MOUNT LEMMON - The pin marking the 9,157-foot summit of this mountain is driven into the asphalt of a road that leads to a cluster of small observatory domes.
But you can't blame this partially paved peak on astronomers.
The Air Force first occupied the summit in the name of national security, beginning in 1956. It built roads to three "arctic dome" radar sites, as Tucson became part of a defensive line of 200 such installations along U.S. borders and coastlines, all watching for incoming Soviet bombers.
As the Cold War deepened in the 1960s, it added three communications masts, blasting into the granite bedrock to mine 85-feet-deep bunkers to protect two of them. If needed, the towers could have burst from their bunkers to relay orders to 18 Titan missile sites around Tucson that stood ready to launch intercontinental ballistic missiles with nuclear warheads.
Eventually relations with the Soviet Union improved and the Air Force left Mount Lemmon in 1972. University of Arizona planetary scientists and astronomers, who had already established observatories on two lower peaks, moved to the summit and took over the buildings left behind by the 150 officers and airmen who had been stationed there.
The importance of the collection of relatively small telescopes known as the Catalina Observatories would ebb and flow over the years, but the mountain is in the midst of a minor Renaissance.
• The Catalina Sky Survey, which operates a 60-inch telescope on the summit and a 30-inch Schmidt telescope on nearby Mount Bigelow, has become NASA's champion finder of near-Earth objects (NEOs).
In every year since 2005, it has discovered more than half the objects reported to NASA.
NASA, ordered by Congress to find objects that could severely impact the Earth, is paying to outfit an additional telescope that will plot the orbits of threatening meteoroids. The $4.1 million NASA grant will also upgrade all of the program's cameras.
• The Mount Lemmon Sky- Center, a public outreach arm of the UA College of Science, is gaining popularity and was recently given a new 32-inch Schulman telescope by a private donor.
• The Korea Astronomy and Space Science Institute (KASI) operates a 40-inch telescope robotically from Seoul, whenever the moon and clouds don't interfere.
• The University of Minnesota has continued to operate a 60-inch telescope since its infrared astronomy program began in 1972.
• Sleeping quarters on the peak have been refurbished and a conference center, complete with commercial kitchen, built.
Steward astronomer Don McCarthy hosts astronomy camps on the mountain each summer, filling the dorms with students.
The rooms are also used for SkyCenter programs and by astronomers and researchers investigating everything from hydrology to hummingbirds.
Site leased to UA
Gerard Kuiper, who founded the UA's Lunar and Planetary Lab, persuaded the U.S. Forest Service to lease the site to the UA when the Air Force left.
Steve Larson, principal investigator for the NASA-funded Catalina Sky Survey, was an undergraduate, working for Kuiper at the time.
"His selling point was it was exactly what they needed," Larson said. "When the UA got it, it had all of three people to run it."
The UA did not need all those buildings.
The Air Force dismantled the radar when it left the peak in 1969, and many of its buildings have since been demolished.
The bunkers are still there, said Chuck Penson, historian at the Titan Missile Museum.
One arctic dome remains.
Its cement pillar would be perfect for a new telescope, said Bob Peterson, assistant director for operations at the UA's Steward Observatory, which operates the site.
The rec center, which once boasted an indoor basketball court and a two-lane bowling alley with automatic pin-setters, is home to astronomers from the University of Minnesota, whose 60-inch telescope is nearby.
A two-story barracks is boarded up, and the old power plant now houses a machine shop for the observatories.
Today, electricity is supplied by Trico Electric Cooperative, through a line running the spine of the mountain's west face.
Tanks that once held diesel fuel for the power plant now hold water for fire emergencies.
Over the years, the Catalina Observatories, which Kuiper turned over to the UA's Steward Observatory in 1972, have remained a shoestring operation.
The telescopes are used for educational programs, mothballed or swapped peak-to-peak as the need for them changes.
"We play musical telescopes here," said Larson.
Viewing still good
"Seeing" atop this urbanized mountain is still fairly good, said Larson.
You can't point the telescopes to the south horizon, where the glow of Tucson is constant dusk-till-dawn, but in most directions it's still plenty dark.
Sunset is Larson's favorite time on the mountain. On a clear October afternoon, he stakes out a spot on the roof of the mothballed radar dome to watch for the green flash that sometimes appears when the sun sets behind the western mountains.
Before that, he points east. On a clear day like this, the shadow of Mount Lemmon appears as a nearly perfect cone on the landscape, stretching all the way to Mount Graham, 60 miles away.
After sunset, the contest to find near-Earth objects is on.
"We all race to the most obvious part of the sky," says astronomer Rich Kowalski.
The sweet spot for NEOs is the ecliptic plane, the path of the Earth's orbit around the sun. "All NEOs cross that plane," Kowalski says.
Tonight, the 60-inch telescope on Mount Lemmon is being pointed by Jess Johnson, a new member of the Catalina Sky Survey staff, who is being supervised by Kowalski.
To be clear: The astronomers are not actually "looking" at the sky.
They sit in a heated, lighted room attached to the telescope dome, drinking coffee and monitoring computer screens.
The computer crunches data from the telescope's digital camera to identify moving objects in a sea of fixed starshine.
It edits out previously discovered objects and satellites of human origin. It flags new objects for the astronomers' perusal.
Good candidates are forwarded to the Minor Planet Center at the Smithsonian Astrophysical Observatory for confirmation. It issues bulletins to an army of amateur astronomers and research institutions for follow-up observations to plot the objects' orbits.
Sometimes, an approach is imminent.
Object hit earth
Kowalski holds the distinction of being the only NEO-watcher to spot one before it struck the Earth.
It exploded over the desert of northern Sudan 19 hours after Kowalski spotted it in October 2008. It was the size of a pickup truck when it entered the atmosphere. The chunks that made it to the surface were no bigger than baseballs.
Kowalski was given a small piece. "I am the first person to observe an astronomical object before it crashed to Earth. I'm also lucky enough to be the first person to own a piece of an astronomical object he discovered."
"Luck" is the operative word, Kowalski says. He just happened to draw the right shift at the right telescope, pointed in the right direction. "Anyone on the team could have been the one to see it that night."
The skill and technology needed to create such "luck" is evident on this clear October night.
Those meteors and comets have lots of places to hide in what looks to be a faint cloud covering a big swath of the night sky.
It is a cloud of stars - the hundreds of billions of suns that make up the Milky Way, our home galaxy.
On StarNet: To read the other parts of this series go to azstarnet.com/news/science
• Oct. 28: How the mountains formed - and how they create what lies beneath them.
• Nov. 4: Tucson's sky island: birds that migrate vertically; native vs. non-native species; fire on the mountain.
• Today: Looking at stars and guarding against meteorites - new uses for aging telescopes and top-secret facilities.
SKY ISLAND EDUCATION, INFORMATION
• UA Science: Flandrau has an exhibit about the geology, biology and ecology of the Sky Island region. Kids can climb a "rock" wall mural of the Wonderland of Rocks in the Chiricahua Mountains and build hoodoos by stacking realistic, but very lightweight, rocks. For info: 621-4516 or www.flandrau.org
• Arizona's Sky Islands are mostly federal preserves and are managed by the Coronado National Forest. For maps and other information, go to: www.fs.usda.gov/coronado
• Saguaro National Park contains a swath of high-mountain wilderness in the Rincon Mountains. Information at: www.nps.gov/sagu
• The Sky Island Alliance website has reports and information on Sky Islands in Arizona and Mexico: www.skyislandalliance.org
Contact reporter Tom Beal at email@example.com or 573-4158.