An artist's concept of Solidaridad 1 orbiting Earth. Photo: Hughes

Controllers are investigating why the computer brain aboard the Mexican Solidaridad 1 communications satellite malfunctioned over the weekend, wiping out television, radio and pager services.

Built by Hughes Space and Communications and owned by Satmex, the satellite suffered the loss of its Spacecraft Control Processor (SCP) at 1545 GMT (11:45 a.m. EDT) Sunday.

Operators at centers in Iztapalapa and Hermosillo received a series of alarms indicating the turn-off of the SCP, Satmex said in a statement.

This is the second on-orbit failure of a Hughes HS601-model satellite due to the loss of their processors. The first was the Galaxy 4 spacecraft in 1998, which resulted in similar communications blackouts in the U.S.

The processors act as a satellite's brain, controlling the craft's position in space and pointing of its antennas and solar arrays.

The Hughes craft have two SCPs but need only one to fulfill their communications relay duties. Solidaridad 1 lost its first SCP a year ago and was running on the backup until Sunday, officials said.

Although engineers aren't sure yet what is to blame in Sunday's breakdown aboard Solidaridad 1, an earlier HS601 processor defect uncovered could be the culprit. The glitch comes from electrical shorts caused by internal tin-plated relay latching switches that act as on/off switches within the SCP.

Hughes investigators have found that under certain conditions, a tiny, crystalline structure, less than the width of a human hair, can grow and bridge a relay terminal to its case, causing an electrical short.

Over the past couple of years, Hughes began using nickel-plated switches and improved processes, which appear to have corrected the processor defect on newer satellites.

Engineers are currently studying data received from Solidaridad 1 to determine if Sunday's failure occurred in a similar fashion to previously recorded incidents, Hughes spokesman Richard Dore said.

There are currently two other Hughes HS601 satellites in space that have lost one processor each: Galaxy 7 and DirecTV's DBS-1.

As for the future of Solidaridad 1, it unclear if any hope remains to salvage the $250 million craft launched on November 19, 1993 aboard an Ariane 4 rocket. The contract design life was 14 years of operation in space.

Two satellites were launched in the Hughes-built Solidaridad series, a second-generation to replace the aging Morelos craft serving Mexico.

Both Solidaridad were manufactured with 18 C-band transponders and 16 Ku-band transponders. Their coverage area includes all of Mexico and reaches into the southwestern United States, Caribbean and Central and South America.

Satmex was in the process Monday of relocating the users of Solidaridad 1 to the three remaining satellites in its fleet, plus to craft in the Loral Global Alliance and to other satellite operators. Loral owns part of Satmex.

"Satmex continues to maintain close communication with the Mexican authorities and with its system users, in strict accordance with its contingency plan," the company said.

Mexican news reports indicated the satellite's loss had cut educational television programming to 12,000 mostly rural secondary schools across the country. Some students in remote schools rely entirely on the televised courses.

Solidaridad 1 is stationed 22,300 miles above the equator at 109.2 degrees West longitude.