[meteorite-list] Comet Pioneer Fred Whipple Dies

From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Tue Aug 31 14:11:31 2004
Message-ID: <DIIE.0000001D000027EF_at_paulinet.de>

Ron Baalke wrote:

> This is sad news. The Whipple Shields on the Stardust spacecraft,
> which protected the spaceraft during its Comet Wild 2 encounter
> earlier this year, were named in his honor. I first corresponded
> with Whipple in 1997, and he wrote this letter to the project:

> http://stardust.jpl.nasa.gov/science/whipple_letter.html

> Fred Whippled was invited by the project to the Stardust
> launch in 1999, where I first met him in person.


WHIPPLE F.L. (1987) The Black Heart of Comet Halley
(Sky and Telescope, Mar 1987, pp. 242-245, excerpt):

Fred L. Whipple, Harvard-Smithsonian Center for Astrophysics

For decades I have wondered what a comet's nucleus would look like. The
idea that comets are flying sand banks (spawned by their association with
meteor showers) dominated the scene for much of the 19th and 20th centuries.
But by 1950 the observations in hand proved to me that a "dirty snowball" was
a much more reasonable description, and it still fits. As for shape, I expected
the nucleus to be irregularly oval, perhaps with knobs or other protuberances.
This bumpy structure, I reasoned, would have resulted from many smaller snowballs
coming together at low speeds, or from the uneven loss of an irregular mixture
of substances. More recently, careful reanalysis of Halley photographs from 1910
had left me prepared for, possibly, large valleys and rifts in the nucleus. I even
entertained the provocative idea that Halley might be a binary object.

The years of anticipation turned to months, then days, as the Vega and Giotto
spacecraft approached their target. I worried whether the surrounding dust cloud,
illuminated by glaring sunlight, would so outshine the nucleus as to render it
unobservable. After all, the encounters coincided with the time of maximum activity,
about a month after perihelion.

They would have been safer a month or so later, giving Halley's dust production a
chance to die down a bit. But the lack of more powerful launch vehicles forced the
spacecraft to intercept the comet near the ecliptic plane, and this geometry dictated
the encounter dates in early March. Even so, I was more optimistic than some, relying
largely on the hope that the opacity of the dust cloud would block enough sunlight to
subdue the nucleus' activity.

The days dwindled to hours then minutes. With a final frantic rush, our robot emissaries
swept through Halley. Motors whirred, shutters opened, and at long last the waiting was over.
Received on Tue 31 Aug 2004 02:11:30 PM PDT