Which observatory improved knowledge about interstellar gases?

The observatory that significantly improved knowledge about interstellar gases is the Orbiting Astronomical Observatory. This observatory was crucial in enhancing our understanding of various celestial phenomena, particularly through its ability to conduct observations beyond the distortion of Earth's atmosphere. By analyzing the spectrum of light emitted or absorbed by interstellar gases, the Orbiting Astronomical Observatory provided vital data that helped astronomers identify different elements and compounds in space, as well as their physical properties and processes.

Other observatories like the Hubble Space Telescope and the Chandra X-ray Observatory have made exceptional contributions to our understanding of the universe in different contexts, such as studying distant galaxies and high-energy astronomical phenomena, respectively. However, when it comes specifically to interstellar gases, the Orbiting Astronomical Observatory played a foundational role in that research area. The Keck Observatory, while notable for its advancements in ground-based astronomy and adaptive optics, focuses on a wide range of astronomical questions but does not specifically highlight interstellar gases in the same impactful manner as the Orbiting Astronomical Observatory.