News from ESA
A model of the Rosetta space craft. Credit: ESA
Firstly, ESA's Rosetta satellite, which is on it's way to comet 67P/Churyumov-Gerasimenko, observed Deep Impact as the impactor hit comet Tempel 1 earlier this year. Rosetta has an instrument called OSIRIS which consists of two cameras: one narrow-field and one wide-field. Both were used to image Tempel 1 just before and just after the impact using a range of filters to help them pick out the water and dust. The scientists involved in the mission have been analysing the data and have just published their results in the journal Nature (who will not let you read the whole article without paying for it, sorry). They have calculated the amount of water (4.5 million kg) and the cross-section of dust (330 km2) released from the interior of the comet by the impact. From this they conclude that the ratio of mass contained in dust to that in ice is likely to be greater than one, so there is probably more dust than ice in the interior. They suggest that comets should be described more accurately as "icy dirtballs" rather than "dirty snowballs".
Venus Express being prepared for launch. Credit: ESA
The other spacecraft they have been working on is Venus Express which is due for launch on the 26th October this year. The craft has now been attached ("mated") to the top section of the Fregat launch vehicle whic will carry it on the first stage of the journey. This was a dangerous part of the launch preparations as both the craft and the upper stage rocket had been filled with the highly flammable fuel needed for course alterations in space. As there is no oxygen in space, rockets have to take their own oxidisers. Some rockets use hypergolics, combinations of fuels and oxidisers which are volatile enough that they ignite on contact. The space shuttle uses hypergolics (monomethyl hydrazine and nitrogen tetroxide) in both its orbital maneuvering system and the reaction control thrusters. The next job with Venus Express will be to attach the umbilical which provides power and communcations while the craft is on the ground. Once that is connected, the engineers can power it up and test that all the systems are functioning correctly.