The calibration tool allows to create and change calibration tables,
as well as apply or de-apply calibration parameters to data. NCDRT
must be in the eight channel mode (no averaging) for this tool to
work properly.
Text windows and buttons
Create New Calibration Table
calibration_display_event.pro
Create a new calibration table and write it to the file selected
with the pick file dialog widget. Any file name can be given.
Read Existing Calibration Table
read_cal_table.pro
Read an existing calibration table. The pick file dialog widget
allows to chose the file. NCDRT checks if the file is a calibration
table or not.
Calibration table information text window
This window contains the information about the currently loaded
calibration table.
Write To Calibration Table
write_2_cal_table.pro
This is the routine which does the actual calibration. The user
must program the calibrators and frequencies. At the time of
writing, three calibrators are included, with the frequencies
corresponding to the maps 1 - 6 of the P3B01 Mars project. The
routine uses the frequency read by load_obs.pro in the pou file to
identify the frequency set to use (parameter central_freq). It next
checks the name of the object (parameter object), also read by
load_obs.pro from the pou file. If it does not find a
correspondance between the object name and the included
calibrators, it will notify that no calibrator was found.
The absolute fluxes for the three calibrators included (3C123,
3C161 and 3C295) are taken from Ott et al. (A&A 284, 331-339,
1994, Table 5).
Once the absolute fluxes are calculated, the routine compares them
to the measured fluxes from the calibrator observation. The
calibration factor for each channel is determined (including the
error, which is the total error, see section 5.1), also for the
averaging channels. It is assumed that the calibrator is non
polarised, so that every channels corresponds to half the total
flux (in fact, the total flux is what is written in these channels
by NAPS).
The results of this exercise are written to the calibration table.
They are also plotted in the calibration plot window (see
calibration plot window for explanation).
Here the channel select string is taken into account ! You can
select the good and bad channels for your calibrator.
Delete From Calibration Table
delete_from_cal_table.pro
Delete the current calibrator from the calibration table, if it
exists in the table.
Create .ps Of Calibration Table: calibration_display_event.pro
Create a postscript file of the calibration table data. The file
name of the postscript file will be the file name of the
calibration table followed by .ps.
Apply Current Calibration
apply_calibration.pro
Apply the calibration factors of the current calibration table to
the current data. Each channel is multiplied by the set of
calibration factors (8+4 channels) from the calibration table that
is closest in time to the current observation. This can be
different for different channels, as not all channels will have
good calibration data for each observation!
In this version, nothing is done with the calibration factor error.
De-apply Current Calibration
calibration_display_event.pro
De-apply any calibration of the current data. In fact, the current
data is restored to its initial values (copy from channel_data_ori
to the channel_data parameter).
Dismiss
calibration_display_event.pro
Dismiss the calibration tool, and kill the plot window if any. If
any calibration table was loaded, this table will stay loaded in
NCDRT.
Explanation on the calibration plot window
In this window the calibration factors for each channel as from the
current calibration table are plotted and updated if any action is
taken (new calibration data or deleting of calibration data). There
are 8 sets of 2 frames. These correspond to the eight channels. The
top frame of each set shows the entire calibration data for that
channel, the lower frame shows a detail of that data only around the
time of the current observation. A dotted vertical line indicates the
position of the current observation time. If this time is out of the
calibrator table range, the whole set is also plotted in the smaller
frame.
In the first seven sets, the dashed line correspond to the average
channels (9-15).
A cross means that the channel was not selected for the particular
time.
If a new data file is loaded, while the calibration tool is active
with calibration table loaded, then the calibration plot window is
updated to show the time of the current observation.