Use Case:  Preset Telescope in Alt/Az Coordinates

Description:  This function sets the telescope to the given axis coordinates (within the interlock limits) and keeps it on this position, in closed loop position control.
Optionally, predefined Alt/Az sets of coordinates can be specified by a conventional name.
The tracking will be automatically disabled.

Role(s)/Actor(s): 
Primary: Operator, Maintenance
Secondary: Tracking Axes

Priority: Critical

Performance: 

• Less than 4 minutes for 360 deg preset
• Less than 10 seconds for 10 deg offset
• Less than 2 seconds for 10 arcmin offset

Frequency: At any time

Package Assignment:  Presetting.

Preconditions:

• Telescope is ONLINE

• Send preset command PRSALAZ with Alt/Az coordinates (Engineering Preset)
  Alternate Course:
  • Send a (partial) setup file (command) with Alt/Az coordinates
  • ATCS Handles Setup File
  Exception Course: Command failed
  
• ATCS Stops Telescope Motion
  Exception Course: Command failed
  Postcondition: Telescope is in state ONLINE, substate IDLE
  i.e. standstill, brakes released, control loops closed
  
• ATCS forwards new reference coordinates to telescope axes

  by Preset to fixed Alt/Az target (TRK/OBJFIX) with new Alt/Az reference coordinates

  Exception Course: Command failed
  Postcondition: Telescope preset on coordinates
• Return OK reply

Exception Course: Command failed

• Return ERROR reply

Postconditions:

• ATCS state ONLINE, substate IDLE, tracking state IDLE
• Telescope is standstill at specified Alt/Az position
• Telescope brakes released, control loops closed

Issues to be Determined or Resolved:

• VLTI SRS at section 3.2.3 requires that an Alt/Az preset can be done specifying only one of the two coordinates. This has not been implemented on the UT Control Software. At the same time a named position Alt/Az preset has been implemented.
  VLTI SRS must be updated accordingly.

Notes:

Last modified: Thu Jun 28 13:51:45 UTC 2001