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Abstract. In the context of the COBRAS/SAMBA mission study 1 , we discuss in-flight calibration of extended sky maps of the microwave sky using celestial sources. We simulate the observations in order to assess the accuracy obtainable for absolute and relative calibration of the Low Frequency Instrument (LFI), operating in the 30 − 130 GHz range. Accurate calibration can be achieved using the CMB dipole signal, ∆T D . With conservative assumptions on the effect of Galactic contamination, we find that the CMB dipole will provide absolute calibration accuracy ∼ 0.7% (limited by the COBE-DMR uncertainty on ∆T D ) on time-scales of about 10 days at all frequencies and for the entire mission lifetime. Long-term calibration with accuracy < 0.2% can be obtained using the spacecraft orbital velocity. Additional, independent calibration will be provided by the observation of external planets. We also describe the capability of the proposed scanning technique to detect and remove long-term instrumental drifts, and show that these effects, if present, can be controlled and removed with an overall negligible impact on the data uncertainty.

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We study tilted cold dark matter (CDM) models, that is OMEGA0 = 1 models with a primordial spectral index n less than or similar to 1. We test these models against three experiments on the cosmic microwave background anisotropy at 7', 3-degrees, and 6-degrees, and against measurements of galaxy peculiar velocities on large scales. These observations together suggest that the whole class of tilted CDM models with n less-than-or-equal-to 1 can be ruled out, for any value of the biasing parameter b

Sugar alcohols have interesting thermodynamic properties that make them good options as heat storage materials (HSMs) to be used in solar cookers. Among sugar alcohols, xylitol is affected by severe supercooling that can significantly alter its usefulness in thermal energy storage (TES) systems. To overcome the supercooling issue, in this work the thermal behavior of a xylitol-based TES installed in a portable solar box cooker was investigated experimentally. The solar cooker has a 4.08 concentration ratio and the TES is a double-pot system filled with 2.5 kg of commercial-grade xylitol. The TES includes a manual mixing device that can be used to trigger the nucleation of xylitol. The effectiveness of the TES system with and without triggering was assessed through several outdoor tests, divided into heating and cooling phases, using silicone oil as absorbing media. It was found that the average load cooling time, in the temperature range of the test fluid from 110 to 80∘C, increased by about 346% when the solar cooker was equipped with the xylitol-triggered TES. The mixing device can therefore be considered an effective solution for regarding xylitol as an actual and performing phase change material.

We test tilted hybrid models against the results of the Owens Valley\ud Radio Observatory, Advanced Cosmic Microwave Explorer, and ULISSE\ud experiments on cosmic microwave background (CMB) anisotropy. We analyze\ud the data using three different statistics (the chi$^{2$, the\ud likelihood ratio, and the Bayesian analyses), and we discuss if and when\ud we get compatible upper limits to the anisotropy. We found stable\ud results only by performing a combined analysis of the three experiments.\ud In this case the differential, single-subtracted, CMB anisotropy at 3\ud deg is bounded to be equal to or less than 34 micro K. This implies an\ud upper limit to the primordial spectral index: n equal to or less than\ud 0.7, or n equal to or less than 0.8 if we consider the presence of a\ud possible gravitational wave background. We also consider the Schuster et\ud al. full-band data set, which suggests an anisotropy of\ud 26$^+18$$_-12$ micro K (at the 90\% confidence level).\ud This would imply n approximately = 0.5, or n approximately = 0.6 (with\ud gravitational waves), and at the 95\% confidence level n equal to or less\ud than 0.9, or n equal to or less than 1 (with gravitational waves). We\ud stress that these estimates of n are basically independent of the\ud relative fraction of cold and hot dark matter.\ud

Abstract. -Decisive progress in cosmology is expected from a space mission dedicated to an extensive mapping of the Cosmic Microwave Background (CMB) with high angular and temperature sensitivity. Based on the European Space Agency COBRAS/SAMBA mission concept, we have studied the attainable sensitivity and sky coverage taking into account the effect of solar-system sources for the two far-Earth candidate orbits (Lagrangian points Moon-Earth L5 and Sun-Earth L2). We also take into account the microwave emission of the Galaxy in limiting the useful sky coverage. Our results provide a quantitative assessment of the relative observational merits of the two orbit options, and show that the Sun-Earth L2 orbit allows significantly better observational conditions.