Receivers

All antennas are equipped with fully operational dual frequency receivers. The available frequency range will be 82 to 116 GHz for the 3mm band, and 205 to 245 GHz for the 1.3 mm band. The 3mm and 1.3mm receivers are aligned to within about $2''$.

Below 105 GHz, receivers offer best performances in LSB tuning with high rejection (20 dB): expected system temperatures are 100 to 150 K for the winter time. Above 110 GHz, best performances are obtained with USB tuning, low rejection (4 to 6 dB): expected system temperatures are 250 K at 115 GHz.

The 1.3 mm receivers have DSB tuning with typical T$_{\rm REC}$ below 50 K. Expected SSB system temperature are 350 to 450 K. The guaranteed tuning range is 205-245 GHz, but it may be possible to reach some lower and higher frequencies. Higher frequencies are not feasible on all antennas because of limitations in the triplers, however. For details about observing at frequencies beyond the guaranteed tuning range of the 3mm and 1.3mm receivers, please get in touch with R.Neri.

Signal to Noise

The rms noise can be computed from

$$\sigma = \frac{\mbox{$J_{\rm pK}$ }\mbox{$T_{\rm SYS}$ }} {\e... ...a}$ }(\mbox{$N_{\rm a}$ }-1) \mbox{$N_{\rm c}$ }T_{\rm on} B}}$$ (1)

where

• $\mbox{$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 $\ge 20^\circ$)
• $\mbox{$J_{\rm pK}$ }$ is the conversion factor from Kelvin to Jansky (22 Jy/K at 3mm, 35 Jy/K at 1.3mm)
• $\eta$ is an efficiency factor due to atmospheric phase noise (0.9 at 3 mm, 0.8 at 1.3 mm)
• $\mbox{$N_{\rm a}$ }$ is the number of antennas (6), and $\mbox{$N_{\rm c}$ }$ is the basic 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 calibrations and antenna slew time, the effective on-source time is about 70% of the total observing time.
• 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 one sigma noise level which is necessary to achieve each individual goal of a proposal, and particularly for projects aiming at deep integrations.