W. M. Keck Observatory

DEIMOS Rotator Safety Plan - Draft Feb. 12, 2002

Original draft by Grant Tolleth (Feb. 1, 2002)

This draft contains proposed revisions to Grant Tolleth's DEIMOS Rotator

Safety Plan dated February 1, 2002. This revised draft was prepared by

Bob Kibrick and Will Deich of the DEIMOS software team.

The Keck Observatory plans to ensure personnel safety from unexpected DEIMOS

rotation by the use of procedures.

1) The Night Attendant procedure shall be modified to include:

a. Disabling the rotator by application of the rotator band brake

b. Flipping the double-sided sign mounted at the DEIMOS interconnect

panel to indicate that the rotator is disabled.

2. The initialization procedure shall be modified to include:

a. Support tech or attendant shall walk around and inspect DEIMOS so

as to verify that no one is either on or inside the instrument and

that no person or non-rotatable equipment (e.g., LN2 tank and fill

hose) is attached to the rotatable portion of DEIMOS.

b. Support tech or attendant shall flip the double-sided sign mounted at

the DEIMOS interconnect panel to indicate the the rotator is enabled.

c. Support tech or attendant shall enable the rotator for remote

operation by:

1. Releasing the rotator band brake

2. Setting the handpaddle toggle switch to "AUTO" (This locks out

local control from the handpaddle and enables remote control.)

3A. The operational procedures shall include instructions to verify that

the rotator brake is applied prior to anyone climbing onto or into

DEIMOS. (The brake is essential in such situations, since without it,

the DEIMOS rotation drive motor can be back driven if the barrel is

sufficiently out of balance, as can occur if people are climbing on

or inside the instrument.) In critical situations, a keyed-lock can

be attached to the handle of the rotator brake to lock it in place.

3B. Both routine operations (e.g., installing slitmasks, filters, or

gratings) and some non-routine repair and maintenance functions are

normally carried out by rotating DEIMOS under the local control of a

support tech or instrument scientist standing on the right Nasmyth

platform and operating the handpaddle. In such cases:

a. Support tech shall update the White board to indicate "local control"

status

b. Support tech or attendant shall walk around and inspect DEIMOS so

as to verify that no one is either on or inside the instrument and

that no person or non-rotatable equipment (e.g., LN2 tank and fill

hose) is attached to the rotatable portion of DEIMOS.

c. Support tech shall announce the change in DEIMOS rotator status to

the observatory via radio.

d. Support tech shall flip the double-sided sign mounted at the DEIMOS

interconnect panel to indicate that the rotator is enabled.

e. Support tech will enable the rotator for local operation by:

1. Setting the handpaddle toggle switch to "MANUAL" (This enables

local rotation control from the handpaddle but locks out remote

control.)

2. Releasing the rotator band brake

f. Support tech will use the local handle paddle to rotate DEIMOS to

the appropriate PA for loading/unloading each mechanism (e.g.,

slitmask cassette, filter wheel, grating sliders) or for conducting

repairs or maintenance. Once at the desired PA, the band brake can

be applied.

g. After completing the loading/unloading of all of the relevant

mechanisms, support tech will:

1. Disable DEIMOS by applying the rotator band brake

2. Flip the double-sided sign mounted at the DEIMOS interconnect

panel to indicate the rotator is disabled.

3. Erase the "local control" status from the White board

4) Daytime enabling of the DEIMOS rotator will be handled in a manner

similar to the existing procedures for placing any telescope function

under remote software control:

a. Rotation requester shall coordinate with the Support tech.

b. Support Tech shall update the White board to indicate "tagged out" status

c. Support Tech shall announce the change in DEIMOS rotator status to

the Observatory via radio

d. Support tech or attendant shall walk around and inspect DEIMOS so

as to verify that no one is either on or inside the instrument and

that no person or non-rotatable equipment (e.g., LN2 tank and fill

hose) is attached to the rotatable portion of DEIMOS.

e. Support Tech shall flip the double-sided sign mounted at the DEIMOS

interconnect panel to indicate that the rotator is enabled.

f. Support Tech shall enable the rotator for remote operation by:

1. Releasing the rotator band brake

2. Setting the handpaddle toggle switch to "AUTO" (This locks out

local control from the handpaddle and enables remote control.)

f. Support Tech shall tape the DEIMOS portion of the Keck 2 Right Nasmyth

area as a "no entry area" if there are no personnel in the immediate

area guarding or working with the rotation exercise. (Alternatively,

if a signed barrier chain is available, that can be used in place of

tape.)