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Frequency multiplexed readout systems for large TES bolometer arrays are in use for ground and balloonbased mm-wavelength telescopes. New digital backend electronics for these systems implement advanced signal processing algorithms on FPGAs. Future satellite instruments will likely use similar technology. We address the challenges of operating FPGAs in an orbital radiation environment using neighbour-neighbour monitoring, where each FPGA monitors its neighbour and can correct errors due to radiation events. This approach reduces the FPGA's susceptibility to crippling events without relying on triple redundancy or radiation-hardened parts, which raise the system cost, power budget, and complexity. This approach also permits earlier adoption of the latest FPGAs, since radiation-hardened variants typically lag the state of the art.

EBEX (the E and B EXperiment) is a balloon-borne telescope designed to measure the polarisation of the cosmic microwave background radiation. During a two week long duration science flight over Antarctica, EBEX will operate 768, 384 and 280 spider-web transition edge sensor (TES) bolometers at 150, 250 and 410 GHz, respectively. The 10-hour EBEX engineering flight in June 2009 over New Mexico and Arizona provided the first usage of both a large array of TES bolometers and a Superconducting QUantum Interference Device (SQUID) based multiplexed readout in a space-like environment. This successful demonstration increases the technology readiness level of these bolometers and the associated readout system for future space missions. A total of 82, 49 and 82 TES detectors were operated during the engineering flight at 150, 250 and 410 GHz. The sensors were read out with a new SQUID-based digital frequency domain multiplexed readout system that was designed to meet the low power consumption and robust autonomous operation requirements presented by a balloon experiment. Here we describe the system and the remote, automated tuning of the bolometers and SQUIDs. We compare results from tuning at float to ground, and discuss bolometer performance during flight.

We present measurements of the electrical and thermal properties of new arrays of bolometeric detectors that were fabricated as part of a program to develop bolometers optimized for the low photon background of the EBEX balloon-borne experiment. An array consists of 140 spider-web transition edge sensor bolometers microfabricated on a 4" diameter silicon wafer. The designed average thermal conductance of bolometers on a proto-type array is 32 pW/K, and measurements are in good agreement with this value. The measurements are taken with newly developed, digital frequency domain multiplexer SQUID readout electronics., in SPIE Proceedings Vol. 7020, Marseille, 2008