.

• 1 GHz Acousto-Optical-Spectrometers (AOS's) (AOSA and AOSB)
  The MPIfR installed two 1 GHz bandwidth AOS's for spectral line work in early 1997. The mean resolutions are 934 kHz for AOSA and 913 kHz for AOSB. The AOS's use 2048 element linear CCD's and thus oversample the spectra by about a factor 2. Therefore, the channel widths in CLASS spectra are about a half of the AOS's resolution.
  The latest maintenance measurements of September 22^nd, 1999 are shown in the following two graphs (click on images to get a larger version). The resolution and frequency linearity are very close to the previous measurements starting in April 1998.
  

  AOSA comb results (GIF)
  
  (PostScript version)

  AOSB comb results (GIF)
  
  (PostScript version)

• 250 MHz AOS (AOSC)
  The MPIfR 250 MHz bandwidth AOS was installed in the fall of 1997. It has a mean resolution of 385 kHz. The same 2048 channel linear CCD is used to detect the spectra which are therefore oversampled by about a factor 3. Thus, the CLASS channel width for spectra taken with this AOS is about a third of the resolution.
  The following graph shows the results of the October 06^th, 1998 maintenance (click on image to get a larger version). We checked AOSC again in September 1999. It appears that the resolution and frequency linearity did not change compared to the previous measurements. However, the comb generator has developed a problem. The comb generator is used only for maintenance measurements and it is not necessary for normal observing. We will check and repair it and then post updated results here.
  

  AOSC comb results (GIF)
  
  (PostScript version)

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  Long integration (~4 hours) data on sky using the 230 GHz receiver with the wobbler are available for AOSB and AOSC. Both AOS's do not show any significant deviation from the expected 1/sqrt(time) law.
  

  AOSB long integration results (GIF)
  
  (PostScript version)

  AOSC long integration results (GIF)
  
  (PostScript version)

• Filter Banks (FBS)
  The filter banks were used at the University of Texas Millimeter Wave Observatory (MWO). The spectrometer has 3 bandwidth modes: 256 channels of 1 MHz, 256 channels of 250 KHz, and 128 channels of 62.5 KHz. It provides a backup of the MPIfR AOSs.

See SMTO Electronic Newsletter Volume 1, Number 2 (April 1998) for more details on these and other (PI) backends.