Use Case:  AT System Start - Day-time to observation mode transition

Description:  This is the normal operation to switch the system from day-time to observation mode.
Each required sub-system used during observation is brought from state STANDBY to state ONLINE, i.e. all sub-systems are completely activated and the telescope is under position control, ready to move at next operative command.
Subsystems used during day-time only, are switched off or to STANDBY state.
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 start of night. Occasionally, a few times per night.

Package Assignment:  Mode Switching.

Preconditions: 

• ATCS is in state STANDBY

Basic Course: 

• Send command STRTATS to Start AT System
  Exception Course: Command failed
• ATCS puts in STANDBY (or OFF) all not ignored subsystems used in day-time mode

  by using Standard Command

  Exception Course: Some sub-systems failed to go in STANDBY (or OFF)
  Postcondition: all not ignored subsystems used in day-time mode are in STANDBY (or OFF) state
• ATCS Start
  Exception Course: Failed to start ATCS
• ATCS Set APD Gate to 0%
  Postconditions: APD Gate is open
• ATCS Set Coude Beam switching device to Light Stop
  Postconditions: Light Stop in Beam
• ATCS Stop Air Conditioning
  Postconditions: Air Conditioning is stopped
• ATCS Open Enclosure
  Postconditions: Telescope enclosure is open
• Open ROS Shutter with Control Relay Optics Structure Shutter
  Postconditions: ROS Shutter is Open

Exception Course:  Command failed

• ATCS returns ERROR reply

Exception Course:  Failed to start ATCS

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

Exception Course:  Some sub-systems failed to go in STANDBY (or OFF)

• ATCS global system state update
  Postcondition: ATCS in state OFF, substate ERROR
• Ignore sub-systems that failed
  Alternate course: Try to put failed sub-systems in STANDBY (or OFF) manually

Alternate Course:  Try to put failed sub-systems in STANDBY (or OFF) manually

• Put in STANDBY (or OFF) all not ignored subsystems used in day-time mode
  Exception Course: Some sub-systems failed to initialize or to go in STANDBY (or OFF)
  Postcondition: all required and not ignored subsystems are initialized and in STANDBY state

Postconditions: 

• ATCS is in state ONLINE, substate IDLE (this implies telescope axes under position control)
• Enclosure is open
• ROS Shutter is open
• Light Stop in Coudé Beam
• APD Gate is 0
• All required and not ignored ATS subsystems used in observation mode are initialized and in ONLINE (control loops are enabled and brakes disengaged)
• All ATCS not ignored subsystems used in day-time mode are in STANDBY (or OFF) state

Issues to be Determined or Resolved: 

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

Notes:

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

Last modified: Thu Jun 28 13:33:00 UTC 2001