PCS Pointing Control Subsystem

1
LBT Q3 2008 Eng/SW Review

• PCS Pointing Control Subsystem
• Michele De La Peña

2
Highlights

• PCS Interfaces (GCS, MCSPU)
• GCS Pointing Correction
• Improved algorithm which applies the difference
  between the PCS predicted versus the GCS
  measured guide star location
• Better handshaking implemented to indicate when
  it is OK for GCS to verify the guide star is
  positioned on the hotspot before closing the
  guide loop
• MCSPU PCS Cold Start and New Target Trajectories
• Better handshaking implemented which alleviates
  having to issue duplicate Presets - Late PCS
  trajectory communication ? mount/rotator enters
  HOLD mode ? reduces observing efficiency
• The philosophy is the mount should react to the
  ever-changing pointing demand - PCS is a pure
  compute engine while MCSPU has the responsibility
  to recognize discontinuities due to new target
  requests
• Functionality to Support Instruments
• New functionality allows the observer to
  reposition where a target is imaged in the
  instrument focal plane (hotspot update)
  pointing origin update vs dither.
• Observers can update the effective target
  wavelength (due to changing filters) and not
  have to issue a new Preset ? improved efficiency

3
Open Issues

• Technical
• Investigation of guiding issues
  (jumps/jiggles/jitters)
• Resolve the LBC guide correction growth problem
  ? random occurrence
• Tuning of gains and filters used to modulate the
  Az/El guiding corrections to avoid
  over-correction and system oscillation
• Discussion on-going and an actual plan being
  formulated for near-term data collection
• Thorough examination of kernel guide correction
  filter and application
• Resolve high elevation guide oscillations
  (somewhat addressed in new kernel)
• Achieve definitive understanding of the various
  kernel angles, transformations, and trajectory
  offsets to apply a comprehensive solution for
  each instrument
• Evaluate and utilize the updated (and slightly
  incompatible) pointing kernel
• Schedule
• Concern not enough on-sky testing time for
  technical observing
• Primarily weather, but also sky time scarce
  resource for testing (unit and integration)
• Reconcile expectations when programmer
  participating in on-sky instrument support and
  required to implement new and robust
  functionality
• Financial
• Continued support for RAL consulting
• Resource
• None

4
Planning (Q4/2008)

• Resolution of the Open Issues (Oct)
• Initiation of a new PCS GUI (Dec)
• Incorporates the functionality from current PCS
  and Preset GUIs
• Provides additional control and monitoring
• Sets the migration path for binocular support
• Implement telemetry module
• True Binocular Support (Dec)
• Implementation of basic structural modifications
  to PCS to accommodate the binocular arbitrator
  (Dec)
• Define/design interface between the PCS and PSF
  for the tip/tilt computation (Q1/2009)
• Elaborate/design the model for co-aligned and
  misaligned observations (Q1/2009)
• Implementation commencement LBC emphasis
  (Q1/2009)