Earth Planets Space, Vol. 50 (No. 3), pp. 235-240, 1998
Tatsuaki Okada1 and Takayuki Ono2
1Division of Planetary Science, Institute of Space and Astronautical Science, Sagamihara, 229-8510, Japan
2Department of Astronomy and Geophysics, Tohoku University, Sendai 980-8578, Japan
(Received July 31, 1997; Revised November 21, 1997; Accepted February 12, 1998)
Abstract: Application of altimeter experiment of Planet-B orbiter to the exploration of Martian surface and subsurface layers is planned by using the ALT mode data from the "PWS (Plasma Waves and Sounder)" instrument. The topographic profile along-the-track from the orbiter to the nadir point of Martian surface can be obtained in detail owing to the high accuracy of the PWS altimetry of about 20m. The characteristics of altimeter echo intensities are also applicable to obtain the electromagnetic properties which were functions of bulk density, humidity, and abundance of ferromagnetic minerals of the uppermost layer of Martian surfaces. The surface macroscopic roughness was also studied since the rise time was slower for the echo from the rougher surface. Another possibility of the application of the altimeter experiment can be given by identifying the subsurface echoes and it is used as a probe for sensing physical properties from tens to hundreds meters below the surface, including possible exploration of liquid water.