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The Low Frequency Instrument aboard the Planck satellite will employ pseudo-correlation radiometers, operating over three broad bands centered at 30, 44, 70GHz. This choice is oriented to maximize the instrumental stability reducing non-white noise effects produced inside the radiometers. The radiometer scheme allows the simultaneous comparison of two input signals, one coming from the telescope and the other coming from a reference blackbody (the "reference load" RL) at a stable temperature near 4 K. In order to minimize non-white noise, typically exhibiting a I If spectrum, the Reference Load temperature must be as close as possible to the sky temperature (about 2.7 K). The accuracy of the measurement is tightly related to the ability of keeping under control and minimizing all systematic effects potentially. perturbing the RL signal, particularly those not easily removable in software during data analysis. A model of the,radiometer and RL system interface, based on the finite elements method, has been developed, together with a detailed thermal modeling, to characterize the physical system and to optimize its performance. The function of the radiometric chain, the modeling and the changes made in the baseline configuration to improve the system performances are described. The impact of systematic effects on the optimized configuration are also quantitatively investigated. (C) 2003 Elsevier B.V. All rights reserved.

The LFI radiometers use a pseudo-correlation design where the signal from the sky is continuously compared with a stable reference signal, provided by a cryogenic reference load system. The reference unit is composed by small pyramidal horns, one for each radiometer, 22 in total, facing small absorbing targets, made of a commercial resin ECCOSORB CR (TM), cooled to approximately 4.5 K. Horns and targets are separated by a small gap to allow thermal decoupling. Target and horn design is optimized for each of the LFI bands, centered at 70, 44 and 30 GHz. Pyramidal horns are either machined inside the radiometer 20K module or connected via external electro-formed bended waveguides. The requirement of high stability of the reference signal imposed a careful design for the radiometric and thermal properties of the loads. Materials used for the manufacturing have been characterized for thermal, RF and mechanical properties. We describe in this paper the design and the performance of the reference system., This is an author-created, un-copyedited version of an article accepted for publication in JINST. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher authenticated version is available online at [10.1088/1748-0221/4/12/T12006]. 14 pages, 34 figures

We study from the point of view of quantum logic the properties of the collective oscillations of a linear chain of ions trapped in a linear Paul trap and composed of two ion species. We discuss extensively sympathetic cooling of the chain and the effect of anharmonicity on laser-cooling and quantum-information processing.

A cooled telescope for astronomical infrared observations at balloon altitudes in the range 2–5 μm was successfully flown on June 12–13, 1995 from the NASA/NSBF base at Palestine, Texas. A cylindrical cryostat (42 cm in diameter, 120 cm high), housing the optics and the detector, was cooled by using liquid He as the refrigerating fluid. During the 11 h flight, the temperatures of the detector, optics, and internal telescope subparts were regulated between 45 and 80 K with very good stability. The cryogenics were controlled by a pressure control equipment designed to operate at both ground level and at 40 km altitude. Further thermal stabilization of the focal plane detector array was provided by a dedicated servocontrol to obtain a stability of ±0.02 K over time scales of a few minutes. The main features of the telescope, as well as on‐ground and in‐flight performances of the cryogenic system are described.

A cooled telescope (250 mm, F/2) has been designed and prepared for measurements of both local and cosmological Near Infrared backgrounds in the waveband 1–5 μm at balloon altitudes (40 km). The separation of various foreground contributions should be possible by applying observing strategies based on multiple sky scans with different filters. The whole apparatus will be tested in flight by using a detection system based on a linear array of 32 InSb pixels cryogenically cooled and thermally controlled at 52 K. The instrument sensitivity will allow the measurement of most of the local backgrounds. The focal plane could be easily re-arranged to house bidimensional array detectors cooled down to ∼ 35 K with performance improvements of a factor at least 100 ÷ 200. A description is given of the main characteristics of the instrument (optics, cryostat, detector), of the control subsystems (cryogenics, pointing systems, electronics, ground equipment) and of the expected performance based on laboratory test results.

24 páginas, 16 figuras, 5 tablas.-- et al., This paper provides an overview of the Low Frequency Instrument (LFI) programme within the ESA Planck mission. The LFI instrument has been developed to produce high precision maps of the microwave sky at frequencies in the range 27–77 GHz, below the peak of the cosmic microwave background (CMB) radiation spectrum. The scientific goals are described, ranging from fundamental cosmology to Galactic and extragalactic astrophysics. The instrument design and development are outlined, together with the model philosophy and testing strategy. The instrument is presented in the context of the Planck mission. The LFI approach to ground and inflight calibration is described. We also describe the LFI ground segment. We present the results of a number of tests demonstrating the capability of the LFI data processing centre (DPC) to properly reduce and analyse LFI flight data, from telemetry information to calibrated and cleaned time ordered data, sky maps at each frequency (in temperature and polarization), component emission maps (CMB and diffuse foregrounds), catalogs for various classes of sources (the Early Release Compact Source Catalogue and the Final Compact Source Catalogue). The organization of the LFI consortium is briefly presented as well as the role of the core team in data analysis and scientific exploitation. All tests carried out on the LFI flight model demonstrate the excellent performance of the instrument and its various subunits. The data analysis pipeline has been tested and its main steps verified. In the first three months after launch, the commissioning, calibration, performance, and verification phases will be completed, after which Planck will begin its operational life, in which LFI will have an integral part., The Planck-LFI project is developed by an International Consortium led by Italy and involving Canada, Finland, Germany, Norway, Spain, Switzerland, UK and USA. The Italian contribution to Planck is supported by the Agenzia Spaziale Italiana (ASI) and INAF. We also wish to thank the many people of the Herschel/Planck Project and RSSD of ESA, ASI, THALES Alenia Space Industries and the LFI Consortium that have contributed to the realization of LFI. We are grateful to our HFI colleagues for such a fruitful collaboration during so many years of common work. The German participation at the Max-Planck-Institut für Astrophysik is funded by the Bundesministerium für Wirtschaft und Technologie through the Raumfahrt- Agentur of the Deutsches Zentrum für Luft- und Raumfahrt (DLR) [FKZ: 50 OP 0901] and by the Max-Planck-Gesellschaft (MPG). The Finnish contribution is supported by the Finnish Funding Agency for Technology and Innovation (Tekes) and the Academy of Finland. The Spanish participation is funded by Ministerio de Ciencia e Innovacion through the project ESP2004-07067-C03 and AYA2007-68058-C03. The UK contribution is supported by the Science and Technology Facilities Council (STFC). C. Baccigalupi and F. Perrotta acknowledge partial support of the NASA LTSA Grant NNG04CG90G.

We present here a ballon-borne experiment to measure the near-infrared cosmological background in the (1÷5) μm range. The instrument, a liquid helium cooled telescope (250 mm,F/2), was built in the infrared laboratory of Istituto TE.S.R.E./C.N.R.-Bologna (Italy) collaboration with the Haverford College (PA-U.S.A.). It will be launched from the NSBF base of Palestine (Texas-U.S.A.) in May 1989.

The Low Frequency Instrument (LFI) on-board the Planck satellite, is composed by an array of 54 receivers. They follow a pseudo-correlation scheme, continuously observing the sky and a stable reference load, at a temperature T∼4 K. The so-called 4 K Reference Load is made of 54 small absorbing targets, mechanically and thermally connected to the High Frequency Instrument (HFI) cryostat. The 4K Reference Load requirements pose severe limits to its mass, dimensions, power dissipation and performance.

We report on a balloon-borne experiment to measure high altitude atmospheric emission in the 90 GHz spectral window. The experiment was carried out with a monolithic microwave integrated circuit (MMIC) Dicke-switched radiometer based on high electron mobility transistor (HEMT) low noise amplifiers. The instrument broad bandpass (87–101 GHz) includes strong ozone lines. The atmospheric emission profile was measured from 6 to 15 km altitude. In addition, zenith-scan measurements at about 38 km altitude have been obtained, yielding an atmospheric antenna temperature T A , atm = 15 ± 6 mK. The results are in good agreement with model predictions which take into account the contribution of O 3 spectral lines. Ozone emission contributes significantly to the signal of balloon-borne Cosmic Microwave Background experiments unless the instrument bands are carefully selected.

A cooled telescope (250 mm, F/2) has been designed and prepared for measurements of both local and cosmological Near Infrared backgrounds in the waveband 1–5 μm at balloon altitudes. The separation of various foreground contributions should be possible by applying observing strategies based on multiple sky scans with different filters. The whole apparatus will be tested in flight by using a linear array of 32 InSb detectors cryogenically cooled and thermally stabilized at 52 K. The instrument sensitivity will allow the measurement of most of the local backgrounds. A description is given of the flight instrumentation and of the expected performances based on laboratory test results.

We show how combined large-beam infra-red and radio observations toward the Virgo Cluster may be explained by assuming the existence of a large tepid halo surrounding the giant galaxy M87. Such a halo would be able to close the cluster gravitationally. If interpreted as being due to bremmstrahlung radiation by a tepid extended halo, it also explains the infra-red observations, and it has important implications for the physics of M87.

An automated station for the detection of radio bursts at 151 and 408 MHz has been operating at Medicina (Italy) since 1976. Radio data associated with 32 gamma-ray bursts, detected between July 1976 and April 1979, have been analysed. The results will be discussed in the present paper.

One year's data on radio pulse from EAS at three frequencies (46, 65, 110 MHz) from the Medicina array have been analysed. The dominance of the geomagnetic production mechanism is confirmed. The frequency spectrum between 46 and 65 MHz appears to be flat. The detected electric field strength Ev has been considered as a measure of primary particle energy, and its value is correlated to shower size N and particle density rho at 50 and 100 m from the shower axis in order to study AES longitudinal fluctuations. Errors on each measured quantity are discussed, and it is shown that fluctuations are present.

Final results obtained from the array at Medicina on radioemission from extensive air showers are presented. It is shown that, although not in contradiction with theory, the frequency spectrum and the radio lateral distribution cannot provide information about the primary-cosmic-ray composition, because measurements are taken at small core distances and intrinsic errors are large. If we take the electric-field strengthEν as a measure of the primary energyEp, it is shown that fluctuations of ∼100% are found in shower parameters such as the sizeN and the density ϱ100. The data suggest the presence of protons in the primary cosmic-ray flux at ∼1017 eV. Uncertainties in measurements and in radiopulse production mechanisms are discussed and it is shown that this method alone is not as reliable as was previously predicted.

An experiment has been performed at 325 MHz, with a 10 m tracking dish, for the search of pulsed radio emission associated with X-ray pulsars. No evidence of radio pulses has been found in the four sources investigated, although the radio pulsar PSR 0329+54, used as a testing object, has been detected successfully.

Between 1972 and 1975 an international collaborative search was carried out for prompt 10 GHz emission at the onset of supernovae. The motivations and techniques involved in this effort are described, and the results of the three years' work are summarized. No pulses from supernovae were detected, the best upper limit being 4×1043 ergs in a 40 MHz band at 10 GHz for a pulse time-scale ≲0.5 s. Methods for improving this limit are briefly described.

Results of our wide beam radio observations of M87 are given here. Combined with the infrared observations of Virgo (Ceccarelli et al. 1982), we show that in order to explain both the radio and infrared observations, it is convenient to postulate an extended tepid (∼(+5) K ) halo, in addition to a hot (∼(+8) K ) halo surrounding M87. This tepid halo would be able to close the system gravitationally.

An automated system for the detection of bursts of cosmic origin at radio frequencies has been built at Medicina (Bologna). The station, completely independent, is part of a network of observatories based in Ireland, United Kingdom, Switzerland and Italy. The receiving apparatus, operating at 151 and 408 MHz, and the experimental method used to reject unwanted events is described. Observational programmes include a search for the radio counterpart of X-and γ-ray bursts, observations of the galactic centre and Cygnus regions, and a full sky monitoring. Sensitivity limits as well as preliminary results are discussed.

COSMIC bursts of electromagnetic radiation, both isolated and in connection with other impulsive astrophysical phenomena, have been sought for many years1, with only one suggestive positive result2, until, in 1973, the discovery of γ-ray bursts3 of cosmic origin prompted a new series of observations4. In 1975 we started a systematic search for electromagnetic bursts at v.h.f. and u.h.f. The system, based at Medicina (Bologna, Italy), is semi-automatic and assures highly efficient data collection. Simultaneous observations at different frequencies facilitate the evaluation of disturbances of local origin and, hopefully, their isolation. Regular observations started in July 1976, and we report here our detection of a radio burst, which seems to be correlated with a γ-ray burst.

We present results of a measurement of the cosmic background radiation temperature at a wavelength of 6.3 cm. We obtained the value T/sub CBR/ = 2.71 +- 0.20 K. This is in good agreement with, and has a smaller error than, any previous measurement at equal or longer wavelengths.

During 1978 balloon borne infrared experiment we observed a signal coming from Virgo Cluster (see Ceccarelli et al., 1982).

Continuous radio records obtained between July 1976 and May 1979 by automatic radiometers operating at 151 and 408 MHz from Medicina, (Italy), have been scanned for radio pulses associated with gamma ray bursts. Sixty five gamma events have been examined. For none of them a definite association with a particular radio pulse detected within ±10 min from the burst onset has been possible. However, a statistical analysis of the delays between each gamma event and the nearest radio pulse suggests to a 89% confidence level that about 20% of the bursts are associated with a weak radio precursor with flux density ≥10−13 erg/sec cm2 MHz.

New measurements of the cosmic background radiation (CBR) intensity at 4.75 GHz (6.3 cm), made as a part of a large experiment to measure the CBR spectrum between 2.5 and 90 GHz, are reported. The present result, T(CBR) = 2.70 + or - 0.07 K, agrees with, but is substantially more accurate than, that previously reported by Mandolesi et al. (1984). Careful new observations of the emission from the atmosphere and from the Galaxy are also presented and discussed. 17 references.

LBL-18602 Preprint Lawrence Berkeley Laboratory UNIVERSITY O F C A L I F O R N I A Physics Division ReeeIuro LAWRENCE BERKELEY LABmUiTORy O t V l ' 9 1984- Submitted t o The A s t r o p h y s i c a l L e t t e r s t o the E d i t o r Journal, LIBRARY AND DOCUMENTS SECTION LOW-FREQUENCY MEASUREMENTS OF THE COSMIC BACKGROUND RADIATION SPECTRUM G.F. Smoot, G. De Amici, S.D. Friedman, C . W i t e b s k y , G. S i r o n i , G. B o n e l l i , N. Mandolesi, S. C o r t i g l i o n i , G. M o r i g i , R.B. P a r t r i d g e , L. Danese, and G. De Z o t t i November 1984 TWO-WEEK LOAN COPY This is a Library Circulating which may be borrowed Copy for two weeks. Prepared for the U.S. Department of Energy under Contract DE-AC03-76SF00098

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We discuss the dynamics and thermodynamics of systems with weak long-range interactions. Generically, these systems experience a violent collisionless relaxation in the Vlasov regime leading to a (usually) non-Boltzmannian quasi stationary state (QSS), followed by a slow collisional relaxation leading to the Boltzmann statistical equilibrium state. These two regimes can be explained by a kinetic theory, using an expansion of the BBGKY hierarchy in powers of 1/N, where N is the number of particles. We discuss the physical meaning of the different functionals appearing in the analysis: the Boltzmann entropy, the Lynden-Bell entropy, the "generalized" entropies arising in the reduced space of coarse-grained distribution functions, the Tsallis entropy, the generalized H-functions increasing during violent relaxation (not necessarily monotonically) and the convex Casimir functionals used to settle the formal nonlinear dynamical stability of steady states of the Vlasov equation. We show the connection between the different variational problems associated with these functionals. We also introduce a general class of nonlinear mean field Fokker-Planck (NFP) equations that can be used as numerical algorithms to solve these constrained optimization problems., Comment: Chapter of the volume "Dynamics and Thermodynamics of systems with long range interactions: theory and experiments", A. Campa, A. Giansanti, G. Morigi, F. Sylos Labini Eds., American Institute of Physics Conference proceedings, 970 (2008)