The high spectral resolution mode of the SpicA FAR-infrared Instrument (SAFARI) is enabled by inserting a Fourier Transform Spectrometer (FTS), based on a Martin-Puplett interferometer, into the signal path of the instrument. The cryogenic FTS mechanism (FTSM) enables linear scans of two back-to-back rooftop mirrors sharing a common apex. ABB Inc. is under contract with the Canadian Space Agency to develop and test at 4 K an FTSM Engineering Demonstration Unit (EDU) for TRL-5 demonstration. The main SAFARI FTSM performance drivers are the stringent mechatronic demands (position stability of roof-top mirrors in step scan mode <10 nm RMS, velocity jitter in constant velocity mode <1% RMS at 85 µm/s, linear stroke <34 mm, error on position feedback laser metrology <10 nm RMS) and ultra-low photon leakage level from laser metrology (<1 pW), severely constrained by a tight thermal budget (heat dissipation <1.5 mW) under a specific micro-vibration environment (30 µg/√Hz external), all at cryogenic temperatures (4 K). In this paper, we describe the FTSM EDU developed and built at ABB with its laser metrology sensor. The FTSM EDU is based on a novel cryogenic design presented in 2020 using a reactionless and long-stroke flexure-based 4-bar linkage with stiffness compensation and a custom moving magnet actuator. Results from FTSM EDU room-temperature characterization and cryogenic proof-of-concept tests conducted at University of Lethbridge as a key step towards TRL-5 demonstration are discussed to assess the compliance of this novel design to the challenging cryogenic SAFARI FTSM performance requirements.
Scientists must reconsider the design of cryogenically cooled spectrometers in order to fully exploit the ever-increasing sensitivity of superconducting far-infrared bolometers. While Fourier transform spectrometers (FTS) have an illustrious history in astronomical research, the sensitivity of modern detectors is such that the multiplex disadvantage of FTS is prohibitive unless the spectral bandpass can be restricted to a few tenths of one percent. One method of achieving this goal is to use a diffraction grating as a post-dispersing component. Unlike a typical FTS, in which a single detector simultaneously measures a broad spectral band, a post-dispersed detection system requires multiple detectors, each with their own unique spectral, spatial and temporal responses. Moreover, the narrow spectral band viewed by each detector results in an interferogram having a large coherence length. In general, the signal is heavily modulated, yet truncated. While simulations play a useful role in modeling instrumental performance, there is no substitute for data obtained from a real implementation of an instrument concept. In this paper we describe the development of a cryogenic, far-infrared, post-dispersed, polarizing FTS (PDPFTS). The end-to-end performance of the PDPFTS will be evaluated in a large cryogenic test facility to simulate a space environment. The results provide valuable insight into the spectral calibration and data processing challenges that will be faced by hybrid spectrometers employing a post-dispersed component.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.