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The mid/far infrared hosts a wealth of spectral information that allows direct determination of the physical state of matter in a large variety of astronomical objects, unhindered by foreground obscuration. Accessing this domain is essential for astronomers to much better grasp the fundamental physical processes underlying the evolution of many types of celestial objects, ranging from protoplanetary systems in our own milky way to 10-12 billion year old galaxies at the high noon of galaxy formation in our universe. The joint ESA/JAXA SPICA mission will give such access for the astronomical community at large, by providing an observatory with unprecedented mid- to far-infrared imaging, polarimetric and spectroscopic capabilities.

The continued improvement in the sensitivity of superconducting far-infrared bolometers necessitates improved designs of cryogenically cooled broadband spectrometers in order to fully exploit the potential of such detectors. While Fourier transform spectrometers (FTS) have an illustrious history in astronomical research, the sensitivity of state-of-the-art detectors is such that the multiplex disadvantage of FTS is prohibitive unless the spectral bandpass can be restricted to less than 1%. One method of achieving this goal, and the one that has been adopted for the SPICA SAFARI instrument, is to use a diffraction grating as the 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; 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 and current status of a cryogenic, far-infrared, postdispersed, polarizing FTS (PDPFTS): a demonstrator for the SPICA SAFARI instrument.

The optical modelling of far-infrared partially-coherent grating spectrometers has long been considered difficult, due to the multi-mode diffractive nature of the grating optics. However, for the next generation of far-infrared space missions the need for understanding the complex behaviour of these grating spectrometers has intensified. Conventional modelling techniques are difficult to apply because i) the field is partially coherent; ii) diffraction and focusing effects are crucially important; iii) diffraction integrals need to be sampled finely over large optical surfaces. We describe an effective approach based on propagating the correlation functions of the radiation field using the natural modes of the optical system. First, the transformation matrix of the system, T, is determined, which captures the natural modes of the optics. Next, the correlations functions are propagated through the optics using T. The result is a modal optics technique that captures all performance information, in terms of the spectral, spatial and coherence details, within a single framework. In the paper, we explain the foundations of the method and demonstrate its applicability based on a number of standard far-infrared optical systems. Our scheme is numerically powerful, and provides insights into the trade-offs needed to optimise performance. The analysis we will extended to partially coherent far-infrared grating spectrometers as a function of the incident spectral field compositions, scattering at the grating optics, and detector geometry to improve our understanding of such systems.

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 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

Over half of the light incident on the Earth from the Universe falls within the Far-Infrared (FIR) region of the spectrum. Due to the deleterious effects of the Earth's atmosphere and instrument self-emission, astronomical measurements in the FIR require space-borne instrumentation operating at cryogenic temperatures. These instruments place stringent constraints on the mechanical and thermal properties of the support structures at low temperatures. With high stiffness, tensile strength, strength-to-mass ratio, and extremely low thermal conductivity, carbon fibre reinforced polymers (CFRPs) are an important material for aerospace and FIR astronomical applications, however, little is known about their properties at cryogenic temperatures. We have developed a test facility for exploring CFRP properties down to 4 K. We present results from our ongoing study in which we compare and contrast the performance of CFRP samples using different materials, and multiple layup configurations. Current results include an evaluation of a cryostat dedicated for materials testing and a custom cryogenic metrology system, and preliminary cryogenic thermal expansion measurements. The goal of this research is to explore the feasibility of making CFRP-based, lightweight, cryogenic astronomical instruments.

Measurements in the infrared wavelength domain allow us to assess directly the physical state and energy balance of cool matter in space, thus enabling the detailed study of the various processes that govern the formation and early evolution of stars and planetary systems in the Milky Way and of galaxies over cosmic time. Previous infrared missions, from IRAS to Herschel, have revealed a great deal about the obscured Universe, but sensitivity has been limited because up to now it has not been possible to fly a telescope that is both large and cold. Such a facility is essential to address key astrophysical questions, especially concerning galaxy evolution and the development of planetary systems. SPICA is a mission concept aimed at taking the next step in mid- and far-infrared observational capability by combining a large and cold telescope with instruments employing state-of-the-art ultra-sensitive detectors. The mission concept foresees a 2.5-meter diameter telescope cooled to below 8 K. Rather than using liquid cryogen, a combination of passive cooling and mechanical coolers will be used to cool both the telescope and the instruments. With cooling not dependent on a limited cryogen supply, the mission lifetime can extend significantly beyond the required three years. The combination of low telescope background and instruments with state-of-the-art detectors means that SPICA can provide a huge advance on the capabilities of previous missions. The SPICA instrument complement offers spectral resolving power ranging from ~50 through 11000 in the 17-230 µm domain as well as ~28.000 spectroscopy between 12 and 18 µm. Additionally, SPICA will be capable of efficient 30-37 µm broad band mapping, and small field spectroscopic and polarimetric imaging in the 100-350 µm range. SPICA will enable far infrared spectroscopy with an unprecedented sensitivity of ~5x10-20 W/m2 (5σ/1hr) - at least two orders of magnitude improvement over what has been attained to date. With this exceptional leap in performance, new domains in infrared astronomy will become accessible, allowing us, for example, to unravel definitively galaxy evolution and metal production over cosmic time, to study dust formation and evolution from very early epochs onwards, and to trace the formation history of planetary systems.

The European/Japanese SPace Infrared telescope for Cosmology and Astrophysics, SPICA, will provide astronomers with a long awaited new window on the universe. Having a large cold telescope cooled to less than 8K above absolute zero, SPICA will provide a unique environment where instruments are limited only by the cosmic background itself. A consortium of European, north American and Asian institutes has been established to design and implement the SpicA FAR infrared Instrument SAFARI, an extremely sensitive spectrometer designed to fully exploit this extremely low far infrared background environment provided by the SPICA observatory. SAFARI’s extremely sensitive Transition Edge Sensing detectors will allow astronomers to very efficiently obtain moderate to high resolution spectra of many thousands of obscured celestial objects in the far infrared, allowing a full spectroscopic characterisation of this objects. Efficiently obtaining such a large number of complete spectra will be essential to address several fundamental questions in current astrophysics: how do galaxies form and evolve over cosmic time?, what is the true nature of our own Milky Way?, and why and where do planets like those in our own solar system come into being? The basic SAFARI instrument is a highly sensitive Grating Spectrometer with a spectral resolution R of about 300 and a line sensitivity of a few x 10^-20 W/√Hz (5σ-1h). By routing the signal through a Martin-Puplett interferometer a high resolution mode is implemented providing R~11000 at 34 μm to R~1500 at 230 μm. The instrument operates in four wavelength bands, simultaneously covering the full 34-230μm range. Each band has three arrays of about 300 TES sensors providing three spatial and 300 spectral outputs. To limit the number of signal wires between the cold focal plan and the warm electronics units a 160 pixel/channel Frequency Domain Multiplexing scheme is employed.

We present the design and performance of a cryogenic, angle-scanned Fabry-Perot interferometer for far infrared astronomical spectroscopy. Novel features of the design are discussed, and the spectral response of the instrument is modeled. Experimental methods being developed to validate the spectral response are presented.

Nature is such that observations at far-infrared wavelengths are optimal for exploring both the nearby and distant Universe. The minute amount of energy carried by far-infrared photons, however, requires extremely sensitive instrumentation for their detection. Moreover, the instrumentation itself must be cooled to

The FP7 project, FISICA (Far Infrared Space Interferometer Critical Assessment), called for the investigation into the suitability of Carbon fiber Reinforced Plastic (CFRP) for a 2m primary mirror. In this paper, we focus on the major challenge for application, the development of a mirror design that would maintain its form at cryogenic temperatures. In order to limit self-emission the primary is to be cooled to 4K whilst not exceeding a form error of 275nm PV. We then describe the development of an FEA model that utilizes test data obtained from a cryogenic test undertaken at the University of Lethbridge on CFRP samples. To conclude, suggestions are made in order to advance this technology to be suitable for such an application in order to exploit the low density and superior specific properties of polymeric composites.

The Japanese SPace Infrared telescope for Cosmology and Astrophysics (SPICA), a 3 m class telescope cooled to ~ 6 K, will provide extremely low thermal background far-infrared observations. An imaging Fourier transform spectrometer (SAFARI) is being developed to exploit the low background provided by SPICA. Evaluating the performance of the interferometer translation stage and key optical components requires a cryogenic test facility. In this paper we discuss the design challenges of a pulse tube cooled cryogenic test facility that is under development for this purpose. We present the design of the cryostat and preliminary results from component characterization and external optical metrology.

We describe recent progress in the development of a lab-based spatial/spectral double Fourier interferometer within the Astronomical Instrumentation Group (AIG) laboratories at the University of Lethbridge, Canada (UL). This testbed interferometer is used in the development of spatial/spectral interferometry observation, data processing, characterization, and analysis techniques in the Far-Infrared (FIR) region of the electromagnetic spectrum. Several interferometry technological development milestones on the FIR astrophysics roadmap are addressed by this ongoing research program of the UL AIG, all of which are needed as precursors to an eventual space-based FIR interferometry mission. This research program is supported by recent CRC, CFI, and NSERC grants.

The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments on board the European Space Agency's Herschel Space Observatory which ended its operational phase on 29 April 2013. The low to medium resolution spectroscopic capability of SPIRE is provided by an imaging Fourier transform spectrometer (iFTS) of the Mach-Zehnder configuration. With their high throughput, broad spectral coverage, and variable resolution, coupled with their well-defined instrumental line shape and intrinsic wavelength and intensity calibration, iFTS are becoming increasingly common in far-infrared space astronomy missions. The performance of the SPIRE imaging spectrometer will be reviewed and example results presented. The lessons learned from the measured performance of the spectrometer as they apply to future missions will be discussed.

We present the latest commissioning results and instrument performance for the SCUBA-2 imaging Fourier Transform Spectrometer (FTS-2) installed at the James Clerk Maxwell Telescope (JCMT). This ancillary instrument provides intermediate spectral resolution (R ~10 to 5000) across both the 450 and 850 μm atmospheric transmission windows with a FOV of ~5 arcmin 2 . The superconducting TES sensors and SQUID readout of SCUBA-2 present unique challenges for operation of an FTS; the sensitivity requirements demand high detector linearity and stability in addition to control of systematic atmospheric and optical spillover effects. We discuss the challenges encountered during commissioning and ongoing efforts to mitigate their effects.

We present the performance characteristics of a water vapour monitor that has been permanently deployed at ESO’s Paranal observatory as a part of the VISIR upgrade project. After a careful analysis of the requirements and an open call for tender, the Low Humidity and Temperature Profiling microwave radiometer (LHATPRO), manufactured by Radiometer Physics GmbH (RPG), has been selected. The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ~2.5 mm). The unit comprises the above humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared radiometer (~10 μm) for cloud detection. The instrument has been commissioned during a 2.5 week period in Oct/Nov 2011, by comparing its measurements of PWV and atmospheric profiles with the ones obtained by 22 radiosonde balloons. In parallel an IR radiometer (Univ. Lethbridge) has been operated, and various observations with ESO facility spectrographs have been taken. The RPG radiometer has been validated across the range 0.5 – 9 mm demonstrating an accuracy of better than 0.1 mm. The saturation limit of the radiometer is about 20 mm. Currently, the radiometer is being integrated into the Paranal infrastructure to serve as a high time-resolution monitor in support of VLT science operations. The water vapour radiometer’s ability to provide high precision, high time resolution information on this important aspect of the atmosphere will be most useful for conducting IR observations with the VLT under optimal conditions.

Cerro Las Campanas located at Las Campanas Observatory (LCO) in Chile has been selected as the site for the Giant Magellan Telescope. We report results obtained since the commencement, in 2005, of a systematic site testing survey of potential GMT sites at LCO. Atmospheric precipitable water vapor (PWV) adversely impacts mid-IR astronomy through reduced transparency and increased background. Prior to the GMT site testing effort, little was known regarding the PWV characteristics at LCO and therefore, a multi-pronged approach was used to ensure the determination of the fraction of the time suitable for mid-IR observations. High time resolution monitoring was achieved with an Infrared Radiometer for Millimeter Astronomy (IRMA) from the University of Lethbridge deployed at LCO since September of 2007. Absolute calibrations via the robust Brault method (described in Thomas-Osip et al . 1 ) are provided by the Magellan Inamori Kyocera Echelle (MIKE), mounted on the Clay 6.5-m telescope on a timescale of several per month. We find that conditions suitable for mid-IR astronomy (PWV < 1.5 mm) are concentrated in the southern winter and spring months. Nearly 40% of clear time during these seasons have PWV < 1.5mm. Approximately 10% of these nights meet our PWV requirement for the entire night.

In support of characterization of potential sites for the European Extremely Large Telescope (E-ELT) the European Southern Observatory (ESO), the Institute for Space Imaging Science (ISIS) and the astrometeorology group of the Universidad Valparaiso have jointly established an improved understanding of atmospheric precipitable water vapour (PWV) above ESO's La Silla Paranal Observatory. In a first step, 8 years worth of high resolution near-IR spectra taken with VLT-UVES have been statistically analysed to reconstruct the PWV history above Paranal. To this end a radiative transfer model of Earth's atmosphere (BTRAM) developed by ISIS has been used. A median PWV of 2.1 mm is found for Paranal based on UVES data covering the period 2001-2008. Furthermore we conclude that Paranal can serve as a reference site for Northern Chile due to the stable atmospheric conditions in the region. The median offset between Paranal and Armazones is derived to be 0.3 mm, but local arbitrary variations of a few tenths of a mm between the sites have been found by measurement. In order to better understand the systematics involved two dedicated campaigns were conducted in August and November 2009. Several methods for determining the water column were employed, including radiosonde launches, continuous measurements by infrared radiometer, and VLT instruments operating at various wavelengths: CRIRES, UVES, VISIR and X-shooter. In a first for astronomical instruments all methods have been evaluated with respect to the radiosondes, the established standard in atmospheric research. Agreement between the radiosondes and the IR radiometer (IRMA) is excellent while all other astronomical methods covering a wavelength range from 700 - 20000 nm have also been successfully validated in a quantitative manner. All available observations were compared to satellite estimates of water vapour above the observatory in an attempt to ground-truth the satellite data. GOES can successfully be used for site evaluation in a purely statistical approach since agreement with the radiosondes is very good on average. For use as an operational tool at an observatory GOES data are much less suited because of significant deviations depending on atmospheric conditions. We propose to routinely monitor PWV at the VLT and to use it as an operational constraint to guide scheduling of IR observations at Paranal. For the E-ELT we find that a stand-alone high time resolution PWV monitor will be essential for optimizing the scientific output.

The SCUBA-2 imaging Fourier Transform Spectrometer (FTS-2) is a dual-band Mach-Zehnder imaging spectrometer, built for use with the SCUBA-2 camera on the James Clerk Maxwell Telescope (JCMT). FTS-2 will provide resolving powers of R ~ 10 to 5000 across the 450 and 850 μm bands, with a FOV up to 5 arcmin2. The instrument has been built and tested, with first light on the telescope planned for fall 2010. We present the alignment process, laboratory test results, and discuss the first science targets in the context of other similar space and ground-based instruments.

FTS-2 is an imaging Fourier transform spectrometer (IFTS) being developed for use with SCUBA-2, the second generation, wide-field, submillimetre camera which will operate at the James Clerk Maxwell Telescope (JCMT). The FTS-2 interferometer uses a folded Mach-Zehnder configuration and will provide simultaneous broadband spectral imaging across both the 850 and 450 μm bands with variable resolution ranging from resolving powers of R ~10 to 5000. Details of the instrument design, optical modeling, data reduction pipeline and calibration plan which have changed since the project CDR are discussed, along with preliminary results of lab integration and testing.

The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments onboard the European Space Agency (ESA)'s Herschel Space Observatory. The low to medium resolution spectroscopic capability of SPIRE is provided by an imaging Fourier transformspectrometer of the Mach-Zehnder configuration. Instrument performance of the SPIRE flight model was evaluated during a series of test campaigns. The SPIRE instrument performance verification was completed with instrument delivery to ESA in early 2007. In this paper we present the resulting performance characteristics of the SPIRE spectrometer flight model as determined from these test campaigns. We verify the instrument's conformance with fundamental design specifications such as spectral coverage and resolution. Variations across the imaging array of such properties as spectral resolution, vignetting, and instrumental line shape are explored. Additionally, instrumental artefacts observed during final verification testing are identified and quantified; with explanations provided for potential causes, and proposed methods to minimize their impact on scientific observations described.

We present simultaneous precipitable water vapour (PWV) measurements made at the Las Campanas Observatory in late 2007 using an Infrared Radiometer for Millimetre Astronomy (IRMA) and the Magellan Inamori Kyocera Echelle (MIKE) optical spectrograph. Opacity due to water vapour is the primary concern for ground based infrared astronomy. IRMA has been developed to measure the emission of rotational transitions of water vapour across a narrow spectral region centred around 20 μm, using a 0.1 m off-axis parabolic mirror and a sophisticated atmospheric model to retrieve PWV. In contrast, the MIKE instrument is used in conjunction with the 6.5 m Magellan Clay telescope, and determines the PWV through absorption measurements of water vapour lines in the spectra of telluric standard stars. With its high spectral resolution, MIKE is able to measure absorption from optically thin water vapour lines and can derive PWV values using a simple, single layer atmospheric model. In an attempt to improve the MIKE derived PWV measurements, we explore the potential of fitting a series of MIKE water vapour line measurements, having different opacities.

International audience; SPIRE, the Spectral and Photometric Imaging Receiver, is a submillimetre camera and spectrometer for Herschel. It comprises a three-band camera operating at 250, 350 and 500 Â\textmum, and an imaging Fourier Transform Spectrometer covering 194-672 \ensuremathμm. The photometer field of view is 4x8 arcmin., viewed simultaneously in the three bands. The FTS has an approximately circular field of view of 2.6 arcmin. diameter and spectral resolution adjustable between 0.04 and 2 cm^-1 ( \ensuremathλ/▵\ensuremathλ=20-1000 at 250 \ensuremathμm). Following successful testing in a dedicated facility designed to simulate the in-flight operational conditions, SPIRE has been integrated in the Herschel spacecraft and is now undergoing system-level testing prior to launch. The main design features of SPIRE are reviewed, the key results of instrument testing are outlined, and a summary of the predicted in-flight performance is given.

An Imaging Fourier Transform Spectrometer (IFTS), named FTS-2, is being developed by the University of Lethbridge for use with the SCUBA-2 sub-millimeter bolometric camera on the James Clerk Maxwell Telescope (JCMT). The FTS-2 optical model was developed and optimized in Zemax by the Institut National d'Optique (INO) to maximize the FOV and efficiency over a range of spectral resolutions. The IFTS has been designed as a folded system including corner cubes in the interferometer moving mirror, and extended polynomial surfaces in the interferometer folding mirrors. The instrument design for FTS-2 is described elsewhere; here we present an analysis of the modeled performance of the IFTS in terms of achievable Field Of View (FOV), spot pattern and vignetting, at Zero Path Difference (ZPD) and for the 2 resolution modes. The predicted imaging performance is compared to that of the SCUBA-2 camera alone.

SPIRE, the Spectral and Photometric Imaging Receiver, is a submillimetre camera and spectrometer for the European Space Agency's Herschel Space Observatory. It comprises a three-band imaging photometer operating at 250, 360 and 520

We present the preliminary design of FTS-2, an imaging Fourier transform spectrometer (IFTS) for use with SCUBA-2, the second generation, wide-field, submillimetre camera currently under development for the James Clerk Maxwell Telescope (JCMT). This system, which is planned for operation at the start of 2007, will provide simultaneous broadband spectral imaging across both the 850 and 450 μm bands with variable resolution ranging from resolving powers of R ~10 to 5000. The spectrometer uses a folded Mach-Zehnder configuration and novel intensity beam dividers. The mechanical and optical design of FTS-2 as of the Critical Design Review stage of the project are discussed, along with the interfaces with SCUBA-2 and the JCMT.

Since February 2005, an Infrared Radiometer for Millimeter Astronomy (IRMA) has been measuring precipitable water vapour levels in Chile at the Gemini South site on Cerro Pachon with a second unit added at the Las Campanas observatories site in August 2005. We have also started data collection with three additional IRMA units at three locations for the TMT site testing effort. After a number of technical modifications to ensure reliable operations at much lower sites than IRMA was designed for, 6 months of near continuous pwv data have been collected at both existing telescope sites and several months of data at TMT candidate locations. These data are enabling us to compare the sites on diurnal as well as seasonal timescales.

The Spectral and Photometric Imaging REceiver (SPIRE) is one of the three scientific instruments to fly on the European Space Agency's Herschel Space Observatory, and contains a three-band imaging submillimetre photometer and an imaging Fourier transform spectrometer. The flight model of the SPIRE cold focal plane unit has been built up in stages with a cold test campaign associated with each stage. The first campaign focusing on the spectrometer took place in early 2005 and the second campaign focusing on the photometer was in Autumn 2005. SPIRE is currently undergoing its third cold test campaign following cryogenic vibration testing. Test results to date show that the instrument is performing very well and in general meets not only its requirements but also most of its performance goals. We present an overview of the instrument tests performed to date, and the preliminary results.

The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments on ESA's Herschel Space Observatory. An imaging Fourier transform spectrometer (IFTS) provides the medium resolution spectroscopic capabilities of SPIRE. This paper compares the measured performance of the SPIRE IFTS, as determined from flight model instrument verification tests, with theoretical expectations. This analysis includes a discussion of the instrument line shape, signal-to-noise, resolution, field of view and spectrometer sensitivity.

The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments on ESA's Herschel Space Observatory. An imaging Fourier transform spectrometer, of the Mach-Zehnder configuration, provides low to medium resolution spectroscopic capability for SPIRE. The performance of the instrument is being evaluated during a series of test campaigns of the flight model before delivery to ESA. In this paper we present preliminary performance characteristics of the SPIRE spectrometer from the first test campaign of the flight model. We verify the instrument's conformance with fundamental design specifications such as spectral coverage and resolution. In addition, we identify, quantify, and explain some instrumental artefacts that have been observed during these tests.

The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments on the European Space Agency's (ESA) Herschel Space Observatory (HSO). The medium resolution spectroscopic capabilities of SPIRE are provided by an imaging Fourier transform spectrometer (IFTS). A software simulator of the SPIRE IFTS was written to create realistic data products, making use of available qualification and test data. A graphical user interface (GUI) provides fast and flexible access to the simulation engine. We present the design and integration of the simulator, as well as results from the simulator predicting the instrument performance under varying operational conditions.

Imaging Fourier transform spectrometers (IFTS) are becoming the preferred systems for remote sensing spectral imaging applications because of their ability to provide, simultaneously, both high spatial and spectral resolution images of a scene. IFTS can be operated in either step-and-integrate or rapid-scan modes, where it is common practice to sample interferograms at equal optical path difference intervals. The step-and-integrate mode requires a translation stage with fast and precise point-to-point motion and additional external trigger circuitry for the detector focal plane array (FPA), and produces uniformly position-sampled interferograms which can be analyzed using standard FFT routines. In the rapid-scan mode, the translation stage is continuously moving and interferograms are often acquired at the frame-rate of the FPA. Since all translation stages have associated velocity errors, the resulting interferograms are sampled at non-uniform intervals of optical path difference, which requires more sophisticated analysis. This paper discusses the processing pipeline which is being developed for the analysis of the non-uniform rapid-scan data produced by the Herschel/SPIRE IFTS.

The Spectral and Photometric Imaging Receiver (SPIRE) is one of three instruments on the European Space Agency's Herschel mission. A detailed understanding of the SPIRE instrument is essential for a successful mission. In particular, it is important to characterize both the in-band spectral profile, and any out-of-band spectral leaks, which would severely degrade performance. A test Fourier Transform Spectrometer (TFTS), with its braod spectral coverage and intermediate spectral resolution, was selected for the spectral characterization of SPIRE. The integration of the TFTS with the existing Ground Support Equipment of the Hershel/SPIRE test facility at the Rutherford Appleton Laboratory imposed several mechanical, optical, electrical, and software constraints. In this paper we describe the design and implementation of the TFTS, and present preliminary results from its use in the SPIRE verification and performance tests.

The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments on ESA's Herschel mission. The spectroscopic capabilities of SPIRE are provided by an imaging Fourier transform spectrometer (IFTS). A software simulator of the IFTS has been constructed to predict the instrument performance under operational conditions. We describe in detail the design and integration of the simulator. Examples of simulated data of astronomical targets are presented.

The Spectral and Photometric Imaging REceiver (SPIRE) is one of the three scientific instruments on the European Space Agency's Herschel mission. At the start of 2004 the Cryogenic Qualification Model (CQM) of SPIRE was tested with the aim of verifying the instrument system design and evaluating key performance parameters. We present a description of the test facility, an overview of the instrument tests carried out on the CQM, and the first results from the analysis of the test data. Instrument optical efficiency and detector noise levels are close to the values expected from unit-level tests, and the SPIRE instrument system works well, with no degradation in performance from stray light, electromagnetic interference or microphonically induced noise. Some anomalies and imperfections in the instrument performance, test set-up, and test procedures have been identified and will be addressed in the next test campaign.

We present the recent developments and current design and of an imaging Fourier transform spectrometer (IFTS) for use with SCUBA-2, the second generation, wide-field, submillimetre camera currently under development for the James Clerk Maxwell Telescope (JCMT). The spectrometer will offer variable resolution with resolving powers ranging from R ~10 to 5000. The IFTS uses a folded Mach-Zehnder configuration with novel intensity beam dividers and dual input ports for continuous atmospheric cancellation. This system, which is planned for operation in 2006, will provide simultaneous, broadband, intermediate spectral resolution imaging across both the 850 and 450 μm bands. The optics, observing modes, and projected telescope performance of the IFTS are discussed.

SCUBA-2, which replaces SCUBA (the Submillimeter Common User Bolometer Array) on the James Clerk Maxwell Telescope (JCMT) in 2006, is a large-format bolometer array for submillimeter astronomy. Unlike previous detectors which have used discrete bolometers, SCUBA-2 has two dc-coupled, monolithic, filled arrays with a total of ~10,000 bolometers. It will offer simultaneous imaging of a 50 sq-arcmin field of view at wavelengths of 850 and 450 microns. SCUBA-2 is expected to have a huge impact on the study of galaxy formation and evolution in the early Universe as well as star and planet formation in our own Galaxy. Mapping the sky to the same S/N up to 1000 times faster than SCUBA, it will also act as a pathfinder for the new submillimeter interferometers such as ALMA. SCUBA-2's absorber-coupled pixels use superconducting transition edge sensors operating at 120 mK for performance limited by the sky background photon noise. The monolithic silicon detector arrays are deep-etched by the Bosch process to isolate the pixels on silicon nitride membranes. Electrical connections are made through indium bump bonds to a SQUID time-domain multiplexer (MUX). We give an overview of the SCUBA-2 system and an update on its status, and describe some of the technological innovations that make this unique instrument possible., 16 pages, 14 figures, Invited talk at SPIE Glasgow 21-25 June 2004, Conference 5498

Embedded microcontroller modules offer many advantages over the standard PC such as low cost, small size, low power consumption, direct access to hardware, and if available, access to an efficient preemptive real-time multitasking kernel. Typical difficulties associated with an embedded solution include long development times, limited memory resources, and restricted memory management capabilities. This paper presents a case study on the successes and challenges in developing a control system for a remotely controlled, Alt-Az steerable, water vapour detector using the Rabbit 2000 family of 8-bit microcontroller modules in conjunction with the MicroC/OS-II multitasking real-time kernel.

We present the conceptual design of an imaging Fourier transform spectrometer (IFTS) for use with SCUBA-2, the second generation, wide-field, submillimeter camera currently under development for the James Clerk Maxwell Telescope (JCMT). This system, which is planned for operation in 2006, will provide simultaneous, broadband, intermediate spectral resolution imaging across both the 850 and 450 µm bands. The spectrometer will offer variable resolution with resolving powers ranging from R ~10 to 5000. When operated at low resolution, the IFTS will provide continuum measurements, well suited to spectral index mapping of molecular clouds, as well as bright nearby galaxies. The IFTS uses a folded Mach-Zehnder configuration and novel intensity beamdividers. The preliminary design, projected telescope performance and scientific impact of the IFTS are discussed. The preliminary design, novel observing modes, projected telescope performance and scientific impact of the IFTS are discussed.

SPIE Astronomical Telescopes + Instrumentation, 2004, Glasgow, United Kingdom, Series: Proceedings of SPIE; no. 5489

Astronomical spectroscopy at submillimeter wavelengths holds much promise for fields as diverse as the study of planetary atmospheres, molecular clouds and extragalactic sources. Fourier transform spectrometers (FTS) represent an important class of spectrometers well suited to observations that require broad spectral coverage at intermediate spectral resolution. In this paper we present the design and performance of a novel FTS, which has been developed for use at the James Clerk Maxwell Telescope (JCMT). The design uses two broadband intensity beamsplitters in a Mach-Zehnder configuration, which provide access to all four interferometer ports while maintaining a high and uniform efficiency over a broad spectral range. Since the interferometer processes both polarizations it is twice as efficient as the Martin-Puplett interferometer (MPI). As with the MPI, the spatial separation of the two input ports allows a reference blackbody to be viewed at all times in one port, while continually viewing the astronomical source in the other. Furthermore, by minimizing the size of the optical beam at the beamsplitter, the design is well suited to imaging Fourier transform spectroscopy (IFTS) as evidenced by its selection for the SPIRE instrument on Herschel.

Astronomical arrays operating at (sub)millimeter wavelengths are seriously compromised by rapid variations in atmospheric water vapor that distort the phase coherence of incoming celestial signals. The signal received by each antenna of the array suffers a phase delay that varies rapidly with time and from antenna to antenna. Unless corrected, these distortions limit the coherence time of the array and seriously compromise its sensitivity and image quality. Building on the success of a prototype infrared radiometer for millimeter astronomy (IRMA), which operates in the 20μm region to measure the column abundance of atmospheric water vapor, this paper describes the latest version of the IRMA concept, which has been developed for operation at Llano de Chajnantor, future site of the Atacama Large Millimeter Array (ALMA). Since there is presently limited infrastructure at the Chilean site the design must pay careful attention to all aspects of remote operation.

Astronomical arrays operating at (sub)millimeter wavelengths are seriously compromised by rapid variations in atmospheric water vapor that distort the phase coherence of incoming celestial signals. The signal received by each antenna of the array suffers a phase delay that varies rapidly with time and from antenna to antenna. Unless corrected, these distortions limit the coherence time of the array and seriously compromise its sensitivity and image quality. Building on the success of a prototype infrared radiometer for millimeter astronomy (IRMA), which operates in the 20μm region to measure the column abundance of atmospheric water vapor, this paper presents results obtained with a second generation IRMA operating at the James Clerk Maxwell telescope (JCMT) between January and July 2001. The results are compared with other measures of water vapor available on the summit of Mauna Kea, including: the JCMT SCUBA bolometer camera, the California Institute of Technology (CSO) opacity monitors, the JCMT 183GHz water vapor radiometer and Hilo-launched radiosonde data.