Soft X-ray emission from ~0.1 to 10 keV (~1-100 Å) provides unique diagnostics for high-temperature plasmas, but observations of the Sun in this energy range that are both spectrally and spatially resolved have been nearly non-existent. The Multi-Order X-ray Spectral Imager (MOXSI) is an instrument concept for a novel, slitless X-ray imaging spectrograph that will make crucial new measurements in this observationally-important wavelength range yet still fit within the limited resource constraints of a CubeSat. MOXSI utilizes a custom pinhole camera with a COTS, back-thinned CMOS sensor combined with a Chandra-heritage X-ray transmission diffraction grating to provide spatially-resolved, full-Sun imaging spectroscopy from ~1 to ~55 Å (~0.2-10 keV) with ~25 arcsec and ~0.25 Å FWHM spatial and spectral resolutions, respectively, and cadence of ~few tens of sec. MOXSI produces images akin to an “overlappograph,” with the 0th-order and dispersed images overlaid on the same detector; the dispersion direction is specifically oriented orthogonal to the latitudinal bands of solar activity to minimize source confusion. Additional pinhole apertures with custom entrance filters provide undispersed broadband filtergram images for additional source information. To mitigate motion-induced smearing, an on-board, real-time motion compensation system co-adds a series of frames for each integration period. MOXSI is one of the instruments of the proposed CubeSat Imaging X-ray Solar Spectrometer (CubIXSS) mission concept, which will improve our physical understanding of thermal plasma processes and impulsive energy release in the solar corona, from quiet Sun to solar flares, and the impact of solar X-rays on Earth’s upper atmosphere.
As a proof-of-concept, we have constructed and tested a cryogenic polarimeter in the laboratory as a prototype
for the MUSIC instrument (Multiwavelength Sub/millimeter Kinetic Inductance Camera). The POLOCAM
instrument consists of a rotating cryogenic polarization modulator (sapphire half-waveplate) and polarization
analyzer (lithographed copper polarizers deposited on a thin film) placed into the optical path at the Lyot stop
(4K cold pupil stop) in a cryogenic dewar. We present an overview of the project, design and performance
results of the POLOCAM instrument (including polarization efficiencies and instrumental polarization), as well
as future application to the MUSIC-POL instrument.
We report measurements of the fluctuations in atmospheric emission (atmospheric noise) above Mauna Kea
recorded with Bolocam at 143 GHz. These data were collected in November and December of 2003 with Bolocam
mounted on the Caltech Submillimeter Observatory (CSO), and span approximately 40 nights. Below ≃ 0.5 Hz,
the data time-streams are dominated by the f-δ atmospheric noise in all observing conditions. We were able to
successfully model the atmospheric fluctuations using a Kolmogorov-Taylor turbulence model for a thin wind-driven
screen in approximately half of our data. Based on this modeling, we developed several algorithms to
remove the atmospheric noise, and the best results were achieved when we described the fluctuations using a
low-order polynomial in detector position over the 8 arcminute focal plane. However, even with these algorithms,
we were not able to reach photon-background-limited instrument photometer (BLIP) performance at frequencies
below ≃ 0.5 Hz in any observing conditions. Therefore, we conclude that BLIP performance is not possible from
the CSO below ≃ 0.5 Hz for broadband 150 GHz receivers with subtraction of a spatial atmospheric template
on scales of several arcminutes.
KEYWORDS: Bolometers, Photometry, Spectroscopy, Sensors, Temperature metrology, Field effect transistors, Data modeling, Signal detection, Interference (communication), Smoothing
The flight model of the SPIRE instrument underwent several test campaigns in a test facility at the Rutherford Appleton
Laboratory (RAL) in the UK. A final dark campaign, completed in March 2007, provided an environment virtually free
from optical radiation. This allowed re-determining the fundamental model parameters of the NTD spider web bolometer
detector arrays in the new environment. The tests reported in this paper produced a fairly homogeneous dataset to
investigate white noise and 1/f noise at different bias voltages, bias frequencies, and bath temperatures. We find that the
white noise performance is in excellent agreement with the model predictions, once we correct the low frequency signal
variations that are due to temperature fluctuations of the thermal bath at about 300 mK. The temperature of the thermal
bath (detector array base plate) is measured by thermistor pixels that are part of the bolometer arrays. A residual 1/f
component beyond those variations is hardly detected. This unexpected stability is very welcome and will positively
impact photometer scan maps, the most popular observing mode of SPIRE.
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 µm, and an imaging Fourier Transform Spectrometer
covering 194-672 μm. 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 ( λ/▵λ=20-1000 at 250 μm). 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.
The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments on ESA's Herschel Space
Observatory. This long wavelength instrument covers 200 to 670μm with a three band photometric camera and a two
band imaging Fourier Transform Spectrometer (IFTS). Following first results reported in a previous paper, we discuss
the in-band optical performances of the flight model as measured extensively during several dedicated test campaigns.
Complementary to the experimentally probed spectral characteristics of the instrument detailed in an accompanying
paper (see L.D. Spencer et al., in these proceedings), attention is focused here on a set of standard but key tests aimed at
measuring the spatial response of the Photometer and Spectrometer end-to-end optical chain, including detector. Effects
of defocus as well as source size extent, in-band wavelength, and polarization are also investigated over respective
Photometer and Spectrometer field-of-views. Comparison with optical modelling, based on instrument design knowledge
and some of the internal component measured characteristics, is performed. Beyond the specific characterisation of each
effect, this allows estimating in each band where optical behaviour and detector behaviour respectively dominates and
also reconstructing some of the contributors to the instrument throughput. Based on this analysis, retrieved optical
performances are finally assessed against the related science-driven instrument requirements.
We describe the on-board electronics chain and the on-ground data processing pipeline that will operate on data from the
Herschel-SPIRE photometer to produce calibrated astronomical products. Data from the three photometer arrays will be
conditioned and digitised by on-board electronics and sent to the ground with no further on-board data processing. On
the ground, the data pipeline will process the data from point source, jiggle-map, and scan-map observations in a fully
automatic manner, producing measured flux densities (for point source observations) or maps. It includes calculation of
the bolometer voltages from the raw telemetry, glitch removal, and corrections for various effects including time
constants associated with the detectors and electronics, electrical and optical crosstalk, detector temperature drifts, flatfielding,
and non-linear response of the bolometers to strong sources. Flux density calibration will be with respect to
standard astronomical sources with the planets Uranus and Neptune being adopted as the baseline primary standards.
The pipeline will compute estimated values of in-beam flux density for a standard flat νS(ν) source spectrum.
The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments on ESA's Herschel Space
Observatory. The instrument covers 200 to 670 μm with a three band photometric camera and a two band imaging
Fourier Transform Spectrometer (IFTS). In this paper we discuss the performance of the optics of the instrument as
determined during the pre-flight instrument testing to date. In particular we concentrate on the response of the
instrument to a point source, the comparison between the visible light alignment and the infrared alignment and the
effect of the optical performance on the overall instrument sensitivity. We compare the empirical performance of the
instrument optics to that expected from elementary diffraction theory.
Bolocam is a millimetre-wave (1.1 and 2.1 mm) camera with an array of 119 bolometers. It has been commissioned at the Caltech Submillimeter Observatory in Hawaii and is now in routine operation. Here we give an overview of the instrument and the data reduction pipeline. We discuss models of the sensitivity of Bolocam in different observing modes and under different atmospheric conditions. We briefly discuss observations of star-forming Galactic molecular clouds, a blank field survey for sub-millimeter galaxies, preliminary results of a blank-field CMB secondary anisotropy survey and discuss observations of galaxy clusters using the Sunyaev-Zel'dovich effect.
We describe the design and performance of Bolocam, a 144-element, bolometric, millimeter-wave camera. Bolocam is currently in its commissioning stage at the Caltech Submillimeter Observatory. We compare the instrument performance measured at the telescope with a detailed sensitivity model, discuss the factors limiting the current sensitivity, and describe our plans for future improvements intended to increase the mapping speed.
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