M. Gervasi

Foregrounds Removal and CMB Fluctuations in a Multiband Anisotropy Experiment: ARGO 1993

We present the results of a diffuse radiation survey carried out at millimeter and submillimeter wavelengths in the Aries and Taurus sky regions. A balloon-borne telescope with 086 FWHM resolution and four millimeter-wave bands scanned 147 independent sky directions. From the multiband observations we were able to separate two independent components: thermal emission from cirrus dust and cosmic microwave background (CMB) temperature fluctuations. A statistically significant detection of anisotropies is found in the data of the CMB channel: ΔTsky = (24 ± 7) μK rms (95% CL plus 10% calibration error). Assuming uncorrelated Gaussian temperature fluctuations we find a band averaged estimate of the CMB anisotropy power spectrum Cl = (20 ± 9) μK2 at l 110. The data are consistent with anisotropies in a standard Ωb = 0.05, n = 1 model normalized to the rms anisotropy detected by COBE Differential Microwave Radiometers.

New far infrared and millimetric telescopes for differential measurements with a large chopping angle in the sky

The optical design of two Cassegrain-type telescopes of 1200- and 2500-mm primary mirrors has been studied by wobbling subreflectors to obtain differential measurements in wavelengths ranging from 300 microm to 2 mm of the spectrum. Wide chopping angles in the sky have been reached in spite of the large apertures and high secondary magnifications. Diffraction-limited performances are maintained by tilting the secondary mirror around the primary focus. This work is included in the TIR (Telescopio InfraRosso) project.

A short-wavelength measurement of the cosmic background radiation anisotropy

The results of a measurement of the cosmic microwave background (CMB) anisotropy at wavelengths between 0.4 and 2 mm, carried out using a balloon-borne 1.2 m telescope, are reported. A high Galactic latitude region about 15 deg wide with a 25 arcmin FWHM beam, switching in the sky with an amplitude of 108 arcmin, was observed. A sky signal correlated with the 100-micron diffuse emission mapped by the IRAS satellite was detected and used for calibration. After removal of this contribution, the residual intensity fluctuations give an upper limit to the anisotropy of the CMB at an equivalent frequency of 9.0/cm. 17 refs.

The BOOMERANG experiment

The BOOMERANG (Balloon Observations Of Millimetric Extragalactic RAdiation aNd Geophysics) experiment is an international effort to measure the Cosmic Microwave Background (CMB) anisotropy on angular scales of 20′ to 4°, with unprecedented sensitivity, sky and spectral coverage. The telescope will be flown from Antarctica by NASA-NSBF with a long duration stratospheric balloon (7–14 days), and is presently scheduled for flight in 1995–1996. The experiment is designed to produce an image of the Cosmic Microwave Background with high sensitivity and large sky coverage. These data will tightly constrain the baryon density, the reionization history, and the formation of large-scale structure in the universe. BOOMERANG will test technologies and return science data that are essential to the design of a future space-borne mission to map CMB anisotropy.

The BaR-SPOrt experiment

BaR-SPOrt (Balloon-borne Radiometer for Sky Polarization Observations) is an experiment to measure the linearly polarized emission of sky patches aboard a long duration stratospheric balloon. It consists of high sensitivity correlation polarimeters operating in the millimeter wavelength region and coupled to a telescope to obtain a sub-degree angular resolution for direct measurements of the Q and U Stokes parameters. This project shares most of the know-how and sophisticated technology developed for the SPOrt experiment aboard the International Space Station. The instrument design, the various solutions to reduce the systematics and the observing strategy are here described.

The SPOrt experiment

SPOrt is a space experimental aimed at studying the polarization of the CMB and of the diffused Galactic Background in the microwave range (22-90 GHz). Here we present the project as well as its main scientific goals.

A balloon borne millimetric telescope: experimental study of the thermal gradients on the primary mirror

Abstract We describe the results of an experiment carried out at balloon altitude in order to monitor the presence of thermal gradients on the surface of the aluminum primary mirror of a Cassegrain telescope.

The TIR project: A balloon telescope for the measurement of CBR anisotropies

We describe the TIR telescope: a 2.6 m telescope which can be carried to balloon altitude, to perform far infrared (FIR) and millimetric (mm) observations. The telescope has been optimized for the search of Cosmic Background Radiation (CBR) Anisotropies and of faint, diffuse mm and FIR sources. We illustrate the scientific problems which this system can deal with and the technical solutions which were considered during the project. Flight experience with a smaller (1.2 m) prototype (the ARGO 1989 telescope) is also described.

Far infrared multi-frequency observation of interstellar dust clouds

Abstract Diffuse interstellar dust emission at wavelengths between 0.5 and 2 mm has been detected by the ARGO 1993 balloon borne telescope. The instrument scanned the Galactic plane in Aquila and several cirrus clouds in Aries, Taurus and Hercules. The data are spatially consistent with the IRAS 100 μm sky maps, and the spectral behaviour is consistent with a single temperature thennal spectrum with Td ∼ 21 K and a spectral index of emissivity α ∼ 1.5.

TheARGO project: Scientific targets, first results and future perspectives

SummaryThe ARGO program consists of a balloon-borne mm and sub-mm telescope, devoted to the observation of diffuse radiation in the wavelength range between 2 mm and 300 μm, at angular scales between 10′ and 5°. We review here the impact of such observations in different fields ranging from Atmospheric Physics to Cosmology. We also quote the results obtained from ARGO’s first flight in 1989, and we describe the improved version of ARGO we are currently developing.