Dynamics Explorer: Difference between revisions

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'''Dynamics Explorer''' ('''[[Dynamics Explorer 1|DE-1]]''' and '''[[Dynamics Explorer 2|DE-2]]''' or '''Explorer 62''' and '''Explorer 63''') was a [[NASA]] mission, launched on 3 August 1981, and terminated on 28 February 1991.<ref>[http://www.daviddarling.info/encyclopedia/D/DE.html DE (Dynamics Explorer)]</ref> It consisted of two unmanned satellites, DE-1 and DE-2, whose purpose was to investigate the interactions between [[Plasma (physics)|plasmas]] in the [[magnetosphere]] and those in the [[ionosphere]]. The two satellites were launched together into [[Polar orbit|polar coplanar orbit]]s, which allowed them to simultaneously observe the upper and lower parts of the atmosphere.<ref name="Display">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1981-070A|title=Explorer 62 (DE-1) 1981-070A|publisher=NASA|date=28 October 2021|access-date=22 November 2021}} {{PD-notice}}</ref>

== Mission ==

[[Image:Auroral oval.gif|thumb|upright=1.0|left|An aurora as seen by one of the Dynamics Explorers]]

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 plasmasplasma and gasesgasses 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.<ref name="Display"/>

== Spacecraft ==

The spacecraft approximated a short polygon {{cvt|137|cm}} in diameter and {{cvt|115|cm}} high. The antennas in the X-Y plane measured {{cvt|200|cmm}} tip-to-tip, and on the Z-axis are {{cvt|9|m}} tip-to-tip. Two {{cvt|6|m}} 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-stabilisation|spin-stabilized]], with the spin axis normal to the orbital plane, and the spin rate at 10 ± 0.1 [[Revolutions per minute|rpm]]. A [[pulse-code modulation]] (PCM) [[Telemetry|telemetry data system]] is used that operates in real time or in a [[tape recorder]] 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 [[Bit rate|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.<ref name="Display"/>

=== Dynamics Explorer 1 instrumentation ===

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== 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.

An overview of the results from the first 5 years of the mission was published in a special edition of [[Reviews of Geophysics]].<ref>Hoffman, R. A. "The magnetosphere, ionosphere, and atmosphere as a system: Dynamics Explorer 5 years later." Reviews of Geophysics 26.2 (1988): 209-214.</ref>

== Atmospheric entry ==