Complex sentence: On 30 September 2015, NASA selected five mission concepts for refinement during the next year, as a first step in choosing one or possibly two of the missions for development in 2016.
Split into simpler sentences: On 30 September 2015, NASA selected five mission concepts for refinement during the next year, as a first step in choosing one. NASA has stated it may choose not just one, but possibly two of the missions for development in 2016.