The NEAR Sunglint Event of 9 January 1998
Last modified on January 12, 1998 by
A. Richichi
On January 9, 1998 a
mail
was circulated by
D. Dunham,
announcing a peculiar type of event to take place later on the same
day, namely a glint produced by solar panels
of the space probe
NEAR
as they reflected shortly the solar light towards
the Earth from a distance of about 8 million km. Click
here
for more details.
At the
TIRGO
observatory, we set out to measure the event although last minute revised
predictions by Dunham were now pessimistic about the actual chance
of observation. The observation was carried out by
A. Richichi
and
M. Sozzi .
We used the NICMOS3-based infrared camera
ARNICA,
in conjunction with a special data acquisition software developed by
Carlo Baffa for
lunar occultation
observations, which allows continuous fast integration on a small
area of the infrared array. A total of 5 minutes were recorded
on a 32 by 32 arcsec area at a rate of 5 Hz, starting at 21:27:00 UT.
The event, if any, was predicted as a brightening to about V=12
for a duration of about 1 second, any time in the 1-2 minutes after
21:28:03 UT. It was unknown to us how this would translate at
2.2 micron, our wavelength of observation, but in any case given
the V-K solar spectrum and the sensitivity of the camera, it was estimated
that we should be able to detect the glint.
The results are shown here as a
plot
of the integrated flux as a function of time, and as a
MPEG movie:
large format full data
, (2.7Mb), or
small format, 1:10 undersampling
, (33kb).
In the plot, a brightness variation is visible on a scale of about
1-2 minutes: this is too slow to be the sunglint event and is
probably only a sky fluctuation. After this preliminary analysis,
we conclude that the event was not visible from the Earth.
Nevertheless, we are prepared to try again at the next opportunity!