When a target source is observed,
a noise level
for each baseline can be expressed as
A resultant image noise level
can be expressed as
|Band||Tsys[K]||SEFD [Jy]||Tsys[K]||SEFD [Jy]|
|Baseline sensitivity [mJy]||Image sensitivity [mJy]|
|Sensitivities (1) are listed in unit of mJy.|
|Integration time of 120 seconds and 4 hours are assumed for baseline and image|
|sensitivities, respectively. Total bandwidth of 256 MHz (for continuum emission)|
|is assumed for all the calculations. In the case of narrower bandwidth of 15.625 KHz|
|(for maser emission), sensitivities can be calculated by multiplying a factor of 128.|
Note that the receiver temperature of the VERA antenna includes the temperature increase due to the feedome loss and the spill-over effect. In Mizusawa, typical system temperature in the K band is K in fine weather of winter season, but sometimes rises above K in summer season. The system temperature at Iriki station shows a similar tendency to that in Mizusawa. In Ogasawara and Ishigakijima, typical system temperature is similar to that for summer in Mizusawa site, with typical optical depth of . The typical system temperature in the Q band in Mizusawa is K in fine weather of winter season, and K in summer season. The typical system temperature in Ogasawara and Ishigakijima in the Q band is larger than that in Mizusawa also.
The typical system temperature in the K band at all KVN stations is around 100 K in winter season.
In summer season, it increases up to 300 K.
In the Q band, the typical system temperature is around 150 K in winter season and 250 K in summer season at Yonsei and Tamna.
The system temperature of Ulsan in the Q band is about 40 K lower than the other two KVN stations.
This is mainly due to the difference in receiver noise temperature (see Table ).