EBEX is a balloon-borne telescope designed to measure the polarization of the cosmic microwave background radiation. During its eleven day science flight in the Austral Summer of 2012, it operated 955 spider-web transition edge sensor (TES) bolometers separated into bands at 150, 250 and 410 GHz. This is the first time that an array of TES bolometers has been used on a balloon platform to conduct science observations. Polarization sensitivity was provided by a wire grid and continuously rotating half-wave plate. The balloon implementation of the bolometer array and readout electronics presented unique development requirements. Here we present an outline of the readout system, the remote tuning of the bolometers and Superconducting QUantum Interference Device (SQUID) amplifiers, and preliminary current noise of the bolometer array and readout system.
We present the design and measured performance of the superconducting magnetic bearing (SMB) that was used successfully as the rotation mechanism in the half-wave plate polarimeter of the E and B Experiment (EBEX) during its North American test flight. EBEX is a NASA-supported balloon-borne experiment that is designed to measure the polarization of the cosmic microwave background. In this implementation the half-wave plate is mounted to the rotor of an SMB that is operating at the sink temperature of 4 K. We demonstrate robust, remote operation on a balloon-borne payload, with angular encoding accuracy of 0.01°. We find rotational speed variation to be 0.2% RMS. We measure vibrational modes and find them to be consistent with a simple SMB model. We search for but do not find magnetic field interference in the detectors and readout. We set an upper limit of 3% of the receiver noise level after 5 minutes of integration on such interference. At 2 Hz rotation we measure a power dissipation of 56 mW. If this power dissipation is reduced, such an SMB implementation is a candidate for low-noise space applications because of the absence of stick-slip friction and low wear.
We present the hardware and software systems implementing autonomous operation, distributed real-time monitoring,
and control for the EBEX instrument. EBEX is a NASA-funded balloon-borne microwave polarimeter
designed for a 14 day Antarctic flight that circumnavigates the pole.
To meet its science goals the EBEX instrument autonomously executes several tasks in parallel: it collects
attitude data and maintains pointing control in order to adhere to an observing schedule; tunes and operates
up to 1920 TES bolometers and 120 SQUID amplifiers controlled by as many as 30 embedded computers;
coordinates and dispatches jobs across an onboard computer network to manage this detector readout system;
logs over 3 GiB/hour of science and housekeeping data to an onboard disk storage array; responds to a variety
of commands and exogenous events; and downlinks multiple heterogeneous data streams representing a selected
subset of the total logged data. Most of the systems implementing these functions have been tested during a
recent engineering flight of the payload, and have proven to meet the target requirements.
The EBEX ground segment couples uplink and downlink hardware to a client-server software stack, enabling
real-time monitoring and command responsibility to be distributed across the public internet or other standard
computer networks. Using the emerging dirfile standard as a uniform intermediate data format, a variety of
front end programs provide access to different components and views of the downlinked data products. This
distributed architecture was demonstrated operating across multiple widely dispersed sites prior to and during
the EBEX engineering flight.
KEYWORDS: Field programmable gate arrays, Logic, Digital signal processing, Bolometers, Space telescopes, Telescopes, Electronics, Sensors, Multiplexing, Control systems
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.
François Aubin, Asad Aboobaker, Peter Ade, Carlo Baccigalupi, Chaoyun Bao, Julian Borrill, Christopher Cantalupo, Daniel Chapman, Joy Didier, Matt Dobbs, Will Grainger, Shaul Hanany, Johannes Hubmayr, Peter Hyland, Seth Hillbrand, Andrew Jaffe, Bradley Johnson, Terry Jones, Theodore Kisner, Jeff Klein, Andrei Korotkov, Sam Leach, Adrian Lee, Michele Limon, Kevin MacDermid, Tomotake Matsumura, Xiaofan Meng, Amber Miller, Michael Milligan, Daniel Polsgrove, Nicolas Ponthieu, Kate Raach, Britt Reichborn-Kjennerud, Ilan Sagiv, Graeme Smecher, Huan Tran, Gregory Tucker, Yury Vinokurov, Amit Yadav, Matias Zaldarriaga, Kyle Zilic
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.
The E and B Experiment, EBEX, is a Cosmic Microwave Background polarization experiment designed to detect
or set upper limits on the signature of primordial gravity waves. Primordial gravity waves are predicted to be
produced by inflation, and a measurement of the power spectrum of these gravity waves is a measurement of
the energy scale of inflation. EBEX has sufficient sensitivity to detect or set an upper limit at 95% confidence
on the energy scale of inflation of < 1.4 × 1016 GeV. This article reviews our strategy for achieving our science
goals and discusses the implementation of the instrument.
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 (see manuscript) 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.
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