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Re: Cassini Earth SwingBy
>Date: Fri, 13 Aug 1999 09:05:27 -0400
>From: Tad Blanchard <Tad.M.Blanchard.1@gsfc.nasa.gov>
>To: RADSAFE@romulus.ehs.uiuc.edu
>Subject: Cassini Earth SwingBy
>Message-ID: <3.0.1.32.19990813090527.0093aa30@pop200.gsfc.nasa.gov>
>
>Just a note,
>
>The Cassini spacecraft carrying 72 pounds of plutonium will be passing by
>the earth on Tuesday, August 17th, at approximately 11PM EDT.
>
>Everyone put on their hard hats. (just kidding)
It may be worth getting out your binoculars, if you live on Easter Island.
The spacecraft, launched on a mission to Saturn in 1997, is now precisely
set to make its closest approach to Earth at an altitude of 1,166
kilometers (725 miles) over the eastern South Pacific at -23.5 degrees
latitude and 231.5 degrees longitude. The spacecraft may be visible from
small islands in that area, such as Pitcairn Island or Easter Island. Two
successful flybys of Venus, next week's flyby of Earth, and a flyby of
Jupiter in December 2000 all give Cassini the additional speed it needs
to reach Saturn in 2004.
>
>Trajectory looks good. The spacecraft will be coming within 2000 miles of
>Earth to use its gravitational field to speed up the craft on its mission
>to Saturn.
>
>
And the last chance to abandon the mission by not doing the targeting burn
[leaving the miss distance at 5000km or so] came and went without protest. Now
we can credibly state that even if we didn't mind abandoning the mission,
leaving this orbit alone is safer than doing a burn just to increase the miss
distance [which has a small but finite chance of backfiring, especially since
it would be hastily computed]. Of course if we get protests two days before
closest approach, that'll tell us something.
-dk
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