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Figure 6.16:
The
Correlator Configuration
panel for the ALMA BL in the SpectralSpec form of the Instrument Setup. The panel for the ACA correlation looks very similar
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Integration Duration
: The integration duration must be a multiple of the dump duration. The Integration Duration is the lenght of time to spend accumulating dumps in the CDP as spectral data blocks. Reasons for preferring shorter integrations include 1) source strong enough to allow self-cal; 2) rapidly varying phase; 3) observations requiring high time resolution (e.g., solar, flare starts[?]); 4) OTF mosaics. The more channels you use, the longer the minimum integration must be, because the time required to read out the maximum number of channels (8192) is 512 ms. UV smearing effects need to be considered at longer baselines.
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Adjust
: Button to force the integration duration to be a multiple of the channel average duration.
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Channel Average Duration
: Also known as sub-integration. The duration of the channel averaging is between 0.5 and 1.024 seconds, such that the smallest number of channel average durations fits into the spectral integration duration. For values
500 msec there will be no channel averages calculated.
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Adjust
: Button to force the channel duration to be a multiple of the channel dump duration.
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Atmos. Phase Correction Data To Save
: Drop down list to determine which Atmospheric Phase corrected data is to be sent: Corrected, uncorrected, both, or mixed.
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Accumulation Mode
: Correlator accumulation mode can be ALMA_FAST (1 msec) or
ALMA_NORMAL (16 msec) which defines the correlator chip level accumulation duration. Note that this must be ALMA_NORMAL for cross-correlations, and this is therefore the default chosen. For ALMA_FAST only auto-correlation products are sent to the CDP. For ALMA_NORMAL, then both auto- and cross-correlation products are sent to the CDP.
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LO Offsetting Mode
: Drop down list for selection the LO Offsetting.
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Enable 90deg Walsh function
: Enable 90 deg Walsh function.
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Enable 180deg Walsh function
: Enable 180 deg Walsh function.
The following field is visible for a spectral specification with the Baseline correlator.
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Dump Duration
: The dump interval must be a multiple of 16 msec (if accumulation mode is ALMA_NORMAL) or 1 msec (for accumulation mode ALMA_FAST).
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The ALMA OT Team, 2011 May 20