Recovering from a subtle timing glitch that knocked NASA's Pluto-bound New Horizons probe out of contact with Earth on Saturday, engineers believe the spacecraft should be able to resume normal operations Tuesday -- one week before the long-awaited flyby -- with no major impact on the mission's science objectives, NASA reported late Sunday.
"I'm pleased that our mission team quickly identified the problem and assured the health of the spacecraft," Jim Green, NASA's director of planetary science, said in a statement. "Now, with Pluto in our sights, we're on the verge of returning to normal operations and going for the gold."
Nine-and-a-half years and three billion miles from Earth, New Horizons went into protective "safe mode" Saturday afternoon -- 10 days before the historic Pluto flyby -- after the probe's autopilot detected an anomaly.
As programmed, the autopilot switched over to a redundant flight computer and began transmitting telemetry to Earth to help engineers troubleshoot the problem. The spacecraft was out of contact with Earth for one hour and 19 minutes.
An anomaly team was assembled at the Johns Hopkins University Applied Physics Laboratory to analyze the glitch but given the probe's enormous distance -- it takes radio signals nine hours to make a round trip -- NASA said it could take "one to several days" to restore normal operations.
In the meantime, science observations were suspended.
Late Sunday, the space agency posted an updated status report on the New Horizons web page saying engineers understood the problem and were confident it would not recur.
"The investigation into the anomaly that caused New Horizons to enter 'safe mode' on July 4 has concluded that no hardware or software fault occurred on the spacecraft," NASA reported.
"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."
NASA said preparations were ongoing to resume normal science operations on Tuesday "and to conduct the entire close flyby sequence as planned."
"The mission science team and principal investigator have concluded that the science observations lost during the anomaly recovery do not affect any primary objectives of the mission, and with a minimal effect on lesser objectives," the statement said.
Alan Stern, the New Horizons principal investigator, said the lost observations "won't change an A-plus even into an A."