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National Geodetic Survey

A Brief History of the NOAA Very Long Baseline Interferometry Program, NOAA 200th Anniversary Website

Historic NOAA Space Observatory 'Recycled' into Maryland Green Space

Gaithersburg Latitude Observatory

The Gaithersburg Latitude Observatory located in Gaithersburg, Maryland, circa 1910. Image courtesy of the City of Gaithersburg.

In a charming residential neighborhood off the noisy main drag of Gaithersburg, Maryland, about a half-hour’s drive northwest of Washington, DC, a place where NOAA scientists once gazed into space has found new life as a public green space.

Nestled amidst Victorian-era cottages like a precious gem at the back of a jewelry box, Latitude Observatory Park is the historic 2.3-acre site of the International Latitude Observatory (ILO). For 83 years, staff from NOAA and its predecessor agencies collected star data there to measure the wobble of the Earth on its axis for navigational purposes.

The observatory, founded in 1899, was one of only three ILOs in the United States and six in the world. The location became a National Historic Landmark in 1989, when the National Park Service decreed that it possessed national significance in commemorating the history of the United States. On May 12, 2011, Latitude Observatory Park officially joined the City of Gaithersburg park system.

The Chandler Wobble

massive Zenith telescope

NOAA observers used this massive Zenith telescope to measure the stars' nightly perambulations. Image courtesy of the City of Gaithersburg.

Rick Foote, a geodesist at NOAA’s National Geodetic Survey, explains the observatory’s historic and scientific importance.

“The American astronomer Seth Carlo Chandler, Jr., first discovered the wobble of the Earth's poles in 1885, and by 1899, the six ILOs had been built to confirm his theory, known as the Chandler Wobble.

“The Chandler Wobble is important because navigational systems, including modern global positioning systems (GPS), must allow for the effect of the poles’ wobble on navigation. Additionally, nautical and astronomical charts must be updated to show the new reference points for the geographic North and South Poles.

“In 1982, the Gaithersburg observatory was closed as computers took over the job of measuring the stars and analyzing the data. Nevertheless, the historic data collected from 1899 to 1982 continues to be used for GPS and other navigational purposes today.”

Shivering for Science

tiny observatory

For 83 years, the nightly research conducted in this tiny (~6'4" square) observatory contributed to the science of global positioning and paved the way for many modern marvels.

As the last NOAA “observer” to work at the observatory, from 1965 until his retirement in 1982, Mac Currin recollects what it was like to track and record star data prior to the advent of supercomputers.

“When the stars came into our field of view, we took measurements through a Zenith telescope and recorded them by hand in a notebook. Every Monday, we photocopied our work and sent it to the ILO in Japan, as did the other ILOs. That’s where the measurements were analyzed and, over time, the Chandler Wobble was calculated.

“It was great working there most of the year, but it sure got cold sometimes!” says Currin, who spent 17 winters on the night shift in the tiny slatted-pine observatory, which was specially constructed so that the indoor and outdoor temperatures matched.

Hard as it is to imagine now, two observers worked side by side -- “Whoever measured was the ‘Head Observer’ and whoever recorded was the “Assistant Observer,” Currin chuckles -- without benefit of heat in wintertime, when the mercury regularly plunged below freezing, because sudden temperature changes could alter the telescope’s delicate instrumentation.

It was so important to record their exacting measurements at the ambient temperature, recalls Currin, that “We read the levels on our gauges with a flashlight, and actually painted the reflecting portion black so it wouldn’t project any warmth.”

The Stars Align Anew

Mac Currin

At the dedication ceremony for Latitude Observatory Park, Mac Currin, NOAA's "observer emeritus," reflected on his 17 years of precision stargazing.

Michele Potter, Director of Parks, Recreation, and Culture for the City of Gaithersburg, is excited for the public to learn about, and relax at, Latitude Observatory Park.

“It’s wonderful for the City of Gaithersburg to be part of both history and the future at this site, which is tied to science and the rest of the world through the important research that occurred here. The park is quiet and the atmosphere conducive for a contemplative walk,” she says.

Observer-of-yore Currin shares her enthusiasm, humorously noting that he and his colleagues’ decades of dedicated stargazing helped lay the groundwork for many marvels of modern science, including space travel.

 “If not for our understanding of the Chandler Wobble and its effects on navigation,” he muses, “the astronauts would blast off from Florida but never get where they’re going.”

Latitude Observatory Park, 100 DeSellum Ave., Gaithersburg, MD 20877, will be open daily from June 15 to August 15.  For more information, visit