Why do spacecraft observe some wavelengths that cannot reach telescopes on Earth?

Spacecraft are used to observe wavelengths that cannot reach telescopes on Earth because Earth’s atmosphere acts as a filter, absorbing or blocking significant portions of the electromagnetic spectrum.12

While visible light, some infrared radiation, and radio waves can penetrate the atmosphere to reach the surface, other forms of radiation are absorbed by atmospheric components before they can be detected by ground-based instruments:12

• Ultraviolet radiation: Far-ultraviolet radiation is strongly absorbed by atmospheric ozone, preventing it from reaching the ground.23
• X-rays and Gamma rays: These high-energy, short-wavelength radiations are absorbed by the atmosphere, making them inaccessible to ground-based telescopes.2
• Infrared radiation: Certain infrared wavelengths are strongly absorbed by atmospheric water vapour and carbon dioxide.2

By placing observatories in space, astronomers can bypass these atmospheric barriers, allowing them to study cosmic phenomena—such as the physical conditions in hot nebulae or cold molecular clouds—across the entire electromagnetic spectrum. Additionally, space-based telescopes avoid the image distortion caused by atmospheric turbulence and airglow.124