SALEM — When an earthquake shook the Washington Monument in 2011, a small company from Salem was there to check its structural integrity.

When searchers needed to scour the sands of Aruba to look for missing Alabama high school student Natalee Holloway, Geophysical Survey Systems Inc. of Salem was there again.

Or at least its equipment was.

GSSI, located at 12 Industrial Drive, is a small company that’s been doing big things for 43 years.

The firm is a leading developer and manufacturing of radar equipment that’s used around the world for everything from geological and archaeological surveys to helping find missing people, especially earthquake victims.

The ground-penetrating equipment is used everywhere from the frigid South Pole to the hot United Arab Emirates. The equipment is also used to locate utilities and to inspect concrete, bridge decks, railroad beds — even the walls of Washington Monument.

The 73-employee firm has such an excellent reputation for its products, that Congresswoman Ann Kuster, D-N.H., stopped off there yesterday as part of her “Congress at Your Company” tour.

Since taking office in January, Kuster, has toured businesses across New Hampshire to highlight the importance of high-tech manufacturing, job creation and economic growth in the state.

Kuster toured the plant with company executives and had the chance to try some of the equipment.

“This is great, this is really impressive,” Kuster told GSSI president Christopher Hawekotte.

Kuster used sophisticated radar equipment, called the Utility Scan, that showed the pipes beneath the plant floor as she pushed it across.

“That’s incredible,” she said.

She also saw the LifeLocator III — a $25,000 piece of search-and-rescue equipment used across the globe to find earthquake victims trapped beneath piles of rubble.

“You put this on the pile and it will pick up if anyone is breathing,” Hawekotte said.

There are only five LifeLocators in the United States, including one used by the Chicago Fire Department for search-and-rescue missions, according to Jack O’Leary, vice president of operations.

Meanwhile, there are at least 300 in China, which is prone to earthquakes, he said.

Kuster said she enjoyed the chance to tour the economy and chat with employees.

“Innovative, high-tech manufacturing companies like GSSI are driving growth and job creation in New Hampshire’s economy,” she said. “When we invest in workforce development and job training, more young people will stay here in New Hampshire, our workers will be more competitive in the job market, and New Hampshire businesses like GSSI will be more successful.”