Caption: 
This “first-light” image from the Europa-UVS instrument shows data at far-ultraviolet wavelengths, photons more energetic than the UV light that gives us sunburns on Earth. Light passes from its telescope into a long, narrow slit onto the detector, left to right, and the top-to-bottom direction of the image captures spatial information along this length in addition to the wavelength separations in spectral bins — a powerful combination for use in astronomical studies. Light from hydrogen atoms in the solar system is the source of the red line in the middle of the image, and this sky-background measurement confirms Europa-UVS is working well.  