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Skydip Observations with EMIR

General Procedure: two skydips are performed in both bands E1 & E2. The central frequency for each band is set to 151.60 GHz USB and 256.68 GHz USB (average of A1 & A3) after calculations of the effective frequency for the NIKA2 bands by J. Macias (A1 => 255.53 GHz, A2 => 151.60 GHZ, A3 => 257.84). The recorded bands are 4 BBCs (LSB & USB in HORIZONTAL & VERTICAL polarizations) and 2 NBC (USB in HORIZONTAL & VERTICAL polarizations). The scans are reduced in MIRA following the procedure outlined here. Opacity results are given in the plots. An ASCII file containig the relevant information of all EMIR skydips can be downloaded here.

2017-02-22, Skydip Azimuth = 134.05°: weather conditions were very similar for both measurements with pwv ~ 7 [mm]. A pointing (dAz = 3.7", dEl = 6.1") and focus (dFz = -2.0 mm) was performed on Mars to check the EMIR settings. Scan numbers for the bands are: 26, 28 for E1 and 32, 34 for E2. WARNING: the E2 frequency used at this day was 256.0 GHz instead of 256.68 GHz due to a typo in the NIKA2.lin file.

Results: E1, s26 here. E1, s28 here. E2, s32 here. E2, s34 here

2017-02-25, Skydip Azimuth = 128.70°: weather conditions for both measurements with pwv ~ 3 [mm] but VERY UNSTABLE. A pointing (dAz = 4.0", dEl = -1.0") and focus (dFz = -2.4 mm) was performed on Jupiter to check the EMIR settings. A focus was done after the skydip measurements to check that the focus correction first applied using the E2 tuning was also adequate for E1 (dFz = -2.5 mm, consistent). Scan numbers for the bands are: 16, 18 for E1 and 11, 13 for E2.

Results: E1, s16 here. E1, s18 here. E2, s11 here. E2, s13 here

2017-02-26, Skydip Azimuth = 225.0°: weather conditions very stable for both measurements with pwv ~ 2.5 [mm]. A pointing (dAz = 0.2", dEl = -2.2") and focus (dFz = -2.05 mm) was performed on Uranus to check the EMIR settings. Scan numbers for the bands are: 376, 378 for E1 and 366, 372 for E2.

Results: E1, s376 here. E1, s378 here. E2, s366 here. E2, s372 here

[CK: A few comments: On 22-Feb, the fits were very poor and the chi**2 was very high. Clearly the atmosphere was not well behaved. On 25-Feb and on 26-Feb, fits were much better. The fitted opacities from the full fit agree quite well with the inital guess. Note that tau-z-guess equals tau-z-cal because the opacity derived from the hot/cold/sky calibration is used as initial guess for the skydip fit. I don't think that we need to look at the opacities in all EMIR bands. Rather, it should be sufficient to only look at the EMIR band closest to the effective frequencies of NIKA2. The ASCII file can hence be shortened. Obviously, comparison with NIKA2 opacities is missing.]]

emir_skydip_n2r9 (last edited 2017-02-27 16:49:34 by CarstenKramer)