Previous Article
Next Article
Table of Contents

Instrumentation News: GRASP Design Review (1Jun95)
(from Director's Office, NOAO Newsletter No. 42, June 1995)

A concept and basic design approach for the multicolor near-infrared
instrument, GRASP, was approved by a non-advocate review committee.
GRASP is destined to be the workhorse IR instrument for the KPNO 4-m. The
current schedule goal is to complete it in two years from this summer.

The principle of GRASP is to divide the input beam into four color bands with
dichroics, based on the proven heritage of SQIID. With this approach, it is
possible to use transmissive optics with highly optimized coatings in order to
maximize throughput. The J, H, K and L arms will each be capable of imaging
and spectroscopy. A slit wheel selects various slits or an open aperture. The
dichroics follow, with lens collimators and a beam-expanding telescope
arrangement. A grating turret in each arm allows a choice of dispersions. The
cameras project to a scale of 0.3"/pixel on the 1024 square ALADDIN InSb
arrays. Possible additional features include a cold multi-slit mechanism and a
high-magnification mode for diffraction-limited imaging at L. A multiple-array
controller for ALADDIN arrays will be designed for this instrument and
SQIID; it will be integrated in operation and design to be much less complex
and costly than four parallel single-array controllers.

The non-advocate design review committee evaluated the GRASP concept and
design on 15-16 March. The committee consisted of Ian McLean (UCLA) as
chair, David Axon (STScI), Darren DePoy (Ohio State), Dan Vukobratovich
(U. of Arizona, Optical Sciences), Bill Binkert (KPNO), Al Fowler and Rich
Reed (NOAO Instrumentation). Their major conclusion was that GRASP
should be built as soon as possible. They urged that GRASP play to the
strengths of the Kitt Peak site and the 4-m as a complement to Gemini, by
emphasizing wider field performance and the three bands covering K and
shortward. They also prioritized a number of the options presented as part of
the original concept. The elimination of some potential modes has led to
significant design simplification, performance increase, and savings in volume,
weight and cost.

IPAC considered the report of the committee at their meeting immediately
following the Design Review. They approved the allocation of design
resources to take the instrument to a Delta-PDR in mid-summer. At that time,
several aspects of the design will be reviewed: the revised optical
configuration, the mechanical layout and optical bench performance, the
volume and weight of the dewar (the envelope may be comparable to that of
the echelle spectrograph), data system requirements and functionality, user
interface, data display, and data reduction impacts.

We are grateful to the Design Review committee, who gave their time and
considerable effort to come up with a thoughtful and immensely helpful set of
recommendations. Ian Gatley, Neil Gaughan, and the GRASP development
team did an impressive job in preparing the design and its description for the
review. Dick Joyce is now the GRASP project scientist. Please contact him
with your suggestions and questions while the development is underway.

Richard Green

Previous Article
Next Article
Table of Contents