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Instrument Overview

  1. INGRID - A near-infrared imager
  2. INGRID and the Adaptive Optics Suite
  3. Applying to use INGRID
  4. Recent Developments

INGRID - A near-infrared imager

INGRID forms an integral part of the ING's adaptive optics suite NAOMI. Since early 2004 it has been permanently attached to one of NAOMI's two science ports in the environmentally controlled enclosure GRACE at the WHT's Nasmyth focus. The 1024x1024 HgCdTe Hawaii detector array has a pixel scale of 0.04"/pixel, with a resulting field of view of approximately 40" x 40", and a wavelength range from 0.8 to 2.5 µm. More information on the detector can be found here. INGRID's two filter wheels contain a range of broad and narrow band filters and a further wheel holds a selection of pupil stops. The diagram below shows a 3D transparent model of INGRID, with the light beam from the telescope focusing on the infrared detector.

Picture credit: Paul Jolley (ING)

INGRID was mostly built and developed at the ING and was commissioned in March 2000. It was originally deployed at both the Cassegrain and Nasmyth focal stations to provide (i) a wide field imaging capability over a ~4´x4´ field of view and (ii) a high resolution imaging mode over a ~40"x40" field of view (with the AO system NAOMI). However, following the successful commissioning of LIRIS in 2003/2004, INGRID's wide field functionality at Cassegrain has been replaced by LIRIS's imaging mode, meaning that INGRID is now one of two dedicated science instruments for NAOMI. In early 2004, INGRID underwent a major reengineering program to improve its mechanism control system, thus enhancing both the reliability and accuracy of its filter and pupil wheels.

INGRID and the Adaptive Optics Suite

INGRID is mounted on the adaptive optics bench in the GRACE enclosure. The light path from the telescope always passes through the adaptive optics system before reaching INGRID. Two keys optical elements in the light path are (a) a tip tilt mirror and (b) a 76 element segmented deformable mirror (DM). INGRID can be operated with NAOMI in three modes:
  • Full AO correction - In this mode, the deformable mirror is used to perform high order corrections and the tip tilt mirror removes low order image motion.
  • No AO correction - In this mode, both the deformable mirror and the tip tilt mirror are "frozen". This mode eliminates all (or most) of the restrictions imposed when performing AO corrections with natural guide stars. For IR imaging without AO correction we would normally recommend the use of LIRIS, however this mode of operation of INGRID will be useful for "target of opportunity" observations.
  • Tip tilt correction - In this configuration, the deformable mirror is "frozen" and the tip tilt mirror is used to perform a low order correction. Although there will be a smaller improvement in image quality than if the full AO correction is used, this mode has the advantage that it can be used with (a) fainter guide stars and (b) with guide stars at larger separations from the science targets, both of which greatly increase the sky coverage that can be observed.
The next section gives an overview of how to apply for INGRID observations. INGRID can also be used with the ING's AO coronograph OSCA - more details on the specific preparation needed for OSCA observations can be found here.

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Contact:  (INGRID Instrument Specialist)
Last modified: 17 June 2012