Background

Requirements

• Time: approx 16 man-hours
• Telescope Restrictions
  • ESI on Keck II Nasmyth deck
  • Telescope restriction: telescope parked at Cassegrain access position.
  • Dome parked to allow use of jib crane
• Tools
  • Allen wrench sets (standard and metric)
  • (2) 6-inch heavy-duty C-clamps
  • Slotted screwdriver
• Materials & supplies
  • ESI rotator controller ("Arnie Box" )
  • Dome remote control unit ("Captain Marvel")
  • Strap hoist
  • 10' length of rope
  • 6' lifting strap
  • Wheeled cart to hold assembly after removal
  • 4" layer of foam atop cart for cushioning
• Personnel
  • Two instrument technicians
  • One crane operator
• Relevant ESI Drawings
  • TBD

Procedure

1. Open the ESI front panels over the triple wheel (panel labeled "A") and over the guider.
2. Remove interior optical baffling and supports as needed to allow access to the triple wheel area.
3. Remove all optics from the aperture, slitmask, and dewar filter wheels. Store optics in cabinet for safekeeping.
4. Cover the ESI guider lens with filter paper and aluminum tape.
5. Remove the drive motor assemblies and their corresponding electronics boxes with mounting plates, plus the stainless steel drive belts for each of the three wheels in the triple wheel assembly.
6. Verify that scribe marks exist for the current location of the following items attached to the triple wheel assembly:
   • mounting plate for calibration lamps
   • mounting plate for pickoff mirror
   • support struts
   If not visible, add them using a scribe awl and/or paint pen.
7. Use 5mm Allen wrench to remove the screws on the mounting plates for the calibration lamps and the pickoff mirror. Note: store all screws back in holes from which they were removed.
8. For each wheel, remove the Renishaw reader head mounting blocks from the mounting plate by unscrewing the 2 screws with the 6mm Allen wrench. Note: when re-installed, these heads will require fine adjusting to achieve the appropriate alignment.
9. Disconnect the Renishaw DB15 connectors using a small flathead screwdriver and store the Renishaw units in a safe location.
10. Move the jib crane into position and lower the hook to about 3 feet above the instrument.
11. Attach C-clamps to the top of the triple-wheel mounting plate with the end loops of the lifting strap held captive in the C-clamp.
12. Insert the middle of the lifting strap into the jib crane hook. Also attach the length of rope to the assembly to act as a tag line.
13. Raise the jib crane slowly until the lifting strap is taut in order to support the wheel assembly.
14. Use the 6mm Allen wrench to remove bolts holding the triple wheel mounting plate to the 2 guider struts, the upper strut, and the mounting points on the optical support structure. DANGER: exercise caution as you remove the final bolts, since the heavy mechanism will swing free. CAUTION: be careful to avoid touching and/or damaging the delicate Renishaw encoder tape on the outside of each wheel.
15. With the mechanism suspended from the jib crane, use the strap hoisr to raise the assembly about 2 inches to clear the guider struts and manually rotate the assembly about 45° clockwise (as seen from above) so that it can be lifted out of the instrument.
16. With one person hand-guiding the assembly, use the jib crane to raise the assembly slowly so that it clears the instrument.
17. Position the cart with foam on top to receive the assembly.
18. Move the dome and the crane as needed to position the assembly over the cart, and slowly lower the assembly onto the cart. CAUTION: lay the assembly so that the mounting plate is down, rather than the wheels being on bottom.
19. Detach strap from crane.
20. Stow and turn off the jib crane.