./toolbox
dcspurinterp.pro

Last modification date:

Wed Sep 28 13:27:10 2016

dcspurinterp

procedure dcspurinterp, dc

Replace data values in the given data containers at the known locations of VEGAS spurs with the average of the two adjacent channel values.

VEGAS produces spurs (spikes) at channels corresponding to integer multiples of the ADC sampler frequency divided by 64. The normal behavior of sdfits is to flag these channels when the data are filled. When flagged data is retrieved by GBTIDL, the flagged channels are replaced with NaNs and will not contribute to most operations. If the skipflag option is used to retrieve the data then flagging is not applied and the original data values will appear at all channels.

It is sometimes useful to replace the spur data values (either NaNs if the flags have been used or the original data values if the flags are ignored) with interpolated values. This routine replaces those values with the average of the two channels on either side of the spur (or the adjacent channel if the spur is at the end of the spectrum).

This spur locations are determined using the VSPDELT, VSPRPIX, and VSPRVAL header values. For data filled using older versions of sdfits, these values are not present in the SDFITS table and will appear as NaN in GBTIDL. In that case, no spur interpolation is possible and a warning message will be printed. The data should be refilled by the most recent version of sdfits to make use of this procedure.

Uses

dcspurchans

Version

$Id$

Parameters
dc in/out, required variable	The data container(s) to alter. May be an array of data containers.