Abstract: One function of the ALMA BL-correlator backend (one master plus 16 nodes) is to bring leads and lags produced by the correlator hardware down to a numeric range commensurable to actual signal levels for auto-correlations and correlation coefficients for visibilities. To do so the online software transforms the digital numbers delivered by the correlator hardware (multiply and accumulate samples) to a normalized form, corrects them for quantization effects and finally normalizes again after transforming into a correlation spectrum. For all that to work, access to some sort of total power measurement per antenna is necessary. The present talk describes the implementation of the procedure outlined above and applicability issues that prevent it to fully work online for FDM observations.
Open floor for discussion on other topics as time permits