Guiding Control Subsystem (GCS)

Overview

10-04-2006

Tasks

Provide information to the PCS to identify tracking errors

Provide information to PSF to compensate for basic wavefront distortions (active optics).

Provide an interface for TCS and humans to select a proper guide star

Activities

Control AutoGuider and Wavefront sensing (AGw)units (MODS, AIP & PEPSI AGw)

Control AzCam guiding and WFS cameras

Acquire and analyze camera images

calculate centroid of GS and Zernike polynomial coefficients describing the Wavefront

frequently send results to PSF and PCS subsystem

GUI

provide different views for engineers and astronomers

designed mainly for the needs of astronomers and telescope operators

graphically keep track of the centroids and WF development over time

major redesign of the GUI coming soon

Communication

GCSGCSsubsystemsubsystem

AGw control AGw control computercomputer

AGw AGw hardwarehardware

AzCam serverAzCam serverWindows XPWindows XP

AzCam serverAzCam serverWindows XPWindows XP

Guide Guide CamCam

WFS WFS CamCam

.... for each AGw unit

PCSPCS

PSFPSF

PEPSI support

PEPSI needs access to the images of the guide cam

GCSGCSsubsystemsubsystem

PEPSI control PEPSI control computercomputer

PEPSI PEPSI hardwarehardware

AzCam serverAzCam serverWindows XPWindows XP

Guide Guide CamCam

PCSPCS

PSFPSF

IIFIIF

IIF is used to request guide cam image

GuidePic PEPSI PEPSI

InstrumentInstrumentRequest

Pic

Guiding Details

Two algorithms available to determine centroid

Default is Gaussian Fit: very precise, not good with irregularly shaped objects or bad SNR

Optionally, instrument or astronomer can select Center-of-Weight (CoW) algorithm

CoW is very stable, disregards shape of object and works with very bad SNR

WFS Details

algorithm just left prototype status and proved reliability under simulated conditions

uses centroiding algorithm

how to initialize the matrices with the necessary values is currently discussed with AIP AGw team

details of implementation yet to be discussed, i.e. derotation, calibration with primary mirror, etc.

TCS interface

currently only a very basic interface is implemented

start / stop guiding and WFS, status data

needs improvement in cooperation with TCS developers

Improvements

Foreseeable is the need for guiding on moving objects

issue has been raised with the AGw teams as neither OSU nor AIP have a solution for this yet

agreed on first do guiding on static objects

after that they want to check how their hardware can support the GCS with moving objects