Schematron using XPath 2.0
The attribute vg2:mission_phase_name must be equal to one of the following values 'Earth-Jupiter Cruise', 'Interstellar Mission', 'Jupiter Encounter', 'Jupiter-Saturn Cruise', 'Launch', 'Neptune Encounter', 'Saturn Encounter', 'Saturn-Uranus Cruise', 'Uranus Encounter', 'Uranus-Neptune Cruise'.