In the past winter period, the MPIFR 7--channel bolometer and later, after a technical and scientific verification phase, also the MPIFR 19--channel bolometer, were offered to the astronomical community, the latter one for the first time. It was installed and tested by the MPIfR bolometer group and IRAM during the second week in March and was then available for observations until the beginning of April.
A plot of the 1.3mm zenith optical depth during the bolometer period is shown in Fig. 1. Except at the beginning of the observing period, where observations were impossible due to weather, the instrument could be used most of the time (with only a few interruptions due to small technical problems). Due to the increased data rate, the computer system was pushed to the limit. Improvements are foreseen for the future.
The bolometer was mainly used in on--the--fly mapping mode, where one gained a factor 2 or more in observing time compared to the 7--channel Bolometer. A single coverage resulted in a map with RMS noise typically between 6 and 12 mJybeam. A report on test results from the 19-channel bolometer will be given in a future copy of the Newsletter.
Figure 1: Zenith optical depth at 1.3 mm during March and beginning of April 1995