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Explorer 33
Explorer 33 Mission to Earth's Moon

Goals: Explorer 33 was designed to become the first U.S. spacecraft to enter lunar orbit, where it was to study interplanetary charged particles, magnetic fields, and solar X-rays.

Accomplishments: Explorer 33's second-stage launch gave it too much velocity, so its retrorocket was unable to slow it down enough to be captured by the Moon's gravity. Instead, it continued to fly in a very long, elliptical orbit around Earth that stretched more than 50,000 km beyond the Moon's orbit. Nevertheless, it returned key data on Earth's magnetic field, the interplanetary magnetic field, and radiation.


Key Dates
1 Jul 1966:  Launch (16:02:25 UT)
21 Sep 1971:  Contact Lost
Status: Partial Success
Fast Facts
Explorer 33 Facts This was intended to be the United State's first lunar orbiter, but it was travelling too fast to be caputred by the Moon's gravity.

NASA's Lunar Orbiter 1 achieved that goal later in 1966, snapping hte first picture of Earth from the Moon (right).

Even though Explorer 33 missed its primary target, it still returned useful information on interplanetary space.
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Last Updated: 29 Nov 2010