The pair of heterodyne receivers, called 3MM1 and 230G1, which are served in transmission by the main polarization grid, were replaced at the end of May by new generation receivers (see report by B. Lazareff in this newsletter). These new receivers are located in the same dewar (labelled A), and they are now designated as A100 and A230, according to their location in dewar A and their nominal center frequencies in GHz.
IRAM plans a complete refurbishment of the receiver cabin of the 30m telescope. This work is scheduled for September and October and includes a new layout of the Nasmyth optics and new generation receivers at all frequencies together with their associated LO and IF systems. The decision to actually go ahead with this plan will be made mid July, based on the state of readiness of various critical hardware components. Please refer to the IRAM web pages for more up-to-date information.
The most likely scenario, as perceived at the time of writing, is that the refurbishment of the receiver cabin will go ahead as planned. Apart from the new generation receivers A100 and A230 already in place, there will then also be available the old 2MM receiver which will be retro-fitted into the new Nasmyth optics. There will therefore always be one receiver available for each of the three principal atmospheric windows.
Construction of a second new generation dewar, hosting receivers B100 and B230, is well advanced. These receivers (orthogonally polarized with respect to and simultaneously usable with A100 and A230) may also be installed in time for the winter scheduling period. However, since the performance of the B-receivers will not be known in time, proposals for 3mm and 1.3mm observations, notablely calculation of integration times, should be based on only one receiver at each wavelength. Proposals which for whatever reason absolutely need two receivers at the same frequency band, either at 3mm or 1.3mm, cannot be accepted for this winter.
The bolometer observations are tentatively scheduled in two sessions, one before the end of the year, the second one early next year. This arrangement should help to optimize the observations for sources at different sidereal times. The MPIfR 19-pixel array is planned to be available for both sessions. The 37-pixel array which experienced considerable spiking in some of last winter's observations is undergoing several modifications. It will not be available for the first session.
Some improvements of the telescope surface were made recently, resulting in slight improvements of efficiencies and beam quality. From last winter's observations at 345 GHz estimates of and were derived . Observations in the 345 GHz window are clearly among the most difficult ones at the 30m telescope, due to fast variations of pointing and focus, particularly during daytime, and a dominant error beam. Proposals for the 0.8mm receiver should address these issues.