Spectral line 25 MHz Correlator offset status

We recently demonstrated that the correlator offset problem present in 25 MHz bandwidth spectral line observations is being triggered by the so-called self-test in the correlator. We were unable to detect any offset in a three hour run taken with self-test turned off. As a result, self-test has been turned off automatically for all 25 MHz bandwidth spectral line observations taken after November 8, 2007. Note that these offsets have never been observed at bandwidths other than 25 MHz, and for those other bandwidths self-test will remain on, as before. Because the correlator self-test is now turned off during all 25 MHz spectral line observations observers need to check their data very carefully, and notify us if there are problems as soon as possible.

For observations taken before that date, the effects of the offset can be removed during post-processing provided there is no emission of interest in the center of the field. See the relevant section in the post-processing chapter for more details.

Modified on Tuesday, 29-Jan-2013 13:57:47 MST by Gustaaf van Moorsel