The point source sensitivity (one level)
for an
antenna array, over a bandwidth
in a time
is given by
![]() |
(1) |
where
For the correlator, is the noise equivalent bandwidth,
equal to 1.88 times the channel separation; the effective channel
width for standard apodization (using a Welch time-lag window) is
1.60 times the channel separation.
The instrumental phase jitter typically ranges between 3
and 5 degrees at 90 GHz, and increases linearly with frequency. The
short and long term atmospheric phase fluctuations
depend on the baseline length and water vapor content of the atmosphere.
15 degrees is a typical value for short (
100m) baselines.
With typical values for Plateau de Bure and assuming 6 antennas, we
find at 90 GHz 0.08mJy (
) to
0.15mJy (
) for a one hour integration in
a 3600MHz bandwidth and using both polarizations. For a full
synthesis (2 configurations, or 11 hours on source), this goes down to
about 0.03mJy (
) to 0.04mJy (
). At 115 GHz, the sensitivity is degraded by
about a factor 2 because of higher system noise and atmospheric phase
fluctuations. At 230 GHz, the expected rms noise is 0.26 to 0.46mJy in
one hour (0.08 mJy to 0.14 mJy after 11 hours in average winter
conditions).