Martin Paetzold, Principle Investigator of the Mars Radio Science observation is smiling.  This morning, before the flyby, he admits to having been anxious.  “There was a very small probability of an occultation at closest approach,” he says.  It was a very small possibility but if it happened, Phobos would have blocked the signal with Earth at the critical moment.

There is nothing to be anxious about any more.  Closest approach took place at 20:55 CET.  It took 6 minutes and 34 seconds for signals to cross the volume of space between Phobos and Earth, and be received on Earth.

If the occultation had taken place, it would have created a gap in the data of five to ten minutes whilst the signal link was re-established with the spacecraft. “We would have had to extrapolate between the two data sets and that would not have been good.  Now we have continuous data,” says Paetzold.

The team will receive the data on Friday, and they will begin the full analysis once they receive the precise orbit determination of Mars Express on its way into the flyby.  They hope to assess the data and the preliminary results in about two weeks time.

Let the analysis begin! -- Stuart