Commissioning Week Overview: Alistair Walker

Report for Week 4 of Commissioning September 21-October 4
October 5, Alistair Walker (DECam Instrument Scientist)
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A.  Here are the goals for this week as written in last week's report:

1.  Do a pointing map, actually probably one before and one after establishing a static look-up table (LUT) for the hexapod.

2.  Continue testing and debugging the guider. 

3.  Quantify tracking rate quality, slew to track times, etc. 

4.  Test and integrate the active optics system (donut + BCam), including the static LUT.

5.  Juan Estrada will investigate the low full well of the two half-F&A CCDs.

6.  As a minority activity, in suitable conditions take "pre-SV" science and technical observations.


B.  Here is what we accomplished this week, addressing the above goals first.

1.  A pointing map was done on the night of October 3.  The hexapod was set to the nominal (zenith) position for this test.   Additional confirmatory measurements were made the following night for some areas iof sky to give a finer grid.  There is some evidence for hysteresis at the 0.5 mm level.

2.  The short visit of Santiago Serrano was very successful.  The guider was successfully made to work in "self" mode and some initial tuning done.  

3.  The tracking, slew to track etc tuning and evaluation remains to be done.

4.   There has been much work on the F&A analysis code and preparing the temperature, filter offsets and position LUT.

5.  Attempts by Juan Estrada to repair the low full well of two halves of two focus and alignment CCDs were not successful.

6.  An improved WCS was installed as from the night of October 3,

7.  Sets of calibration frames (flats, zeros) were obtained regularly,

8.  Morning twilight exposures were taken to test the function of the protection diodes and to ascertain the level at which they should be set trip.   The trip level was subsequently revised,

9.   Data were taken to investigate scattered light as the telescope is moved to within 5 deg. of the Full Moon.

10.  Some science data were taken.

11.  Many improvements and bug fixes made to SISPI.


C.  Issues

1.  Early in the week SISPI developed poor reliability for the loading-phase.  Once loaded it was OK, although the need to refresh GUIs due to memory leak is annoying.    Cleanup of stale processes and files, and some attention to interactions between the Labview and the python codes have improved the situation.


D.  Goals for Next Week

1.  On-sky is short, after Monday night the telescope is off-sky in order to remove the filter change module to zap the LEDs.  

2.  Priority over the next three nights is installing the LUT, and doing more guiding tests. Some of this work should be done as part of "observing".

3.  Evaluate the pointing and TCS performance as soon as the new pointing model is installed.