Use Case:  Stop FSS Acquisition

Description:  Stop the APD measurements setting the APD gate to 0 and opening the APD loop.
As soon as the loop is open M6 goes automatically to center position. The center position is defined as (0,0) plus the offset value set in the SETUP database branch.

Role(s)/Actor(s): 
Primary: Operator/Maintenance
Secondary: FSS Strap

Package Assignment:  Field Stabilization Subsystem.

Preconditions: 

• FSS Strap is ONLINE

Basic Course: 

• Send command STOP to stop the FSS Strap System
  Exception Course: Command failed
• ATCS Sets APD Gate to 0%
  Exception Course: Command failed
• ATCS Opens APD Loop
  Exception Course: Command failed
• ATCS sends command to stop FSS Strap System

  Interface:  IfFss.Control.Stop

  Exception Course: Command failed
• ATCS returns OK reply

Exception Course: Command failed

• ATCS returns ERROR reply

Postconditions: 

• FSS Strap is idle

Issues to be Determined or Resolved:  The behaviour of the M6 as controlled by the APD system must be still analyzed on more details. This will most probably cause modifications in the FSS and M6 Use Cases and the introduction of new Use Cases for the M6.

ACTION MCO: Verify the following points regarding the interaction of the STRAP system with the M6:

• the actual sequence to be used at FSS Acquisition STOP time is:
  • Set the gate to 0
  • Open the loop
  or
  • Open the loop
  • Set the gate to 0
• that M6 actually goes to the defined center position, using properly the defined offset from (0,0)
• if the offset position is applyed:
  • As soon as the SETUP with the new offset is sent
  • When the loop is OPENED/CLOSED
  This has an impact on the implementation of chopping, as will be discussed in the following sections.
• what happens when the gate is set to 0 ?
  • M6 stays in previous position (should be!)
  • M6 goes to defined offset position
• is it the same when the loop is open or closed?
• what is the behavious when the loop is opened/closed?

  Notes:

  Last modified: Thu Jun 28 13:19:01 UTC 2001