( ( Some ( of ( ( Saturn 's ) ( smaller moons ) ) ) ) ( ( were ( discovered ( by ( ( ( the ( Voyager spacecraft ) ) , ) ( which ( ( passed ( the planet ) ) ( in ( ( 1980 and ) 1981 ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT Some)) (PP (IN of) (NP (NP (NNP Saturn) (POS 's)) (ADJP (JJR smaller)) (NNS moons)))) (VP (VBD were) (VP (VBN discovered) (PP (IN by) (NP (NP (DT the) (NNP Voyager) (NN spacecraft)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBD passed) (NP (DT the) (NN planet)) (PP (IN in) (NP (CD 1980) (CC and) (CD 1981)))))))))) (. .)))
Some of Saturn's smaller moons were discovered by the Voyager spacecraft, which passed the planet in 1980 and 1981.
(ROOT (S (NP (DT The) (NN voyager) (CD 1) (NN spacecraft)) (VP (VBD visited) (NP (NN saturn)) (PP (IN in) (NP (CD 1980)))) (. .)))