A-STEP: The AstroPix Sounding Rocket Technology Demonstration Payload

Wide-field telescopes capable of detecting seconds-long transient astrophysical phenomena and localizing their origin in the sky within ~10 degrees are an important tool for supporting the growing fields of time domain astronomy and multi-messenger astrophysics. AstroPix is a monolithic CMOS active pixel sensor that enables high spatial (250 um) and spectral resolution (<9.7% FWHM at 122 keV) tracking of charged particle interactions within the detector medium. Layered AstroPix sensors can reconstruct the trajectories and energies of incident 25-700 keV gamma rays over large fields of view. A prototype multi-layered AstroPix instrument, called the AstroPix Sounding Rocket Technology Demonstration Payload (A-STEP), will provide a testbed for three layers of 4 x 4 cm
²
"quad chips". These quad chips, 2 x 2 undiced AstroPix detectors, form the building block of future large area AstroPix detector arrays. This payload will be the first suborbital demonstration of AstroPix’s technological readiness for use in next-generation gamma-ray astrophysical observatories and nuclear physics applications. In this presentation we overview the design and state of development of the first AstroPix multi-layer payload. We anticipate measuring 1000 cosmic ray events within a 5-minute sounding rocket flight window, and will attempt to reconstruct particle tracks through three payload layers.