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VLA Correlator Page
This page controls the correlator and data collection process.
The correlator mode and integration time can be set for all observations.
For spectral line data it is also possible to specify filtering done
in the Array Processor and select some of the spectral channels.
Correlator Mode
The items in the Choice are relatively self explanatory:
- Continuum
- Single IF spectrum, correlation AA
- Single IF spectrum, correlation BB
- Single IF spectrum, correlation CC
- Single IF spectrum, correlation DD
- Dual IF spectrum, correlation AA, BB
- Dual IF spectrum, correlation AA, CC
- Dual IF spectrum, correlation AA, DD
- Dual IF spectrum, correlation BB, CC
- Dual IF spectrum, correlation BB, DD
- Dual IF spectrum, correlation CC, DD
- Four IF spectra, correlations AA, BB, CC, DD
- Two IF, polarization spectra, correlation AA, AC, CA, CC
- Two IF, polarization spectra, correlation BB, BD, DB, DD
where "A", "B", "C", and "D" refer to the IFs involved in the correlation.
Integration Time
This is the integration time in seconds.
Allowed values are:
- 0 ( 10 sec)
- 1 ( 1 2/3 sec)
- 2 ( 3 1/3 sec)
- 3 ( 3 1/3 sec)
- 4 ( 5 sec)
- 5 ( 5 sec)
- 6 ( 6 2/3 sec)
- 7 (8 1/3 sec)
- 8 (8 1/3 sec)
- 9 (10 sec)
- 10
- multiples of 10
Array Processor mode (Spectral Line Only)
The Array Processor Options.
If the
Correlator Mode
is Continuum or blank, these fields are not applicable; OBSERVE will
not allow you to set or modify it.
Up to three options may be selected together.
If all options are blank, they are written to the OBSERVE file as
such.
The VLA on-line system will interpret blanks as standard observing
with no special options.
The options are:
- blank
- bandpass normalize
- hanning smoothing
- sum of baselines
- lag spectrum
Lag Spectrum is mutually exclusive from all other options.
Channel Count (Spectral Line Only)
Specifies the Number of Channels to use on all baselines.
If the
Correlator Mode
is Continuum or blank, this field is not applicable;
OBSERVE will not allow you to set or modify it.
The number of channels selected here is a power of 2, which is less
than or equal to the maximum number of channels (this is indicated by
the option selected under
Bandwidth).
Select "all" to record the maximum number of channels for your
observing mode.
Before choosing a value here, it is essential to have selected
first the correct
Correlator Mode
and the correct
Array Processor Option
(in particular Hanning Smoothing if desired), and then subsequently the
Bandwidth (on the LO or Source Page).
The Number of Channels is currently constrained in the on-line
system to be the same for all IFs.
Starting Channel (Spectral Line Only)
Specifies the Starting Channel for all baselines.
If the
Correlator Mode
is Continuum or blank, this field is not applicable; OBSERVE will not
allow you to set or modify it.
In order that valid data appears in all of the selected channels, the
Starting Channel selected here is an integer (n) which must be 0 <= n
< max, where max = maxchannels - number of channels and maxchannels is
the maximum number of channels, which is indicated by the option
selected under Bandwidth, and number of channels is as set on this
Page as Channel Count.
Before choosing a value here, it is essential to have selected
first the correct
Correlator Mode
and the correct
Array Processor Option
(in particular Hanning Smoothing if desired), and then subsequently the
Bandwidth (on the LO or Source Page).
If left blank, it is written to the OBSERVE file as such.
The VLA on-line system will interpret a blank as 0 (zero).
The Starting Channel is currently constrained in the VLA on-line
system to be the same for all IFs.