USA-179 - OrbitThe map shows the sub-satellite ground track at 2006 November 17. USA-179 itself is above Italy at an altitude of 81,884 kilometres, close to the morning day/night terminator. The plot is based on this element set from Mike McCants's "classified.tle" file:
1 90027U 04841A 06322.78169364 0.00001111 00000-0 63148-0 0 01 It describes an orbit of 1,499 x 38,858 kilometres at 62°.6 inclination with an anomalistic period of 717.80 minutes.
The shape of the ground track plot is produced by a combination of USA-179's motion around its orbit and the rotation of the Earth. The symmetry is driven by the fact that the argument of perigee is very close to 270° which puts apogee at northern apex. There is almost zero atmospheric drag on a satellite in an orbit like the one occupied by USA-179. However, there are gravitational influences that pull it away from its elliptical shape and pull it out of position. They come from the Sun, the Moon and the fact that the Earth itself is not a uniform shape. Because of these influences, controllers find it necessary to correct the orbit every 20 days or so in order to keep things as they want them. The year pages listed in the left hand menu tell the story from mid-2006. One interesting fact is that USA-179's orbital adjustments are carried out mainly at the weekend from Friday afternoon through to Monday morning.
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