Alpha particle x-ray spectrometer developed in Mainz to be used on comet Churyumov–Gerasimenko

Instrument for measuring chemical composition of the surface of the comet will soon be subjected to initial testing


On its ten-year journey to comet P67/Churyumov–Gerasimenko, the Rosetta space probe was taken out of its hibernation mode in January 2014 and the Philae robotic lander on board was activated shortly afterwards. The Philae lander is equipped with an instrument developed in Mainz. "We are looking forward to the moment when the APXS alpha particle x-ray spectrometer is activated and we can see how it does on its first test," said Dr. Göstar Klingelhöfer of the Institute of Inorganic Chemistry and Analytical Chemistry at Johannes Gutenberg University Mainz (JGU). The small instrument weighing roughly 500 grams will be activated in April. Klingelhöfer and his colleague Dr. Johannes Brückner and their international team of researchers – including Tom Economu, Ralf Gellert, Jordi Jirones-Lopez, Rudolf Rieder, Dirk Schmanke, Christian Schröder, Claude d’Uston, and many others – will then test its functioning. In November 2014, when the Philae lander will be the first device in the history of space travel to touch down on the surface of a comet, the APXS from Mainz will be there.

The purpose of the alpha particle x-ray spectrometer is to analyze the chemical composition of the surface of comet Churyumov–Gerasimenko. Together with the Mainz Mimos II Mössbauer spectrometer, the APXS has already played an important role in the successful NASA MER 2003 double mission to Mars. In order to investigate a particular material, the device bombards its surface with alpha particles and x-rays. Measuring the backscatter from the particles, scientists can deduce the chemical composition of the material and obtain information about the presence of the important elements carbon and oxygen.

During the upcoming first AXPS function test on board Philae, its beam will be directed at a calibration target. Klingelhöfer and Brückner are optimistic: "Of course, we don't yet know what will happen after several years of the system being in hibernation. Nothing like this has ever been done before," explains Klingelhöfer. "But the APXS passed all the tests in previous years with flying colors." Philae does not have any other instrument on board that can supply comparable information.