Probe update

Not as dodgy as it sounds, I promise!

• Following a successful launch, ESA scientists have begun checking out the instruments on the Venus Express probe, by pointing them back at the Earth-Moon system and taking some pictures with the VIRTIS spectrometer. VIRTIS stands for 'Visible and Infrared Thermal Imaging Spectrometer' (it can apparently measure at ultraviolet wavelengths too but that would have mucked up the acronym...) and is designed to measure the composition of the lower atmosphere by measuring in spectral windows which are not blocked out by clouds in the upper atmosphere - according to this site you might also be able to make some surface measurements at near-infrared frequencies, which would be pretty cool.
  
  The probe is already 3.5 million kilometres away, so the data collected are not particularly ground-breaking, but they confirm that the instrument is in good shape for the real observations, starting when the probe enters Venus orbit in April next year, and are useful for calibration purposes.
  
  
• The MARSIS radar on the Mars Express has now been operating for four months, as is summarised here. The orbiter has a highly eccentric orbit, and during most of the observation time so far the time of closest approach has been in the daytime. This means that the best measurements are being made when the upper atmosphere (ionosphere) is excited by solar radiation, making it more opaque to the lower radar frequencies required to penetrate the sub-surface. We're still getting lots of data about the structure of the Martian atmosphere and surface, but the real fun begins next month, when the closest approach will be at night; the search for underground water can then start in earnest. This delay in sub-surface measurements was not intentional, but a conseqeunce of the delay in deploying the radar booms last year. I'm glad the mission has been extended to compensate
  
  
• Meanwhile, New Scientist reports that the Japanese Hayabusa probe, which managed to land on an asteroid and collect surface samples over the weekend (on the second attempt - on the first landing attempt last week the pellet gun designed to dislodge material from the surface of the asteroid failed to fire) is suffering from a thruster malfunction.
  Problems with the thrusters and control systems have plagued this mission from the start, so even if they get it working it's not clear if there's enough fuel to return the samples to Earth. Fingers crossed.
  
  
• Finally, another in the seemingly non-ending stream of fabulous images from Cassini:
  
  
  
  This image of Enceladus is backlit by the Sun, and illuminates plumes of water vapour rising up from its south pole. The cause of this geological activity is not yet understood, but it's still pretty cool!
  
  A larger image can be found here,and an enhanced false colour image here.