The Moon as Source for G/T Measurements

Johannsen, Klaus G.; Koury, Albert

doi:10.1109/taes.1974.307869

Cited by 13 publications

(5 citation statements)

References 3 publications

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“…They act as an interference and effect on the communication link between the earth and the moon. The loss caused by them is assumed to be 4 ∼ 6 dB (Johannsen et al 1974, Park et al 2009).…”

Section: Lunar Flux Density Lossmentioning

confidence: 99%

Design and Performance Analysis of Downlink in Space Communications System for Lunar Exploration

Lee¹,

Cho²,

Yoon³

et al. 2010

Journal of Astronomy and Space Sciences

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This paper designs a data link between a Lunar Orbiter (LO) and an Earth Station (ES), and analyzes the downlink performance of a space communications system for lunar exploration, conforming to the recommendations by the Consultative Committee for Space Data Systems (CCSDS). The results provided in the paper can be useful references for the design of reliable communication link for the Korean lunar exploration in the near future.

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Section: Lunar Flux Density Lossmentioning

confidence: 99%

Design and Performance Analysis of Downlink in Space Communications System for Lunar Exploration

Lee¹,

Cho²,

Yoon³

et al. 2010

Journal of Astronomy and Space Sciences

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“…For small antenna-earth terminals only the sun or moon [39] emit sufficient radiation to allow a G/T measurement to be made (see eq. (6)).…”

Section: Bandwidth Correction Factormentioning

confidence: 99%

Error equations used in the NBS precision GT measurement system

Daywitt¹

1976

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Equations presently being used in the precision NBS G/T measurement system are presented in this report.Included are the assumptions upon which these equations are based and sample calculations showing how the measurement errors vary with antenna elevation angle . This report summarizes the approximate error equations presently being used by NBS in its precision satellite earthterminal G/T (system gain/system noise temperature) measurement system [1]. These equations are the result of a four-year evolution begun in 1972 with a G/T measurement [2] of the earth terminal located at Camp Roberts, California, using the G/T equations then available in the literature [3][4][5][6][7][8].The equations presented here represent the final results of a comprehensive G/T error analysis. This analysis was preceded by a thorough study [9] of the literature concerning the use of Cassiopeia A in G/T measurements. A further study [10] of the errors involved in the absolute flux density measurement of Cassiopeia A was subsequently performed since the literature was found to be lacking in this respect; this study does not identify an absolute flux density value for Cassiopeia.The equations to be presented are approximations of "exact" equations derived in the analysis. The^-requirements of high accuracy and the use of models naturally narrows the validity of the resulting equations, and although the range of validity of each equation will be clearly stated, it should be mentioned initially that most of the equations are appropriate to the 1 GHz to 10 GHz frequency region.Most of the financial support for these studies has come from the U.S. Army Communication Command (ACOM) Headquarters, Fort Huachuca, Arizona, and is gratefully acknowledged.The radio star method [3,11,12] of measuring G/T involves measuring the ratio of two noise powers at some point in the IF portion of the earth-terminal receiving system (for a complete definition of the word "system" see reference [9]). These two powers and correspond respectively to powers received when pointing the earth-terminal antenna at and then adjacent to the calibrated radio star. The measured ratio Y is related to these two powers by I.A is the free-space wavelength corresponding to the earth-terminal receive frequency; S is the radio star flux density calibrated at the receive frequency; k is Boltzmann's constant;and k^through k^are correction factors defined to insure the equality in eq. (3).All of the k factors (k^through k^) involve integrations of the radio-star brightness distribution with various quantities over the power pattern of the antenna. However, if the power pattern were precisely known, G/T could be simply and accurately determined without the aid of a radio star. This is seldom the case. Furthermore, accurate brightness distributions are difficult to obtain. The usefulness of the radio star method is based upon three commonly present conditions: 1) for brightness distributions with angular extents less than the antenna HPBW, the smoothing effect of the antenna allows ...

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“…Oprócz tego na rozchodzenie się fal radiowych wpływają różne od wyidealizowanego przypadku propagacji w wolnej przestrzeni warunki rozchodzenia się fal radiowych. W tym kontekście należy wskazać wpływ: (1) atmosfery ziemskiej (w tym czynników klimatyczno-atmosferycznych w niej zachodzących) [3,5,22,25,28,41,42]; (2) naturalnych źródeł szumów o podłożu ziemskim, jak i pozaziemskim [4,7,23,27,28,31,32,35,36,39,42,46,47]; (3) strat wynikających z braku precyzji ustawienia anteny oraz (4) zastosowania rzeczywistych, stratnych elementów systemu odbiorczego (m.in. straty cyfrowej modulacji, całkowite straty w łączu, szumy fazowe konwertera LNB, nieliniowe charakterystyki filtrów w demodulatorze i stopnia mocy w satelicie, działanie dekoderów itp.)…”

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Wpływ Wybranych Parametrów Technicznych Systemu Na Odbiór Fal Radiowych

Wilk-Jakubowski

2018

IAPGOŚ

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Artykuł omawia wpływ wybranych parametrów systemu na odbiór fal radiowych, co ma zastosowanie w optymalizacji systemów łączności. Cel ten realizuje się poprzez dobór parametrów technicznych urządzeń np. współczynnika sprawności anteny odbiorczej. Zwiększenie współczynnika dostępności dla danego systemu wiąże się z minimalizacją wpływu wielu niepożądanych czynników na transmisję fal radiowych (w tym tłumienia podstawowego oraz influencji klimatyczno-atmosferycznej). W rezultacie możliwe staje się zoptymalizowanie istniejących już systemów teletransmisyjnych oraz projektowanie nowych systemów, pozwalających na znaczną poprawę jakości i wiarygodności przekazywanych informacji (zaprezentowane wyniki ograniczą się do częstotliwości z zakresu pasma Ku – powszechnie wykorzystywanego w łączności satelitarnej).

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The Moon as Source for G/T Measurements

Cited by 13 publications

References 3 publications

Design and Performance Analysis of Downlink in Space Communications System for Lunar Exploration

Design and Performance Analysis of Downlink in Space Communications System for Lunar Exploration

Error equations used in the NBS precision GT measurement system

Wpływ Wybranych Parametrów Technicznych Systemu Na Odbiór Fal Radiowych

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