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| == April, 19th (Wednesday) == [Samuel & Laurence, 8:00-16:00] check list: turbo pump working fine, mixing chamber temperature stable around 182 milliK, cryostat inclination stable, number of tuned kids good we did a first beammap on Neptune (20170419s124), then 2 otf maps of Neptune for calibration stability checking while the te;perature of the telescope stabilize after the Sun rise. We did a defocus beammap series. |
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April, 19th (Wednesday)
[Samuel & Laurence, 8:00-16:00] check list: turbo pump working fine, mixing chamber temperature stable around 182 milliK, cryostat inclination stable, number of tuned kids good we did a first beammap on Neptune (20170419s124), then 2 otf maps of Neptune for calibration stability checking while the te;perature of the telescope stabilize after the Sun rise. We did a defocus beammap series.
April, 18th (Tuesday)
Start of the official run.
First things first: verification of the alignment (since it changed for an unknown reason between run 8 and 9!)
- Expectations: Radio axis has been measured (see run 8 daily report) to be 5mm left from centre (toward the M4 wall), and 1.5mm up from centre (toward ceiling).
- Measurement radio with ecosorb plate: roughly centred at +/- 3-4mm ; sky is too noisy to get better accuracy, so it's compatible with previous measurement; we will double check once the sky is good (it takes only about 10 minutes to check)
- Measurement laser spot on window removing M3 mirror: 3.5mm +/- 0.5mm up from centre when at 85° elevation, and 4.5mm +/- 0.5mm when at 0° elevation ; 3.5mm +/- 0.5mm left from centre when at 85° and 0° elevation.
==> ~2.5mm too high and ~1.5mm too much right w.r.t radio axis. Given the measurement errors and the expected effect on pupil illumination of the primary we think it's preferable to let it as it is. Indeed below you can see the Zemax simulations of illumination of the primary by various field taken over the FOV (various positions on the array) with a good alignment and with the offsets we measured. The effects on the beam are negligible (changes of structure at 10-3 level), it's also negligible for pointing. Zemax can't simulate the effects on the real data quality of the asymmetric illumination of the primary; we can just infer that as long as we stay inside M1 we should be fine, though we might have a small increase of background due to slightly higher spillover.
We start the observations in poor weather (tau=0.5), and without a properly functioning turbo pump. Since Mars is bright, we intended to follow it for some beam maps, though by the time we managed to get focused, the turbo pump was having trouble and the cabin was too warm again. Once the cabin was cool again, Mars was too low, so we moved onto the quasar 3C273.
AlR,AR [16h00-00h00]: In the evening we carried out observations of the QSO 3C273 and 3C279 at different elevations.
HA and JFMP [00h00:08h00]: During the night the average tau was 0.3 and very stable. We continue observing the two QSOs 3C273 and 3C279. We also did a beammap in 3C279. After that we switched to secondary calibrators (NGC7027, CRL2688 and MWC349) observations at different elevations. We repeated the same commands than for the QSO, doing OTF maps in azel and RADEC , and in az and elevation. We also performed some skydips.
April, 14th (Friday)
Alessia at the telescope and Juan remotely.
We started doing two dark scans. We tried to point using 3C84 but the source was far from the center -38,-20 arcsec. After discussions with Juan Peñalver we decided to use nasmyth offset computed by Nicolas on run 9: offsets -18.8 -5 /sys nasmyth, However, this did not solve either the problem. We switched to Mars but encountered the same problem. Finally, we found that the problem was related to a wrong reference kidpar - we corrected this and everything started work fine. However the weather during the day was very unstable although tau was not that bad: about 0.3-0.4 from IRAM taumeter. We have performed a small pointing session to verify the current model. We tried to get some Mars beammaps after focus X,Y, Z. We did a couple of skydips. Finally, we tried to go to PSZ2G144.85 to do a first test but had no enough time. Really a pity because the weather improved quite a lot.
Alessandro 22h45. I stop the turbo for the weekend. Plan to switch it ON on Monday in the late evening. Alessia, could you put the NIKA2 window back in place so we can check the noise between Monday and Tuesday ? Good night !