Home The Institute of Space and Astronautical Science Report A Feasibility Study for Observing Small Lunar and Martian Ionospheres by Radio Occultation Technique

2.3 Lunar Ionosphere

For the calculation of the typical phase shift by the lunar ionosphere, the electron den-sity profile observed by the Luna 22 mission (see Section 1.2 ) is adopted (Figure 6a). The adopted velocity is taken from the planned orbit of Selene (Figure 6b).



Fig.6.Calculation condition for the lunar ionosphere.
(a)Electron density profile measured by Luna 22[Vyshlo et al.,1976].
(b)Planned orbit of Selene.

The phase shifts caused by the radio occultation of the lunar ionosphere is shown in Figure 7. The phase shifts due to the fluctuation of the terrestrial ionosphere are also shown for comparison. When the terrestrial ionosphere is very calm, the phase shift due to the lunar ionosphere would be detected if the lunar ionosphere is as thick as the elec-tron layer observed by Luna 22. Since we can carry out the measurement many times during the Selene mission, we will be able to show statistically whether the lunar ionos-phere exists or not.



Fig.7.Phase shift cused by theradio occultation of the lunar ionosphere(dashed curve).Solid curve and dotted curve indicate the phase shiftsdue to the fluctuation of the terrestrial ionosphere for disturbed and quiet conditions,respectivel, that are calculated from GPS data (Section 3).

The maximum total electron content along the ray path, the maximum phase shift, and the time scale of the observations are summarized in Table 2. In order to discuss the feasibility of the measurements of the Martian nightside ionosphere and the lunar ionos-phere in more detail, the properties of the fluctuation of the terrestrial ionosphere will be investigated in Section 3.



Table 2 Maximum total electron content along the lay path,
maximum phase shift, and time scale of the obsevations.


*Very thick inosphere reported by the luna 22 mission is adopted

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Home The Institute of Space and Astronautical Science Report A Feasibility Study for Observing Small Lunar and Martian Ionospheres by Radio Occultation Technique