(mission to create and observe an impact with a comet)
Deep Impact was a 2005 NASA mission to study the
cometTempel 1 (aka 9P/Tempel), by sending an impactor to
crash into it, then observing the results.
After successful completion of this mission, a follow-on mission
for the spacecraft was carried out, which was termed EPOXI (for
Extrasolar Planet Observation and Deep Impact Extended Investigation)
which continued until 2013.