NORTH ANDOVER, MASS.
In four minutes, the Russians are coming.
Dusk passes on this cold, still day just after winter solstice, and Russ Pinizzotto directs a visitor to look skyward. Venus blazes to the southwest, but Mr. Pinizzotto peers in the general direction of Mars, and waits.
Right on schedule, a celestial occurrence of the man-made kind: Cosmos 1222, a satellite lobbed up in the waning days of the cold war, ambles across the sky like a slow-motion meteor without a tail. "There," says Mr. Pinizzotto, not bothering to raise his binoculars.
Minutes later, in a different orbit, comes the discarded body of the rocket that launched it. And then, knifing brightly across the constellation Cassiopeia, a Lacrosse 4 US radar satellite.
"People are surprised," says Pinizzotto. "They ask, 'What night can I see a satellite?' No, it's 'How many satellites can I see on any given night?' "
Pinizzotto logged 40 one summer evening from a lawn chair in Maine. The dean of science and engineering at Merrimack College here, he's also an avid satellite observer, one in a subset of skygazers who like their astronomy with an earthbound twist.
Part bird-watchers, part train-spotters, these people know their star charts. But they are as likely to rhapsodize about a sighting of the International Space Station, XM Radio's geostationary duo (dubbed "Rock" and "Roll"), or an iridium flare (a flash of reflected sunlight from a communications satellite) as they are to gush about a glimpse of Saturn's rings.
This game is as old as Sputnik, and it can often be played from any dark spot with the unaided eye. (Warning: It's hard to stop.) But participants' skills have improved along with sky-tracking software and good, inexpensive telescopes and mounts.
Hobbyists can share and network on the Web. Heavens-above.com, for example, provides a remarkably simple guide to the galaxy, complete with local satellite-viewing times organized by magnitudes of brightness and showing precise trajectories.
Amateurs contributed some of the data in a major aggregation of satellite specifics posted online last month by the Union of Concerned Scientists, according to Laura Grego, a staff scientist for the Cambridge, Mass., organization. As part of its push for public awareness of space-based government activities, the UCS (ucsusa.org/satellite_database) lists some 800 active satellites by launch date, country of origin, sponsor, and orbital coordinates. It ignores inactive satellites and other space junk.
"There are many thousands of things in this [junk] category ... from large, spent, rocket bodies and abandoned satellites to small bolts and bits of paint," says Dr. Grego. The rate of launches has declined since the 1990s, which saw about 125 a year. But in five years, she figures, 1,000 actives will be in orbit - more traffic for space shuttles to negotiate.
Satellites range from softball-size to 15-by-6-footers such as the Lacrosse series and the European Space Agency's Envosat, an environment monitor. Many small, relatively inexpensive satellites - some go up as placeholders for licensees planning later launches - will never be seen from backyards.
Hard-core watchers become immersed in the arcane. Occasionally a satellite will be lost while having its orbit adjusted. "Once they start to tumble - game over," says Pinizzotto, who first saw satellites as a child when his father pulled him outside to see a passing Echo (an early US communications satellite).
Hobbyists have been known to time a tumbler's flashes to determine spin rates. Some "X-Files" types even eye surface-area-to-mass ratios, says Grego, in hopes of sorting possibly secret satellites from space debris.
The government has been frosty toward private observers. "The less people know or think they know about what we have, that is certainly our preference," a National Reconnaissance Office spokesman told the Associated Press.
"I think amateur observers have improved the US space-surveillance-network catalog, even on unclassified objects," says Grego. "They check up on things that don't get high priority. They find errors more quickly."
Plenty of satellite-watchers harbor a simpler fascination.
"If you go to a star party, where people go out to look at the stars with telescopes, and a satellite goes overhead, people always ooh and ahh," says John Goss, secretary of the Astronomical League, a 17,000-member association of astronomy clubs. "It's kind of a mark of human achievement that is somewhat out of reach, in the unknown, yet there it is, right there," he says of the allure.
Mr. Goss is not starry-eyed about artificial orbiters. "If you're an astrophotographer and you're taking pictures of star clusters or nebula, you don't want a satellite streaking across your picture."
Others see the far reach of mankind as being worth a glance. Some 200,000 Americans call themselves at least occasional amateur astronomers. If they'll come out for a comet, they might want to see the Space Shuttle transit the moon.
"I have looked though an 8-in. telescope that was tracking the International Space Station when a shuttle was docked to it," says Michael Bakich, an associate editor at Astronomy magazine. "And you could make out the outline ... that's kind of fun."
On this cold night, Pinizzotto holds out for one more fly-by, another rocket body that arcs close to the horizon, beneath the Pleiades star cluster.
"You're outside, you think you want to look at some satellite, and another one comes across your field of view that you didn't know about," he says. "And you just have to go figure out what it is."