August 2002 Sky from Keeble Observatory
With the rocket's bright exhaust plume brightening the pre-dawn
sky, NASA's latest comet probe was successfully launched from Cape
Canaveral at 2:43 am on the 3rd of July. CONTOUR (Comet Nucleus
TOUR) was placed by its Boeing Delta II launch vehicle into
an eccentric 42-hour elliptical orbit about Earth, from where it
will be boosted into solar orbit on August 15, on its way to rendezvous
with two comets in 2003 and 2006. The ambitious Discovery class
mission will cost a total of $159 million, and is expected to provide
our most detailed ever knowledge of comets - which are understood
to be remnants of the formation of our Solar System some 4.6 billion
While in its phasing orbit - which ranges from a mere 124 miles
at its closest approach out to over 71,000 miles (200 km - 115,000
km) - the Earth and the two target comets will shift relative positions
until they are aligned for a simple slingshot trajectory to carry
CONTOUR past its targeted comets. On the 15th of August, somewhere
over the Indian Ocean, the probe's solid rocket booster will initiate
a 50 second burn to carry the spacecraft away from Earth. Instrument
check-out will take place over the following months, until mid-October,
when the spacecraft will be powered down for its cruise mode,
with only communications and guidance systems active.
Sometime in mid-July of 2003 all systems will be brought on line
for its encounter with Comet Enke on 2003 November 12. A
full array of cameras and spectrometers will study the comet nucleus
from as close as 100 km (62 miles). The environs of an active comet
are hazardous, with rock and dust accompanying the vented gas from
the comet, at speeds of tens of kilometers per second. The probe
is protected by a 10 inch thick layer of Kevlar armor - the same
material used for bullet proof body armor for police and military.
After the first flyby, the probe will return to cruise mode until
its encounter with Comet Schwassmann-Wachmann 3 in 2006.
The mission profile is designed with sufficient flexibility that
CONTOUR could be retargeted should some newly discovered comet (a
la Hale-Bopp of recent memory) happen to make an appearance
in the inner solar system.
Lunar phases for August: Last Quarter at 6:22 am on the
1st (and again on the 30th at 10:31 pm); New Moon at 3:25 pm on
the 8th; First Quarter on the 15th at 6:12 am; Full Moon on the
22nd at 6:29 pm.
The Perseid meteor shower will peak 10-13 August. Best viewing
will be in the pre-dawn on the 12th, but expect increased numbers
of shooting stars for about a week around those dates. Get away
from city and town lights for the best chance of seeing this annual
Early evening planet viewers will have to content themselves with
Venus this month. It's still the brightest thing emerging
from the western twilight. Mercury is particularly low on
the horizon, and not likely to be seen in the twilight before it
sets. Jupiter and Saturn can be seen in the pre-dawn, to
the east and east southeast. Saturn rises about 3 hours before dawn
at the beginning of the month, and is high in the sky in Taurus,
where it will appear as the brightest star in that constellation.
Jupiter emerges from the Sun's glare, and climbs higher at dawn
as the month advances. Saturn stays about 40 degrees ahead of Jupiter
on the sky for the whole month. Overhead at about 10:00 pm at mid-month
you will see the bright star Vega close to zenith. It marks
the western end of a triangle of bright stars - Deneb is
a bit to the northeast, Altair to the southeast. Deneb is
at the tail of the constellation Cygnus (the Swan), which
marks the general direction in space towards which Earth and Sun
are orbiting in the Galaxy. The center of the Galaxy lies to the
south, in the constellation Sagittarius. To the southwest you will
see the bright red star Antares, in the constellation Scorpio.
From Vega to the west, you will see the irregular square of Hercules,
and closer to the horizon the bright star Arcturus. To the
northwest is the big dipper of Ursa Major. The pointer
stars at the end of the bowl of the dipper direct your eyes to
Polaris, which is approximately due north.
For your own monthly star chart, you can direct your web browser
You will find extensive descriptions of what's worth looking for,
and you can download and print a single copy for your personal use.