|Russian Fobos-Grunt probe with the upper stage Fregat-SB.|
November 25 developments
When the first opportunity of the day to downlink telemetry from Phobos-Grunt came to ESA's station in Perth, nothing was heard from the spacecraft. According to ESA, the slots for communication, timed to coincide when Phobos–Grunt was passing over in direct line-of-sight with the station, began at 20:12 GMT and ran until 04:04 GMT. Each lasted just 6–8 minutes, providing very limited windows for sending commands and receiving a response.
"Our Russian colleagues provided a full set of telecommands for us to send up," Wolfgang Hell, ESA's Phobos–Grunt Service Manager was quoted on the agency's web site, "and Perth station was set to use the same techniques and configurations that worked earlier. But we observed no downlink radio signal from the spacecraft."
At the same time, ESA reported that observations from the ground had indicated that the orbit of Phobos–Grunt had become more stable. "This could mean that the spacecraft's attitude, or orientation, is also now stable, which could help in regaining contact because we’d be able to predict where its two antennas are pointing," said Manfred Warhaut, ESA's Head of Mission Operations at the European Space Operations Centre, Darmstadt, Germany, "The team here at ESOC will do their utmost to assist the Russians in investigating the situation."
At 14:30 GMT, ESA announced that the next scheduled communication slot for ESA's Perth station is set for the night of November 25, when it will again be allocated to support Phobos-Grunt. However later, the Perth station would have to take a break in its effort until Monday, November 28, in order to address communication needs of other missions, which accumulated during its unscheduled work on Phobos-Grunt. Controllers also needed some rest after a sleepless night.
During November 26, the Perth station was expected to have four windows to communicate with Phobos-Grunt: 00:11 - 00:20 (with the spacecraft in the shadow during a part of the pass), 01:45 - 01:52, 06:30 - 06:38 and 08:04 - 08:12 Moscow Time.
In the meantime, the spacecraft also reappeared over Baikonur, starting a seven-minute (or a less than 10-minute) pass within range of its tracking station at 16:00 Moscow Time, with the spacecraft on a daylight part of its orbit. However no news was released on the effort to communicate with the spacecraft, indicating a lack of progress. Still, Roskosmos representatives and the official Russian press reported that the telemetry data acquired previously had shown that Phobos-Grunt's main radio-system had been functioning and exchanging data with the main BKU computer. However the status of BKU was yet to be determined.
According to reliable sources, ground controllers were continuing sending commands to Phobos-Grunt to downlink telemetry frames, as had been achieved earlier and, in addition, they were trying to downlink telemetry from the BKU flight control computer and sending commands to activate onboard rechargeable battery.
Available telemetry from the BRK radio complex of the cruise stage yielded little information, an industry source said. An emergency telemetry frame did carry data on the condition of some components within BRK, for example, readings on the operational voltage and temperature of those components. It was also possible to conclude that a system for the exchange of data with the main BKU computer had been in operational condition. The data also contained a log of switches between a primary and a secondary transmitter. None of this information was essential for the analysis of the emergency situation onboard. Both Russian and US observations confirmed that the spacecraft had been maintaining its solar orientation.
November 26 developments
All attempts to contact Phobos-Grunt from Perth on November 26 proved fruitless, after which ESA's ground station had to take a break in its effort, in order to support other missions. At the time, the facility was not scheduled to communicate with a stranded Russian probe until the night from November 28 to November 29.
Although popular press was making wild proposals on the future plans for the Phobos-Grunt mission, the only realistic goal for ground controllers at the time was to receive useful information on the cause of its failure. If the culprit could be found and if critical systems onboard the spacecraft could be reactivated, attempts to establish some or even full control over the spacecraft would be made.
Only then, it would be possible to consider what, if any, further steps could be made to continue the mission. Obviously, the first priority would be boosting the spacecraft to a higher, longer-lasting orbit, giving mission planners additional time to develop new flight scenarios.
Depending on the probe's remaining resources and technical condition, it could be sent away from Earth for safety reasons and for testing or even aimed at one of potential destinations in the Solar System, such as an asteroid, the Moon or even Mars, for a flyby or some other abbreviated mission. As a very last resort, the spacecraft could be directed into the Earth atmosphere to burn up over an unpopulated area. All these options were long shots, given a complete lack of control over the spacecraft and only sporadic communications.