Radar Studies of the Moon

Evans, J. V.; Hagfors, T.

doi:10.1016/b978-0-12-003208-2.50007-5

Cited by 29 publications

(25 citation statements)

References 61 publications

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“…Precise measurements of the time delay to surface elements provide topographic maps and powerful information on planetary motions and tests of gravitational theories such as general relativity. In this paper, we limit our discussion to surface and near-surface probing of Mercury, Mars, and Titan and review the using the traditional range-gated Doppler strip mapping procedure [which was, apparently, developed theoretically at the Lincoln Laboratory by Paul Green, based on a citation in Evans (1962)]. Richard Goldstein was the first to obtain range-gated planetary maps of Venus as reported in Carpenter & Goldstein (1963).…”

Section: Introductionmentioning

confidence: 99%

Radar Investigation of Mars, Mercury, and Titan

Muhleman¹,

Grossman²,

Butler³

1995

Annu. Rev. Earth Planet. Sci.

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Section: Introductionmentioning

confidence: 99%

Radar Investigation of Mars, Mercury, and Titan

Muhleman¹,

Grossman²,

Butler³

1995

Annu. Rev. Earth Planet. Sci.

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“…The solar ultraviolet light and soft/hard X-rays interact with Earth's upper atmosphere and its constituents through photo-ionization processes (Evans & Hagfors 1968;Ratcliffe 1972;Davies 1990). This interaction causes the formation of an ionized layer called the ionosphere.…”

Section: Earth's Ionospherementioning

confidence: 99%

“…The electron densities in the ionosphere change significantly due to the effect of solar activity (Evans & Hagfors 1968;Ratcliffe 1972;Davies 1990). The presence of the Earth's ionosphere results in three effects relevant for the detection of the redshifted HI 21cm signal.…”

mentioning

confidence: 99%

“…The presence of the Earth's ionosphere results in three effects relevant for the detection of the redshifted HI 21cm signal. The ionosphere refracts all transionospheric signals including the Galactic and extragalactic foregrounds, causes attenuation to any trans-ionospheric signal (Evans & Hagfors 1968;Davies 1990) and also produces thermal emission (Pawsey et al 1951;Steiger & Warwick 1961). Moreover, these effects are intrinsically time variable due to the solar forcing of the ionosphere (Evans & Hagfors (Vedantham et al 2014).…”

mentioning

confidence: 99%

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THE EFFECTS OF THE IONOSPHERE ON GROUND-BASED DETECTION OF THE GLOBAL 21 cm SIGNAL FROM THE COSMIC DAWN AND THE DARK AGES

Datta

Bradley

Burns

et al. 2016

ApJ

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Detection of the global HI 21 cm signal from the Cosmic Dawn and the Epoch of Reionization is the key science driver for several ongoing ground-based and future ground-/space-based experiments. The crucial spectral features in the global 21 cm signal (turning points) occur at low radio frequencies 100 MHz. In addition to the human-generated RFI (Radio Frequency Interference), Earth's ionosphere drastically corrupts low-frequency radio observations from the ground. In this paper, we examine the effects of time-varying ionospheric refraction, absorption and thermal emission at these low radio frequencies and their combined effect on any ground-based global 21 cm experiment. It should be noted that this is the first study of the effect of a dynamic ionosphere on global 21 cm experiments. The fluctuations in the ionosphere are influenced by solar activity with flicker noise characteristics. The same characteristics are reflected in the ionospheric corruption to any radio signal passing through the ionosphere. As a result, any ground based observations of the faint global 21 cm signal are corrupted by flicker noise (or "1/ f " noise, where " f " is the dynamical frequency) which scales as ν −2 (where ν is the frequency of radio observation) in the presence of a bright galactic foreground (∝ ν −s , where s is the radio spectral index). Hence, the calibration of the ionosphere for any such experiment is critical. Any attempt to calibrate the ionospheric effects will be subject to the inaccuracies in the current ionospheric measurements using GPS (Global Positioning System) ionospheric measurements, riometer measurements, ionospheric soundings, etc. Even considering an optimistic improvement in the accuracy of GPS-TEC (Total Electron Content) measurements, we conclude that the detection of the global 21 cm signal below 100 MHz is best done from above the Earth's atmosphere in orbit of the Moon.

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“…Ex cellent summaries of the history of lunar radar obser vations and early interpretations are given by Evans (1962) and Evans and Hagfors (1971).…”

Section: Reflection Of Radar Waves From Earth-based Stationsmentioning

confidence: 99%