Background

Requirements

• Time: approx 2 hours
• Telescope Restrictions
  • ESI on Keck II Nasmyth deck
  • Telescope AZ restriction (telescope parked at Cassegrain access position)
  • Dome parked to allow use of jib crane (during lift)
• Tools
  • ESI collimator lifting fixture
  • Allen wrench set (metric)
  • Strap hoist
  • Shackle
  • Nitrile gloves for all personnel handling optics
• Materials & supplies
  • ESI rotator controller ("Arnie Box" )
  • Dome remote control unit ("Captain Marvel")
  • 4" layer of foam atop cart for cushioning (or a secure box for storing mirror)
  • Wheeled cart to hold assembly after removal
• Personnel
  • Two instrument technicians
  • One crane operator
• Relevant ESI Drawings
  • TBD

Procedure

1. Set the Keck II telescope AZ to the Cassegrain access position.
2. Move ESI handler about 8 feet toward the telescope in order to provide enough clearance for jib crane access to the back of the instrument.
3. Connect the "Arnie Box" to the ESI rotator control panel. Rotate ESI so that electronics box 3 is at the 6 o'clock position.
4. Use 4mm Allen wrench to remove the 9 socket-head cap screws (SHCS) securing the collimator cover to the back of the instrument. Remove the collimator cover and set aside. [photo]
5. Use 4mm Allen wrench to remove the temperature sensor attached to the autocollimation fixture at the 12 o'clock position on the collimator mirror cell. [photo]
6. Use 5mm Allen wrench to remove the 6 SHCS on the black triangle on the back of the collimator mirror. [photo] Note: keep track of the rubber grommets on each of these screws.
7. Apply the ESI collimator mirror lifting fixture [drawing] per instructions on web [link]. Make sure to attach the lifting fixture through the autocollimator fixture hole in the collimator mirror. [photo] Note that you must tilt the mask about 20° to insert the Delrin nut.
8. Lower jib crane hook to about 8 feet off the ground.
9. Attach lifting fixture to strap hoist, and attach strap hoist to jib crane hook using shackle. Note that you will only use the strap hoist to lift the mirror, not the jib crane!
10. Tension the hoist until the strap is just taut.
11. Remove each of the three "nodes" from the collimator mirror as follows. Note: remove the bottom node last!
    • Use the 5mm Allen wrench to remove the 2 SHCS securing the node to the mask.
    • Gently pull the node off of the puck to disengage the pin.
    • Pull the node away from the mirror by about 1 inch so that it aligns with the alternate (outer) set of holes on the mask.
    • Re-attach the node to the mask via the outer holes, using the two SHCS you just removed.
    Repeat these steps for each node in turn. Note: be sure to always leave two nodes attached to the mask!
12. At this point the mirror is detached from the instrument and is supported by the hoist and jib crane.
13. Carefully swing the mirror away from the instrument and lower it onto the foam padding atop the rolling cart. Note: jib hoist may be used at this point.
14. Stow and power off the job crane.