Those are pictures of the reflection of the light from the sun off of a mirror. "The final elements, a pair of tunable Michelson interferometers, enable MDI to

Those are pictures of the reflection of the light from the sun off of a mirror. "The final elements, a pair of tunable Michelson interferometers, enable MDI to record filtergrams with a FWHM bandwidth of 94 mÅ. Normally 20 images centered at 5 wavelengths near the Ni I 6768 spectral line are recorded each minute."