Tonight the observing gods are on our side - clear skies, low to zero humidity, and no problems with the telescope or its instruments. So Tom Stallard and I managed to get ~2 hours observing Saturn, whilst the Cassini spacecraft took a series of infrared images. Our infrared spectra of H-three-plus are designed to complement Cassini's Visual and Infrared Mapping Spectrometer (VIMS).
Our spectra on the Keck II telescope have nearly 100 times the ability to find the emission lines of individual molecules. But VIMS gets a much broader sweep of the whole spectrum of Saturn. Our spectra scan the planet from north-to-south, but only at one longitude - the noonday meridian, where the local time on Saturn is 12 noon. Cassini VIMS, however, gets a full picture of the northern hemisphere facing the spacecraft.
Tonight our Keck observations are also being backed up by Henrik Melin and James Donaghue working on the NASA Infrared Telescope Facility. They are getting images of the northern and southern aurora, at a wavelength sensitive to the H-three-plus emissions.
That means that, between the ground-based observations and the spacecraft, we should build up a really good picture of what's happening to Saturn's atmosphere on a semi-global scale. And that's important, because it enables us to understand all the pressures pushing and pulling the ringed planet.
Europe's planetary scientists have not been so good at carrying out this ground-based support for their space missions as their American colleagues. That's one of the reasons for Europlanet's NA1 "Ground-based support for space missions" activity.
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