[Launch Alert] Thursday Vandenberg Launch

Mon, 23 Jun 2003 18:19:37 -0700

		ASTRONOMY/SPACE ALERT FOR SOUTHERN CALIFORNIA

				    Brian Webb
			   Ventura County, California
			 E-mail: [email protected]
		 Web Site: http://home.earthlink.net/~kd6nrp

	    Reaching more than 2,020 e-mail addresses worldwide

						   2003 June 23 (Monday) 18:10 PDT
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	   The following is a news release from Vandenberg AFB

			    PEGASUS LAUNCH SCHEDULED

VANDENBERG AIR FORCE BASE, Calif. - Team Vandenberg is set to launch
an Orbital Sciences Corporation Pegasus rocket from the underbelly of
an L-1011 aircraft. The launch window is 11:50 a.m. to 12:05 p.m.
Thursday*.

The spacelift commander for this mission is Col. Wayne Louis, 30th
Space Wing vice commander.

The rocket will place Orbimage's OrbView-3 satellite into a near-polar
orbit. The satellite provides high-resolution imagery from space, to
include one-meter resolution panchromatic and four-meter resolution
multi-spectral imagery. One-meter imagery enables it to create highly
precise digital maps showing houses, cars and even aircraft.

The L-1011 will reach an altitude of 39,000 feet, traveling at about
500 mph when the rocket is released. The rocket will then free-fall
horizontally for five seconds before the primary engine takes over and
accelerates the Pegasus to Mach 8. 

*Thursday June 26th
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			    INVISIBLE CLOUDS - PART I

Each year from about late May to mid-July, television viewers in the
northern hemisphere experience substandard reception. Affecting
channels 2 through 6 (but especially 2 and 3), the picture may slowly
pulsate, have stripes moving across it, or contain a different program
in the background. The problem is actually interference from a distant
TV station on the same channel hundreds of miles away.

Channels 2 through 6 lie in the VHF portion of the radio spectrum, a
swath of frequencies running from 30 to 300 MHz. VHF signals usually
follow a line-of-sight path that limits their reception to about 150
miles. This is the norm, unless of course, something prevents the
signals from escaping into space and reflects them back toward Earth.

Several times per year, but especially during late spring and early
summer evenings, thin, dense clouds of ions capable of reflecting
radio waves form high above the Earth. These invisible clouds occur at
an altitude of 70 miles - just below the E-layer of the ionosphere.
Known as "Sporadic-E", "e-skip", or "Es", these ionized patches allow
for the reception of television and other VHF signals from 375 to
1,300 miles away.

During a good Sporadic-E opening, distant stations can be received on
TV channels 2, 3, and 4. Even more intense openings can provide long
haul reception on channels 5 and 6.

The majority of readers are probably content with knowing the cause
of their annual TV reception problems. However, if you find this
phenomenon interesting, you might want to try your hand at receiving
and identifying these distant stations.

The trick is to recognize when a distant TV station is interfering
with your local channel 2 through 6 TV station. When that happens,
check the channels between 2 and 6 that are unused in your area. If
you see a station that's not normally there, start your VCR and wait
for station identification at the top of the hour and on the half
hour.

If your cable TV company has filled the otherwise unused channels
between 2 and 6 with other programming, disconnect the cable and use
a pair of rabbit ears.

The best way to bag distant TV stations via E-skip is to use a TV to
detect the presence of skip followed by a high-end police scanner
with a good antenna to listen for TV audio on the unused channels. The
audio for TV channels 2 through 6 is broadcast in wide FM mode on
59.750, 65.750, 71.750, 81.750, and 87.750 MHz, respectively.

If you're lucky enough to receive a distant TV station, you can
identify it by going to the following TV station lists:

	http://home.earthlink.net/~w9wi/tvdb/channels/2.htm

	http://home.earthlink.net/~w9wi/tvdb/channels/3.htm

	http://home.earthlink.net/~w9wi/tvdb/channels/4.htm

	http://home.earthlink.net/~w9wi/tvdb/channels/5.htm

	http://home.earthlink.net/~w9wi/tvdb/channels/6.htm

A sound clip of a distant TV station received via Sporadic-E skip is
posted on my web site at:

	http://home.earthlink.net/~kd6nrp/library.htm

under the name "skip_kenw.mp3".