Somebodys getting fired for this!
http://news.bbc.co.uk/2/hi/science/nature/4115251.stm
Titan probe gets early alarm call
The Huygens space probe will be woken up from its slumber four hours before its January descent into the smoggy atmosphere of Saturn's moon Titan.
Ground controllers are waking Huygens up earlier than originally planned to boost data transmission from the probe.
On Tuesday, ground controllers set the timer for Huygens' wake-up call, to bring it out of hibernation mode prior to entry on 14 January.
The probe will be transmitting data back to Earth throughout its descent.
Huygens will detach from its "mothership" Cassini on 25 December, on the final leg of its journey to the Saturnian moon.
"We uploaded the settings for the timer and it worked fine," said Michael Kahn, mission analyst at the European Space Agency's operations centre in Darmstadt, Germany.
When the alarm goes off, Huygens' computer will switch on and wake up the probe's scientific instruments.
Early to rise
Huygens was originally to be woken up minutes, not hours, before its descent to Titan's surface. But ground controllers re-designed the mission following the discovery of a communications glitch in 2000.
Engineers realised Huygens' transmitter had not been designed to adjust for the Doppler effect as it sends signals to the moving Cassini.
The Doppler effect describes the way light appears to have different wavelengths depending on how a source and an observer are moving relative to each other.
Scientists calculated that Cassini's movement relative to Huygens could Doppler-shift the signals enough to cut data transmission by 90%.
Switching on Huygens' instruments earlier heats up the craft, which affects the frequency at which the probe transmits data.
"The frequency is generated by a quartz oscillator, and when that has a slightly higher temperature, it transmits slightly differently. That offsets the Doppler shift," said Mr Kahn.
"It gives us a slight edge, a slightly higher chance that we will get all the data we need through."
Ground controllers will also fly Cassini at right angles to Huygens as the probe transmits data, in another measure to offset the Doppler shift.
Mr Kahn said that, following the outcome of the probe's Mission Readiness Review, Huygens team members were now "very confident" of success on 14 January.