1. Click on the CUSTOMIZE button in the top window of PIA to define the
"PIA path" leading to where the pipeline ERD FITS files are.
for example, /home/ISO/iso_data/NGC6946/pht-s/p0014581/20700516/
2. Click on the FILES button in the top PIA window and select "file
manager." After the "file manager" window pops up, select "ERD" and
"SS/SL" in the two filter windows. After this, the PHT40 ERD file
names should appear in the "files" subwindow. If not, you can click
one of the directory names shown in the "Subdirectories" subwindow
to see if you can navigate to the desired file. Once you have located
the correct file in the "Files" subwindow, click on the file name
there. Finally click on "read file" button to read the selected
file into the PIA buffer.
Select an ERD measurement for porcessing:
1. Click on the BUFFERS button in the top PIA window and select "buffers
manager." After the "buffers manager" window pops up, select
"ERD" and "SL/SS." All the measurements in the selected category
should show up in the "measurement" window. Usually, there are
2 measurements: the first one is a "pseudo" dark measurement and
the 2nd one is the real observation. Normally, you click on the
2nd file.
Option: you can look at the FITS header, Compact Status, or
even the data themselves by clicking on "SHOW ..." button in
this "buffers manager" window.
Plot and reduce the ERD data to SPD stage:
1. ERD to SRD:
Within "buffers manager" window, click on the PLOT & REDUCE DATA button.
After a few seconds, it pops up a new window displaying the read-out
ramps as a function of time for 4 out of the 128 detector pixels.
Some readouts are masked out (shown as red crosses) by default.
Option: you can click on ZOOM & PRINT button to blow up a displayed
pixel in order to see individual ramps more clearly or to print
the display on the laser printer.
Option: click on the SELECTION button allows you to change the read-out
mask scheme from the default.
The next thing to do is to click on the CORRECTION button and select
the following functions in order, each at a time:
Non-linearity (not available for PHT-S at this time)
Read-out deglitching
Finally, click on the PROCESS MEAS button and select "1st order polynomial"
to fit a slope to each integration ramp. This brings you to the next
stage, SRD.
2. SRD to SCP:
Displayed in the SRD window are time series of the ramp slopes for 4 out
of the 128 detector pixels. Again, the masked slopes by default are shown
in red crosses. Click on the CORRECTION button and select the following
functions in order, each at a time:
deglitching (to filter out badly deviated slopes)
dark current subtraction (subtract out a default dark)
Finally, click on the PROCESS button and select the "no drift handling"
option to proceed further to the SCP stage.
Option: you can give a try of the "with drift handling" option under
the PROCESS button. But if you only a few ramps per chopper plateau,
the fits may not be satisfactory at this point.
3. SCP to SPD:
Displayed in the SCD window are the average slopes per chopper plateau
as a function of time.
The next thing to do is a background subtraction if a sky spectrum is
avaliable or if this is a chopped observation. Click on the PROCESS
button and select "background subtraction." If you have a chopped
observation, select the sub-menu "within measurement," otherwise, select
"another measurement."
In the case of a chopped measurement, a window labelled as "PIA background
subtraction menu" pops up, together with a graphic window displaying the
"grand average signal" per chopper step. Usually, one just needs to click
on the "OK" button in this window. Then the following choices on how the
subtraction should be done become avaliable:
, (SRC-BCGH)/Ch-plateau,/Ch-plateau,..
Normally, you select the first choice unless there is a large drift in
the data. After having done this, click on the "Subtracted meas -> buffer"
button to save the subtracted spectrum to the buffer.
In the case that the sky measurement is from another observation whose SPD
spectrum has been saved on the disk. A pop-up window will display all saved
files and you click on the right file. The subtraction will be done.
Note: if the sky measurement was processed in an independent PIA session and
the result was saved on your hard disk, you need to read it back to the PIA
buffer before you do the sky subtraction here. Using the "File manager"
to read the saved spectrum into PIA.
The last thing to do is to click on the "DATA" button in the SCP display
window and load the sky-subtracted result back for display. After
the spectrum has been displayed, click on the PROCESS button and select
"power calibration" --> "default responses" to convert V/S to Watts.
This pops up an SPD window.
4. SPD stage:
The SPD window is similar to the SCP window, except that the slopes are
now in units of Watts and that only SS or SL part of the whole spectrum
is displayed. By default, the SS part is displayed automatically.
==> SS part of the spectrum:
Click on "PROCESS" button and select "extract flux density" to calculate
Jy (assuming a point source) and MJy/sr (assuming an extended source) and
to write an AAP file.
==> SL part of the spectrum:
You need to load the SL part of the spectrum from the buffer for display.
To do so, click on the DATA button in the SPD window and select "load."
When a pop-up window displaying all the files in the buffer, click on
the correct one.
After the SL spectrum is displayed, you can repeat the above steps for
the SS part of the spectrum.
Option: you can now see the final spectrum (flux density vs. wavelength index)
by loading the AAP file in the "buffer manager" window. To do so, click on
"AAP" and "SL" (or "SS") in that window, and then click on the file
you want to look at. Finally click on "SHOW ..." button located on top
of the window and choose the "data values" menu. This bright up a
"show structures & plot curves" window in which you can select parameters
as Y-axis for a plot. For example, you can choose "mean flux" --> Y-axis
and "mean uncertainty flux" --> Y-error bar, and click on PLOT button to
plot the spectrum. To plot the sepctrum as a function of wavelength in
micron with the current PIA, you have to read on.
Congratulations! your ERD -> SPD data reduction has been completed.
Display the AAP Result
AAP (=Auto Analysis Product?) result is comparable to the pipeline AAR
results when both softwares become stable. The AAP result can be displayed
and analyzed to some extent by using the "Astrophysical Work" subpackage
within the PIA.
Go to the PIA top window and click on the BUFFER window and select "astrophysical
work" function there. An Astrophysical Application Menu window should
appear on your screen. Select "Spectro-photometry" function.
Another window pops up, and you click on the "FILE" button there to
"select measurement." After the correct measurement is loaded, click on
the "PLOT" button to plot the spectrum in a number of different ways
or on "PROCESS" button to do some analysis.
similar to that in the interactive data reduction described above.
Using the Batch mode of Data Reduction:
1. click SEQUENCE button in the top window of PIA and select "Batch processing
--> general" option.
2. A "PIA batch processing decision" window pops up. You can select from ERD
to AAP. Click on the OK button to activiate the batch processing.
3. This brings up a "selection" window in which you select the input file format,
correction criteria, and which intermediate results to save. Click on
the OK button when you are done with this. This brings up a "file
selection window" where you can select the file(s) to process. Finally,
click on the OK button to proceed.
4. When the batch process it's finished, you can exam the results in the PIA
buffer as you would do in the interactive mode.
Last update: Nov 1997