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Open Access

A new altimeter for Mars land shape observations utilizing the ionospheric sounder system onboard the Planet-B spacecraft

Earth, Planets and Space201450:BF03352108

Received: 24 September 1997

Accepted: 12 January 1998

Published: 6 June 2014


A new altimeter has been developed for the observation of the land shape of a planet from an orbiting spacecraft by transmitting RF pulses. The present system utilizes an RF sounder for observing the electron density profile of the topside ionosphere by selecting a transmission frequency f higher than the local cutoff frequency of the ionosphere by adding upper and lower side band modulations with a frequency p; i.e. at frequencies f + p and f −p. The phase difference of the propagating signals at the upper and lower side band frequencies gives a fine delay time with a range resolution of 100 m for p = 50 kHz and 20 m for p = 250 kHz with f = 9 MHz corresponding to a resolution of 6 ° of the phase detector of the system onboard the spacecraft. Using 600 Watts transmitting power applied to a 52 m tip-to-tip dipole antenna, the altitude of the spacecraft and the land shape can be measured while the spacecraft is in the range below 300 km altitude at the planet.


Phase DetectorDipole AntennaPlanetary SurfaceTopside IonospherePulse Arrival Time