HAWK-I Overview

HAWK-I is a near-infrared (0.85-2.5 μm ) wide-field imager. It is being offered for the first time in Period 81. The instrument is cryogenic (120 K, detectors at 80 K) and has a full reflective design. The light passes four mirrors and two filter wheels before hitting a mosaic of four Hawaii 2RG 2048 * 2048 pixels detectors. The final F-ratio is F/4.36 ( 1 arcsec on the sky corresponds to169 μm on the detector).

Since P102 HAWK-I offers the Ground Layer Adaptive Optic  (GLAO) mode of the VLT Adaptive Optics Facility (AOF) via the GRAAL adaptive optics module, offering an AO corrected 7.5'x7.5' field of view. The GRAAL+HAWK-I GLAO is operated in the Tip-Tilt free mode.

Imaging mode

The two filter wheels of six positions each host ten filters: Y, J,H, K (identical to the VISTA filters), as well as 6 narrow band filters (Br_γ , CH4, H2 and three cosmological filters at 1.061, 1.187, and 2.090 μm ). Presently (Sept 2012 on) the filter at 1.187 is not available, since a visitor filter at 0.984 is mounted. The Field of View of HAWK-I on the sky is 7.5 arcmin * 7.5 arcmin,covered by the mosaic of the four Hawaii-2RG chips. The four detectors are separated by a cross-shaped gap of ~ 15 arcsec. The pixel scale is0.1064 arcsec/pix with negligible distortions (< 0.3 %) across the field of view. The image quality is seeing limited down to at least 0.4 arcsec seeing (i.e., 0.3 arcsec measured in K).

HAWK-I Field of View

Limiting magnitudes

Typical limiting magnitudes of HAWK-I (S/N of 5 on a point source, 3600 s integration on source) under average conditions (0.8 arcsec seeing, 1.2 airmass) are:

Filter Limiting mag Limiting mag
  [Vega] [AB]
J 23.9 24.8
H 22.5 23.9
K 22.3 24.2
HAWK-I limiting magnitude examples

The read-out noise is around 5 electrons, while the dark current of the instrument is around 2 electrons/pix/s.For a more detailed exposure time calculation, in particular for narrow band filters, we encourage you to use the exposure time calculator .

HAWK-I intervention log

July 2007 First Installation
September 2007 Improvement of flexure
December 2007 Implementation of fresh coated entrance window
June 2008 Change to LN2 cooling
August 2008 Cleaning of contaminated entrance window
January 2009 Improvement of LN2 Cooling
November 2009 Filter wheel stacked solution
November 2010 Cooling pump recover

HAWK-I based publications

Here below you can track all the publications which made use data acquired with HAWK-I: HAWK-I Publications