Shane AO  

SHARCS Problem: Filter Wheel Bearings

Manifestation:

• ShARCS filter wheel has difficulty calibrating (requiring multiple attempts) or fails to calibrate.
• Unhealthy audible noise from within the ShARCS dewar when filter wheel turns.

Solution/Recovery (Temporary):

• Manually move the filter to known (e.g. Open) position and disable/lock-out software commands to this function until a hardware repair can be effected.
• To enable Darks, move filter wheel #1 to the Br-G filter and the aperture wheel to an offset pinhole position. This configured using the following script:

  user@shimmy > /u/user/observers/lgs/scripts/darkpos

Solution/Recovery:

• Repair hardware/bearings.
• July 2018: Filter wheel had bearings replaced. Now working well.

  March 2018: The plan is to remove ShARCS and send it down to UCSC after 2018-04-04 so the bearings can be investigated or replaced. During the April 2018 intervention, all other necessary measurements (o-rings, etc.) preparatory to the servicing foreseen for June 2018 (Shane AO shall be dismounted 2018-05-30 and re-mounted 2018-07-02, so we need to ensure work on ShARCS is completed by 2018-06-25 so there is time to re-integrate and align ShARCS back into the Shane AO system).

Cause:

• Poor/decaying mechanical bearings.

Associated Issues:

• Issue 9930.

Change Log:

2018-07-05: Updated following maintenance.

2018-03-29: First version.