GPI IFS Data Handbook

This document describes the GPI Integral Field Spectrograph (IFS), the properties of its output data, including various systematics and noise sources that one may encounter, and how these data should be calibrated. Its goal is to summarize in one place all the properties of GPI data that a new user should be familiar with to usefully work with the data.

See also the Pipeline User’s Guide, which describes the user interface and operation of the software used to process these data.

Warning

This is a WORKING DRAFT document, which is not fully complete and may be in error in some places. It represents our current understanding of these aspects of instrument performance, and is likely to evolve with time. Use your own scientific judgement when reducing and analyzing data from GPI.

Read carefully, examine your data, evaluate the systematics, and let’s find some planets...

Contents

• GPI IFS Detector Properties
  • Readout Modes and Read Noise
  • Readout Times and Overheads
  • Detector Gain
  • Linearity
  • Saturation
  • Operable Pixels
• Field of View and Lenslet Geometry
  • IFS Field of View
  • Lenslet Pixel Scale and Distortion
  • Lenslet Array Details
• Filters and Spectra
  • Filters
  • Spectral Layout
• Satellite Spots
  • Locations
  • Flux ratios
  • Variability
• Photometry and Throughput
• Polarimetry
• GPI Data Formats
  • Multi-Extension FITS format
  • Main Image Extension “SCI”
  • Data quality flags extension “DQ”
  • Types of GPI IFS Files
  • FITS Keywords
  • Time Formats in FITS Headers
• Processing GPI Data, Step by Step
  • Darks
  • Thermal/Sky Backgrounds
  • Bad Pixels
  • Destriping and Microphonics
  • Saturation and Nonlinearity
  • Persistence
  • Flat Fielding
  • Flat Fielding: Lenslet Array Flat
  • Wavelength Calibration
  • Datacube Extraction
  • Satellite Spot Calibrations
  • Astrometric Calibration and Distortion Correction
  • Photometric Calibration
  • PSF Subtractions
  • Spectral Extraction of Companions