The rover had gone mostly silent Wednesday, returning only beeps to acknowledge it was alive. For unknown reasons, Spirit could not transmit data.
NASA officials said in a statement this morning they had received a signal at the agency's Deep Space Network antenna complex near Madrid, Spain at 7:34 a.m. ET.
Spirit communicated for 10 minutes initially and then later for 20 minutes more, for a total of a half-hour of data transmission.
The transmissions arrived during 90-minute window of opportunity after the rover woke in the Martian morning. Data was transmitted at a rate of either 10 bits per second or 120 -- two separate NASA statements give differing numbers. Officials did not indicate whether the rate was normal or how optimistic they are based on the transmissions.
"The spacecraft sent limted data in a proper response to a ground command, and we're planning for commanding further communication sessions later today," said Mars Exploration Rover Project Manager Pete Theisinger at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Engineers worked late into Thursday night trying unsuccessfully to establish normal communications with Spirit. Efforts to relay signals using NASAs Mars Global Surveyor (MGS) at 10:10 p.m. ET resulted in no data being sent back. Spirit did send a radio signal via MGS, but that transmission did not carry any data. After a signal had been sent to the rover Thursday morning, Spirit replied with a simple tone but would not send data.
Officials yesterday expressed serious concern for the health of the rover but remained optimistic. If the problem involved hardware, they said, the situation would be grave. A software problem, they said, might be fixable -- fresh commands and even new software patches can be possibly uploaded to Spirit if it is in listening mode.
Indications Thursday were that the craft's batteries were in good shape, that its temperature was being properly maintained, and that it was indeed listening.
Scientists said Spirit's flight software or computer memory might have become corrupted. Either glitch could leave the robot's power supply healthy and allow adequate time for recovering control of the rover.
No single explanation considered so far fits all of the events observed, Theisinger said. Engineers tried to replicate the situation in a test facility at JPL, and the testbed rover did not have any trouble communicating.
"We have a very serious situation," Theisinger said late Thursday. Spirit landed on Jan. 3 and is slated to scour the Gusev crater, near Mars' equator, for three months. Its twin, Opportunity, is due to land Saturday. The combined mission cost is $820 million.
Earlier Thursday, JPL Director, Charles Elachi, advised that everyone "stay calm, thoughtful and careful" and avoid making hasty decisions. "Sometimes you can do more harm than good by reacting too quickly," Elachi said.
Spirit can communicate with Earth directly via an onboard "X-band system," or it can beam signals up to either of NASA's two orbiting spacecraft using a UHF antenna. There are four chances each day to reach the orbiters.
NASA receives signals from spacecraft through its Deep Space Network (DSN) of tracking stations in Australia, Spain and California.
Direct Mars-to-Earth communications are reserved for critical Spirit mission data, such as rover health and engineering. It takes about 10 minutes for a radio message, moving at the speed of light, to travel between planets. Signals transmitted to NASA's two Mars orbiters -- MGS and Mars Odyssey -- can be delayed as little as 90 minutes to as long as 24 hours because of the way each orbiter works and communicates with Earth.
advertisement
