# RDI and RED

Both programs have been extensively modified. RED has disappeared. RDI now only computes atmospheric calibration and writes data. An additional program (named AFF) monitors the running acquisition (subscan number) and computes the real-time amplitude and phases for display by STS C.

In order to save time, RDI returns control to OBS immediately after data is read into memory. It then completes the calibration steps and writes up the data, while the acquisition of the next command is already started. This is normally OK because the computation time is less than the minimum integration time on the correlator (5 seconds + 3 seconds of setup or delays + 2-3 seconds to read the data) even in the worst cases.

An even faster automatic mode is available for cross-correlation loops, using the SET SCAN Nscans) command. In this mode, acquisition continues even while RDI reads, calibrates and stores the previous scan. The minimum integration time is 30 seconds in this case.