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Open Access

Electron temperature probe onboard Japan’s Mars orbiter

  • Koh-ichiro Oyama1Email author,
  • Takumi Abe1,
  • Kristian Schlegel2,
  • Andrew Nagy3,
  • Jhoon Kim4 and
  • Katsuhide Marubashi5
Earth, Planets and Space201451:BF03351604

Received: 7 August 1997

Accepted: 6 October 1999

Published: 20 June 2014


Japan’ s first Mars spacecraft PLANET-B was successfully launched on 4th of July, 1998 and was named “NO-ZOMI” after the launch. One of the scientific instruments is a unique electron temperature probe which was developed in Japan and has been used for more than 20 years on sounding rockets as well as on scientific satellites (Oyama, 1991). The electron temperature probe dubbed PET (Probe for Electron Temperature measurements) consists of two planar electrodes, 150 mm in diameter, placed at the edges of the two solar cell panels of the “NOZOMI” spacecraft. Electron temperatures can be measured in plasmas with densities exceeding 1000 cm−3 with sufficient accuracy. The maximum sampling rate of 8 data points per satellite spin for each probe allows high resolution measurements (i.e., an angular resolution around the spin axis of 23 degrees). Additionally, the probe can measure the anisotropy of the electron temperature, if it exists. It is also possible to infer the existence of nonthermal electrons.


Solar WindElectron TemperatureSine WavePotential ShiftRadio Occultation