A.J.S. Rayl • Jan 22, 2004
Spirit Suffers "Serious Anomaly," But Continues 'Beeping' Home
Something is wrong with Spirit, but what exactly it is -- and just how serious it is -- the Mars Exploration Rover team isn't sure. Although the robot field geologist continues to 'beep' home, she has not returned any data since yesterday.
An unknown event or series of events has stopped direct transmission of data for almost 24 hours, and prevented the rover from receiving its commands, announced MER project managers Pete Theisinger, and his deputy Richard Cook, at the daily press briefing today. The rover remains, they said, in the same position they left her yesterday, standing before the rock Adirondack, with her arm extended.
The lack of direct communication yesterday was assigned to the rain and thunderstorms over Canberra, Australia station of the Deep Space Network (DSN) and DSN configuration issues.
But Theisinger said: "We now know we have had a very serious anomaly on the vehicle."
The announcement followed an official press released issued by Jet Propulsion Laboratory (JPL) late yesterday afternoon that announced that there was "an unresolved issue" with the status of the Mars rover. The "serious anomaly" is that unresolved issue -- and it remained unresolved this morning, they said.
Early this morning, the team sent a command to Spirit to respond. "We sent a command that said, 'If you get this, send us a beep,'" Theisinger said.
Midway through the briefing, Jennifer Trosper, mission manager for Spirit surface operations, delivered the news that the rover had responded to that missive with a 'beep' through its direct link to Earth. Still, the robotic geologist has not returned any data since early Wednesday.
The MER flight-team engineers and scientists have been meeting and working all the possible scenarios throughout the night last night and into this morning, and continue to consider the possibilities, Theisinger said. "There is no one single fault that explains all the observables we have. Our ability to determine exactly what has happened has been limited by our ability to receive telemetry from the vehicle."
While no one is saying anything for certain -- and even though Spirit has some corruption fail-safes built into its software, the inkling seems to be that it is probably some kind of software glitch.
"If this issue on Spirit is somehow a software corruption issue and there is not a serious power fault to the vehicle, then Spirit can go a long time and we can pick up the pieces," noted Theisinger. "But if, on the other hand, it's a major power fault, it may not be able to recover from that."
The news Trosper delivered was "more information." If that signal is confirmed, "[t]hat would tell us that the spacecraft has power . . . the software's working, everything's working," Theisinger responded. "We'll let you for sure if it's for sure."
Spirit can send transmissions direct-to-Earth using its onboard "X-band" system to NASA's Deep Space Network (DSN) tracking stations in Australia, California, and Spain. Or it can use its UHF antenna to send data up to either Mars Odyssey or Mars Global Surveyor (MGS), which have been in orbit around the Red Planet for the last couple of years and have been communicating regularly with the rover.
Through these resources, the MER team and Spirit have a number of opportunities to communicate with the spacecraft each day, including four via the orbiters Odyssey and MGS. The direct-to-Earth communications -- which now take about 20 minutes one-way -- are generally reserved for the most important data, although signals sent via the orbiters can be delayed from 90 minutes to 24 hours for a variety of reasons.
The plan now is to continue working through scenarios and consider and analyze the upcoming signals from the MGS and Odyssey passes this evening and tonight. "Then we will decide what our go-forward plan will be for tonight," Theisinger said.
"What we've spent the last 24 hours doing is mapping out [the possibilities] -- if this happened, then that what we would expect to see," added Cook.
As sophisticated as the various communications systems are, there is "quite a bit" that has to work for seamless communication to occur between ground teams and the rover, noted Cook. "You have to have the whole avionics system working, the computer has to work, your ability to talk with the radio needs to work, the radio itself has to work, and the amplifier and antenna and all switches between those things all have to work. So, whenever we get confirmation that its working, receiving and transmitting, that means a number of things in the chain are working. The things we don't know about are exactly what is the state of the software relative to sending out these beeps."
One of the "lessons learned" from Pathfinder and Mars Polar Lander, Cook continued, was the need for the rover to have the capability to communicate whenever it can. "If we can't get a command to it, then it will try send things to do us," he explained "To do that we've implemented into the software this capability of autonomously scheduling communications windows, if it got confused as to what window it's supposed to be transmitting in."
From the signal received this morning, it would appear that Spirit is making use of that capability.
The sequence of events leading to the "serious anomaly," were, Theisinger said, as follows:
"Yesterday afternoon, local solar time on Mars, about 1 p.m., we sent [a command sequence] to the vehicle, and we got a response that indicated the rover had received that sequence and that it was activating that sequence," he continued. Then, at 2 p.m., local solar time on Mars, a scheduled direct-to-Earth communication with the high gain antenna pass "did not occur, and the 4:30 p.m., Odyssey pass did not occur." And there was no indication by Odyssey that it had received UHF transmission.
Spirit was in the process of taking imaging data, mini-thermal emission spectroscopy (Mini-TES), and the microscopic imager (MI) when things when the signals started glitching, Cook said.
"Last night, we had a 1:30-2 a.m., MGS pass, and MGS believes it saw a UHF transmission in its receiver telemetry," Theisinger said. "We did not have direct-to Earth link session. We did not receive data on the normal direct-to-Earth session nor did we receive data on what would have been the fault session at 11 a.m. -- which is where the spacecraft has gone into fault mode, knows that, and tells us to communicate at a different time."
For now, it's back to "re-look" at the scenarios, said Cook. "The last full-up scenario discussion was last night. We've gotten more [information] since then, through both the MGS data and its characteristics, plus what happened on the Odyssey overnight pass, with what happened today during the day. Later, this evening, we will again go and map out all the scenarios and see if we can get something that correlates with the observables we've seen and then from there decide what actions to take."
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