WISPI - The Wide Field Spectral Imager

Click the image for a view without covers.

The Wide Field Spectral Imager (WISPI) seen here in the Roll Roof Facility provides visible and near-infrared spectra of the sky across 4 degree fields. The instrument uses a high speed optical system to form an image on the entrance slit of a matching stigmatic spectrometer, which disperses a spectrum of a 4 degree by 4 arsceond strip of the sky onto a charge coupled device detector. A computer controlled mounting automates the acquisition of 2-D rastered spectral images.

WISPI was used by Pamela Graham for studies of bright comets, including Hale-Bopp and Hyakutake. A description of the instrument and her work appeared in "A Wide-Field Spectral Imager", Publications of the Astronomical Society of the Pacific, 112, 801-808 (2000). WISPI was renovated in 2010 to take advantage of improvements available in CCD detectors, drive systems, and software since its construction. It is currently used by Jeremy Huber in his research on emission line ratios in extended star forming regions of the Milky Way.

WISPI is shown here under development in the Applied Optical Physics Laboratory at the University of Lousville in 1994. Click here for a look at WISPI when it was in the main dome at Moore Observatory for observations of Comet Hale-Bopp.

This 1995 photo of WISPI with its covers removed shows the internal optical system. Light from the sky enters the large 400mm lens at top center, is imaged on the slit, collimated by the smaller 180 mm lens, and diffracted by the grating at the bottom toward the 200mm lens and CCD camera on the right. This CCD was cooled with liquid nitrogen. A Questar tracking telescope, also since replaced, is on the left.

As seen in 2009 while being renovated, a 300 groove/mm grating on the right is illuminated with collimated light and the dispersed spectrum is imaged by a fast camera lens.

This view from the grating shows the collimator on the left with the entrance slit behind it, and the fast camera lens that forms the spectral image on a CCD detector to the right.

In its original design, WISPI required an operator on site to fill the dewar and adjust the pointing based in part on visual centering in the guide telescope. To enable remote operation, a sensitive video camera was added that feeds a live image of the field to a network video server, the original liquid-nitrogen cooled Tektronix detector was replaced with a Peltier-cooled Truesense/Kodak detector in an Apogee U6 camera of nearly the same size and sensitivity, the stepping motor drive system was replaced with an encoded Galil DC servo motion controller, and the original Forth-based software was replaced with a Python-based system using XmCCD and XmTel under Linux.

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Last update: March 16, 2013
kielkopf at louisville dot edu