Signal to Noise

Owing to uncertainties in the installation planning of the NGRx, we ask to take the parameters of the current receivers into account. The rms noise can be computed from

$$\sigma = \frac{\JpK\Tsys } {\eta \sqrt{\Na (\Na -1) \Nc T_{\rm ON} B}}$$ (1)

where

• $\hbox{$J_{\rm pK}$}$ is the conversion factor from Kelvin to Jansky (22 Jy/K at 3mm, 35 Jy/K at 1.3mm)
• $\hbox{$T_{\rm sys}$}$ is the system temperature (150 K below 110 GHz, 200 K at 115 GHz, 400 K at 230 GHz for sources at $\ge 20^\circ$)
• $\eta$ is an efficiency factor due to atmospheric phase noise (0.9 at 3mm, 0.8 at 1.3mm).
• $\hbox{$N_{\rm a}$}$ is the number of antennas (6), and $\hbox{$N_{\rm c}$}$ is the number of configurations: 1 for D, 2 for CD, 2 for BC, and so on.
• $T_{\rm ON}$ is the on-source integration time per configuration in seconds (2 to 8 hours, depending on source declination). Because of various calibration observations the total observing time is typically 1.4 $T_{\rm ON}$.
• $B$ is the spectral bandwidth in Hz (580 MHz for continuum, 40 kHz to 2.5 MHz for spectral line, according to the spectral correlator setup)

Investigators have to specify the $1\sigma$ noise level which is necessary to achieve each individual goal of a proposal, particularly for projects aiming at deep integrations.