The exposure time of the result is = t_sig * t_ref * smoothref / (t_sig+t_ref*smoothref), where t_sig and t_ref are the exposures of the signal and reference data container and where smoothref=1 in when smoothref has not been supplied. That is the effective integration time appropriate for use in the radiometer equation. Note that in the two limits of smoothref (1=no smoothing and large smoothing), if t_sig = t_ref then exposure = 1/2 * t_sig or exposure = t_sig. With no smothing, the noise increases due to the subtraction of an equally noisy reference spectrum. With smoothing, the noise is as it would be for just the signal spectrum. Smoothing should be done with caution, though, because it can emphasize systematic glitches present in both signal and reference spectra that are not fully subtracted as a consequence of the smoothing.

All of the other header values are copied from dcsig.

If smoothref is set, the dcref values are smoothed using the IDL smooth function. This does a simple boxcar smooth where the smoothref parameter is the width of the boxcar. smoothref is only used if it is larger than 1. In certain cases this can improve the signal to noise ratio, but it may degrade baseline shapes and artificially emphasize spectrometer glitches. Use with care. A value of smoothref=16 is often a good choice

The dcresult data container is created as necessary. If it already exists, the internal pointer will be reused. It is the responsibility of the calling procedure or functiosdn to free that pointer using data_free. Failure to do that will result in a memory leak.

Version

$Id

Parameters
dcresult out, required variable	The result.
dcsig in, required data_container	The signal data container.
dcref in, required data_container	The reference data container.
smoothref in, optional integer	Boxcar smooth width for reference spectrum. No smoothing if not supplied or if value is less than or equal to 1.