  The Apache Point Observatory Galactic Evolution Experiment (APOGEE), part of
the Sloan Digital Sky Survey III, explores the stellar populations of the Milky
Way using the Sloan 2.5-m telescope linked to a high resolution (R~22,500),
near-infrared (1.51-1.70 microns) spectrograph with 300 optical fibers. For
over 150,000 predominantly red giant branch stars that APOGEE targeted across
the Galactic bulge, disks and halo, the collected high S/N (>100 per
half-resolution element) spectra provide accurate (~0.1 km/s) radial
velocities, stellar atmospheric parameters, and precise (~0.1 dex) chemical
abundances for about 15 chemical species. Here we describe the basic APOGEE
data reduction software that reduces multiple 3D raw data cubes into
calibrated, well-sampled, combined 1D spectra, as implemented for the
SDSS-III/APOGEE data releases (DR10, DR11 and DR12). The processing of the
near-IR spectral data of APOGEE presents some challenges for reduction,
including automated sky subtraction and telluric correction over a 3 degree
diameter field and the combination of spectrally dithered spectra. We also
discuss areas for future improvement.
