Dynamics Explorer was a NASA

NASA

The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 mission, launched on August 3, 1981 and terminated on February 28, 1991. It consisted of two unmanned satellites, DE-1 and DE-2, whose purpose was to investigate the interractions between plasmas in the magnetosphere

Magnetosphere

A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...

 and those in the ionosphere

Ionosphere

The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...

. The two satellites were launched together into polar

Geographical pole

A geographical pole is either of the two points—the north pole and the south pole—on the surface of a rotating planet where the axis of rotation meets the surface of the body...

 coplanar orbits, which allowed them to simultaneously observe the upper and lower parts of the atmosphere.

Design

Both spacecraft had a polygonal shape, and were approximately 137 cm in diameter and 115 cm high. Each also had a 200-cm radio antenna and two 6-meter booms which were needed to distance some of the equipment from the main body of the spacecraft. They were stacked on top of each other and launched aboard a Delta 3000 booster rocket. Upon reaching orbit, the two spacecraft departed from the booster and entered separate orbits. Dynamics Explorer 1 was placed into a high altitude elliptical orbit, while DE-2 was put into a lower orbit that was also more circular.

Dynamics Explorer 1 Instrumentation

The main instrument aboard Dynamics Explorer 1 was the Plasma Wave Instrument (PWI). This instrument, designed and built by the Plasma Wave Group, measured auroral kilometric radiation, auroral hiss, Z-mode radiation, and narrow band electromagnetic emissions. Additional Instruments aboard the spacecraft included:

• The Spin-scan Auroral Imager (SAI)
• The Retarding Ion Mass Spectrometer (RIMS)
• The Energetic Ion Mass Spectrometer (EIMS)

Dynamics Explorer 2 Instrumentation

The Dynamics Explorer 2 carried the following instruments for data collection:

• A Retarding Potential Analyzer, which measured the ion flux along the velocity vector of the spacecraft. This data was then used to determine the ion temperature and drift velocity in the spacecraft's area.
• An Ion drift meter
  Ion drift meter
  An ion drift meter is a device used to measure the velocity of individual ions in the area of a spacecraft. This information can then be used to calculate the ion drift in the space surrounding the instrument as well as the strength of any electric field present, provided that the magnetic field...
  
  , which measured the ambient ion drift.
• A Magnetometer
  Magnetometer
  A magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature...
  
  
• A Vector Electric Field Instrument 
  
• A Neutral Atmosphere Composition Spectrometer
• A Wind and Temperature Spectrometer
• A Fabry–Pérot interferometer
• A Low-Altitude Plasma Instrument
• 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...
  
  

Mission Results

As a result of a malfunction in the Delta 3000 booster rocket in which its main engine shut off slightly early, DE-2 was placed into a slightly lower orbit than was anticipated. This was not a serious problem, however, and the spacecraft had lasted its expected lifespan when it re-entered the Earth's atmosphere on February 19, 1983. DE-1, being in a higher orbit, continued to collect data until 1991, when the mission was officially terminated.