Background

Resource Summary

• Time: 4 hours required to remove guider
• Personnel: 2 people minimum, 3rd person helpful
• Tools: Standard tools
• Drawings:
  • DEIMOS Drawing 8739A
  • DEIMOS Drawing 8140A
  Note: drawings located in instrument lab shelves in 11x17 blue binders.

Procedure

1. Position telescope. Align telescope so that the tube elevation is greater than 45° and azimuth position aligns DEIMOS (NRT1 or NRT2) with RT4 on the Nas Deck. Lock out and tag out telescope for az or el moves.
2. Position DEIMOS. Drive DEIMOS back far enough to gain ample access to front of snout:
   • Release 2 seismic restraints at front of instrument.
   • Hook up handler power to RT4 outlet.
   • Turn handler motor to RUN
   • Press REMOVE button on the tractor control box to pull DEIMOS back away frm the elevation bearing.
   • Drive until tractor gear is just at the transition between the deck and the platform.
   • Turn handler motor to STOP.
3. Rotate DEIMOS.
   • At the left front side of the instrument (as seen from the collimator end) locate and unlock the DEIMOS rotator band brake.
   • Locate the instrument handpaddle on the right side of the instrument.
   • Set the bottom switch to Manual mode. Note: you should leave the handpaddle set to Manual until all work is completed!
   • Set the Mode switch to 0=Fast Jog.
   • Rotate DEIMOS to the 270° position, as indicated by the numbers on back of the instrument. This will put the A side hatch (the only used hatch) on the snout in a horizontal position on the lower half of the snout.
   • Re-apply the band brake to lock out rotation.

   Figure 1. View of snout from front

4. Disassemble front end. Remove components on the DEIMOS snout to gain access to the camera region.
   • Remove 2 forward lower quarter panels on snout. One of two panels shown in Figures 2 and 3 below.
   • Also remove left quarter panel on other side of snout.

     Figure 2. Right front quarter panel -- installed

     Figure 3. Right front quarter panel -- removed

   • Remove B-side hatch. This is the unused hatch. There are four fasteners holding the hatch plate in place. The one pointed to has a nut and washer on the inside so you need someone to catch them as you loosen the bolt from the outside. There is another identical setup on the other side. The other two fasteners near the top just need to be loosened and the hatch comes free.

     Figure 4. B-side hatch

5. Protect Optics The window under the hatch has a very delicate optical coating which cannot be touched. Protect this coating as follows:
   • Carefully apply low-lint cloth to the back side of the window.
   • Also apply some to the front side of the window.

   Figure 5. Protective cloth applied to window

6. Disconnect Air & Glycol.
   • Disconnect air supply from back of instrument, and bleed off air. This will enable you to open and close the hatch without requiring an operator. Leave hatch closed to protect window, unless otherwise directed.
   • Turn off power to the PXL CEU2 electronics unit. It is in electronics bay #2 at the rear of the instrument. You can power it down from software by issuing the following command from a window on polo:

     	tvpower off

   • Verify that power is off at the CEU2 by checking that the reset button is dark and the LCD display is blank. You'll need to remove the vertical bay #2 cover to see the front of the CEU2. In this orientation, bay 2 is near the 12 o'clock position so you'll need a ladder to access.
   • Record glycol flow rate to camera and then turn off glycol to camera (flow meter is found at back of DEIMOS). As of this writing it is at 0.2 GPM. Turn the needle valve all the way shut.
   • In the snout on the front right when facing the telescope, disconnect the two glycol hoses. They have quick disconnect fittings.
   • Remove the filter carousel from the filter wheel mechanism. It is a quick disconnect connection. The filter wheel disconnects from the mechanism by grasping the hub of the wheel and pushing your thumb in on the center of the hub, disengaging the wheel.

     Figure 6. Filter wheel shown on mechanism

   • Disconnect the four cables to the back of the PXL camera head. Cut any tie wraps on glycol hoses. The idea is to be able to free the head so when it is unmounted it won't be connected to the instrument.
7. Remove camera.
   • Scribe the alignment of the PXL mounting plate to the cross member before loosening it (we didn't do this, so not sure where to put best scribe mark). Here's a photo of the PXL mounting bracket removed from the instrument, with PXL hardware removed from the bracket:

     Figure 7. PXL mounting bracket

   • Remove the filter mechanism and PXL head. Read these instructions carefully before proceeding. Because of the mounting, you have to remove both at the same time. You need two, preferably 3 people. One person is on the outside of the snout loosening the mounting bolts. The other person is on the inside of the snout supporting the weight of the filter assembly and camera head as they are released. The third person is useful as a helper to pass tools, equipment and provide lighting.

     Here are photos showing where to access the mounting bolts (need to add captions and arrows)

     Figure 8.

     Figure 9.

     Note that the two bolts holding in the camera head mount are special. The shafts are machined down (a.k.a. "Chicago-ed") This gives a clockwise or counter clockwise adjustment capability of the head when viewing the camera body from the snout. This was done to accommodate the tilt of the CCD in the camera head.