DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) was a French micro-satellite operated by

CNES The (CNES; French: ''Centre national d'études spatiales'') is the French government space agency (administratively, a "public administration with industrial and commercial purpose"). Its headquarters are located in central Paris and it is und ...

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 A circular orbit is an orbit with a fixed distance around the barycenter; that is, in the shape of a circle. Listed below is a circular orbit in astrodynamics or celestial mechanics under standard assumptions. Here the centripetal force is ...

with an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

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 was always located either shortly before the local noon (10:30

local time Local time is the time observed in a specific locality. There is no canonical definition. Originally it was mean solar time, but since the introduction of time zones it is generally the time as determined by the time zone in effect, with daylight s ...

) or local midnight (22:30 local time). The satellite performs 14 orbits per day and measures continuously between -65° and +65° of

invariant latitude Invariant and invariance may refer to: Computer science * Invariant (computer science), an expression whose value doesn't change during program execution ** Loop invariant, a property of a program loop that is true before (and after) each iteratio ...

. DEMETER observed an increase in

ultra low frequency Ultra low frequency (ULF) is the ITU designation for the frequency range of electromagnetic waves between 300 hertz and 3 kilohertz, corresponding to wavelengths between 1,000 to 100 km. In magnetosphere science and seismology, alternative defin ...

radio waves in the month before the

2010 Haiti earthquake A disaster, catastrophic Moment magnitude scale, magnitude 7.0 Mw earthquake struck Haiti at 16:53 local time (21:53 UTC) on Tuesday, 12 January 2010. The epicenter was near the town of Léogâne, Ouest (department), Ouest department, a ...

. During the 2010 eruption of Mount Merapi, DEMETER noted anomalies in the

ionosphere The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an ...

. Scientific operations ended December 9, 2010.

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's 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 * IDP: an energetic

particle detector In experimental and applied particle physics, nuclear physics, and nuclear engineering, a particle detector, also known as a radiation detector, is a device used to detect, track, and/or identify ionizing particles, such as those produced by nuc ...

Modes of Operation

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

References

External links

CNES project web page

DEMETER data server providing a free access to the low-resolution "quicklook" data

Spacecraft Saw ULF Radio Emissions over Haiti before January Quake , MIT Technology Review
{{DEFAULTSORT:Demeter (Satellite) Earth observation satellites of France Spacecraft launched in 2004 Spacecraft launched by Dnepr rockets CNES