The term 'APOLLO INSTRUMENT' is composed of three crossword solutions: LYRE (4 letters), MOON (4 letters), and LEM (3 letters). The LYRE is a stringed musical instrument that was used in Ancient Greece and is often associated with the Greek god Apollo. The MOON is a celestial body that Apollo astronauts visited during the Apollo program. The Lunar Excursion Module (LEM) was the spacecraft used by the Apollo astronauts to land on the MOON.