Preliminary Procedure for removal/installation of the SDSS 2.5m primary mirror

Patrick Waddell, French Leger

Note: this procedure must be updated to include mechanical collimation.

Removal

Assumptions for removal:

Pneumatic mirror support is operating and the mirror is stable

Mirror hard points, Galil channels A-D, are at nominal positions for observations

Lateral link drives, Galil channels E & F, are at nominal positions for observations

Install telescope-wind baffle turnbuckles

Pin telescope at horizon, apply telescope altitude and azimuth brakes, depress emergency stop button and disable wind baffle drive

Remove wind baffle (see wind baffle rem. proc.)

Install counterweight mounting blocks to upper wind baffle mount frame

Transfer 1 pair of wind baffle counterweights to upper frame mounting blocks to allow altitude axis motions

Remove remaining 2 pair of wind baffle counterweights

Remove Secondary Truss (see truss rem. proc.)

Remove spectrograph dummy weights

Adjust moveable counterweights to balance

Move wind baffle + telescope to +60 (or so) degrees elevation and disable wind baffle drive

Read and record all 6 M1 linear gauges

Take depth mic readings of M1 from the mirror lifter mic pads

Read and record Gallil position values for channels A-F

Move wind baffle + telescope to zenith "bird bath", install pin, apply telescope altitude brake, depress emergency stop button and disable wind baffle drive

Remove lower light baffle (procedure is TBD)

Install bridge rigging (ladder) on PSS

Remove M1 light baffle

Install plywood cover segment in crane pathway

Install C1 cover

Remove C1

Remove C1 lower mount

Remove plywood cover segment

Remove the perimeter seal and aperture stop

Remove upper earthquake bumpers

Install all 3 segments of plywood cover

Retract M1 transverse hard point / Galil channel D

Wait 5 seconds

Retract (or "home") M1 axial hard points / Galil channels A-C only

Turn off M1 pneumatic support system

Turn off air to lateral link fuses using regulator (not solenoid drive)

Remove transverse hard point assembly

Remove transverse linear gauge

Disconnect lateral links from M1 pads

Remove 2 lateral link linear gauge contact blocks

Install the Hydraset on the crane and lift the spider into position over the M1 lifter

Install central spider into M1 lifter and unbolt lifter from PSS

Install the lifter guide pins

Procedure now requires 4 persons to monitor the position of the mirror and Hydraset gauge level, one person in the center monitoring the mirror, operating the crane

Raise and align the M1 lifter to meet the primary

Lift the primary watching for clearance on all sides...

Once clear of the PSS remove guide pins and attach tag line to M1 circumference

Installation

Assumptions for installation:

Pneumatic mirror support is off

Lateral link fuse air regulator is off

Mirror hard points, Galil channels A-D, are at retracted positions (recent "home")

Lateral link drives, Galil channels E & F, are at nominal positions for observations

M1 Galil is on (to verify above)

Read and record Gallil position values for channels A-F

M1 is on lifting fixture (with plywood cover), Hydraset and crane and ready for installation

PSS is turnbuckled to wind baffle

Ensure that PSS is level and pinned at "birdbath" and the wind baffle drive is disabled

Ensure that lateral links are properly positioned to align with M1

Ensure that transverse hard point quill is free and hard point assembly is connected and

ready for installation

Turn on M1 pneumatic support system (support belloframs should stabilize in a retracted state within a few minutes)

Lift M1 off the pedestals

Center M1 over the PSS and remove the M1 tag line

When within 3-4" of PSS install M1 lifter guide pins

Procedure now requires 4 persons to monitor the position of the mirror and Hydraset gauge level, one person in the center monitoring the mirror, operating the crane

Watching for clearance from all sides, and Using plastic M1 centering guides lower M1 near to axial supports

Attach lateral links to M1 pads

Remove plastic guides and slowly turn on air to lateral link fuses using regulator

Reinstall plastic guides and lower the mirror onto axial supports

Lower M1 lifter and connect it to the PSS

Remove M1 lifter central spider and guide pins

Install 2 lateral link linear gauge contact blocks

Install transverse linear gauge

Carefully install transverse hard point assembly

Install bridge rigging (ladder) on PSS

Install C1 lower and upper assemblies

Remove cover of C1

Temporarily remove bridge rigging

Remove plywood cover segments from M1

Install the perimeter seal and upper earthquake bumpers

Install aperture stop

Install bridge rigging (ladder) on PSS

Install M1 baffle

Remove bridge rigging

Drive M1 axial hard points to nominal pos. for obs. / Galil channels A-C only

Wait 5 seconds

Drive M1 transverse hard point to nominal pos. for obs. / Galil channel D

Move wind baffle + telescope to +60 (or so) degrees elevation and disable wind baffle drive

Verify M1 support stability

Read and record all 6 linear gauges and compare with earlier measurements

Bring telescope to horizon, pin and disable wind baffle drive

Remove PSS balance weights

Install Secondary Truss

Install wind baffle

Install wind baffle counterweights