Milstar 3 to enter and exit shadow within 10 minute period tonight.

Ted Molczan (
Sun, 6 Jun 1999 17:21:22 -0400

Tonight, during passes over N. America, Milstar 3 will enter the Earth's
shadow for nearly 10 minutes, and then come back into sunlight.

Based on the elements I posted earlier today,

Milstar 3       15.0  4.5  4.5  3.8 d
1 25724U 99023  A 99157.21149306  .00000000  00000-0  00000-0 0    03
2 25724  28.2000 200.3000 2135000 129.0000 138.9000  9.37361000    02

here are approximate times for the key events:

7 Jun 99 UTC

05:13:49  enters penumbra
05:14:46  enters umbra
05:23:30  leaves umbra
05:24:21  leaves penumbra

The above is more likely to be observed from the eastern half of the
continent. The west will be better placed to see the following pass:

07:47:40  enters penumbra
07:48:39  enters umbra
07:56:56  leaves umbra
07:57:50  leaves penumbra

I caution that there remains some uncertainty about the orbit, so the above
times could prove significantly in error, though probably well within 1 or 2
minutes. Also, the object's standard magnitude is still uncertain, so I
recommend using binoculars.

If your ephemeris program cannot predict both shadow entry AND exit events
during a single pass, then I suggest setting it to ignore the existence of
the shadow, and simply note the above times on the ephemeris.

The long period spent in the penumbra is expected, since the object is
making a grazing pass into the umbra.

Timing the eclipse events will aid in refining the orbit.

A similar event will occur tomorrow night, but the time in umbra should be

Ted Molczan