Collaboration Case:  Autoguiding Control Loop

Description:  The Auto Guiding Loop is triggered by a timer and is responsible for sending Low Frequency corrections to the axes using the error vectors provided by the FAS device.

Priority: Major

Performance: TBD

Frequency: Up to 1 Hz

Package Assignment:  Auto Guiding.

Preconditions: 

• ATCS is ONLINE Tracking
• FAS sub-system is ONLINE

Basic Course: 

• TRS timer trigger
  
• ATCS Checks Autoguiding Conditions (for auto guiding). Typically this check is not performed at every loop, but with a lower frequency.
  Exception Course: Guiding conditions not met
• ATCS Retrieve and Check Error Vector from the FAS
  Exception Course: No error vector
  
• ATCS sends Autoguider Offset to the tracking axes
  Exception Course: Command failed
  

Exception Course: No error vector

• ATCS log an error
• ATCS checks for too many consecutive invalid error vectors
  (to allow for temporary failures, like in the case of a cloud passing by).
  Exception Course: Too many errors

Exception Course: Too many errors

• ATCS Stops Autoguiding

Exception Course: Guiding conditions not met

• ATCS Stops Autoguiding

Exception Course: Command failed

• ATCS Stops Autoguiding

Postconditions: 

• Telescope main axes position updated

Issues to be Determined or Resolved: 

Notes:

Last modified: Thu Jun 28 13:04:49 UTC 2001