Subject: DIS status report 950901


Submitted: Sat, 2 Sep 1995 01:09:44 +0700

Message number: 4 (previous: 3, next: 5 up: Index)

DIS STATUS - 01 September, 1995

I.   Chips
II.  Hardware
III. Software
IV.  Documentation

I.   Chips

Earlier this year the red chip bias level was sporadically jumping
from it's usual value of ~4400 ADU up to ~6300 ADU.  There have been
no reports of this bias jump since June 23rd.  During his June
engineering visit, Richard Lucinio checked the circuit boards and
touched up a few weak solder joints.  The total mean bias level in the
overscan regions of 85 recent images was 4336 ADU, the standard
deviation was 40.4 ADU.  None of the overscans had mean bias levels
higher than 4357 ADU.

Images taken with the blue chip still have a low level noise pattern.
The pattern is roughly sawtooth with a total amplitude of 15 ADU, and
repeats every 40 pixels along an axis tilted 36 degrees with respect
to the y-axis of the chip.

II.	Hardware

Richard Lucinio worked on the DIS hardware in early June of this year.
Here is a brief summary of the DIS hardware problems he addressed.

Turret - was not properly detenting and its motor was dropping steps.
The action of the motor was modified to allow the turret to seat
itself in the detent, and the turret assembly was balanced.
Subsequent tests and observations indicate that the turret position is
accurate and repeatable (within the expected limits of the design).

Firmware was added to verify turret position before and after moves.
This was done to reduce the chance of the turret moving to a different
position than the one requested through the remote interface.

Grating - The blue high resolution grating tilt was not very
repeatable.  Its tilt home switch was found to be loose.  After
tightening the switch the tilt repeatability improved dramatically.

III.	Software

Brian Yanny and Bob Lowenstein have updated the MC and Remark software
to enable users to readout an image early and save it to disk.  

We are still restarting the DIS ICC software each afternoon to avoid
the occasional floating stack overflow that occurs after the software
has been running for a long time.

IV.	Documentation

The DIS users documentation was last updated on 1 June, 1995.  There
is a new WWW document, Remark - Frequently Asked Questions, that has
some (hopefully) helpful information for observers who operate the DIS
through the Remark interface.  The URL is

-K. Gloria
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