Observations dedicated to the comparison between MRTCAL and MIRA


Table: Observing setups. The covered frequency range is indicated for FTS 200, and the center frequency of the 120 MHz wide windows for VESPA. The last column lists the observing modes for the according setup (with WSW wobbler switching, FSW frequency switching, and PSW position switching).
Tuning Setup FTS200 coverage VESPA center Observing
name [GHz] [GHz] mode
E150 150.000 UI POINT2MM 147.70–155.48 WSW
E150 176.500 UI L170250 158.52–166.30 & 174.20–181.98 176.553 WSW
E230 230.500 UI L224250 212.52–220.30 & 228.20–235.98 217.9102 & 230.538 WSW, PSW, FSW
E330 345.139 UI L338890 342.84–350.62 345.94 WSW

Observations on the approximately point-like source IRC$+$10216 were obtained under the technical time T06-16 during 2016 November 15–17 under mostly stable weather with opacities of 0.1–0.2 at 225 GHz. Four EMIR frequency setups (and one setup for HERA not included in this report) were tested, including the 1mm band around the CO(2–1) line of frequent interest for observers, as well as a setup close to the edge of the atmospheric window of the 2mm band, which is expected to be especially sensitive to the calibration. All spectral line backends - WILMA, FTS in its wide resolution mode, and VESPA configured to 40 kHz resolution and 120 MHz bandwidth - were connected. The 1mm band setup was observed in all three switching modes available for spectral line observations: wobbler switching (designated WSW in the following) observations used a throw of $\pm$90  $^{\prime\prime}$ in azimuth with a phase time of 2 s, frequency switching (FSW) a throw of $\pm$23.4 MHz at a phase time of 0.2 s, and position switching (PSW) was done relative to an off position 600  $^{\prime\prime}$ west (in right ascension) of the source. Table [*] lists the observing setups and table [*] lists the spectral lines that are used in the following work.