PILOT (Polarized Instrument for Long wavelength Observations of the Tenuous interstellar medium) is a balloonborne astronomy experiment designed to study the polarization of dust emission in the diffuse interstellar medium in our Galaxy. The PILOT instrument allows observations at wavelengths 240 μm and 550 μm with an angular resolution of about two arcminutes. The observations performed during the two first flights performed from Timmins, Ontario Canada, and from Alice-springs, Australia, respectively in September 2015 and in April 2017 have demonstrated the good performances of the instrument. Pilot optics is composed of an off axis Gregorian type telescope combined with a refractive re-imager system. All optical elements, except the primary mirror, which is at ambient temperature, are inside a cryostat and cooled down to 3K. The whole optical system is aligned on ground at room temperature using dedicated means and procedures in order to keep the tight requirements on the focus position and ensure the instrument optical performances during the various phases of a flight. We’ll present the optical performances and the firsts results obtained during the two first flight campaigns. The talk describes the system analysis, the alignment methods, and finally the inflight performances.
PLANCK is a project of the European Space Agency to be launched in February 2007 by an ArianeV rocket with the Herschel Space Observatory . It is designed for imaging the temperature and polarization anisotropies of the millimetre and submillimetre radiation over the whole sky with unprecedented sensitivity, accuracy and angular resolution using 9 frequency channels ranging between 25 and 1000 GHz. The main source at these frequencies is the Cosmic Microwave Background (CMB), i.e. the radiation emitted by the early universe when, about 300000 years old, ionised hydrogen recombined and became transparent from the visible to radio frequencies of the electromagnetic spectrum. The main goal of the PLANCK mission is to retrieve the main cosmological parameters of the Universe with accuracies of a few percent from the observation and analysis of random small contrast (10–4) features in the CMB. The angular power spectrum of the CMB anisotropies is a function of the fundamental cosmological parameters. A proper measurement of all the angular frequencies of the CMB is essential for an accurate interpretation of the data. In consequence the optical performances of Planck will directly impact the ability of retrieving theses parameters. Recent results of the Willkinson Microwave Anisotropy Probe (WMAP) mission show that polarization information of CMB radiation is very challenging, and that the precise measurement of the CMB could completely change the knowledge we have on our universe ([1]). The focal plane assembly (FPA) of the PLANCK telescope is composed of two instruments. The High Frequency Instrument (HFI) of PLANCK is the most sensitive CMB experiment ever planned ([2]). Together with the Low Frequency Instrument (LFI), this will make a unique tool to measure the full sky and to separate various components of its spectrum. This paper describes the main performances of the HFI beams and compares results obtained with 2 different softwares: GRASP8 [3] and an home-made software developed at the Ireland National University of Maynooth [4]. Specials attention will be paid to polarized beams (100, 143, 217, 353 GHz) and multimoded channels (545 and 857 GHz).
PILOT is a balloon borne experiment, which will measure the polarized emission of dust grains, in the interstellar medium, in the sub millimeter range (with two photometric channels centered at 240 and 550 μm).
The primary and secondary mirror must be positioned with accuracies better than 0.6 mm and 0.06°. These tolerances include environmental conditions (mainly gravity and thermo-elastic effects), uncertainties on alignments, and uncertainties on the dilatation coefficient. In order to respect these tolerances, we need precise characterization of each optical component. The characterization of the primary mirror and the integrated instrument is performed using a dedicated submillimeter test bench.
A brief description of the scientific objectives and instrumental concept is given in the first part. We present, in the second and in the third part, the status of these ground tests, first results and planned tests.
PILOT is a balloon borne experiment which aims at measuring precisely the polarized emission of the interstellar dust emission, in the submm range (240 and 550 μm). These measurements will be used to reach a better understanding of the galactic magnetic field role in the structure of the Galaxy and the star formation process. They will be useful too for CMB experiments by providing a precise knowledge of galactic foreground emission. Simulations including realistic instrument performances show that after three flights (around 24 hours each), it will be possible to cover the full galactic plane map (±30° in latitude). In addition, several deep surveys will be performed at high galactic latitude. As the level of polarized emission of interstellar dust is less than 5%, an accurate knowledge of the instrumental polarization is mandatory for the data processing and analysis.
PILOT (Polarized Instrument for the Long-wavelength Observations of the Tenuous ISM), is a balloon-borne astronomy experiment dedicated to study the polarization of dust emission from the diffuse ISM in our Galaxy [1]. The observations of PILOT have two major scientific objectives. Firstly, they will allow us to constrain the large-scale geometry of the magnetic field in our Galaxy and to study in details the alignment properties of dust grains with respect to the magnetic field. In this domain, the measurements of PILOT will complement those of the Planck satellite at longer wavelengths. In particular, they will bring information at a better angular resolution, which is critical in crowded regions such as the Galactic plane. They will allow us to better understand how the magnetic field is shaping the ISM material on large scale in molecular clouds, and the role it plays in the gravitational collapse leading to star formation. Secondly, the PILOT observations will allow us to measure for the first time the polarized dust emission towards the most diffuse regions of the sky, where the measurements are the most easily interpreted in terms of the physics of dust. In this particular domain, PILOT will play a role for future CMB missions similar to that played by the Archeops experiment for Planck. The results of PILOT will allow us to gain knowledge about the magnetic properties of dust grains and about the structure of the magnetic field in the diffuse ISM that is necessary to a precise foreground subtraction in future polarized CMB measurements. The PILOT measurements, combined with those of Planck at longer wavelengths, will therefore allow us to further constrain the dust models. The outcome of such studies will likely impact the instrumental and technical choices for the future space missions dedicated to CMB polarization.
The PILOT instrument will allow observations in two photometric channels at wavelengths 240 μm and 550 μm, with an angular resolution of a few arcminutes. We will make use of large format bolometer arrays, developed for the PACS instrument on board the Herschel satellite. With 1024 detectors per photometric channel and photometric band optimized for the measurement of dust emission, PILOT is likely to become the most sensitive experiment for this type of measurements. The PILOT experiment will take advantage of the large gain in sensitivity allowed by the use of large format, filled bolometer arrays at frequencies more favorable to the detection of dust emission.
This paper presents the optical design, optical characterization and its performance. We begin with a presentation of the instrument and the optical system and then we summarise the main optical tests performed. In section III, we present preliminary end-to-end test results.
PILOT (Polarized Instrument for Long wavelength Observations of the Tenuous interstellar medium) is a balloonborne astronomy experiment designed to study the polarization of dust emission in the diffuse interstellar medium in our Galaxy. The PILOT instrument allows observations at wavelengths 240 μm (1.2THz) with an angular resolution about two arc-minutes. The observations performed during the first flight in September 2015 at Timmins, Ontario Canada, have demonstrated the optical performances of the instrument.
PILOT is a balloon-borne astronomy experiment designed to study the polarization of dust emission in the diffuse
interstellar medium in our Galaxy at wavelengths 240 μm with an angular resolution about two arcminutes. Pilot optics
is composed an off-axis Gregorian type telescope and a refractive re-imager system. All optical elements, except the
primary mirror, are in a cryostat cooled to 3K. We combined the optical, 3D dimensional measurement methods and
thermo-elastic modeling to perform the optical alignment. The talk describes the system analysis, the alignment
procedure, and finally the performances obtained during the first flight in September 2015.
PILOT is a stratospheric experiment designed to measure the polarization of dust FIR emission, towards the diffuse interstellar medium. The first PILOT flight was carried out from Timmins in Ontario-Canada on September 20th 2015. The flight has been part of a launch campaign operated by the CNES, which has allowed to launch 4 experiments, including PILOT. The purpose of this paper is to describe the performance of the instrument in flight and to perform a first comparison with those achieved during ground tests. The analysis of the flight data is on-going, in particular the identification of instrumental systematic effects, the minimization of their impact and the quantification of their remaining effect on the polarization data. At the end of this paper, we shortly illustrate the quality of the scientific observations obtained during this first flight, at the current stage of systematic effect removal.
Future cosmology space missions will concentrate on measuring the polarization of the Cosmic Microwave Back- ground, which potentially carries invaluable information about the earliest phases of the evolution of our universe. Such ambitious projects will ultimately be limited by the sensitivity of the instrument and by the accuracy at which polarized foreground emission from our own Galaxy can be subtracted out. We present the PILOT balloon project which will aim at characterizing one of these foreground sources, the polarization of the dust continuum emission in the diffuse interstellar medium. The PILOT experiment will also constitute a test-bed for using multiplexed bolometer arrays for polarization measurements. We present the results of ground tests obtained just before the first flight of the instrument.
The Polarized Instrument for Long wavelength Observation of the Tenuous interstellar medium (PILOT) is a balloon borne experiment designed to measure the polarized emission from dust grains in the galaxy in the submillimeter range. The payload is composed of a telescope at the optical focus of which is placed a camera using 2048 bolometers cooled to 300 mK. The camera performs polarized optical measurements in two spectral bands (240 μm and 550 μm). The polarization measurement is based on a cryogenic rotating half-wave plate and a fixed mesh grid polarizer placed at 45o separating the beam into two orthogonal polarized components each detected by a detector array. The Institut d’Astrophysique Spatiale (Orsay, France) is responsible for the design, integration, tests and spectral calibration of the camera. Two optical benches have been designed for its imaging and polarization characterization and spectral calibration. Theses setups allow to validate the alignment of the camera cryogenic optics, to check the optical quality of the images, to characterize the time and intensity response of the detectors, and to measure the overall spectral response. A numerical photometric model of the instrument was developed for the optical configuration during calibration tests (spectral), functional tests (imager) on the ground, and flight configuration at the telescope focus, giving an estimate of the optical power received by the detectors for each configuration.
KEYWORDS: Point spread functions, Sensors, Deconvolution, Zemax, James Webb Space Telescope, Imaging systems, Mirrors, Lawrencium, Fermium, Frequency modulation
The Mid Infra Red Instrument (MIRI) is one of the four instruments onboard the James Webb Space Telescope (JWST),
providing imaging, coronagraphy and spectroscopy over the 5 - 28 μm band. To verify the optical performance of the
instrument, extensive tests were performed at CEA on the flight model (FM) of the Mid-InfraRed IMager (MIRIM) at
cryogenic temperatures and in the infrared. This paper reports on the point spread function (PSF) measurements at 5.6 μm,
the shortest operating wavelength for imaging. At 5.6 μm, the PSF is not Nyquist-sampled, so we use am original technique
that combines a microscanning measurement strategy with a deconvolution algorithm to obtain an over-resolved MIRIM
PSF. The microscanning consists in a sub-pixel scan of a point source on the focal plane. A data inversion method is used
to reconstruct PSF images that are over-resolved by a factor of 7 compared to the native resolution of MIRI. We show that
the FWHM of the high-resolution PSFs were 5 - 10 % wider than that obtained with Zemax simulations. The main cause
was identified as an out-of-specification tilt of the M4 mirror. After correction, two additional test campaigns were carried
out, and we show that the shape of the PSF is conform to expectations. The FWHM of the PSFs are 0.18 - 0.20 arcsec,
in agreement with simulations. 56.1 - 59.2% of the total encircled energy (normalized to a 5 arcsec radius) is contained
within the first dark Airy ring, over the whole field of view. At longer wavelengths (7.7 - 25.5 μm), this percentage is
57 - 68 %. MIRIM is thus compliant with the optical quality requirements. This characterization of the MIRIM PSF, as
well as the deconvolution method presented here, are of particular importance, not only for the verification of the optical
quality and the MIRI calibration, but also for scientific applications.
The present paper describes the different steps leading to the Flight Model integration of the Mid-Infra Red IMager
Optical Bench MIRIM-OB which is part of the scientific payload of the JWST. In order to demonstrate a space
instrument capability to survive the challenging space environment and deliver the expected scientific data, a specific
development approach is applied in order to reduce the high level of risks. The global approach for MIRIM-OB, and the
principal results associated to the two main models, the Structural Qualification Model for vibration and the Engineering
and Test Model for optical performance measured in the infra red at cryogenic temperature will be described in this
paper.
The Molecular Hydrogen Explorer (H2EX) proposed for the 2015 - 2025 Cosmic Vision Call issued by ESA in
2007 was designed to make surveys of the molecular gas from its first rotational lines in various extragalactic and
galactic sites. The design study led to the proposition of a mid-infrared (8 to 29 μm) Imaging Fourier transform
Spectrometer (IFTS) making possible integral field spectroscopy on a 20' wide field and a maximum resolution
up to 3×104 at 10 μm. To reach this goal, an all-mirror payload was outlined, made of a 1.2m telescope matched
to a dual output interferometer, imaging the field on two 1024×1024 Si:As IBC detectors. The payload was
designed to re-use the platform developed for the Planck mission. Such a wide field and high spectral resolution
IFTS on a large spectral domain can have further applications, with the necessary adaptation to each case, for
future large aperture cryogenic telescopes in the mid-infrared, or in the near-infrared behind future ELTs, in a
site like Dome C in Antarctica, and out of astronomy, for remote sensing of Earth atmosphere.
The future ESA space mission Planck Surveyor mission will measure the Cosmic Microwave Background temperature and polarisation anisotropies in a frequency domain comprised between 30GHz and 1THz. On board two instruments, LFI based on HEMT technology and HFI using bolometric detectors. We present the optical solutions adopted for this mission, in particular the focal plane design of HFI, concept which has been applied already to other instruments such as the balloon borne experiment Archeops.
The SUMER (solar ultraviolet measurements of emitted radiation) instrument on the SOHO (solar and heliospheric observatory) satellite is sensitive to the state of polarization of the incident radiation primarily due to two optical elements, the scan mirror and the holographic grating. The angle of incidence of light striking the scan mirror varies from roughly 73.3 to 81.6 degrees (with respect to the mirror normal), which causes the mirror reflectance to be sensitive to the state of polarization of the incident radiation. Therefore, the measurement and characterization of this polarization sensitivity as a function of wavelength was performed using the engineering model optics (scan mirror and grating) and synchrotron radiation, which is nearly 100% linearly polarized, from the SUPERACO (Super Anneau de Collisions d'Orsay) positron storage ring in Orsay, France. The polarization sensitivity or modulation factor of the SUMER instrument was found to be between 0.4 to 0.6, depending on the wavelength and the angle of incidence of light striking the scan mirror, and agrees with the calculated polarization properties based on the measured optical constants for silicon carbide (SiC).
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