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  • Article
  • 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:


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 Detector
  • Dipole Antenna
  • Planetary Surface
  • Topside Ionosphere
  • Pulse Arrival Time