The Deep Space Optical Communication (DSOC) project at the Jet Propulsion Laboratory aims to perform a bidirectional laser communication technology demonstration from deep space, at ranges from 0.1 - 3 AU. To support high data rates over such distances while keeping the mass and power on the spacecraft comparable to radio-frequency communication systems, extremely high-performance single photon detectors are required at the ground receiver. To this end, JPL has been developing 64-pixel tungsten silicide superconducting nanowire single photon detector (WSi SNSPD) arrays suitable for use in the DSOC ground terminal. To efficiently couple to a 5-meter telescope aperture in the presence of atmospheric seeing, the arrays are free-space coupled and have a combined 320-micron diameter active area. The development is targeting 70% system detection efficiency at an operating wavelength of 1550 nm, 150 ps time resolution, a maximum count rate approaching 109 counts per second, a numerical aperture capable of supporting an f/1.2 beam, a background-limited dark count rate, and an operating temperature of 1 Kelvin. In this paper, we will present our progress toward these goals, both in terms of focal plane array development and cryogenic readout technology.
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