  Observational cosmology employing optical surveys often require precise flux
calibration. In this context we present SNIFS Calibration Apparatus (SCALA), a
flux calibration system developed for the SuperNova Integral Field Spectrograph
(SNIFS), operating at the University of Hawaii 2.2 m telescope. SCALA consists
of a hexagonal array of 18 small parabolic mirrors distributed over the face
of, and feeding parallel light to, the telescope entrance pupil. The mirrors
are illuminated by integrating spheres and a wavelength-tunable (from UV to IR)
light source, generating light beams with opening angles of 1 degree. These
nearly parallel beams are flat and flux-calibrated at a subpercent level,
enabling us to calibrate our "telescope + SNIFS system" at the required
precision.
