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The MPIfR Bolometer arrays

The 19-pixel MPIfR bolometer array which was used at the telescope last winter will be again available. The horns are located at the center and on the corners of two concentric hexagons with beam spacings tex2html_wrap_inline1354 . Each channel has a sensitivity of tex2html_wrap_inline1356 mJy s tex2html_wrap_inline1361 under good weather conditions and a HPBW of 11''.

The 37-pixel array has an additional hexagonal ring of horns, but is otherwise very similar to the 19-pixel array. The 37-pixel array was also used at the telescope last winter successfully, but several technical imperfections, notably excessive spiking, make some modifications necessary. It will therefore not be available before early next year.

The bolometers are used with the wobbling (typically at a rate of 2 Hz in azimuth) secondary mirror. The orientation of the beams on the sky changes with hour angle due to parallactic and Nasmyth rotation, as the array is fixed in Nasmyth coordinates. Special software is made available at the telescope for data reduction (NIC [11] and MOPS [12]).

It is planned to have two bolometer sessions, one near the beginning of the winter scheduling period, the second one probably early next year. The 37-pixel array will not be available for the first session. Observers are invited to express their preference for one or the other observing session, based on sidereal time considerations and/or array size.