Interactive Reprocessing of LWS Observations

A very brief description is given of the main steps in the reduction of LWS observations.

Dark Current (DC) subtraction

The estimate and subtraction of the DC is a critical point particularly for faint sources and for FP observations in general; in these cases signal received is at the detector noise level and hence an incorrect DC subtraction may lead to negative photocurrents; as these are later divided by the instrumental transmission profiles profiles (RSRF) the resulting calibrated spectrum will be potentially difficult to interpret.

NOTE: Going interactively through this stage is NOT advised to the general observer and it is ONLY endorsed for calibration and expert use

Click here for a full description of the interactive tool to estimate and subtract DC.

Responsivity Drift (RD) correction

It is well known that the LWS detectors present a temporal drift in responsivity . Its removal is based on the evaluation of the time series of averages of spectral scans; the obvious requirement is that the scan range and the source's intrinsic signal does not vary. The sole case in which this requirement is met is with single pointing L01 AOTs (fortunately the majority of LWS observations).

Click here for a full description of the interactive tool for RD correction.

Absolute Responsivity Correction (ARC) factors

ARCs are the values used to scale the detector responsivities to the values measured when the LWS primary calibrator (Uranus) was observed, and on which the instrumental traansmission profiles of the instrument have been derived.

Click here for a full description of the interactive tool for ARC estimate.

IMPORTANT: Remember that these routines are not producing a fully calibrated (LSAN) file. To accomplish this you still need to run SHORT_AAL : look carefully at the documentation for this routine because you will need to run it with certain keywords which will depend on the use you have done of the three routines above.
Here follows a scheme of processing options available with SHORT_AAL (but please read also the documentation available for that routine).

DC	TRD	ACF	KEYWORDS to SHORT_AAL
N	N	N	no keywords
N	N	Y	/newabs
N	Y	N	/newdrift
N	Y	Y	/newdrift, /newabs
Y	N	N	/newdarks
Y	N	Y	/newdarks, /newabs
Y	Y	N	/newdarks, /newdrift
Y	Y	Y	/newdarks, /newdrift, /newabs

DC -- Dark Current subtraction
TRD - Time Responsivity Drift division
ACF - Absolute Correction Factor estimate