LDG Commissioning: April 25-26, 2010 UT

Performance Verification Plan

General Description

There are three types of data set that need to be collected, which are described later, to verify performance at the Left Direct Gregorian focal station:

  1. Presets
  2. Guiding and Collimation
  3. Offsets (5-Dice)

Several of each of these sets will be needed to get a complete picture of the performance of the focal station. Several type of information can be gleaned from each data set type.

Description of Data Set Types


A presets data set consists of multiple presets to the same target and off-axis guide star with the same position angle (PA). The purpose is to check the repeatability of the all the systems needed to preset, in ACTIVE mode, at different elevations and at different times.

Data Set Requirements

It would be best to have four sets of Preset Data sets.

  • 6 to 8 presets in the elevation range from 30 to 85 degrees
  • Same off-axis (off the Y-axis would be best) guide star
  • Same position angle (say PA=0 for a correctly orientated guide star)
  • Offset telescope by 30"
  • Collect background IRTC images with same parameters as above
  • Allow active optics corrections (Note, one correction can be performed during background collection)
  • Collect IRTC for 30 seconds total integration time (cubes 15 images with 2 second integrations)

Each set, with 6 to 8 points, could be all increasing or decreasing in elevation, or could be both increasing and decreasing elevation (ie collect data on a star from 30, through zenith, and back down to 30)

*Note:* Some data points could be drawn from the Guiding and Collimation Data Sets (See below)

Guiding and Collimation

A guiding and collimation data set consists of presetting the telescope to a target, that can be seen on IRTC and using an off-axis guide star, and allowing the telescope to follow the star for at least 15 minutes. These data sets will contain information about:

  • How well is Guiding working
  • How well Active Optics is working
  • Image quality from IRTC (FWHM to compare to guider value, ellipticity)

Data Set Requirements

We should collect 6 to 8 sets with a range of conditions:

  1. Elevation from 30 to 85 degrees
  2. Range of off-axis guide probe positions
  3. Two sets at the same elevation with all parameters the same expect PA=0 and PA=INDEF
  4. Various guide star magnitudes (10th to 16th magnitude...should be to 18th mag)

The steps to acquire these data are

  • pointto "Star" TelMode=Active gs=# PA=0 (or 90, or 180, or -90)
  • Acquire background - offset 0 30 - Acquire 30 sec IRTC cube - offset 0 0
  • Acquire 30 sec IRTC Cubes continuously for 15 to 20 minutes

Offsets (dice5)

A Dice5 data set consists of presetting the telescope to a target that can be seen on IRTC and then offsetting a given amount in a pattern of the five spots on a di. These data will allow us to understand the accuracy and repeatability of the offsets. Plus these data can be used to analyze image quality.

Data Set Requirements

Dice5 data sets should include the following parameters:

  • Offsets should span a range of distances, say 1", 10" and 3'
  • They should span elevations from 30 to 85

The steps to acquire these data are

  • pointto "Star" TelMode=Active gs=# PA=0 (or 90, or 180, or -90)
  • Acquire background - offset 0 30 - Acquire 60 sec IRTC cube - offset 0 0
  • Start dice5 IRAF routine with appropriate offset amount and 2 sec. exposures and 30 image

Inverse Field Data

This data set will yield a direct measurement, with the wavefront sensor camera, of the on-axis wavefront when guiding and collimation on an off-axis star.

Data Set Requirements

-- DougMiller - 24 Apr 2010
Topic revision: r4 - 25 Apr 2010, DougMiller
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