Use Case:  Set FSS Filter Wheel

Description:  Set the Field Stabilization filter wheel to one of the 4 (to become 6) neutral density filter positions
This action is dedicated to optical alignment procedures and during normal operation to adjust the GS brightness by means of a neutral density filter on the light path to FSS.

Role(s)/Actor(s): 
Primary: Operator,Maintenance,STRAP
Secondary: FSS Filter Wheel

Priority: Major

Performance: TBD

Frequency: At any time, mainly during optical alignment procedures

Package Assignment:  Field Stabilization Subsystem.

Preconditions: 

• FSS is ONLINE

Basic Course: 

• Send command SETNDF <n> to set the FSS filter wheel to given position
  Exception Course: Command failed
  
• ATCS sends command to FSS sub-system

  Interface:  IfFssFilterWheel.Motor

  Exception Course: Command failed
• ATCS returns OK reply

Exception Course: Command failed

• ATCS returns ERROR reply
  Postcondition: FSS Filter wheel not moved

Postconditions: 

• FSS filter wheel at given position

Issues to be Determined or Resolved:  FSS legal positions

Notes:

Last modified: Thu Jun 28 13:18:54 UTC 2001