Other Issues

The ASAC re-iterates its earlier recommendations on various other important ALMA receiver issues:

• Total Power Stability: See March 2000 ASAC Report
• WVR Specifications: These are discussed in section 5. We simply note here that a robust WVR system is critical to the success of ALMA. The present baseline is for an uncooled design, but further research will be required to determine whether such systems can in fact meet the scientifically mandated specifications.
• Polarization: Again, the ASAC recommends that careful consideration be given to optimizing the polarization properties of the 345 GHz receiver for both continuum and molecular line work, and that the different polarization behavior of the two prototype antennas and other polarization properties of the test interferometer and single-dish techniques should be carefully measured as they may be a consideration in procurement decisions.
• Calibration Accuracy: The ALMA calibration specification of 1% is adequate scientifically, perhaps even a bit aggressive, but, as discussed in section 4 might be difficult to achieve at submillimeter wavelengths. A cold calibration load in the primary dewar is unnecessary.