Keywords: astro-noema-sensitivity-estimator

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## Line vs continuum system temperature

Figure 1: Top: Summer (red) and Winter (blue) semester for different precipitable water vapor (PWV) amount and for a source at zenith. The numbers indicate PWV values assumed in the computation. Middle: Assumed forward effiencies in the computation. Bottom: Assumed receiver temperatures in the computation.

Figure 2: Top: Minimum and maximum obtained in the intermediate frequency bandwidth as a function of the local oscillator frequency used in the tuning. Middle: Assumed forward effiencies in the computation. Bottom: Assumed receiver temperatures in the computation.

Figure 3: Top: Averaged ``continuum'' as a function of the local oscillator frequency used in the tuning. Middle: Assumed forward effiencies in the computation. Bottom: Assumed receiver temperatures in the computation.

In the online estimator (to be used for proposal preparation), the is interpolated in frequency and airmass from tabulated values (see Fig. 1). The airmass is estimated using the maximum elevation of a source at the chosen Declination. The values are different for summer and winter due to the different atmospheric characteristics. Moreover, the chosen amount of precipitable water vapor depends on the receiver band (in addition to the season) because the NOEMA operation team schedule the different receiver bands according to the actual weather (high frequency bands are scheduled only during the best weather conditions).

In the ASTRO detailed sensitivity estimator, the system temperature is computed using an atmospheric model (ASTROATMOSPHERE command) with ambient temperature and precipitable water amount as input.

The can vary significantly over the large bandwitdh of the 2SB NOEMA receivers. Figure 2 shows the minimum and maximum system temperature inside the IF bandwidth for all possible local oscillator tunings. As a result, for continuum estimation, a frequency averaged is interpolated from a pre-computed table. The relevant frequency in that case is the LO frequency of the tuning (see Fig. 3). The averaging is done such as .

This is not implemented in the ASTRO detailed estimator, due to the prohibitive computing cost of the atmospheric model over the GHz.

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