New Horizons returns to normal science operation, ready for historic Pluto flyby

NASA's New Horizons mission is returning to normal science operations after an anomaly and is locked and loaded for its historic flyby of Pluto, the agency said Tuesday.

"Science operations resume today," NASA said on Twitter.

"Team celebrates confirmation from mission control that we're Pluto bound, Pluto FlyBy sequence officially underway," the mission team said.

The piano-sized probe experienced an anomaly at 1:54 p.m. EDT (1754 GMT) on July 4, 10 days from arrival at Pluto, leading to a loss of communication with Earth.

The mission operations center at the Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, then regained communications with New Horizons after about 1.5 hours through NASA's Deep Space Network.

According to the space agency, during that time the autonomous autopilot on board the spacecraft recognized a problem and switched from the main to the backup computer. The autopilot placed the spacecraft in "safe mode," and commanded the backup computer to re-initiate communication with Earth. New Horizons then began to transmit telemetry to help engineers diagnose the problem.

The investigation into the anomaly has concluded that no hardware or software fault occurred on the spacecraft. The underlying cause of the incident was a hard-to-detect timing flaw in the spacecraft command sequence that occurred during an operation to prepare for the close flyby. No similar operations are planned for the remainder of the Pluto encounter.

The anomaly is no reason to doubt that New Horizons will perform its encounter science as planned. The science observations lost during the anomaly recovery do not affect any primary objectives of the mission, with a minimal effect on lesser objectives.

"In terms of science, it won't change an A-plus even into an A," said New Horizons Principal Investigator Alan Stern of the Southwest Research Institute, Boulder.

After a voyage of nine years, New Horizons is almost 3 billion miles (4.8 billion km) away, where radio signals, even traveling at light speed, need 4.5 hours to reach Earth. Round trip communication between the spacecraft and its operators requires about nine hours.

Pluto's closest approach is scheduled for July 14, when New Horizons will pass within 6,200 miles (10,000 km) of the dwarf planet's surface, travelling at a speed of 27,000 miles (43,000 km) per hour.

The probe will perform the first close range study of the distant, icy world and its five attendant moons before continuing its journey deeper into the Kuiper Belt to examine one or two of the ancient, icy small worlds in that vast region, which is at least 1 billion miles (1.6 billion km) beyond Pluto. Endi