Invoking the Interactive Tool
; Example ia_drift,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.
If not specified the routine assumes that files to be read are called l*.fit
(viz the SOC 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 LSPD+tdt+_newdarks.fits
file is read in input instead of the standard LSPD file
NOTE: be sure to specify /newdarks keyword if you went through
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.
In the example above the 'SW3' button has been hit (see below) and the
data (not yet calibrated either in flux or wavelength) collected in the
AOT for detector SW3 are shown as a function of time (ITK).
The user can zoom in by clicking and dragging using the left button of
the mouse. Below the plot area the following groups of button are visible
from left to right:
A text area at the bottom of the window displays useful messages.
Information about the properties of each data point is also reported in
this message window; just click on the plot area with central button of
the mouse, and the characteristics of the nearest data point will be reported:
time, photocurrent, raster point ID, detector number, line number and scan
The 10 LWS detectors buttons
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.
Key Points buttons: the two options for estimating the Time
Responsivity Drift ; these options will be discussed below in
Fit Method buttons: the two available methods to interpolate the
responsivity drift between the Key Points (see below)
Operations buttons: let the user divide out the interpolated responsivity
drift , write a new LSPD accordingly, or quit
The Responsivity Drift Correction Cookbook
The following is the list of the steps that should be followed for the
Drift (---> RD) correction:
Select one detector by clicking on one of the detector buttons; a plot
similar to the one shown in the example above should appear.
Determine the Key Points (---> KP): these are the points (one per scan)
which are then used to interpolated the RD throughout the AOT. Click
here for a brief description of how the RD is estimated by OLP
; the present tool follow the same principles but in a more flexible way.
Two methods are available to estimate KP (the two buttons under the 'Key
Points' area of the widget):
'Find Key Points' let the routine free to choose which points in
each scan are going to be averaged (scan per scan). Only Grating
positions for which valid data (not discarded to be contaminated by
transients) are found for all scans (overplotted as +)
are considered and averaged to find KP (overplotted as *);
after zooming a bit the above example plot and after pressing 'Find
Key Points' button something like this should be seen:
It should be noted that the number of grating
positions for which valid data are found in each scan is decreasing
with the number of scans because transients occurrence is not selective
with respect to grating position and so after a certain number of scans
every grating position will have experienced a transient at least once.
It is also worth noting that valid data does not mean good data. A data
point may be bad although flagged as valid: looking at the example above
it is clear that the highest +for
each scan are bad points to be included in the average as their time series
behaves differently from the averages (*)
themselves. Forcing these points not to be included in the average
is simple and can be done using the masking buttons.
'Set Key Points' allows the user to select
directly which data are going to be averaged to produce KP. Hit the button
and the data will be plotted as photocurrent versus grating
position (so all the scans will be seen on top of each other; use the
right button of the mouse (click & drag) to select desired ranges (unlimited
number) of grating positions (points in selected ranges turn to green);
should look like this:
Repeat all described operations for all 10 detectors (user can also repeat
a detector already done, iterated actions are always performed on the original
data set, so no danger of chain corrections).
When finished hit 'Write new LSPD and Exit' ; a new LSPD file called LSPD+tdt+_newdrift.fits
is produced and user can go on with processing.
Document by: Sergio Molinari, IPAC/Caltech
Last Update: Jan 19, 1999