These are spectrometers with a bandwidth of about 215 MHz. There were
originally three of these with a resolution of 60-80 kHz. They had about
30%more noise than an ideal spectrometer due to defects in their Surface
Acoustic Wave filters.
In August 2004, a 2nd prototype of a CTS based on digital technology was
installed. This one only has <10% more noise compared to an ideal
spectrometer and it has even higher resolution (about 40 kHz). It will
eventually be replaced by three digital CTS's. The new ones will be more
carefully adjusted and perhaps will have even less noise than the prototypes.
The CTS backend cannot be reliably used for OTF mapping.
The 250 KHz filterbanks and AOSC and the CTS use the same IF
processor. Due to the different input IF frequencies required for these
instruments, the CTS and AOSC can only be used if the 250 KHz filters are
CTS-A Comb Results
Below are four spectra showing a comparison of the newest CTS with the
|Sample 12CO(2-1) spectrum of NGC 7027 taken with the
1.3mm JT receiver and the wide band AOS, AOS-A. This was a beam switched
observation with a 4 minute integration time. Unlike the old receivers,
the JT receivers have a
bandwidth larger than the bandwidth of the AOS-A and AOS-B, so all 2048
channels are shown in this plot.
|Sample spectrum of W75N taken with the 1.3mm JT
receiver and the other wide band AOS, AOS-B. This was a position switch
observation with a 44 minute integration time. The receiver was tuned
double sideband with the 12CO(2-1) line in the upper sideband. The line at
about -180 km/sec is actually the 13CO(2-1) line in the lower sideband.
(There is a 13CO line is in the AOS-A spectrum too, but there only barely
enough integration in that one to detect it.)
|Same as the AOS-B spectrum, but taken with the narrower
|Same as the AOS-B spectrum, but taken with the high
resolution Chirp Transform Spectrometer. This spectrometer has a bandwidth
of 215 MHz and a resolution of 40 kHz (0.06 km/sec at the 12CO(2-1) line).