Anisotropy and intensity time profiles of the SEP event on 17 May 2012 observed by STEREO B (left), ACE (middle), and STEREO A (right). Anisotropy plotted in lighter color denotes periods of background intensity for which the anisotropy calculation is very uncertain. Gray shading in ACE observations marks a period where the electron measurements (and following the anisotropy) are contaminated by ions. The small shaded area in STEREO A measurements denotes a period of very poor pitch-angle coverage, which led to an incorrect anisotropy determination.