Initially assigned to the USNO's Time Service, he switched to work observing double stars alongside Kaj Strand.

Walker continued his focus on double stars after transfer to the USNO Flagstaff Station in 1966, ultimately making 8,000 measurements over the course of his career.

Initially identified with Audouin Dollfus's newly-discovered Janus, it was confirmed as a separate moon twelve years later and named Epimetheus.

He joined the American Astronomical Society in 1960, on the urging of Matsushima, and graduated with a BA in astronomy and physics in 1963.

[5]Through 1966, Walker also became involved in telescopic searches for additional Saturnian satellites as Earth passed through the plane of Saturn's rings.

[7][8] However, in October 1978, astronomers Stephen M. Laerson and John W. Fountain identified them as two separate objects; Walker's observations were instead realized to be the discovery of the moon Epimetheus.

[7] Voyager's observations also led to the discovery of Prometheus, a small moon with a similar brightness and orbital period to Epimetheus.

[9] Due to lifelong interests in Egyptology and archaeoastronomy, he studied hieroglyphs and traveled to Egypt in 1977, hiking along the Nile from Aswan to Cairo.

[1][10] He calculated that Thuban, then the star closest to the northern celestial pole, would not have been visible from the entranceway during Khufu's reign.