The replacement of the subreflector on antenna 3 with a new generation subreflector made from a solid block of aluminum, foreseen for October, had to be deferred until the end of the current observing period. Despite evident signs of surface delamination on the current subreflector, the antenna efficiency is still comparable to the efficiencies of the other antennas.
Because of the accumulated delay, we also deferred replacing the 3mm and 1.3mm receivers on antenna 1 until the end of the current observing period.
The 1.3mm receivers of all antennas have now been equipped with new generation LO2 systems to reduce the overall phase noise budget of the interferometer. Improvements in the antenna efficiency are expected at a level of 10%-20%. Surface adjustments and optimization of the receiver alignment have also been carried out on all antennas last autumn.