On Sunday, 9 January, Mars Express will make its closest approach to Phobos, with the spacecraft passing just 111 km above the moon's centre at 14:09 UT (15:09 CET). Of course, we all know that science is about a lot more than pretty pictures; but we can’t help ourselves can we? The first question any of us ask when we hear about a new flyby is, "When do we get the images?" We want to see Phobos, and we want to see it now!

While closest approach takes place this coming Sunday, Olivier Witasse, ESA Project Scientist for Mars Express, explains below that all things come to those who wait. I asked him when we can expect the first image? Olivier replied:

We will have to be patient! The whole Phobos data set will be downloaded to Earth by Tuesday, 18 January. The HRSC team will then process the data, and we can expect a release of images (including a 3D view) on Friday, 21 January.

Why wait for nine days after the closest approach?

The reason is that besides this Phobos event, there are other camera observations of Mars and many observations by the other Mars Express instruments. Software plans and optimises the data downlink to make sure that no instruments lose any data, and it uses the biggest data storage on board (the one for the camera) to act as a buffer when downlink capabilities are scarce. This avoids overwriting valuable data! Once the other data are safely on the ground, then Mars Express sends the camera files.

An interesting aspect of this story is that starting on 19 January, contact with Mars Express will be much reduced for five weeks. We will even loose contact for some days due to the solar conjunction, when the Sun will block our view of Mars and Mars Express. During this period, the spacecraft will be fully autonomous but perform no observations. Luckily, the Phobos close encounter occurs more than a week before and its images will be on the ground just in time! -- Stuart

Note: To help pass the time, enjoy are a pair of recent images captured in March 2010 by the HRSC.