Total Power

On the Fly Mapping The on-source auto-correlations are taken while the antennas are driven across the sky in a pre-defined pattern. Every so many scans, a reference auto correlation on blank sky is needed.

Position Switched Mapping Mainly on-source auto-correlation scans. Every so many scans, a reference auto correlation on blank sky (off-scan) is needed. The optimal integration time on off source scans depends on the number of on-source positions and the integration spent time on each one. Occasional amplitude calibrations (auto-correlations on hot and cold loads).

Frequency Switched Mapping On-source auto-correlation scans. The frequency is switched to a slightly different value to obtain the reference scan. Useful if no clean reference field can be found, or if the receivers/atmosphere stability does not allow for the antennas to be switched to a different position.