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A new concept radio occultation experiment to study the structure of the atmosphere and determine the plasma layers in the ionosphere. Kotelnikov Institute of Radio Engineering and Electronics of RAS. Gavrik A.L. alg248@ire216.msk.su. октября 2011 ВЕНЕРА - Д ИКИ РАН. - PowerPoint PPT Presentation

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  • A new concept radio occultation experiment to study the structure of the atmosphere and determine the plasma layers in the ionosphere.Gavrik A.L.Kotelnikov Institute of Radio Engineering and Electronics of RAS alg248@ire216.msk.su 2011

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  • Dual frequency radio wave sounding on the ray path Orbiter Earth

    The scientific goals in the project VENERA-D1. Variation in the Solar wind plasma.(analysis of amplitudes and phases of two coherent radio signals)

    2. Monitoring the electron density onthe Venus ionosphere. (analysis of amplitudes and phases of two signals during occultation)

    3. Thermal and density profiles forthe Venus atmosphere. (analysis of amplitudes and phases of two signals during occultation)

    4. Investigate of Venus surface.(analysis of bistatic echoes from Venus surface)The electron densities in the Venusian day and night time ionosphere Changes in parameters of Solar wind plasmaVariations in the temperature profiles of atmosphereAnomalous reflectivityfrom bistatic radar echoesVenera 11-16Vishlov et.al.Venera -15,-16 Savich et. al.MagellanJenkins et.alVenera-15 Pavelyev et.al.Day-time N(h) pass into night-time N(h)Night-time N(h)

  • Dual frequency VENERA-15,-16 occultation (4 & 1 GHz or 8 & 32 ) The electron densityof daytime Venusian ionosphere

    N(h), -3Measured refraction attenuationsinduced by daytime Ionosphere and atmosphere

    D 8 32 Measured residual frequency in the ionosphere and atmosphere

    fD32 The time of occultation

    2 20 minutesatmosphereRadio rays to the Earth ionosphereThe theory of occultation experiments is based on integral equations that relate the electron density N(h) to the measured characteristics of radio signals.

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    100 102 103 104 105 102 103 104 105 102 103 104 105 102 103 104 105 Altitude, Electron density, -3Altitude distributions N(h) of the electron densities in the Venus day-time ionosphere

    N(h) 12.10.83. 56020.03.84. 52023.09.84. 610

    Coincidenceof N(h) forsome days09.09.84. 82012.10.83. 81030.10.83. 820

    Time-to-timevariability14.10.83. 82012.10.83. 81028.03.84. 820

    Coincidence of N(h) for some days

    19.09.84. 56014.10.83. 58020.09.84. 550

    Time-to-time variability

  • 102 103 104 1050 0.5 1.0 1.5 2.0300

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    80102 103 104 105 about the bottom ionosphere.

    We can see discrepancies between the model and calculated N(h). The error can be greater than the actual value of N(h) at altitudes of h < 120 km.

    That is why we can see the bottom boundary of the ionosphere at altitude of h = 117 km on the experimental profile N(h). But the real influence of ionospheric plasma is observed up to 85 km in the occultation data. The traditional method to determine N(h) leads to wrong conclusions Model N(h)

    Calculation N(h)

    Calculation N(h)N(h)VENERA-1525.10.1983 .bottom part of the ionosphereAltitude, km Electron density, m-3Refraction attenuation

  • In the field of heights 80 < h < 120 kmit is impossible to define atmosphere temperature precisely.

    It is impossible to define any parameters of Venus atmosphere for h < 35 kmfrom occultation databecause of super refraction of the radio rays.VENUS-EXPRESSM. Ptzold et al.

  • The following result is obtained from p(t), (t), X(t) :The well-known relationshipsThe ray asymptote distance the altitude of straight-line ray The refractive bending angle f residual frequency in the ionosphere F residual frequency in the atmosphere The refraction attenuation L the distance between the spacecraft and point V the velocity of the satellites ingress The electron density f the radiated frequency (1 GHz)Variations of the defocusing attenuation X(t) in the occultation experiments are proportional to the velocity of residual frequency changes.

  • It is necessary to determine same parameters from the experimental data:

    XDM(t) - the refraction attenuations of L-band (32 cm) signal.

    XCM(t) - the refraction attenuations of C-band ( 8 cm) signal.

    f(t) = 16/15 (fDM(t) - fCM(t)/4) - the reduced frequency difference (plasma influence).

    f(t) = function [f(t)] - frequency variation of L-band (32 cm) signal.

    Xf (t) = 1 + value*d/dt[f(t)] - predicted refraction attenuation of the L-band signal.

    Coincidence between variations of refraction attenuationof the radio signal XDM(t) and variations Xf (t) will be indicative of the influence of the regular structuresof the ionosphere under investigation.

    The absence of this correspondence is an indication of the influence of the noise or other factors that are not taken into account.

    This method considerably increased the sensitivity of the radio probing method to refractive index variations and makes possible to detect small variations of electron density and atmosphere density.New method provides a possibility to distinguish the layers in the atmosphere and ionosphere during occultation.

  • A variations of refraction attenuation of DM signal coincide with calculated data f(t) in the day-time ionosphere of Venus.

    Altitude of spacecraft-Earth straight-line h, The refraction attenuation, Venera-15,-16Gavrik A. et al.

    A variations of refraction attenuation of DM signal coincide with calculated data f(t) in the night-time ionosphere of Venus.

    bottomionosphereOne layer night-time ionosphereTwo layers night-time ionosphere

  • This technique will allow one to investigate wave processes in the top atmosphere and the bottom ionosphere.

    We observed wave processes in the top atmosphere and bottom ionosphere of Venus. 25 50 75 100 125Refraction attenuation of a D-signal in the atmosphereRefraction attenuation of a C-signal in the atmospherelayered structure in the atmosphereCorrelation between the powers of DM- and CM-signals due to the wavestructureRefraction attenuation in the ionospherecalculated from the frequency of a D-signal and f are different in the atmosphere

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    0Layers in the bottom ionosphere:correlation between D and f Altitude of the spacecraft-to-Earth straight line h, km

  • L1 the distance between the first spacecraft and point of ray closest to the surface of planet.L2 the distance between the second spacecraft and point of ray closest to the surface of planet.

    The method is correct for high-precision measurementsof signal power and phase during dual frequency radio sounding.This method can be extended to occultation experimentSatellite Satellite

  • R e s I d u a l f r e q u e n c y, HzAltitude of radio ray straight line h, kmhttp://isdc.gfz-potsdam.deL1= 19 cm, L2= 24 cm, t = 0.02 s GPS CHAMP In these occultation experiments GPS CHAMP we can see very high frequency fluctuations and the lack of coherence of the signals of two ranges L1 & L2.

    Hence, the onboard USO must be very stable on short time intervals.

  • Realization of informative experiments requires the development of a good on-board receiver.Small frequency fluctuations in the occultation experiments VENERA-15,-16 Earthachieved by the high output transmitter power (100 W) and large diameter (>2m) on-board antenna.In these occultation experiments GPS CHAMP we can see the frequency fluctuations, which exceed the influence of the ionosphere.http://isdc.gfz-potsdam.deplasma influence-16 = 32 , t = 0.058 s = 19 , t = 0.02 s GPS CHAMP invalid measurements (little signal/noise)Residual frequency, HzAltitude of radio ray straight line h, kmMean-square deviation f(t) from 0.003 to 0.03 HzThe frequency f(t)in the Venus daytime ionosphere

  • If we choose a very long measurement interval t, then the effects of focusing of a signal and layered structures will not manifest themselves.

    Therefore, it is necessary to provide a high S/N ratio during the experiments.Altitude of radio ray straight line h, kmThe refraction attenuation, t = 0.06 s t = 0.11 s t = 0.23 s t = 0.47 s The method gives correct results for high-precision measurements during dual frequency radio sounding.Invaliddata(little S/N)

  • High S / N ratio can be achieved if emit powerful coherent radio signals from Earth.

    In this case, at the same time we can perform six radio physical experiments,in addition to the work of other onboard devices.

    High S / N ratio give the possibility of obtaining new information concerning the structure of the planetary ionospheres and atmospheres.radar experimentbistatic radar experimentInterplanetary plasma on the two separated tracks Earth OA and Earth SSSSTwo-frequency radio sounding of the ionosphere Two-frequency radio sounding of the atmosphere signals to the ETs

  • It is important that the high potential allows regular bistatic location.

    We can determine the parameters of the Venus atmosphere near its surface from the characteristics of the echo signals.

    Consequently, it is possible to monitor the bottom of the Venusian atmosphere, details of whic