Dynamics Explorer ( DE-1 and DE-2 or Explorer 62 and Explorer 63) was a

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the US federal government responsible for the civil List of government space agencies, space program ...

mission, launched on 3 August 1981, and terminated on 28 February 1991. It consisted of two unmanned satellites, DE-1 and DE-2, whose purpose was to investigate the interactions between plasmas in the magnetosphere and those in the ionosphere. The two satellites were launched together into polar coplanar orbits, which allowed them to simultaneously observe the upper and lower parts of the atmosphere.

Mission

The Dynamics Explorer (DE) mission's general objective is to investigate the strong interactive processes coupling the hot, tenuous, convecting plasmas of the magnetosphere and the cooler, denser plasma and gasses corotating in the Earth's ionosphere, upper atmosphere, and plasmasphere. Two satellites, DE-1 and DE-2, were launched together and were placed in polar coplanar orbits, permitting simultaneous measurements at high and low altitudes in the same field-line region. The DE-1 spacecraft (high-altitude mission) uses an elliptical orbit selected to allow (1) measurements extending from the hot magnetospheric plasma through the plasmasphere to the cool ionosphere; (2) global auroral imaging, wave measurements in the heart of the magnetosphere, and crossing of auroral field lines at several Earth radii; and (3) measurements for significant periods along a magnetic field flux tube.

Spacecraft

The spacecraft approximated a short polygon in diameter and high. The antennas in the X-Y plane measured tip-to-tip, and on the Z-axis are tip-to-tip. Two booms are provided for remote measurements. Power is supplied by a solar cell array, mounted on the side and end panels. The spacecraft is spin-stabilized, with the spin axis normal to the orbital plane, and the spin rate at 10 ± 0.1

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(PCM) telemetry data system is used that operates in real time or in a

tape recorder An audio tape recorder, also known as a tape deck, tape player or tape machine or simply a tape recorder, is a sound recording and reproduction device that records and plays back sounds usually using magnetic tape for storage. In its present ...

mode. Data have been acquired on a science-problem-oriented basis, with closely coordinated operations of the various instruments, both satellites, and supportive experiments. Data acquired from the instruments are temporarily stored on tape recorders before transmission at an 8:1 playback-to-record ratio. Additional operational flexibility allows a playback-to-record ratio of 4:1. The primary data rate is 16,384 bits per second. Since commands are stored in a command memory unit, spacecraft operations are not real time, except for the transmission of the wideband analog data from the Plasma Wave Instrument (1981-070A-02). On 22 October 1990, the science operations were terminated. On 28 February 1991, Dynamics Explorer 1 operations were officially terminated.

Dynamics Explorer 1 instrumentation

Dynamics Explorer 1 carried the following instruments: * Energetic Ion Composition Spectrometer (EICS) * High Altitude Plasma Instrument (HAPI) * Magnetic Field Observations Triaxial Fluxgate Magnetometer (MAG-A) * Plasma Wave Instrument (PWI), which measured auroral kilometric radiation, auroral hiss, Z-mode radiation, and narrow band electromagnetic emissions * Retarding Ion Mass Spectrometer (RIMS) * Spin-scan Auroral Imager (SAI) In addition, there were two Earth-based investigations, Auroral Physics Theory and Controlled and Naturally Occurring Wave Particle Interactions Theory. The later involved broadcasting very-low-frequency/low-frequency (0.5–200-kHz) signals from a transmitter located at

Siple Station Siple Station was a research station in Antarctica (), established in 1973 by Stanford's STAR Lab, to perform experiments that actively probed the magnetosphere using very low frequency (VLF) waves. Its location was selected to be near the Earth' ...

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...

, which were received by the PWI instrument on Dynamics Explorer 1.

Regions traversed

Ionosphere, magnetosphere,

plasmapause The plasmasphere, or inner magnetosphere, is a region of the Earth's magnetosphere consisting of low-energy (cool) plasma. It is located above the ionosphere. The outer boundary of the plasmasphere is known as the plasmapause, which is defined ...

plasmasphere The plasmasphere, or inner magnetosphere, is a region of the Earth's magnetosphere consisting of low-energy (cool) plasma. It is located above the ionosphere. The outer boundary of the plasmasphere is known as the plasmapause, which is defined ...

, and trapped particle belts.

Dynamics Explorer 2 instrumentation

The Dynamics Explorer 2 carried the following instruments for data collection: * Fabry–Pérot interferometer (FPI), which measured the meridional component of the neutral winds. (The meridional wind component is the component in the direction of lines of longitude - i.e. North–South.) * Ion Drift Meter * Langmuir probe * Low-altitude Plasma Instrument * Magnetometer * Neutral Atmosphere Composition Spectrometer * 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. * Vector Electric Field Instrument * Wind and Temperature Spectrometer (WATS), which measured the zonal and vertical components of the neutral winds, as well as the kinetic temperature.Spencer, N. W., Wharton, L. E., Carignan, G. R. and Maurer, J. C. (1982), Thermosphere zonal winds, vertical motions and temperature as measured from Dynamics Explorer. Geophys. Res. Lett., 9: 953–956. doi:10.1029/GL009i009p00953. (The zonal wind component is the component in the direction of lines of latitude - i.e. East–West.) The WATS instrument on DE-2 is one of the few satellite instruments which has measured thermosphere vertical wind speeds, with the Neutral Atmosphere Temperature Experiment (NATE).Spencer, N. W., Theis, R. F., Wharton, L. E. and Carignan, G. R. (1976), Local vertical motions and kinetic temperature from AE-C as evidence for aurora-induced gravity waves. Geophys. Res. Lett., 3: 313–316. doi:10.1029/GL003i006p00313. on Atmospheric Explorer C (AE-C) being one other.

Mission results

As a result of a malfunction in the Thor-Delta 3913 launch vehicle 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 19 February 1983.

Atmospheric entry

DE-1, being in a higher orbit, continued to collect data until 28 February 1991, when the mission was officially terminated.

References

External links

Dynamics Explorer image gallery
{{Explorers Program NASA satellites orbiting Earth Geospace monitoring satellites Twin satellites