GISMO run #5 (March 2012): new optics and permanent position

Staffing of the test run

• GSFC: J. Staguhn, D. Fixsen, A. Kovacs, S. Maher, E. Sharp,
• IRAM: S. Leclercq, IRAM Granada staff

Test run schedule: 02.03. - 12.03.2012

IRAM 30m schedule page: http://www.iram.fr/IRAMFR/PV/sche/12/s09v1.html

GISMO does not appear with an explicit project number because the idea is to take up to 20 hours of the telescope time on the heterodyne pool (project 440-11). The decision for the time slots allocated to GISMO will be taken in real time (few to several hours in advance) through discussion between the GISMO team and the pool manager, based on observiong pool constraints (e.g. LST) and weather conditions.

Summarized schedule of the run:

More details on schedule, people, organization, hardware, and test plan: GISMO-On_Sky_Test_Plan_2012_v2.pdf

GISMO final version

• Same 8x16 pixels as 2nd to 4th runs, working at 2mm (the –3dB window is 140-162 GHz), with an individual pixel size = 0.9 Fλ.

• Same special features from previous runs: 2 motorized neutral density filters, controllable shutter, automated observing procedures usable via a dedicated GUI (see observer's manual), CRUSH reduction package.

• New updates: cold baffle, final position in the receiver cabin with corresponding warm optics.

Daily reports

Friday 02 March - Sunday 05

Elmer, Steve and Dale arrived at the telescope, and start mounting GISMO, then cool it down.

Monday 05 March

Johannes and Samuel arrived at the telescope. GISMO was close to base temperature. Water on the entrance window of the big baffle. Blow boil off nitrogen to it, then just use a fan. Look at the sky through the open window. Nice IV curves even without neutral density filter ==> very good sign that there's much less stray light than last year, so sensitivity should improve...

Tuesday 06 March

The installation of GISMO into the receiver cabin took most of the day and part of the night: check measurements and installation plan, built a crate, machine the shelve, etc., install the shelve first. Then in the afternoon move GISMO and all the other parts up in the cabin, and start mounting. Plug the electronics: few things to adjust but everything looks fine in the end. Some small offset in positions (less then 2.5cm) and orientation (less than a degree) of some of the elements. Simulate the effects of these offsets in Zemax: position offsets have almost no effect as long as the optical axis is well aligned (which we take care using the laser), angle offset very critical for the illumination of the pupil: we need a perfect alignment of the orientation of M6 toward M5; this will be done on the sky minimizing the load from the background (impossible to do it otherwise since a fraction of a degree is critical).

Wednesday 07 March

We tried to get the correct radio alignment using sky, then a hot load around M5 edges, but were not successful. 3 problems: a touch of one of the M6 rods with the bottom of the shelve, SL mistake on which rotation should be applied to M6 to optimize pupil illumination. We dismounted M6 and got the bottom of the shelve machined. Gave back the telescope. Work on a better plan for alignment, and simulations: cold pupil a bit too big, some non negligible spillover on M1 may remain even at best alignment.

Tuesday 08 March

We mounted again M6, and used correct rotations to optimize illumination minimizing background on the sky. Time to fix some incompatible pako scripts with the current system (2 backends were define in the config script), we just had the time do take our first maps on Saturn (Mars too low) and derive first pointing parameters.