Earth's atmosphere is wavelength-dependent
The atmosphere does not transmit every part of the electromagnetic spectrum equally. Some wavelength ranges reach the ground readily, while others are partly or almost completely absorbed.
| Radiation | Atmospheric transmission | Typical positioning |
|---|---|---|
| Radio | Most radio wavelengths pass through the atmosphere. | Ground-based. |
| Visible | Visible wavelengths largely reach the ground, although atmospheric effects can distort observations. | Ground-based optical observatories are practical. |
| Infrared | Much of the infrared region is absorbed, particularly by atmospheric water vapour, although narrow transmission windows exist. | Mostly space-based; some ground observatories use dry, high-altitude sites. |
| Ultraviolet | Strongly absorbed by the atmosphere. | Space-based. |
| X-rays | Strongly absorbed by the atmosphere. | Space-based. |
Advantages of observing from space
- Radiation can be detected without absorption by Earth's atmosphere.
- Ground-level light pollution and similar local interference are avoided.
- Atmospheric scattering and fluctuations do not distort the observation or produce scintillation.
Exam Tip: If asked why a telescope operates in space, identify the radiation being detected and state that the atmosphere absorbs that wavelength range. Do not rely only on saying that the view is clearer.