Catch a Manmade Star
By Philip Chien


The once difficult and obscure geek sport of observing orbiting
satellites from Earth is today within reach of most anyone, thanks to
the web.
But a few hobbyists still take it extremes.
Hundreds of artificial satellites are visible to the naked eye. Just go
outside on a clear evening immediately after sunset, or just before
sunrise, and you may see a star-like object cross the sky. Satellites
are visible when they're in sunlight but the ground is still relatively
dark.
In the early days of the space program, satellite viewing opportunities
were calculated with grease pencils on plastic overlays and onionskin
printouts of pages filled with arcane numbers. Now satellite tracking is
incredibly simple. Chris Peat's popular Heavens Above website
automatically calculates which satellites are visible from any location
in the world. All you need to know is the name of your town.

One of the easiest satellites to view is the International Space
Station, or ISS. It's large, travels at a relatively low altitude and
moves very rapidly -- 17,500 miles per hour. Contrary to NASA's claims,
it's not the third brightest object in the night sky -- the Moon, Venus
and Jupiter are all brighter, and some far smaller satellites can shine
brighter than ISS under the correct circumstances.

But if home satellite viewing is easy, some folks take it to the level
of an extreme sport.
John Locker in Wirral, England, uses a computer-controlled telescope
with a video camera to track satellites. The amateur astronomer captured
his most recent trophy last Wednesday, when he took a video of the space
station as it flew in front of the Sun.

"For me, this was a go, no-go, go situation, as the weather here closed
in," Locker wrote in an e-mail to a space-watching list. "On a spur of
the moment decision I decided to make the 30-mile round trip to a
pre-surveyed location, just in case things cleared up. Fortunately the
sky improved sufficiently to grab a couple of frames." In the resulting
video, ISS appears as a small triangle silhouetted against the sun.
A week earlier, satellite observer Jim Albers reported observing ISS as
it passed in front of the Cal Sky website is an excellent resource for
those pursuing this sport). Solar and lunar transits are extremely rapid
and the ISS takes only a fraction of a second to flick across the face
of the sun or moon -- the span of just a couple video frames.

Radar provides another extreme method for tracking satellites. The U.S.
Navy Space Surveillance System, or NAVSPASUR, is a chain of radar
stations across the southern United States that transmit a powerful
fan-shaped radar beam at 216.98 MHz. As satellites pass through this
invisible wall their reflected radar signals wash over ground stations.

Any UHF radio (available from Radio Shack and ham radio stores) that
receives that frequency can hear the radar pings as the signals bounce
off satellites. It's even possible to hear radar reflections from the
moon twice a month as it passes through the NAVSPASUR fence.

Amateur radio operator Pieter Ibelings managed to log a radar
observation of the ISS as it crossed the fence over Alabama last week.
"The one amazing fact is that I was able to see the ISS for about one
minute on the Lake Jordan transmitter," he reported on a mailing list.
"I did not expect it to last that long."
Ibelings posted a recording of his electronic sighting, and used a
shareware spectrum analyzer program to convert it into a graphic.

But of course satellite tracking doesn't have to be so challenging to be
interesting. Last Monday this reporter was at a restaurant in Cape
Canaveral, Florida. I knew the Space Station -- with the space shuttle
Discovery attached -- would soon be passing overhead, and the weather
looked promising, so I encouraged about 50 people to join me on the
balcony.

Many had never seen a satellite before; others were NASA workers who had
prepared the shuttle Discovery. Together, we craned our necks and
watched as a dot of light described a smooth arc across the night sky --
all of us knowing it was a couple of hundred miles above us and nine
people were onboard.