A 45-MHz continuum survey of the southern hemisphere

Álvarez, H.; Aparici, J.; May, J.; Olmos, F.

doi:10.1051/aas:1997196

Cited by 52 publications

(43 citation statements)

References 8 publications

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“…Note that (S sys + S sky ) must be evaluated at the same time resolution as the measurements of P r , while DS sky is a single number evaluated by considering the daily variation of the noise over several days, to eliminate effects of interference and anomalous absorption of the sky noise (primarily a problem in Kiruna). DT sky is estimated using published maps of calibrated surveys of the radio-sky at 45 MHz [Maeda et al, 1999;Alvarez et al, 1997]. Values at 45 MHz are reduced by the expected frequency dependence of galactic noise ( f À2.8 ) and by a factor 2 since we receive only a single polarisation [see e.g., Ellington, 2005].…”

Section: Calculation and Cross-calibration Of Pmse Volume Reflectivitiesmentioning

confidence: 99%

Polar mesosphere summer echoes at Wasa, Antarctica (73°S): First observations and comparison with 68°N

Kirkwood

Wolf

Nilsson

et al. 2007

Geophysical Research Letters

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Section: Calculation and Cross-calibration Of Pmse Volume Reflectivitiesmentioning

confidence: 99%

Polar mesosphere summer echoes at Wasa, Antarctica (73°S): First observations and comparison with 68°N

Kirkwood

Wolf

Nilsson

et al. 2007

Geophysical Research Letters

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“…Several sky surveys at different frequencies in the VHF band, established by radio telescopes, were published. Among others, at our knowledge, is a list of these surveys as a function of frequency: 22 MHz (Roger et al, 1999), 38 MHz (Milogradov-Turin andSmith, 1973), 45 MHz (Alvarez et al, 1997), 64 MHz (Hey et al, 1947), 81.1 MHz (Baldwin, 1955, 81.5 MHz (Purton, 1966), 150 MHz (Landecker and Wielebinski, 1970). Beam resolution, declination coverage, or frequency make these surveys more or less adaptable to our data.…”

Section: Calibration Of the Radarsmentioning

confidence: 99%

“…Ionospheric attenuation has a time scale from a few minutes up to several hours (Alvarez et al, 1997), and affects more low frequency radiation and data acquired at low elevation angles. Ionospheric opacity is first controlled by solar activity (linked to the solar spot number), so that nighttime observations are practically free from absorption (Milogradov-Turin and Smith, 1973).…”

Section: Main Difficultiesmentioning

confidence: 99%

A partial 45 MHz sky temperature map obtained from the observations of five ST radars

et al. 2001

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Abstract.A sky temperature map at 45 MHz covering declination between +30 • and +60 • is presented. The sampling in right ascension is 20 min (∼5 • ) and 2 • in declination in most of the map. The originality of the work was to use cosmic emission measurements from five VHF StratosphereTroposphere (ST) radars collected during long periods of routine meteorological surveys. This map, which has an accuracy in temperature of about 600 K, is intended first for radar reflectivity calibration and system performance monitoring. The presence of two strong radio sources, Cassiopeia A and Cygnus A, can also serve as the verification of the beam diagram, beam width, and beam pointing direction of the antenna. Finally, this work is an attempt to show the potentiality of ST radar for astronomical purposes.

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“…Higher resolution surveys in this frequency range have been obtained with single-dish antennas at 1.4 MHz (Reich et al 1990a(Reich et al , 1997, 2.4 MHz (Duncan et al 1995), and 2.7 MHz (Reich et al 1984Fürst et al 1990); but their sky coverage has been limited to within a few degrees of the Galactic plane. At lower frequencies, low-resolution antenna arrays have been used to conclude three other major surveys with 69% and 95% of total sky coverage, respectively, at 22 MHz (Roger et al 1999) and 45 MHz (Alvarez et al 1997;Maeda et al 1999).…”

Section: Large-scale Galactic Emission and The Gem Projectmentioning

confidence: 99%

The 2.3 GHz continuum survey of the GEM project

Tello¹,

Villela²,

Torres³

et al. 2013

A&A

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Context. Determining the spectral and spatial characteristics of the radio continuum of our Galaxy is an experimentally challenging endeavour for improving our understanding of the astrophysics of the interstellar medium. This knowledge has also become of paramount significance for cosmology, since Galactic emission is the main source of astrophysical contamination in measurements of the cosmic microwave background (CMB) radiation on large angular scales. Aims. We present a partial-sky survey of the radio continuum at 2.3 GHz within the scope of the Galactic Emission Mapping (GEM) project, an observational program conceived and developed to reveal the large-scale properties of Galactic synchrotron radiation through a set of self-consistent surveys of the radio continuum between 408 MHz and 10 GHz. Methods. The GEM experiment uses a portable and double-shielded 5.5-m radiotelescope in altazimuthal configuration to map 60-degree-wide declination bands from different observational sites by circularly scanning the sky at zenithal angles of 30 • from a constantly rotating platform. The observations were accomplished with a total power receiver, whose front-end high electron mobility transistor (HEMT) amplifier was matched directly to a cylindrical horn at the prime focus of the parabolic reflector. The Moon was used to calibrate the antenna temperature scale and the preparation of the map required direct subtraction and destriping algorithms to remove ground contamination as the most significant source of systematic error. Results. We used 484 h of total intensity observations from two locations in Colombia and Brazil to yield 66% sky coverage from δ = −51.• 73 to δ = +34.• 78. The observations in Colombia were obtained with a horizontal HPBW of 2.• 30 ± 0.• 13 and a vertical HPBW of 1.• 92 ± 0.• 18. The pointing accuracy was 6. 84 and the RMS sensitivity was 11.42 mK. The observations in Brazil were obtained with a horizontal HPBW of 2.• 31 ± 0.• 03 and a vertical HPBW of 1.• 82 ± 0.• 12. The pointing accuracy was 5. 26 and the RMS sensitivity was 8.24 mK. The zero-level uncertainty of the combined survey is 103 mK with a temperature scale error of 5% after direct correlation with the Rhodes/HartRAO survey at 2326 MHz on a T -T plot. Conclusions. The sky brightness distribution into regions of low and high emission in the GEM survey is consistent with the appearance of a transition region as seen in the Haslam 408 MHz and WMAP K-band surveys. Preliminary results also show that the temperature spectral index between 408 MHz and the 2.3 GHz band of the GEM survey has a weak spatial correlation with these regions; but it steepens significantly from high to low emission regions with respect to the WMAP K-band survey.

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A 45-MHz continuum survey of the southern hemisphere

Cited by 52 publications

References 8 publications

Polar mesosphere summer echoes at Wasa, Antarctica (73°S): First observations and comparison with 68°N

Polar mesosphere summer echoes at Wasa, Antarctica (73°S): First observations and comparison with 68°N

A partial 45 MHz sky temperature map obtained from the observations of five ST radars

The 2.3 GHz continuum survey of the GEM project

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