Was there a first spacecraft put in a polar orbit?

It might not be clear if it's too hard to say what high inclination orbit is or is not polar, for example if 91 satellites were launched in 0, 1, 2... and finally 90 degree orbits in sequence.

But if there were several high inclination spacecraft used by unnamed northern hemisphere countries to look at each other or in Molniya orbits and then suddenly there was a definitively first sun-synchronous orbit, then that might be it. A quick check of that article shows no instance of the word "first".


Discovery 1, launched Feb 28, 1959. The orbit wasn't quite high enough, it crashed a few days later, but it was the first, with an inclination of 90 degrees.

Launch date         28 February 1959, 21:49:16 GMT
Rocket              Thor DM-18 Agena-A  (Thor 163 - Agena 1022)
Launch site         Vandenberg, LC 75-3-4

Reference system    Polar orbit
Regime              Low Earth
Perigee altitude    163 km
Apogee altitude     968 km
Inclination         89.7°
Period              96.0 minutes
  • 1
    $\begingroup$ Discoverer 2 (14 April 1959) was more successful in reaching an orbit for more than just a few days. The very low perigee altitude of 163 km was the reason for the very short orbit livetime of Discoverer 1, the apogee altitude was 968 km. $\endgroup$
    – Uwe
    Feb 22 '20 at 16:58
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    $\begingroup$ More successful, but still not fully successful. But yes, you are right. Still, the question was which was the first spacecraft put in a polar orbit. Orbiting for several days is still orbit! $\endgroup$
    – PearsonArtPhoto
    Feb 22 '20 at 17:17
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    $\begingroup$ To me a single orbit above the Karman line counts toward being "put in a polar orbit" so this certainly seems like the clear winner, thanks! $\endgroup$
    – uhoh
    Feb 22 '20 at 23:50
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    $\begingroup$ @uhoh Rather than the Kármán line, you better follow the American FAA and NASA definition of the space border at 50 mi of altitude because it is more scientific. Except you mean the true Kármán line which is at 57 mi. Just meant as a good advice. $\endgroup$
    – user35272
    Mar 26 '20 at 13:27
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    $\begingroup$ @uhoh For example the FAA defines the 50 mi border. That's one for U.S. aerospace. The FAI definition is more of an opinion. It's not an "accepted" definition unless a nation does. $\endgroup$
    – user35272
    Mar 26 '20 at 16:29

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