MDM Trouble Report for 2012 Apr 26

Telescope: 2.4m
Observer(s): Brown, Yan, Runge, Musin (University of Missouri-Columbia)
Instrument: OSMOS+R4K

Problem(s) Encountered:
When we were opening up at the beginning of the night, we heard a
strange sound within the OSMOS box, which was not there before. It
was pretty steady, and sounded like something is rotating inside.
We didn't do anything about it because we had no idea what that
was.

While trying to take the twilight flats we saw strange things
happened to our test images: one frame could be saturated, while
the next could be close to the bias value. And then we saw 
a straight, bright stripes across the field in two subsequent
images, but along different directions. This made us to connect
to the strange sound in the OSMOS. Then we noticed that the
slit status was not available in the Prospero status window, 
which showed  * ****  in red. Executing  slit reset  was not
successful, and returned an error message complaining about not
able to communicating to an IP address. The detailed information
has been sent to Paul Martini.

All this seem to point to a problem with the OSMOS slit wheel:
the sound could be from the rotation of the slit wheel, and the
strange behavior in the twilight flats could be that the wheel
blocking the light. However it is not clear what could have
triggered this problem, as we didn't use slit at all throughout
the run and never rotated the slit wheel. The regular 
procedures, such as restarting in Prospero, restarting xtcs etc.
didn't work. Finally we found an entry in the OSMOS user manual,
which describes how to shut down the OSMOS and restart. We
followed the procedure, and for a moment we were able to command
the slit wheel to respond. It was put to an open slot. However,
only after a short period it was out of communication again,
although the rotating sond no longer appeared. We were able to
observe, however the upper (northern) edge of the field was 
slight blocked. This could be explained if the slit wheel was 
not exactly at an open slot. 

    Paul Martini called after seeing the emergent email that we
sent for help, and under his instruction we opened up the OSMOS
hatch, and set the slit wheel to a locked position. The
communication was never restored, but our field was all cleared
now.

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Submitted on 2012 Apr 27 [6:04:28]