PLATO stands for PLAnetary Transits and Oscillation of stars and is a Medium sized mission selected as M3 by the
European Space Agency as part of the Cosmic Vision program. The strategy behind is to scrutinize a large fraction of the
sky collecting lightcurves of a large number of stars and detecting transits of exo-planets whose apparent orbit allow for
the transit to be visible from the Earth. Furthermore, as the transit is basically able to provide the ratio of the size of the
transiting planet to the host star, the latter is being characterized by asteroseismology, allowing to provide accurate
masses, radii and hence density of a large sample of extra solar bodies. In order to be able to then follow up from the
ground via spectroscopy radial velocity measurements these candidates the search must be confined to rather bright stars.
To comply with the statistical rate of the occurrence of such transits around these kind of stars one needs a telescope with
a moderate aperture of the order of one meter but with a Field of View that is of the order of 50 degrees in diameter. This
is achieved by splitting the optical aperture into a few dozens identical telescopes with partially overlapping Field of
View to build up a mixed ensemble of differently covered area of the sky to comply with various classes of magnitude
stars. The single telescopes are refractive optical systems with an internally located pupil defined by a CaF2 lens, and
comprising an aspheric front lens and a strong field flattener optical element close to the detectors mosaic. In order to
continuously monitor for a few years with the aim to detect planetary transits similar to an hypothetical twin of the Earth,
with the same revolution period, the spacecraft is going to be operated while orbiting around the L2 Lagrangian point of
the Earth-Sun system so that the Earth disk is no longer a constraints potentially interfering with such a wide field
continuous uninterrupted survey.
The Euclid Imaging Channels Instrument of the Euclid mission is designed to study the weak gravitational lensing
cosmological probe. The combined Visible and Near Infrared imaging channels will be controlled by a common data
handling unit (PDHU), implementing onboard the instrument digital interfaces to the satellite. The PDHU main
functionalities include the scientific data acquisition and compression, the instrument commanding and control and the
instrument health monitoring. Given the high data rate and the compression needs, an innovative architecture, based on
the use of several computing and interface modules, considered as building blocks of a modular design will be presented.
The Euclid dark energy mission is currently competing in ESA's Cosmic Vision program. Its imaging instrument,
which has one visible and one infrared channel, will survey the entire extragalactic sky during the 5 year mission.
The near-infrared imaging photometer (NIP) channel, operating in the ~0.92 - 2.0 μm spectral range, will be
used in conjunction with the visible imaging channel (VIS) to constrain the nature of dark energy and dark
matter. To meet the stringent overall photometric requirement, the NIP channel requires a dedicated on-board
flat-field source to calibrate the large, 18 detector focal plane.
In the baseline concept a 170 mm Spectralon diffuser plate, mounted to a pre-existing shutter mechanism
outside the channel, is used as a flat-field calibration target, negating the need for an additional single-point-failure
mechanism. The 117 × 230 mm focal plane will therefore be illuminated through all of the channel's
optical elements and will allow flat-field measurements to be taken in all wavelength bands. A ring of low power
tungsten lamps, with custom reflecting elements optimized for optical performance, will be used to illuminate
the diffuser plate.
This paper details the end-to-end optical simulations of this concept, a potential mechanical implementation
and the initial tests of the proposed key components.
The NIP is a near infrared imaging photometer that is currently under investigation for the Euclid space mission
in context of ESA's 2015 Cosmic Vision program. Together with the visible camera (VIS) it will form the basis of
the weak lensing measurements for Euclid. The NIP channel will perform photometric imaging in 3 near infrared
bands (Y, J, H) covering a wavelength range from ~ 0.9 to 2 μm over a field of view (FoV) of ~ 0.5 deg<sup>2</sup>. With
the required limiting point source magnitude of 24 mAB (5 sigma) the NIP channel will be used to determine
the photometric redshifts of over 2 billion galaxies collected over a wide survey area of 20 000 deg<sup>2</sup>. In addition
to the photometric measurements, the NIP channel will deliver unique near infrared (NIR) imaging data over
the entire extragalactic sky, enabling a wide variety of ancillary astrophysical and cosmological studies. In this
paper we will present the results of the study carried out by the Euclid Imaging Consortium (EIC) during the
Euclid assessment phase.
Euclid is an ESA Cosmic Vision wide-field space mission concept dedicated to the high-precision study of Dark Energy
and Dark Matter. The mission relies on two primary cosmological probes: Weak gravitational Lensing (WL) and Baryon
Acoustic Oscillations (BAO).
The first probe requires the measurement of the shape and photometric redshifts of distant galaxies. The second probe is
based on the 3-dimensional distribution of galaxies through spectroscopic redshifts. Additional cosmological probes are
also used and include cluster counts, redshift space distortions, the integrated Sachs-Wolfe effect (ISW) and galaxy
clustering, which can all be derived from a combination of imaging and spectroscopy.
Euclid Imaging Channels Instrument of the Euclid mission is designed to study the weak gravitational lensing
cosmological probe. The combined Visible and Near InfraRed imaging channels form the basis of the weak lensing
measurements. The VIS channel provides high-precision galaxy shape measurements for the measurement of weak
lensing shear. The NIP channel provides the deep NIR multi-band photometry necessary to derive the photometric
redshifts and thus a distance estimate for the lensed galaxies.
This paper describes the Imaging Channels design driver requirements to reach the challenging science goals and the
design that has been studied during the Cosmic Vision Assessment Phase.
The Euclid mission is currently being developed within the European Space Agency's Cosmic Vision Program.
The five year mission will survey the entire extragalactic sky (~ 20 000 deg<sup>2</sup>) with the aim of constraining the
nature of dark energy and dark matter. The spacecraft's payload consists of two instruments: one imaging
instrument, which has both a visible and a near-infrared channel, and one spectroscopic instrument operating in
the near-infrared wavelength regime. The two channels of the imaging instrument, the Visible Imaging Channel
(VIS) and the Near-Infrared Imaging Photometer Channel (NIP), will focus on the weak lensing science probe.
The large survey area and the need to not only image each patch of sky in multiple bands, but also in multiple
dithers, requires over 640 000 operations of the NIP channel's filter wheel mechanism. With a 127 mm diameter
and a mass of ~ 330 g per element, these brittle infrared filters dictate highly demanding requirements on this
single-point-failure mechanism. To accommodate the large filters the wheel must have an outer diameter of
~ 400 mm, which will result in significant loads being applied to the bearing assembly during launch.
The centrally driven titanium filter wheel will house the infrared filters in specially designed mounts. Both
stepper motor and brushless DC drive systems are being considered and tested for this mechanism. This paper
presents the design considerations and details the first prototyping campaign of this mechanism. The design and
finite element analysis of the filter mounting concept are also presented.
FIFI-LS is a Field-Imaging Line Spectrometer designed for the SOFIA airborne observatory. The instrument will
operate in the far infrared (FIR) wavelength range from 42 to 210 μm. Two spectrometers operating between
42-110 μm and 110-210 μm allow simultaneous and independent diffraction limited 3D imaging over a field of
view of 6" × 6" and 12" × 12" respectively. We have developed a telescope simulator to test the imaging and
spectral performance of FIFI-LS in the FIR. Here, we present the telescope simulator as well as the performance
verification of FIFI-LS using the simulator. Finally we compare the measurements with the theoretical expected
performance of FIFI-LS.
<i>FIFI LS</i> is a far-infrared integral field spectrometer for the SOFIA airborne observatory. The instrument is designed to maximize the observing efficiency by simultaneous and nearly independent imaging of the field-of-view in two medium spectral resolution bands. We present a summary of the <i>FIFI LS</i> design and the current status of instrument development. Its unique features as the large far-infrared photoconductor detectors, its integral field concept, and control system will be highlighted. Special attention will be given to the Extended Observing Opportunity Program, which will allow general access to <i>FIFI LS</i> on SOFIA.
Fluorescence microtomography is a hard x-ray scanning microscopy technique that has been developed at synchrotron radiation sources in recent years. It allows one to reconstruct non-destructively the element distribution on a virtual section inside a sample. The spatial resolution of this microbeam technique is limited by the lateral size of the microbeam. Since recently, nanofocusing refractive x-ray lenses (NFLs) are under development that were shown to produce hard x-ray microbeams with lateral resolution in the range of 100nm. Future improvements of these optics might reduce the microbeam size down to below 20nm. Using nanofocusing lenses, fluorescence microtomography with sub-micrometer resolution was performed. As an example, the element distribution inside a small cosmic dust particle is given. Tomographic reconstruction was done using a refined model including absorption effects inside the sample.