The next generation of space-based mm-wave telescopes, such as JAXA’s LiteBIRD mission, require focal planes with thousands of detectors in order to achieve their science goals. Digital frequency-domain multiplexing (dfmux) techniques allow detector counts to scale without a linear growth in wire harnessing, sub-Kelvin refrigerator loads, and other scaling problems. In this paper, we introduce Technology Readiness Level 5 (TRL5) electronics suitable for biasing and readout of LiteBIRD’s Transition Edge Sensor (TES) bolometers using dfmux techniques. These electronics sit between the spacecraft’s payload computer and the cryogenic focal plane, and provide detector biasing, tuning, and readout interfaces between these detectors and the spacecraft’s on-board storage. We describe the overall architecture of the electronics, including functional decomposition into modules, the numerology and interconnection of these modules, and their internal and external interfaces. We describe performance measurements to date, including power consumption, thermal performance, and mass, volume, and reliability estimates. This paper is a companion piece to a description of the electronics’ on-board Field-Programmable Gate Array (FPGA) firmware.
The Tunable Filter Imager of the James Webb Space Telescope will be based on blocking filters and a tunable Fabry-
Perot etalon with an average resolution of about 100. It will operate in two wavelength bands from 1.6 μm to 2.5 μm and
from 3.1 μm to 4.9 μm at a cryogenic temperature of about 35K. It will respectively be used to study the First Light and
re-ionization of the universe by surveying Lyman-alpha sources and to provide an in-depth study of proto-planetary
systems as well as giant planets of nearby stars.
The Tunable Filter Imager (TFI) is designed to image a sky field of view of 2.2' by 2.2' (magnified to 4.6 deg. x 4.6 deg.
at the etalon). Its tunable etalon has an aperture of 56 mm. It operates at low orders 1 and 3 for the two wavelength bands
which reduces the number of blocking filters to a number of eight. The etalon gap tuning between 2.5 μm and 5.5 μm is
provided by piezoelectric actuators and will be servo controlled by using capacitive displacement sensors.
In this paper, we present the etalon's opto-mechanical design that allows us to achieve the stringent requirements in
terms of resolution over a wide infrared wavelength band, and operation at low gap at cryogenic temperature. Cryogenic
test results will be shared as well.
We present the prototyping results and laboratory characterization of a narrow band Fabry-Perot etalon flight model
which is one of the wavelength selecting elements of the Tunable Filter Imager. The latter is a part of the Fine Guidance
Sensor which represents the Canadian contribution to NASA's James Webb Space Telescope. The unique design of this
etalon provides the JWST observatory with the ability to image at 30 Kelvin, a 2.2'x2.2' portion of its field of view in a
narrow spectral bandwidth of R~100 at any wavelength ranging between 1.6 and 4.9 μm (with a gap in coverage
between 2.5 and 3.2 μm). Extensive testing has resulted in better understanding of the thermal properties of the
piezoelectric transducers used as an actuation system for the etalon gap tuning. Good throughput, spectral resolution and
contrast have been demonstrated for the full wavelength range.
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