Simplify the following text for a Grade 6 native English-speaking person.
Original: The word `` pixel '' was first published in 1965 by Frederic C. Billingsley of JPL , to describe the picture elements of video images from space probes to the Moon and Mars . However , Billingsley did not coin the term himself .
Simplified: The word `` pixel '' was first used in a paper by Frederic C. Billingsley in 1965 .