Fabrizio Villa

THE BACKGROUND EMISSION ANISOTROPY SCANNING TELESCOPE (BEAST) INSTRUMENT DESCRIPTION AND PERFORMANCES

The Background Emission Anisotropy Scanning Telescope (BEAST) is a millimeter wavelength experiment designed to generate maps offluctuations inthecosmicmicrowave background (CMB). The telescope is composed of an off-axis Gregorian optical systemwith a 2.2 mprimary thatfocuses the collected microwave radiation onto an array of cryogenically cooled high electron mobility transistor (HEMT) receivers. This array is composed of six corrugated scalar feed horns in the Q band (38 to 45 GHz) and two more in the Ka band (26 to 36 GHz) with one of the six Q-band horns connected to an ortho-mode transducer for extraction of both polarizations incident on the

A Map of the Cosmic Microwave Background from the BEAST Experiment

We present the first sky maps from the BEAST (Background Emission Anisotropy Scanning Telescope) experiment. BEAST consists of a 2.2 m off-axis Gregorian telescope fed by a cryogenic millimeter wavelength focal plane currently consisting of six Q band (40 GHz) and two Ka band (30 GHz) scalar feed horns feeding cryogenic HEMT amplifiers. Data were collected from two balloon-borne flights in 2000, followed by a lengthy ground observing campaign from the 3.8 km altitude University of California White Mountain Research Station. This paper reports the initial results from the ground-based observations. The instrument produced an annular map covering the sky over 33? < ? < 42?. The maps cover an area of 2470 deg2 with an effective resolution of 23 FWHM at 40 GHz and 30 at 30 GHz. The map rms (smoothed to 30 and excluding Galactic foregrounds) is 57 ? 5 ?K (Rayleigh-Jeans) at 40 GHz. Comparison with the instrument noise and correcting for 5% atmospheric attenuation gives a cosmic signal rms contribution of 29 ? 3 ?K (R-J) or 30 ? 3 ?K relative to a Planck blackbody of 2.7 K. An estimate of the actual cosmic microwave background (CMB) sky signal requires taking into account the l space filter function of our experiment and analysis techniques, carried out in a companion paper. In addition to the robust detection of CMB anisotropies, we find a strong correlation between small portions of our maps and features in recent H? maps. In this work we describe the data set and analysis techniques leading to the maps, including data selection, filtering, pointing reconstruction, mapmaking algorithms, and systematic effects.

The Optical Design of the Background Emission Anisotropy Scanning Telescope (BEAST)

We present the optical design of the Background Emission Anisotropy Scanning Telescope (BEAST), an offaxis Gregorian telescope designed to measure the angular distribution of the cosmic microwave background radiation (CMBR)at30and 41.5 GHzonangularscalesrangingfrom 20 0 to10 � .Theapertureof thetelescope is1.9m, and our design meets the strict requirements imposed by the scientific goals of the mission: the beam size is 20 0 at 41.5 GHz and 26 0 at 30 GHz, while the illumination at the edge of the mirrors is lower than � 30 dB for the central horn.Theprimarymirror isanoff-axissectionofaparaboloid,andthesecondaryanoff-axissectionofanellipsoid.A spinning flat mirror located between the sky and the primary provides a two-dimensional chop by rotating the beams around an ellipse on the sky. BEAST uses a receiver array of cryogenic low noise InP High Electron Mobility Transistor (HEMT) amplifiers. The baseline array has seven horns matched to one amplifier each and one horn matchedtotwoamplifiers(twopolarizations)foratotalofnineamplifiers.Twohornsoperatearound30GHz,andsix operate around 41.5 GHz. Subsequent campaigns will include 90 GHz and higher frequency channels. Subject heading gs: cosmic microwave background — cosmology: observations — telescopes

The Cosmic Foreground Explorer (COFE): A balloon-borne microwave polarimeter to characterize polarized foregrounds

The COsmic Foreground Explorer (COFE) is a balloon-borne microwave polarimeter designed to measure the low-frequency and low-‘ characteristics of dominant diffuse polarized foregrounds. Short duration balloon flights from the Northern and Southern Hemispheres will allow the telescope to cover up to 80% of the sky with an expected sensitivity per pixel better than 100 lK/deg 2 from 10 GHz to 20 GHz. This is an important effort toward characterizing the polarized foregrounds for future CMB experiments, in particular the ones that aim to detect primordial gravity wave signatures in the CMB polarization angular power spectrum. 2006 Elsevier B.V. All rights reserved.

Low-frequency instrument of Planck

The main scientific object of the Planck ESA (European Space Agency) mission is the imaging of the anisotropies of the Cosmic Microwave Background (CMB) over the whole sky, with unprecedented sensitivity and angular resolution. This target will be achieved by the synergic performance of the two instruments onboard: the High Frequency Instrument (HFI) and the Low Frequency Instrument (LFI). The first is composed of 48 bolometers observing in six spectral bands from 100 GHz to 857 GHz; the latter is an array of 46 radiometers covering four microwave bands from 30 to 100 GHz. A description of the Low Frequency Instrument, together with its characteristics and performance, is reported in this paper.

The White Mountain Polarimeter Telescope and an Upper Limit on Cosmic Microwave Background Polarization

The White Mountain Polarimeter (WMPol) is a dedicated ground-based microwave telescope and receiver system for observing polarization of the cosmic microwave background. WMPol is located at an altitude of 3880 m on a plateau in the White Mountains of Eastern California, at the Barcroft Facility of the University of California White Mountain ResearchStation.Presentedhereisadescriptionof theinstrumentandthedatacollectedduring2004AprilthroughOctober. We set an upper limit on E-mode polarization of 14� K (95% confidence limit) in the multipole range 170 < l < 240. This result was obtained with 422 hr of observations of a 3 deg 2 sky area about the North Celestial Pole, using a 42 GHz

Planck low-frequency instrument: a study on the performances of the Planck millimeter space telescope coupled with LFI feed horns

PLANCK represents the third generation of mm-wave instruments designed for space observations of Cosmic Microwave Background anisotropies within the new Cosmic Vision 2020 ESA Science Programme. The PLANCK survey will cover the whole sky with unprecedented sensitivity, angular resolution, and frequency coverage. The expected scientific return will be enormous, both for the cosmological constraints that will be set and for the gold mine of information contained in the astrophysical foregrounds. To reach these ambitious scientific goals, the control of systematic effects is mandatory and a careful instrument design is needed, as well as an accurate knowledge of instrumental characteristics. The Low Frequency Instrument (LFI), operating in the 30 ÷ 70 GHz range, is one of the two instruments onboard PLANCK Satellite, sharing the focal region of a 1.5 meter off-axis dual reflector telescope together with the High Frequency Instrument (HFI) operating at 100 ÷ 857 GHz. We present a detailed study carried out by the LFI team on the performances of the PLANCK telescope coupled with LFI feed horns, both in the main beam and in the sidelobe region.

Trade - off between angular resolution and straylight contamination in CMB anisotropy experiments. 2. Straylight evaluation

The last generation of CMB anisotropy experiments operating either from space, like the WMAP and PLANCK satellite, from the atmosphere, such as balloons, or from the ground, like interferometers, make use of complex multi-frequency instruments at the focus of meter class telescopes to allow the joint study of CMB and foreground anisotropies, necessary to achieve an accurate component separation. Between ∼70 GHz and ∼300 GHz, where foreground contamination is minimum, it is extremely important to reach the best trade-off between the improvement of the angular resolution, necessary for measuring the high order acoustic peaks of CMB anisotropy, and the minimization of the straylight contamination mainly due to the Galactic emission. This is one ol the most critical systematic effects at large and intermediate angular scales (i.e. at multipoles f less than 100) and consists in unwanted radiation entering the beam at large angles from the direction of the antenna boresight direction. We consider here the 30 and 100 GHz channels of the PLANCK Low Frequency Instrument (LFI). Assuming the nominal PLANCK scanning strategy, we evaluate the straylight contamination introduced by the most relevant Galactic foreground components for a reference set of optical configurations, accurately simulated as described in Sandri et al. (2004, A&A, 428, 299) (hereafter Paper 1). Given the overall constraints to the LFI optical design, we show that it is possible to improve the angular resolution by 5-7% by keeping the overall peak-to-peak signal of the Galaxy straylight contamination (GSC) below the level of few μK (and about 10 times smaller in terms of rms). A comparison between the level of straylight introduced by the different Galactic components for different beam regions (intermediate and far beam) is presented. We provide approximate relations, both for the intermediate and the far beam, for the rms and the peak-to-peak levels of the GSC as functions of the corresponding contributions to the integrated beam or of the spillover. For some reference cases we compare the results based on Galactic foreground maps derived from radio, IR, and Hα templates with those based on WMAP maps including CMB and extragalactic source fluctuations. The implications for the GSC in the PLANCK LFI polarization data are discussed. Finally, we compare the results obtained at 100 GHz with those at 30 GHz, where the GSC is more critical.

Sources variability with Planck LFI

Planck LFI (Low Frequency Instrument) will produce a complete survey of the sky at millimeter wavelengths. Data stream analysis will provide the possibility to reveal unexpected millimeter sources and to study their flux evolution in time at different frequencies. We describe here the main implications and discuss data analysis methods. Planck sensitivities typical for this kind of detection are taken into account. We present also preliminary results of our simulation activity.

ATHENA X-IFU thermal filters development status toward the end of the instrument phase-A

The X-ray Integral Field Unit (X-IFU) is one of the two instruments of the Athena astrophysics space mission approved by ESA in the Cosmic Vision 2015-2025 Science Programme. The X-IFU consists of a large array of transition edge sensor micro-calorimeters that will operate at ~100 mK inside a sophisticated cryostat. A set of thin filters, highly transparent to X-rays, will be mounted on the opening windows of the cryostat thermal shields in order to attenuate the IR radiative load, to attenuate radio frequency electromagnetic interferences, and to protect the detector from contamination. Thermal filters are critical items in the proper operation of the X-IFU detector in space. They need to be strong enough to survive the launch stresses but very thin to be highly transparent to X-rays. They essentially define the detector quantum efficiency at low energies and are fundamental to make the photon shot noise a negligible contribution to the energy resolution budget. In this paper, we review the main results of modeling and characterization tests of the thermal filters performed during the phase A study to identify the suitable materials, optimize the design, and demonstrate that the chosen technology can reach the proper readiness before mission adoption.