SCORE 1+: enhancing a unique mid-infrared spectrograph

SCORE is a cross-dispersed echelle spectrograph, built as a prototype for the Short-High module of SIRTF's IRS instrument. It operates over the 7.5-15 micrometers N-band atmospheric window, and has ben used on Palomar's Hale telescope several times since November, 1996. Since the initial run, a number of improvements have ben undertaken or are in the process being undertaken which enhance SCORE's performance and simplify its operation. One such addition, now completed, is a second detector array which serves as a slit-viewer with 12 inch diameter field of view around the slit. This viewer allows easy acquisition and guidance for sources with dim or absent optical counterparts, and accurately registers the position of the slit on the source with the recorded spectrum. Software written in the IDL environment optimizes the extraction of spectra form SCORE's mid-IR crossed-echelle data. The echelle, while providing the advantage of increased pixel utilization, introduces several difficulties, including curved orders, order cross- talk, and differentially slanted lines. These and other instrumental artifacts must be removed to achieve the highest spectral signal-to-noise. The pixel efficiency will be further increased by the use of a grism predisperser. The grism will provide approximately even spacing between orders of the echelle, in contrast with the decreasing spacing towards shorter wavelength orders generated by the current grating. SCORE is already one of the most powerful short- slit spectrographs operating in this wavelength band, and, with the implementation of these improvements, will deliver even greater capability.