Performance of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) high-resolution near-infrared multi-object fiber spectrograph

The Apache Point Observatory Galactic Evolution Experiment (APOGEE) usesa dedicated 300-fiber, narrow-band near-infrared (1.51-1.7 μm), highresolution (R~22,500) spectrograph to survey approximately 100,000 giantstars across the Milky Way. This three-year survey, in operation sincelate-summer 2011 as part of the Sloan Digital Sky Survey III (SDSS III),will revolutionize our understanding of the kinematical and chemicalenrichment histories of all Galactic stellar populations. We present theperformance of the instrument from its first year in operation. Theinstrument is housed in a separate building adjacent to the 2.5-m SDSStelescope and fed light via approximately 45-meter fiber runs from thetelescope. The instrument design includes numerous innovations includinga gang connector that allows simultaneous connection of all fibers witha single plug to a telescope cartridge that positions the fibers on thesky, numerous places in the fiber train in which focal ratio degradationhad to be minimized, a large mosaic-VPH (290 mm x 475 mmelliptically-shaped recorded area), an f/1.4 six-element refractivecamera featuring silicon and fused silica elements with diameters aslarge as 393 mm, three near-infrared detectors mounted in a 1 x 3 mosaicwith sub-pixel translation capability, and all of these componentshoused within a custom, LN2-cooled, stainless steel vacuum cryostat withdimensions 1.4-m x 2.3-m x 1.3-m.