Frontend-Backend Channel Layout

Note on Number of Channels (GS 5.9.06)

Even though the bolometer array has 295 detectors, LABOCA provides 320 channels, in the frontend as well as in the backend: in fact, we have 320 amplifiers which are connected to 320 backend channels. Channels not connected to bolometers are anyway connected to some other devices, at the level of the bolometer array (low or high impedance monitors), which are needed (especially in the first days) to characterize the system and to monitor microphonics and system noise in general. In other words, channels not connected to bolometers are channels anyway and they must be acquired and must be stored in the FITS files exactly like bolometer signals because they provide essential information needed to monitor the system and reduce the data.

In the past, the number 295 was erroneously used: it was a mistake, 295 is the number of bolometers but not the number of channels which is 320.

To make an example, MAMBO-2 has 117 bolometers but it provides 121 channels stored in the FITS files: 117 AC coupled bolos, 3 DC coupled bolos, 1 wobbler status monitor.

Starting from today, keep in mind that LABOCA has 295 bolometers BUT they only are a part of the full set of 320 channels.

boawiki: Documentation/Laboca_Technical_Info (last edited 2009-12-17 15:40:30 by localhost)