By Jennifer Dobner

SALT LAKE CITY (Reuters) - Three activist groups flew a blimp emblazoned with the words "Illegal Spying Below" over the National Security Agency's data center in Utah on Friday in protest against the federal government's mass surveillance programs.

The one-hour flight over the high-tech facility was launched by the environmental group Greenpeace, digital rights activists the Electronic Frontier Foundation, and a conservative political organization, the Tenth Amendment Center.

The 135-foot-long (41-meter-long) blimp, which is owned by Greenpeace, was adorned with a sign that read, "NSA Illegal Spying Below."

In an email to Reuters, the agency declined to comment.

But a spokesman did note there is no restricted airspace over the data center, housed on the grounds of the Utah National Guard's Camp Williams, in Bluffdale, 23 miles (37 km) south of Salt Lake City.

The facility, which the NSA says provides the government with intelligence and warnings about cyber security threats, is thought to be the agency's largest data storage center.

The blimp protest coincided with the launch of an online campaign that rates members of Congress on actions the activists say either further or stop data collection efforts by the NSA.

Greenpeace said the report cards on the site standagainstspying.org were created with input from the more than 20 grassroots groups and companies that are partners in a lawsuit against the NSA.

"Our right to privacy is not a partisan issue. It's a human rights issue," said Tom Boldin, founder of Tenth Amendment Center, which advocates for decentralized government.

"This coalition gives great hope for the future because it shows that people across the political spectrum can set aside differences to work together."

(Reporting by Jennifer Dobner; Editing by Daniel Wallis and Sandra Maler)