Use Case: Make Pointing Model from Given Measurements

Description: Use a measurement file as input for calculation of a pointing model.
Three types of model creation are shall be supported:

• total pointing model build-up
  It calibrates all reproducible pointing errors using a large number of stars. It may use, in addition, temperature sensors if required. The model shall contain a telescope-dependent part and a station-dependant part.
• medium pointing model upate
  It uses a relatively small numbers of stars and calibrates out medium term variations.
• small pointing model update
  It calibrates out the 3 angular offsets associated with the non-reproducible positioning errors of the AT on a specific station. Compensation for misalignments introduced by relocation process.

Role(s)/Actor(s):
Primary: Operator, Maintenance

Priority:

• total pointing model build-up
  Critical
• medium pointing model upate
  Desirable
• small pointing model update
  Desirable

Performance:

Frequency:

• total pointing model build-up
  During provisional acceptance and redone whenever necessary
• medium pointing model upate
  Every day.
• small pointing model update
  When AT has moved to a new station.

Package Assignment:  Pointing Modelling.

Preconditions:

Basic Course:

• Select pointing terms according to model type (small/medium/total)
• Select measurement file
• Tell ATCS to fit measurements to selected pointing terms
  Postcondition: Pointing terms calculated
• Check pointing error
• Check if some error measurements are completely out of the system (e.g. wrong star was picked), remove them and recalculate the terms.
• Save pointing model

Postconditions:

• Pointing model is available for usage in a file

Issues to be Determined or Resolved:

Notes:

Last modified: Thu Jun 28 13:50:33 UTC 2001