A federal judge gave Zhao Qianli the maximum sentence after his guilty plea on Tuesday of one count of photographing defense installations.

Zhao's attorney, Hongwei Shang, declined comment to CNN when reached by phone Wednesday evening.

According to court documents, Zhao entered the Joint Interagency Task Force South military property, located on Naval Air Station Key West, on September 26 without permission "by circumnavigating the installation's primary fence line, and entering the military property from the beach."

"The primary installation fence line contained multiple signs that stated the Farm area was a 'RESTRICTED AREA' and the 'KEEP OUT'."

The court documents give no specific indication whether Zhao was attempting to commit espionage.

A US Navy video calls the Key West facility "one of the leading intelligence fusion centers in the world."

It tracks more than 1,000 suspect targets a day, the Navy says, turning intelligence images into virtual reality programs.

The center monitors more than 42 million square miles of the Earth's surface to detect threats to US security, including narcotics shipments from the Americas, according to the video.

Personnel from all five branches of the US military plus representatives from 13 other nations work at the facility.

Zhao was in the United States to study musicology as part of a summer exchange program from North University of China, according to CNN affiliate WFOR.

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