LOS ANGELES (AP) _ Millions of pagers that keep loved ones, doctors and colleagues in touch with each other stopped working nationwide when a $250 million communications satellite suddenly lost track of Earth.

The Galaxy 4 satellite stopped relaying pager messages, as well as behind-the-scenes television feeds, at about 6 p.m. EDT Tuesday when its onboard control system and a backup switch failed.

Technicians were able to send commands to the craft but failed to restore its proper orientation toward Earth, said Robert Bednarek, senior vice president and chief technology officer for PanAmSat, which owns the satellite.

``We're analyzing the situation and determining if there's a way to restore service,'' said Dan Marcus, spokesman for PanAmSat. ``Obviously, we're working on a fast timeline here.''

PanAmSat expected the satellite to remain down until at least this morning, Marcus said.

An industry official said a majority of pager companies rely on Galaxy 4. Scott Baradell, a spokesman for PageNet, one of several paging companies whose services were interrupted, estimated that 80 to 90 percent of the 40 million to 45 million U.S. pager users lost service.

``This is the first time in 35 years that pagers have gone silent,'' said John D. Beletic, chairman and chief executive officer of Dallas-based PageMart Wireless Inc. ``Virtually all paging companies have been affected.''

The only customers not affected were those whose connections are through ground-based radio transmitters, he said.

Baradell said it would take about a day for his company to switch service to another satellite for most of its 10 1/2 million customers.

``You have to make adjustments to your system,'' he said. ``If it's at all possible to get Galaxy 4 back in service, that's much preferred.''

The pager problem was of particular concern to doctors. Dr. Steve Dickens, a cardiologist at Cedars-Sinai Medical Center in Los Angeles, said he was spending the night at the hospital because of the problem.

``I have to tell (the hospital) what to do and how to respond,'' he said. ``We have a good support staff, but protocol says they can't make a decision without first calling the doctor.''

Dickens also talked to his brother, an obstetrician, about the pager problem.

``He says it's a nightmare,'' Dickens said. ``He's got eight ladies in labor right now. Thank God for cell phones.''

In a statement, Greenwich, Conn.-based PanAmSat said it was working with engineers to determine the cause of the failure, which occurred in the onboard spacecraft control processor.

One option being examined was moving a backup satellite into Galaxy 4's orbit _ a process that could take several days, Marcus said.

Television stations also use Galaxy 4 to transmit feeds of advance shows, said Marguerite Sullivan, satellite coordinator for KCAL-TV in Los Angeles. But it was not clear what _ if any _ television programming might be affected.

``Hopefully, TV stations will be able to work around it,'' she said. ``It's just satellite space is going to be very tight. It's going to be a problem for syndication.''

In addition to the syndicated programs, CBS radio and television, the Chinese Television Network and the CNN Airport Network send feeds through Galaxy 4.

CBS relied most heavily on Galaxy 4 but had a backup plan switch over to the Galaxy 7 satellite. It has not been affected by the outage, said spokeswoman Amy Malone. ABC and NBC also said their operations have not been affected.

Galaxy 4 was launched in June 1993 aboard an Ariane rocket. Its coverage area is primarily the United States and Caribbean, according to PanAmSat's World Wide Web sites.

PanAmSat is 81 percent owned by Los Angeles-based Hughes Communications Inc.