Characteristic  Value  Units  Notes  

Detector Operating Temperature  285  mK  measured at Northwestern  
Beam FWHM  predicted: 4.1 measured: < 6.0 
arcmin  predicted as follows: add (in quadrature) the pixel spacing (3.5 arcmin) and the diffractionlimited beam FWHM of approx. (0.45 mm/0.7 m)  
Detector Noise  50  nV/Hz^{1/2}  measured with spectrum analyzer at 3.1 Hz  
Responsivity (S)  4 K blankoff wheel closed  5.0*10^{8}  V/W  varies by about 20% from detector to detector 
blankoff wheel open 300 K load 
Austral Winter 2000: 3.8*10^{8}
after 2001 upgrade: 2.1*10^{8 }  V/W  varies by about 20% from detector to detector  
blankoff wheel open 200 K load (theoretical; interpolated) 
Austral Winter 2000: 4.1*10^{8}
after 2001 upgrade: 2.9*10^{8} 
V/W  Interpolated using result of empirical fit to pre2001 vs. 2001
load curves
that gives (S_{closed}  S_{open}) = (const.)(load power)^{0.83} 

Noise Equivalent Power  (atmospheric)  Austral Winter 2000: 1.10*10^{16}[1e^{tau*sec(z)}]
^{1/2}
after 2001 upgrade: 1.88*10^{16}[1e^{tau*sec(z)}] ^{1/2} 
W/Hz^{1/2}  Fundamental noise from a 200K atmosphere with optical depth tau at 450 microns and zenith angle z 
(detector)  1.2*10^{16}  W/Hz^{1/2}  detector NEP = (det. noise)/S  
Noise Equivalent Flux Density  (atmospheric)  Austral Winter 2000: 62*[e^{2*tau*sec(z)}e^{tau*sec(z)
}]^{1/2}
after 2001 upgrade: 27*[e^{2*tau*sec(z)}e^{tau*sec(z)}]^{1/2} 
Jy/Hz^{1/2}  theoretical estimates based on 4' beam 
(detector)  Austral Winter 2000: 68*e^{tau*sec(z)}
after 2001 upgrade: 17.4*e^{tau*sec(z)} 
Jy/Hz^{1/2}  theoretical estimates based on 4' beam  
Instrumental Transmission (cold optics)  Austral Winter 2000: 1.87
after 2001 upgrade: 5.5 
%  determined from load curves with BOW closed vs. BOW open (Note this is measured with unpolarized light, so a perfect polarimeter would have 50% transmission in each of the two corresponding orthogonallypolarized detectors.)  
Overall Instrumental Transmission  Austral Winter 2000: 1.12
after 2001 upgrade: 4.4 
%  Cold Optics transmission times warm optics transmission (pressure window [80%]; black polyethylene OVCS filter [75%] that was used in 2000 but not 2001). Again, 50% is theoretical maximum transmission.  
Fractional Bandpass  0.1  (none)  Bandpass centered at 450 microns 