Music Term: - First or lowest note of the harmonic series.?

Questions

In 1980 US space probe ---------- I approaches 77,000 miles of Saturn. ?

In 1981 First ---------- crossing of Pacific completed (Double Eagle V). ?

In 1981 Second Space Shuttle Mission - ---------- 2 is launched. First time a spacecraft is launched twice. ?

In 1982 Yuri V. ---------- succeeds Leonid Brezhnev. ?

In 867 St ---------- I (the Great), pope (858-67) dies. ?