Born in Groningen, Netherlands. Studied astronomy at Leiden University under Jan Oort, one of the pioneers of radio astronomy. In 1959, moved to the USA and began working at the California Institute of Technology. Became professor of astronomy at Caltech, later directed the Hale Observatories. Member of the U.S. National Academy of Sciences. Awarded the Bruce Medal, the Henry Norris Russell Lectureship, and other honors. The asteroid 10430 Martschmidt is named after him.