Use Case:  Switch On/Off Nasmyth Beacon Light Source

Description:  Switch On/Off Nasmyth Beacon light source. This action is dedicated to optical alignment procedures and is therefore not foreseen to be used during normal operation. Only one beacon can be switched on at a time. This constraint applies as well for the Pupil beacon (M2 sub-system).

Role(s)/Actor(s): 
Primary: Operator,Maintenance
Secondary: Nasmyth sub-system

Priority: Desirable.

Performance: <1 second

Frequency: Asynchronous, typically while alignment procedure.

Package Assignment:  Nasmyth Focus Device Subsystem.

Preconditions: 

• Nasmyth sub-system is ONLINE
• Coudé Sensor Unit is protected for saturation (FSS Neutral Density filter)
  (no automatic check: this pre-condition shall be checked using a dialog box from the engineering panel, or an acknowledge from osf scripts).
• Nasmyth wheel on position 3 or 4 (TOOL #1 or #2)
  (in operation only these 2 positions make sense; in the other 2 wheel positions, switching on the Nasmyth beacon has little effect).

Basic Course: 

• Send command SETNBCN <1|2>,<ON|OFF> to switch On/Off Nasmyth beacon light source #n
  Exception Course: Command failed
• ATCS sends the command to Nasmyth sub-system

  Interface:  IfNasmythBeacon.No1On/Off,  IfNasmythBeacon.No2On/Off

  Exception Course: Command failed
  Postcondition: Nasmyth beacon light source switched On/Off

  Interface:  IfNasmythBeacon.No1Status,  IfNasmythBeacon.No2Status

• ATCS returns OK reply

Exception Course: Command failed

• ATCS returns ERROR reply

Postconditions: 

• Nasmyth beacon light source is switched Off or On with the default intensity (configurable in the database).

Issues to be Determined or Resolved:  Check preconditions

Notes:

• The assignment of the beacons to the tool positions is performed by the optical staff. This information is configurable in the database. The 2 tools may be assigned 2 light sources (laser diode) among 3 available offering 3 different wavelengths.
• The command GETNBCN returns the status of the 2 Nasmyth beacons:
  On/Off state and Intensity in % if On

Last modified: Fri Nov 23 11:31:07 UTC 2001