Just weeks before the Supreme Court is due to hear a case that has dominated his life for the past three years—and may affect the lives of thousands of fellow government contractors—Robert Nelson’s thoughts are a billion miles away. “Right now I’m sitting at my desk looking at a spectral image of the surface of Titan,” he says by phone from his office at the Jet Propulsion Laboratory in Pasadena, California, where he’s a planetary astronomer.

Nelson’s role in NASA’s Cassini mission is to pore over data coming back from the probe, which is now in orbit around Saturn. He and his colleagues are investigating evidence that the planet’s largest moon is volcanically active. One of their theories is that ice volcanoes spew a slurry of frozen water and liquid methane onto Titan’s frigid surface.

That’s a normal day for a research scientist at JPL, which is run by the California Institute of Technology. But Nelson is also the lead plaintiff in a case going before the Supreme Court next month. He and 27 of his JPL colleagues are suing NASA, which funds the lab. The question facing the court: whether the federal government has a right to investigate the personal lives of employees who have access to federal facilities, even if they never go near sensitive or classified material.

Nelson’s fellow plaintiffs, who are mostly scientists and engineers, do everything from studying the evolution of galaxies to driving the Mars rovers. For the last three years they and many other JPL employees have split their time between exploring the cosmos and fighting for their constitutional right to privacy.

After a 2004 presidential directive required standardized ID badges for all federal employees and contractors, NASA informed Caltech that it was instituting background checks in order to comply with the new federal requirement. Caltech told its JPL employees that if they didn’t submit to the checks, the university would consider them to have voluntarily resigned from their positions.

The plaintiffs in the Supreme Court case have two problems with the background checks. First, that they have to submit to them at all. Many JPL researchers have been working at the lab for decades. Security has never been an issue, and personal background checks—beyond supplying routine application information and employment verification when they first took their jobs—have never been required before.

“We have no secrets,” says Nelson. “Come out here and I’ll show you my lab notebook, anytime you’d like to see it.”

The second, larger concern is that the background checks are essentially limitless. Third parties like former landlords and employers are encouraged by investigators to provide any information, “derogatory as well as positive,” that they feel might affect the employee’s suitability to work for the government.

Concerned that people they once knew might suddenly have direct influence on their job security, the JPL employees asked NASA how exactly the information would be used. In response, NASA released a “suitability matrix,” which lists “sodomy,” “cohabitation,” “attitude” and “loitering” among the potential factors in considering whether JPL researchers should keep their jobs. NASA refuses to rule out that it might use any part of the matrix to evaluate JPL employees.

When Caltech told its employees to comply with the background checks, Nelson says many of his colleagues were at first indifferent to the additional red tape. “People did not believe that NASA investigators were going to conduct an investigation into their past sexual activity. But when we showed them that that’s exactly what they were signing away, people became more sympathetic.”