Use Case:  AT System Stop - Observation to day-time mode transition

Description:  This is the normal operation to switch the system from observation to day-time mode.
The telescope is parked.
Each required sub-system used during observation is brought in state STANDBY.
Subsystems used during day-time only, are switched ON and brought to ONLINE.
A failure will leave the ATCS in state STANDBY substate ERROR.

Role(s)/Actor(s): 
Primary: Operator, Maintenance
Secondary: Standard Packages

Priority: Desirable. The sequence can always be performed step by step by the operator.

Performance: 10 minutes

Frequency: Typically, once per day at end of night.

Package Assignment:  Mode Switching.

Preconditions: 

• ATCS is in state ONLINE

Basic Course: 

• Send command STOPATS to Stop AT System
  Exception Course: Command failed
• ATCS Close Enclosure
  Exception Course: Close Enclosure Command failed
  Postconditions: Telescope enclosure is closed
• ATCS closes ROS Shutter with Control Relay Optics Structure Shutter
  Postconditions: ROS Shutter is Closed
• ATCS Set Coude Beam switching device to Light Stop
  Postconditions: Light Stop in Beam
• ATCS sends telescope to PARK position

  by Preset Telescope to Named Position PARK

  Exception Course: Command failed
  Postconditions: Telescope is in PARK position
• ATCS Stop
  Exception Course: Command failed
• ATCS Start Air Conditioning
  Exception Course: Start Air Conditioning command failed
• ATCS switches ON / puts ONLINE all not ignored subsystems used in day-time mode

  by using Standard Command

  Exception Course: Command failed
  Postcondition: all not ignored subsystems used in day-time mode are in ONLINE state

Exception Course:  Command failed

• ATCS global system state update
  Postcondition: ATCS in state STANDBY, substate ERROR
• ATCS returns ERROR reply

Exception Course:  Close Enclosure Command failed

• ATCS raise Alarm to Close Enclosure manually if still open
  Postconditions: Telescope enclosure is closed
• ATCS returns ERROR reply

Exception Course:  Start Air Conditioning Command failed

• ATCS raise Alarm to if Air COnditioning cannot start
  
• ATCS returns ERROR reply

Postconditions: 

• Enclosure is closed
• Telescope is in PARK position
• Air COnditioning is running
• ATCS is in state STANDBY, substate IDLE
• All required and not ignored ATS subsystems used in observation mode are in STANDBY (control loops are disabled and brakes engaged).
• All not ignored ATS subsystems used in day-time mode are in ONLINE state.

Issues to be Determined or Resolved: 

• The list of sub-systems to be switched On has to be identified

Notes:

The module osf has been successfully used with the UTs shutdown. osf should be reused.

Last modified: Thu Jun 28 13:33:01 UTC 2001