The Mysterious Interloper - is it space junk?
(23 March 2009) back

At 01:08:38 UT on this night an unknown satellite trails through the field of view. It's pretty faint. At the mid-point of the 50-second exposure (arrow), the satellite's position is RA= 09:09:04.07 and Dec= +09:36:17.2, and it's in the sky at alt= 57.092 degrees and az= 148.934 degrees. It's moving west to east (right to left) at a rate of 9.89 arcsec per sec. The brightest flashes compare with the 15.1 magnitude star, ZN075:0900 (circled). The 4-flash cycle in the satellite's image trail shows that, in the space of 50 seconds, the satellite has tumbled about 5½ times.

Can we learn anything more about this object? There would be several questions we'd need to answer first:

  • How high is the Earth's shadow? (the satellite is in the sun, after all)
  • How high is the satellite (it has to be above the Earth's shadow)?
  • How fast is a satellite at that altitude actually moving? (in meters per second)
  • Is that in agreement with the angular rate of motion we see here? (9.89 arcsec per second)
  • If we get all this, can we make an estimate of its size based on it's apparent magnitude?

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