In late 1998 the International Gemini Project Office identified a need for a low cost, near-infrared spectrograph to be commissioned on the Gemini South telescope on the shortest possible timescale. In response, the Research School of Astronomy and Astrophysics of the Australian National University proposed to design, construct, and commission a near-infrared, integral-field spectrograph on Gemini. The science drivers and novel design of the Near-infrared Integral-Field Spectrograph (NIFS) are described in this paper. NIFS will achieve significant economies in cost and schedule in several ways:
• By addressing targeted science with high efficiency. NIFS will primarily target velocity measurements in galaxies to study the demographics of black holes in galactic nuclei and the evolution of structural properties in high redshift galaxies. However, NIFS will also be applied to a wide range of general astronomical topics, but these will not dictate the instrument design.
• By adopting a largely fixed-format design. A 3·2″ × 3·2″ ‘stair-case’ integral field unit (IFU) will feed a near-infrared spectrograph with four fixed-angle gratings mounted on a single grating wheel. A single, fixed-format camera will form the spectral image on a 2048 × 2048 Rockwell HgCdTe HAWAII-2 array. Two-pixel spectral resolving powers of ∼5400 will be achieved with complete wavelength coverage in each of the J, H, and K photometric bands through 32 optimally sampled 0·1″ wide slitlets. The velocity resolution of ∼55 km s−1 will be sufficient to achieve the targeted science objectives, and will allow software rejection of OH airglow lines.
• By packaging the NIFS instrument within a duplicate of the Near-Infrared Imager (NIRI) cryostat. The NIRI cryostat, On-Instrument Wavefront Sensor (OIWFS), detector focusing mechanism, control system, and EPICS software will all be duplicated with only minimal change. Construction of the duplicate NIRI cryostat, OIWFS, and control system will be done by the University of Hawaii.