He is principal investigator of a NASA-supported sounding rocket program and has been responsible for over three dozen sounding rocket launches primarily for the study of the Earth's upper atmosphere, the aurora and the airglow, the atmospheres of comets and planets, the spectra of hot stars, and cosmic background radiation. This program also developed the UVX experiment which flew on the Space Shuttle Columbia in January 1986. He was principal investigator for a program of comet studies (which included comet Halley in 1985-1986) using the International Ultraviolet Explorer satellite observatory. Feldman is a co-investigator on the team which developed the Hopkins Ultraviolet Telescope for FUV astronomy as part of the Astro payload that flew on the space shuttle in December 1990 and again in March 1995. He is a general observer with the Hubble Space Telescope and served on the Space Telescope Users Committee from 1992 to 1995. He is also a member of the FUSE science team and a co-investigator on the HST Advanced Camera for Surveys.