NIFS

Critical Design Review

Documentation

Vol. 1

Submitted to the International Gemini Project Office

under

AURA Contract No. 9414257-GEM00234

Research School of Astronomy and Astrophysics

Australian National University

Canberra, Australia

April 19-20, 2001

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Executive Summary

The Gemini Near-infrared Integral-Field Spectrograph (NIFS) was proposed by the Research School of Astronomy and Astrophysics of the Australian National University at the March 1999 “Filling the Gap” meeting of the Gemini Instrument Forum. The NIFS Conceptual Design Review was held in March 2000. The NIFS Critical Design Study contract was signed in November 2000. Shipment to Hawaii is scheduled for 20 February 2003. This document presents the results of the Critical Design Study. The Critical Design Review will be held in Canberra, Australia, on 19-20 April 2001.

In keeping with the intent of the “Filling the Gap” meeting, NIFS is designed as a fast-tracked instrument for use with the ALTAIR adaptive optics system on Gemini North. It will combine an integral-field unit with a moderate resolution near-infrared spectrograph to perform near diffraction-limited imaging spectroscopy over a 3.0″×3.0″ field-of-view. The primary purpose of NIFS is to study moderate surface brightness structures around discrete objects that are revealed at high spatial resolution by ALTAIR. The requirement for adaptive optics guide stars will restrict the scientific scope of NIFS. NIFS will be capable of measuring predominantly Galactic objects with the ALTAIR natural guide star system. This will extend to significant numbers of extragalactic objects once the ALTAIR laser guide star system is available.

Nevertheless, NIFS with ALTAIR will always by a niche instrument which is able to measure only a limited number of objects.

The design, construction, and commissioning of NIFS will be fast-tracked by re-using many of the components designed for the Gemini Near-InfraRed Imager (NIRI) by the Institute for Astronomy of the University of Hawaii. Duplication of the NIRI cryostat, the On-Instrument Wavefront Sensor (OIWFS), the mechanism and temperature control systems, and the EPICS software are currently underway at the Research School for Astronomy and Astrophysics. The detector system for the duplicate OIWFS will be developed at the Institute for Astronomy. The detector system for the NIFS spectrograph will be developed jointly by the Research School of Astronomy and Astrophysics and the Institute for Astronomy. This approach has led to significant savings in schedule and budget.

The detailed design for the NIFS spectrograph differs from the design presented at the Conceptual Design Review in three major respects; the grating drive, the acquisition flip mirror, and the camera field flattener mount. The gratings are now supported by a shaft attached to the Cold Work Surface plate in a manner similar to that planned for GNIRS. This provides much stiffer support for the gratings, but slightly compromises wavelength repeatability when gratings are interchanged. A flip mirror is now included to bypass the grating and deliver undispersed acquisition images to the detector. This avoids the need to move the grating when acquiring faint objects. The silica field flattener in the spectrograph camera is now thermally isolated from other components and cooled to 65 K by a cold strap in order to prevent 4-5 μm radiation illuminating the detector. This blocking is sufficient to permit the future use of a 5 μm cut-off science detector without modification to the spectrograph optics.

This Critical Design Review Documentation consists of three volumes. Volume 1 contains the Technical Review of the instrument design. This includes extensive appendix material printed in A4 format. Volume 2 contains design drawings of the detector system and control system printed in A3 format. Electronic versions of the software design have been made available to the review committee separately. Volume 3 has eleven sections; a Management Plan for the detailed design, fabrication, and commissioning of the instrument, the Operational Concept Definition Document, the Functional and Performance Requirements Document, the Acceptance Test Plan, the Verification and Commissioning Plan, ICD 1.9f/3.1 Science Instrument to OCS Interface, ICD 1.9f/3.2 Science Instrument to DHS Interface, the Spares List, and outlines of the Users Manual, the Service and Calibration Manual, and the Software Maintenance Manual.