The Silicon X-ray Imager (SIXI)

We present a new mission concept, the Solid-state X-ray Imager (SIXI). SIXI is a follow-on to the successful Unconventional Stellar Aspect (USA) X-ray timing experiment flown in 1999-2000 by NRL. SIXI will pursue a multi-theme program of applied and basic research goals similar to USA, but will do so using solid state technology, large-area thick silicon strip arrays and coded apertures. Dual-sided silicon strip detectors are position-sensitive, light weight, and have no consumables, unlike the proportional counters used on previous large-area X-ray missions. Like USA, it will fly under the USAF Space Test Program (STP) with launch expected approximately 2007. A collaboration is forming to build the instrument, including LLNL and UC Berkeley.

The scientific goals will emphasize variability of compact objects in three areas (i) variability of galactic sources (QPOs, transient outbursts); (ii) variability of extragalactic sources, in conjunction with identification of counterparts for GLAST sources, and (iii) deep surveys. The instrument will feature thick silicon strips effective over the range ∼3-30 keV combined with a coded aperture. To optimize for the scientific objectives (which do not include all-sky monitoring), the field of view will be restricted to be modest (smaller than 5 degrees square); in this manner the lowest thresholds in hard X-rays are reached. Identification of GLAST counterparts will be pursued primarily through refinement of GLAST error regions and by concurrent measurement of variability. The applied program will continue that of USA with experiments in navigation, atmospheric diagnostics, and reliable computation in space.

Basic research in X-ray Astronomy at NRL is funded by NRL/ONR.