Test phase of ALMA and debugging

The Band 1 receivers will be in a separate dewar from the SIS mixers. They could be used before the much more complicated SIS receivers are installed or when they are being upgraded, etc. The HEMT receivers are very robust and are simple to operate and maintain. We have found that the enormous gain in sensitivity when the 30 GHz receivers are installed at BIMA and OVRO (low Tsys; bright point sources, stable atmosphere) allowed us to check out the system at levels not even remotely possible using the mm-wave bands - we are able to tune up the arrays with our receivers. This will also be true for ALMA. I think it will be extremely useful for initial stages of the array. Frankly, I feel this alone is worth the cost (a percent or less of the cost of the total project!). Interestingly, the Q-band (40 GHz) is the only band ready for the testbed interferometer at Socorro.