ESA’s comet-chasing mission Rosetta was launched on the 2nd of March 2004 and through a complex series of flybys (three times past Earth and once past Mars) arrived ten years after at its destination: comet 67P/Churyumov–Gerasimenko.

In June 2011, Rosetta was put into deep-space hibernation for the coldest, most distant leg of the journey (800 million kilometres from the sun) and was woken up on 20th of January 2014. Finally, Rosetta was set on comet’s orbit on August 2014 to achieve a successful landing of Philae lander on 12th of November 2014.

Comets are the primitive building blocks of the Solar System and the likely source of many elements such as water and perhaps the ingredients that helped life evolve. By studying the nature of a comet close up with an orbiter and a lander, Rosetta will show us more about the role of comets in the evolution of the Solar System.

Rosetta orbiter consists in 11 state-of-the-art instruments. Among these 11 instruments, the Ultraviolet Imaging Spectrometer – ALICE instrument is equipped with a HORIBA Jobin Yvon diffraction grating. ALICE is a lightweight (2.2 kg), low power (2.9 W) imaging spectrograph optimized for cometary far-ultraviolet (FUV) spectroscopy. With a spectral range from 70 to 205 nm, ALICE role is to make measurements of noble gas abundances and atomic budget in the coma, and major ion abundances in the tail and in the region where solar wind particles interact with the ionosphere of the comet. ALICE determines the production rates, variability, and structure of H2O, CO, and CO2 gas surrounding the nucleus and the FUV properties of solid grains in the coma. ALICE began mapping the comet’s surface last August, recording the first FUV light spectra of the comet’s surface. From the data, the Alice team discovered the comet is unusually dark when viewed in UV wavelengths. ALICE also detected both hydrogen and oxygen in the comet’s coma, or atmosphere.