EUV imaging spectrometer for the Solar Orbiter mission

The results from missions such as Yohkoh, Trace or SOHO have advanced our understanding of the solar corona and heliosphere, but also have raised many new questions. Measurements at higher spatial resolution and cadence are needed, some regions such as the solar poles or the inner heliosphere remain unexplored. The Solar Orbiter mission addresses those questions. UV imaging spectrometers may be included in the remote sensing instruments package for this mission. Fourier transform spectrometry (FTS) is an ideal solution for imaging systems as there is no need to scan the region of interest with a slit to get a 2D map, and the spectral range covered is only limited by the bandpass of the filter and the maximum optical path difference that can be obtained. FTS systems also allow to make observations at high cadence (100 Hz). Working in the far UV (below 200 nm) requires the use of reflective only optical systems. A solution for such an instrument has been designed at IAS and a mock-up has been built in order to test and validate the working principle. The first results of the alignment phase are shown.