Irony alert: radio astronomy organization hands out fitness devices that threaten interference to radio-telescope operation.

gbt-fitbit-1Wrist-worn activity monitors like the Fitbit are good for radio astronomers. But not so good for radio astronomy.

Much as traditional astronomers use optical telescopes to see with visible light, radio astronomers use “radio telescopes” to observe distant objects by the radio waves they emit. With huge antenna dishes that focus on selected points in the sky, these telescopes are the most sensitive radio receivers on the planet. That makes them highly vulnerable to interference from other radio sources.

The biggest steerable radio telescope in the world, and probably the most sensitive, is at the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia. Having a dish 100 meters across and an antenna boom that makes it 60 percent taller than the Statue of Liberty, this is the world’s largest moving object on land.

To protect the telescope and others nearby from interference, the FCC maintains a National Radio Quiet Zone in and around Green Bank. Radio transmissions are severely limited, especially within 10 miles of the big telescope. There is no cell service; Wi-Fi and Bluetooth are prohibited; radio and TV reception are poor. The town has become a haven for people who think they are allergic to radio waves.

The NRAO Human Resources department, which does not think people are allergic to radio waves but is nonetheless concerned about the well-being of its staff, issued Fitbits to help personnel track their activity levels and thereby encourage exercise. Anywhere else in the country, this would have been a laudable initiative. But Green Bank is a different kind of place.

A Fitbit device syncs with the user’s phone via Bluetooth, a form of low-power radio communication. Although Bluetooth is not allowed near the telescopes, NRAO people can be trusted not to sync their devices on site. But NRAO scientists, at least the ones we know, are skeptical by nature. On a hunch, they put a Fitbit into a radio-emissions test chamber and monitored Bluetooth frequencies. Their skepticism paid off. The Fitbit transmitted data not only while syncing, but also in short bursts every second of the day. A worker wearing one of these while on the telescope structure could create an interfering signal 10,000,000,000 times stronger than international recommendations permit.

The scientists who ran the tests note that a Fitbit can be carried safely if stuffed into a modified metal pill fob. But we’re guessing that most NRAO personnel, accustomed to measuring the Universe and its expansion with the most sophisticated equipment known to science, will go back to measuring their own expansion with a tape measure and bathroom scale.

(Thanks to Dr. Harvey Liszt of NRAO.)