                  APOD: 2018 January 31 - The First Explorer

                         Astronomy Picture of the Day

    Discover the cosmos! [1] Each day a different image or photograph of our
 fascinating universe is featured, along with a brief explanation written by a
                           professional astronomer.

                                2018 January 31
                                      [2]
                              The First Explorer
                            Image Credit: NASA [3]

Explanation: Sixty years ago, on January 31, 1958, the First Explorer [4]  was
successfully launched by the Army Ballistic Missile Agency on a Jupiter-C [5]
rocket. Inaugurating the era [6]  of space exploration for the United States,
Explorer I was [7] a thirty pound satellite that carried instruments to
measure temperatures, and micrometeorite impacts, along with an experiment
designed by James A. Van Allen [8]  to measure the density of electrons and
ions in space. The measurements made by Van Allen's experiment led to an
unexpected and then startling discovery of two earth-encircling belts of high
energy electrons and ions trapped in the magnetosphere. Now known as the Van
Allen Radiation belts [9] , the regions are located in the inner
magnetosphere, beyond low Earth orbit [10] . Explorer I ceased transmitting on
February 28, 1958, but remained in orbit until March of 1970.

                    Tomorrow's picture: spiral comet [11]

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    Authors & editors: Robert Nemiroff [23] (MTU [24] ) & Jerry Bonnell [25]
                                  (UMCP [26] )
          NASA Official:  Phillip Newman Specific rights apply [27] .
              NASA Web Privacy Policy and Important Notices [28]
              A service of: ASD [29]  at NASA [30]  / GSFC [31]
                           & Michigan Tech. U. [32]
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Site notes:
  [1] archivepix.html
  [2] image/1801/explorer1_liftoff.jpg
  [3] https://www.nasa.gov/
  [4] https://www.nasa.gov/feature/
americas-first-satellite-established-foothold-in-space
  [5] https://history.nasa.gov/sputnik/expinfo.html
  [6] https://www.nasa.gov/feature/
explorer-1-the-beginning-of-american-space-science
  [7] https://explorer1.jpl.nasa.gov
  [8] http://history.nasa.gov/sputnik/vanallen.html
  [9] https://en.wikipedia.org/wiki/Van_Allen_radiation_belt
  [10] https://en.wikipedia.org/wiki/
Van_Allen_radiation_belt#Implications_for_space_travel
  [11] ap180201.html
  [12] ap180130.html
  [13] archivepix.html
  [14] lib/apsubmit2015.html
  [15] lib/aptree.html
  [16] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [17] calendar/allyears.html
  [18] /apod.rss
  [19] lib/edlinks.html
  [20] lib/about_apod.html
  [21] http://asterisk.apod.com/discuss_apod.php?date=180131
  [22] ap180201.html
  [23] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [24] http://www.phy.mtu.edu/
  [25] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [26] http://www.astro.umd.edu/
  [27] lib/about_apod.html#srapply
  [28] https://www.nasa.gov/about/highlights/HP_Privacy.html
  [29] https://astrophysics.gsfc.nasa.gov/
  [30] https://www.nasa.gov/
  [31] https://www.nasa.gov/centers/goddard/
  [32] http://www.mtu.edu/
