seconds for the
continuum mode to 20 seconds for 512 channel spectral line modes.
Note that in order to ensure the complete removal of correlator
offsets, averaging times should be an integer multiple of 
seconds (which is the period of the Walsh functions that are used to
negate cross-coupling between antenna signal lines).
Averaging times shorter than those listed above can be selected, but only
at the cost of removing antennas from the array. For the spectral
line modes, the approximate relation is that the minimum integration
time in seconds equals the total number of baselines plus antennas
(
) multiplied by the total number of correlated channels
(less than or equal to 512) divided by 10,000.
In continuum mode, integration times as short as 0.4
seconds are available, but are appropriate only for EVLA/VLA testing
and for fast flaring activity such as solar flares.
Contact Ken Sowinski for details on their use.
Users should keep in mind the data rate of the VLA when planning their observing. The array's maximum data rate of more than 3 GByte per day presently is only a minimal problem for the modern computers that most astronomers use for their data reduction. If necessary, this rate may be reduced by increasing the averaging time and/or decreasing the number of spectral channels. Consult one of the spectral line experts listed in Table 16 for advice.
The maximum recommended integration time for any VLA observing
is 60 seconds. The maximum allowable integration time in the spectral
line modes is 90 seconds. There is no formal limit in the continuum
modes, but it is generally reasonable to use the default of 10 seconds.
For high frequency observers with short scans (e.g., fast switching, as
described in Section 3.13.2), a second
integration time may be preferable.