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.
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.
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.
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.