SMT Beam Efficiency

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Measurements of Mars and Saturn for the above chart were done in fall 2007-spring 2008. The beam efficiency is consistent across the 1 mm band. A slight difference exists between h_pol and v_pol values due to optics-related beam squint.

The error values above are 95% confidence intervals. Efficiencies were calculated using the technique described in Magnum (1993)¹. In our calculations, the factor of ½ was omitted from equation 1 of Magnum (1993)¹, because the SMT 1mm receiver is a single-sideband instrument. For T_saturn we used values plotted in Figure 4 of Weisstein & Serabyn (1994)². The measured n_b values agree with the displayed Ruze formula:

where σ is the surface rms of the SMT (15 micron), ε is the aperture efficiency (0.64), and λ is the observing wavelength.

A PDF file of this data located here.

¹ Magnum, J.G. PASP, 1993, 105, p 117-122

² Weisstein, E.W. & Serabyn, E. Icarus, 1994, 109, p 367-381