start the adjustment procedure with a relatively wide azimuth scanning span (e.g. >=50°) and start the scan (click Start Scan). After the scan is finished, the misalignment between the real north direction and the positioner’s north direction is printed in the Misalignment box. A positive misalignment indicates that the stand is directed towards the West and should be rotated eastwards. In an iterative process the stand’s orientation can be adjusted to the real North with an accuracy of better than 0.5°.
The radiometer uses the detector voltage of the first channel of receiver 1, if present (e.g. the 22.24 GHz channel in a RPG-HATPRO radiometer), otherwise it takes the first channel of receiver 2 (e.g. in the RPG-TEMPRO radiometer).