Double-Fourier interferometry (DFI) from a space-based platform provides a path to achieve broadband imaging spectroscopy in the far-infrared with sub-arcsecond angular resolution. To provide further study of the technique and improve its technology readiness, we have constructed a laboratory-based DFI testbed. This instrument is coupled to a custom array of 25 feedback-controlled transition-edge sensor (TES) bolometers. We present the results of characterisation experiments to optimise the detector system as an integrated component of the DFI assembly. We demonstrate that tuning the proportional-integral-derivative (PID) feedback control loops of the detectors and the timing of the multiplexed measurement process can modify the detector array’s noise performance and speed of response to optical modulation for this purpose. From these, we have determined a set of optimised detector settings that reduce spectral noise in the spatial-spectral interferometer by 37–79%. In addition, we present further thermal characterisation of the detector array.
KEYWORDS: Sensors, Multiplexing, Signal to noise ratio, Modulation, Signal detection, Detector arrays, Field programmable gate arrays, Space operations, Time division multiplexing, Cryogenics
We describe the commissioning and operation of a 25 element Transition-Edge Sensor (TES) cryogenic detector array system for use in the far-infrared band of the electromagnetic spectrum. This detector system, supplied by QMC Instruments Limited, is an integral component to the development of a spatial/spectral double Fourier laboratory-based interferometer testbed instrument within the Astronomical Instrumentation Group laboratories at the University of Lethbridge, Canada. The 5x5 rectangular grid of TES elements is feedhorn-coupled and operates at ∼6K within a dedicated cryostat providing both optical and thermal shielding. Cryogenic cooling of ∼0.5W is provided by a CryoMech PT405RM/CP2850 pulse-tube cooler/compressor suite. The detector readout system uses time-division multiplexing controlled by a dedicated National Instruments field-programmable gate array board and computer interface. This paper describes the characterization and optimization of this detector system, including the evaluation and validation of the readout electronics, hardware, software, detector noise properties, the multiplexing parameter space, optical sensitivity, and the integration of this system within a laboratory testbed interferometer instrument.
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