TRIS I: Absolute Measurements of the Sky Brightness Temperature at 0.6, 0.82 and 2.5 GHz

TL;DR

This paper presents absolute measurements of sky brightness temperature at 0.6, 0.82, and 2.5 GHz using a specialized radiometer system to analyze the contributions of Galactic, cosmic, and extragalactic sources.

Contribution

The study introduces TRIS, a new radiometer system with geometrically scaled antennas, for precise sky temperature measurements at multiple frequencies to disentangle different radiation components.

Findings

Measured sky temperature at three frequencies along a specific declination.

Analyzed the relative contributions of Galactic, CMB, and extragalactic sources.

Provided data to improve models of diffuse sky radiation.

Abstract

At frequencies close to 1 GHz the sky diffuse radiation is a superposition of radiation of Galactic origin, the 3 K Relic or Cosmic Microwave Background Radiation, and the signal produced by unresolved extragalactic sources. Because of their different origin and space distribution the relative importance of the three components varies with frequency and depends on the direction of observation. With the aim of disentangling the components we built TRIS, a system of three radiometers, and studied the temperature of the sky at $\nu =0.6$, $\nu = 0.82$ and $\nu = 2.5$ GHz using geometrically scaled antennas with identical beams (HPBW = $18^{\circ} \times 23^{\circ}$). Observations included drift scans along a circle at constant declination $\delta=+42^{\circ}$ which provided the dependence of the sky signal on the Right Ascension, and absolute measurement of the sky temperature at selected points along the same scan circle. TRIS was installed at Campo Imperatore (lat. = $42^{\circ}~26'$ N, long.= $13^{\circ}~33'$, elevation = 2000 m a.s.l.) in Central Italy, close to the Gran Sasso Laboratory.