David Dunham wrote on 31 July:

Edwin Goffin predicts 289 occultations by (37655) Illapa

     Earlier this month, Sergio Foglia in Italy asked Edwin Goffin
to predict occultations by the 900-meter asteroid (37655) Illapa
during its close approach (within 0.03 A.U.) in mid-August.  Edwin
has calculated 289 occultations by this object, about which he
writes:

"Predicting occultations of an asteroid that comes close to Earth poses
a bit of a problem:

- occultation durations will be very short (small diameter & fast motion)
- there will be many possible occultations due to the large parallax

Anyhow, I ran my occultation program and found 289 possible events
for the 2 weeks from Aug. 5 till Aug 19.  A plain ASCII text file at
http://iota.jhuapl.edu/37655724.txt gives details, one line per
event.  I also created a 1.4-megabyte PDF file that you can obtain at
http://iota.jhuapl.edu/37655724.pdf which shows the essential data
for each event & a view of the occultation track across the Earth as
seen from the asteroid (the night side of the Earth is enclosed by
the thick curve).  On the second text line of each view, you will
find: number & name of the asteroid, predicted duration of the
occultation, vis. magnitude of the star, and distance and %
illumination of the moon."

The current orbit could be in error by a few hundred kilometers.
But Jon Giorgini at the Jet Propulsion Laboratory writes:

"You probably know 37655 Illapa is scheduled for Goldstone radar
August 13, 14, 15 (prior to close-aproach), then again Aug 18, 19.
If the experiment proceeds as planned, the orbit will be updated as
part of the radar experiment and that new orbit, covariance will be
available in the publicly accessible Horizons system on the 14th
(and the radar astrometry will be posted)."

Then it should be possible to determine the orbit to an accuracy
smaller than the asteroid.  At that point, the predictions can be
updated and paths accurate to about a km might be predicted (errors
in the star positions will contribute an error of a few to several
hundred meters).  If the updated paths can be generated and
distributed quickly, video observers might be able to record some of
these events.  Since the events will be so quick, there will be
little value in such observations except for astrometry.  An
occultation will last only a few frames at best so that it will not
be possible to improve the shape over what will be done with radar.

Hopefully, updated predictions can be posted at either Steve
Preston's site at http://www.asteroidoccultation.com or at the
asteroidal occultation section of the main IOTA site at
http://www.lunar-occultations.com/iota/asteroids/astrndx.htm .

The PDF charts are numbered consecutively in the upper left corner.
Of these, events of interest to North American observers are numbered
13, 21, 22, 23, 37 (all of the preceding will be before the radar orbit
update), 48, 52, 54, 55 (probably before the update), 93, 94 (good,
mag. 9.1, east USA), 96, 98, 101 (mag. 8.9, east USA), and 108.  Some
good events visible elsewhere are listed below:

PDF      star
 #  Aug. mag. Area
 59  14   7.4 s.e. Australia?
 76  14   9.7 Red Sea, s.e. Europe
 78  14   8.7 n.e. Africa, Sardinia
 81  15  11.5 Africa, Iberia
 82  15  10.8 n.e. Africa, Sadinia, France
 93  15   9.7 s. Brazil to Yucatan
102  15   5.5 Antarctic Peninsula, Tahiti?
142  15   7.7 s. NZ, Australia (s.e & n.), Kalimantan
162  15   6.1 s. & w. Australia, Sri Lanka, s. India
211  16   7.1 Antarctica, s. Africa?
213  17   9.1 southern Africa
241  17   4.8 Indian Ocean
244  18   5.7 Indian Ocean
263  18   7.0 southern Africa
264  18   9.1 southern Africa
286  18   7.8 Antarctica (South Pole)
287  18   6.5 Antarctica (South Pole?)
288  18   7.4 s.e. Australia

[Top of Page][Return to Home Page]