8,619 research outputs found
Superconducting On-chip Fourier Transform Spectrometer
The kinetic inductance effect is strongly nonlinear with applied current in NbTiN, TiN and NbN thin films. This can be utilized to realize novel devices. We present results from transmission lines made with these materials, where DC (current) control is used to modulate the phase velocity thereby enabling on-chip spectrometers. Utility of such compact spectrometers is discussed, along with their natural connection with parametric amplifiers
A Compact Millimeter-Wavelength Fourier-Transform Spectrometer
We have constructed a Fourier-transform spectrometer (FTS) operating between
50 and 330 GHz with minimum volume (355 x260 x64 mm) and weight (13 lbs) while
maximizing optical throughput (100 sr) and optimizing the
spectral resolution (4 GHz). This FTS is designed as a polarizing
Martin-Puplett interferometer with unobstructed input and output in which both
input polarizations undergo interference. The instrument construction is simple
with mirrors milled on the box walls and one motorized stage as the single
moving element. We characterize the performance of the FTS, compare the
measurements to an optical simulation, and discuss features that relate to
details of the FTS design. The simulation is also used to determine the
tolerance of optical alignments for the required specifications. We detail the
FTS mechanical design and provide the control software as well as the analysis
code online.Comment: Submitted to Applied Optics. [Copyright 2019 Optical Society of
America]. Users may use, reuse, and build upon the article, or use the
article for text or data mining, so long as such uses are for non-commercial
purposes and appropriate attribution is maintained. All other rights are
reserve
Imaging Fourier transform spectrometer
There are many applications that require spectral information from either objects or scenes. This paper will describe the design, construction, and evaluation of an imaging Fourier transform spectrometer (FTS) that will gather such spectral information. The design of the spectrometer is based on that of a Michelson interferometer. Theory, limitations, alignment, and cost will all be considered in this work
Fourier Transform Spectrometer System
A Fourier transform spectrometer (FTS) data acquisition system includes an FTS spectrometer that receives a spectral signal and a laser signal. The system further includes a wideband detector, which is in communication with the FTS spectrometer and receives the spectral signal and laser signal from the FTS spectrometer. The wideband detector produces a composite signal comprising the laser signal and the spectral signal. The system further comprises a converter in communication with the wideband detector to receive and digitize the composite signal. The system further includes a signal processing unit that receives the composite signal from the converter. The signal processing unit further filters the laser signal and the spectral signal from the composite signal and demodulates the laser signal, to produce velocity corrected spectral data
Calibration of the Herschel SPIRE Fourier Transform Spectrometer
The Herschel SPIRE instrument consists of an imaging photometric camera and
an imaging Fourier Transform Spectrometer (FTS), both operating over a
frequency range of 450-1550 GHz. In this paper, we briefly review the FTS
design, operation, and data reduction, and describe in detail the approach
taken to relative calibration (removal of instrument signatures) and absolute
calibration against standard astronomical sources. The calibration scheme
assumes a spatially extended source and uses the Herschel telescope as primary
calibrator. Conversion from extended to point-source calibration is carried out
using observations of the planet Uranus. The model of the telescope emission is
shown to be accurate to within 6% and repeatable to better than 0.06% and, by
comparison with models of Mars and Neptune, the Uranus model is shown to be
accurate to within 3%. Multiple observations of a number of point-like sources
show that the repeatability of the calibration is better than 1%, if the
effects of the satellite absolute pointing error (APE) are corrected. The
satellite APE leads to a decrement in the derived flux, which can be up to ~10%
(1 sigma) at the high-frequency end of the SPIRE range in the first part of the
mission, and ~4% after Herschel operational day 1011. The lower frequency range
of the SPIRE band is unaffected by this pointing error due to the larger beam
size. Overall, for well-pointed, point-like sources, the absolute flux
calibration is better than 6%, and for extended sources where mapping is
required it is better than 7%.Comment: 20 pages, 18 figures, accepted for publication in MNRA
Systematic characterisation of the Herschel SPIRE Fourier Transform Spectrometer
A systematic programme of calibration observations was carried out to monitor
the performance of the SPIRE FTS instrument on board the Herschel Space
Observatory. Observations of planets (including the prime point-source
calibrator, Uranus), asteroids, line sources, dark sky, and cross-calibration
sources were made in order to monitor repeatability and sensitivity, and to
improve FTS calibration. We present a complete analysis of the full set of
calibration observations and use them to assess the performance of the FTS.
Particular care is taken to understand and separate out the effect of pointing
uncertainties, including the position of the internal beam steering mirror for
sparse observations in the early part of the mission. The repeatability of
spectral line centre positions is <5km/s, for lines with signal-to-noise ratios
>40, corresponding to <0.5-2.0% of a resolution element. For spectral line
flux, the repeatability is better than 6%, which improves to 1-2% for spectra
corrected for pointing offsets. The continuum repeatability is 4.4% for the SLW
band and 13.6% for the SSW band, which reduces to ~1% once the data have been
corrected for pointing offsets. Observations of dark sky were used to assess
the sensitivity and the systematic offset in the continuum, both of which were
found to be consistent across the FTS detector arrays. The average point-source
calibrated sensitivity for the centre detectors is 0.20 and 0.21 Jy [1 sigma; 1
hour], for SLW and SSW. The average continuum offset is 0.40 Jy for the SLW
band and 0.28 Jy for the SSW band.Comment: 41 pages, 37 figures, 32 tables. Accepted for publication in MNRA
Superconducting On-chip Fourier Transform Spectrometer
The kinetic inductance effect is strongly nonlinear with applied current in NbTiN, TiN and NbN thin films. This can be utilized to realize novel devices. We present results from transmission lines made with these materials, where DC (current) control is used to modulate the phase velocity thereby enabling on-chip spectrometers. Utility of such compact spectrometers is discussed, along with their natural connection with parametric amplifiers
Observing Extended Sources with the \Herschel SPIRE Fourier Transform Spectrometer
The Spectral and Photometric Imaging Receiver (SPIRE) on the European Space
Agency's Herschel Space Observatory utilizes a pioneering design for its
imaging spectrometer in the form of a Fourier Transform Spectrometer (FTS). The
standard FTS data reduction and calibration schemes are aimed at objects with
either a spatial extent much larger than the beam size or a source that can be
approximated as a point source within the beam. However, when sources are of
intermediate spatial extent, neither of these calibrations schemes is
appropriate and both the spatial response of the instrument and the source's
light profile must be taken into account and the coupling between them
explicitly derived. To that end, we derive the necessary corrections using an
observed spectrum of a fully extended source with the beam profile and the
source's light profile taken into account. We apply the derived correction to
several observations of planets and compare the corrected spectra with their
spectral models to study the beam coupling efficiency of the instrument in the
case of partially extended sources. We find that we can apply these correction
factors for sources with angular sizes up to \theta_{D} ~ 17". We demonstrate
how the angular size of an extended source can be estimated using the
difference between the sub-spectra observed at the overlap bandwidth of the two
frequency channels in the spectrometer, at 959<\nu<989 GHz. Using this
technique on an observation of Saturn, we estimate a size of 17.2", which is 3%
larger than its true size on the day of observation. Finally, we show the
results of the correction applied on observations of a nearby galaxy, M82, and
the compact core of a Galactic molecular cloud, Sgr B2.Comment: Accepted for publication by A&
Calibration of the AKARI Far-Infrared Imaging Fourier Transform Spectrometer
The Far-Infrared Surveyor (FIS) onboard the AKARI satellite has a
spectroscopic capability provided by a Fourier transform spectrometer
(FIS-FTS). FIS-FTS is the first space-borne imaging FTS dedicated to
far-infrared astronomical observations. We describe the calibration process of
the FIS-FTS and discuss its accuracy and reliability. The calibration is based
on the observational data of bright astronomical sources as well as two
instrumental sources. We have compared the FIS-FTS spectra with the spectra
obtained from the Long Wavelength Spectrometer (LWS) of the Infrared Space
Observatory (ISO) having a similar spectral coverage. The present calibration
method accurately reproduces the spectra of several solar system objects having
a reliable spectral model. Under this condition the relative uncertainty of the
calibration of the continuum is estimated to be 15% for SW, 10% for
70-85 cm^(-1) of LW, and 20% for 60-70 cm^(-1) of LW; and the absolute
uncertainty is estimated to be +35/-55% for SW, +35/-55% for 70-85 cm^(-1) of
LW, and +40/-60% for 60-70 cm^(-1) of LW. These values are confirmed by
comparison with theoretical models and previous observations by the ISO/LWS.Comment: 22 pages, 10 figure
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