Absolute Responsivity Correction Factors
This tool can be used for all LWS AOTs.
Invoking the Interactive Tool
; Example ia_abscorr,dir='/user/iso/data/',tdt='44700574',/newdarks
; Arguments Name
I/O Type Description
I string the tdt number associated
with the observation. For example if the tdt number
is 44700574 then the routine will look for data files l*44700574.fits.
specified the routine assumes that files to be read are called l*.fit (viz
processed files from the CD_ROM).
I string the directory
from which the input files are to be read. It can be a relative or
absolute path. e.g. dir='data/'.
If not specified then the data are read from the user's curent working
I keyword If set, the routine reads the MC-FITS
format data files from the ARC_DAT
directory. Only expected to be used by the instrument team.
/newdarks I keyword If set, the routine
will assume that the user has previously interactively estimated
and subtracted the DC. In this case the LIAC+tdt+_newdarks.fits file is
input instead of the standard LIAC file
/update I keyword
If set, the routine will assume that the user wants to work on a previously
modified set of files, or wants to resume a previous session
The following Widget will pop-up (the plot area will be empty; button
'SW3' has been hit in the example below):
A Description of the User Interface
The black area is the plot window,
with its control buttons (Replot, Unzoom, Hardcopy) on its right side.
Below the plot area the following groups of buttons are visible from left
At the bottom of the Widget there is a text area where messages
are prompted to the user about actions to be performed and displaying information.
The 10 LWS detectors buttons
Opaque Flashes buttons: there is 1 button for each dark
current (DC) measurement performed in the AOT. Aside each of these
buttons there is a text field which will show the estimated Absolute
Responsivity Correction Factor (---> ARC) value (see below); further
on the right there are other text fields (again, 1 for each DC measurement)
showing the ARC values estimated automatically by the OLP.
Masking buttons: pressing one of them make
the right button of the mouse active (click and drag) to select portions
of the data to be masked/unmasked. In the first case data within the selected
area will turn to blue and will be ignored in further processing; in the
second case data previously masked are brought back to white colour and
become again available for processing.
Operations buttons: a series of buttons to estimates the ARC, write
results in a file which will be used by in final calibration step and Exit,
or simply Quit.
The ARC Estimate Cookbook
The following is the list of the steps that should be followed for the
Select one detector by clicking on one of the detector buttons; nothing
still happens. Pay attention to the message window; it is telling you to
select one of the Flashes found.
Select the 'Flash # n' button (likely starting from the first).
A plot in linear scale (to allow 0s and negative numbers to appear - as
they could enter in the processing) is shown where the signal observed
during that illuminator flash
is plotted in white crosses as a function of time (ITK);
data from the Reference Illuminator flash
are overplotted as red crosses. 0s are automatically
flagged as bad data and overplotted in blue crosses:
the n-sigma clipped median average of all
crossesratios will produce the ARC. The
user should zoom the plot to get a feeling of the data quality; bad points
can be discarded using the masking buttons.
In case of an Illuminator
Flash scheme of old type (two flash sequences per flash), be aware
the data from the first sequence are masked by default
as unreliable just as done in the standard OLP
Press 'Estimate' (in the 'Operations' area)
to actually compute the ARC. A plot is shown with all the single white/red
crossesratios plotted as green
crosses; the n-sigma clipped median average is presented as a white
horizontal full line. Note that ratios involving previously masked data
can appear as red crossesbut
are not included in the average. The estimated
ARC is printed in the text field aside of the 'Flash #n' button
previously pressed, in the text area at the bottom of the widget and on
the terminal window. A small widget will also pop-up to ask the user how
'I am happy with that' accept that value: click it if you are happy
with the result.
'I want to change clip level': you are not satisfied with the estimate
and want to try again the n-sigma median averaging but with a different
Just input a new n value in the small text area and click teh button:
the average is soon recomputed and the new value overplotted.
'Fix it by hand': there is no way of getting what you think is the
correct value (use a grain of salt and a lot of common sense) via averaging
so you want to set a particular value by hand. Click that button and then
click again on the plot with the right button of the mouse just
at the Y position you think is correct.
'Do not accept' if you are not sure how to proceed and you want
to think a little bit about it.
The user can also insert his own estimate of the absolute correction
factor in the relevant text field under 'Opaque Flashes' ; remember
to hit 'return' button
Everything done till now should be repeated for each Illuminator
Flash (each 'Flash #n' button) and for each detector; note that
when ARC values have been estimated for all dark measurements an asterisk
'*' will appear in the relevant detector button. In some cases the user
may want, for a particular detector and illuminator flash, to adopt the
ARC value that OLP has automatically estimated;
this can be done by clicking on the 'left arrow' button in the 'Opaque
Flashes' section (see below)
When the user is happy with the estimated set of 10 ARCs, it is time to
press 'Write new LGIF and Exit'; a new version of the LGIF file
(with appended '_newabs'), to be used in the last steps of data reduction
and calibration, will be produced.
Document by: Sergio Molinari, IPAC/Caltech
Last Update: Jan 19, 1999