Demeter (satellite)
Encyclopedia
DEMETER is a French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 micro-satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

 operated by CNES
CNES
The is the French government space agency . Established under President Charles de Gaulle in 1961, its headquarters are located in central Paris and it is under the supervision of the French Ministries of Defence and Research...

 devoted to the investigation of the ionospheric disturbances due to seismic and volcanic activity. It was launched on June 29, 2004 on a quasi Sun-synchronous circular orbit
Circular orbit
A circular orbit is the orbit at a fixed distance around any point by an object rotating around a fixed axis.Below we consider a circular orbit in astrodynamics or celestial mechanics under standard assumptions...

 with an inclination
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...

 of about 98.23° and an altitude of about 710 km. The altitude was changed to about 660 km in December, 2005. Due to the specific orbit, DEMETER is always located either shortly before the local noon (10:30 local time) or local midnight (22:30 local time). The satellite performs 14 orbits per day and measures continuously between -65° and +65° of invariant latitude.

Scientific Objectives

  • to study the ionospheric disturbances in relation to the seismic activity and to examine the pre- and post-seismic effects
  • to study the ionospheric disturbances in relation to the volcano activity
  • to survey the ionospheric disturbances in relation to the anthropogenic activity
  • to contribute to the understanding of the generation mechanism of these disturbances
  • to give a global information on the Earth electromagnetic environment

Scientific Payload

  • IMSC: three magnetic sensors from a few Hz up to 18 kHz
  • ICE: three electric sensors from DC up to 3.5 MHz
  • IAP: an ion analyzer
  • ISL: a Langmuir probe
    Langmuir probe
    A Langmuir probe is a device named after Nobel Prize winning physicist Irving Langmuir, used to determine the electron temperature, electron density, and electric potential of a plasma. It works by inserting one or more electrodes into a plasma, with a constant or time-varying electric potential...

  • IDP: an energetic particle detector

Modes of Operation

Due to the limited capacity of the telemetry, there are two different modes of operation. During the "Survey mode", averaged data are collected all around the Earth. The telemetry flow in this mode is reduced by the on-board data processing to 25 kb/s. During the "Burst mode", high-precision data are collected above the specific areas of interest, corresponding mostly to the seismic regions. The data bit rate in this mode is 1.7 Mb/s.

External links

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