Selective atmospheric absorbers — different molecules absorb different wavelengths:

• Ozone (O₃) — absorbs harmful ultraviolet (protects the biosphere).
• Carbon dioxide (CO₂) — absorbs in the far infrared (thermal band, hence its role in the greenhouse effect).

• Water vapor (H₂O) — absorbs in the longwave infrared and shortwave microwave.

• Consequence: we can’t image at every wavelength — see slide 15 for the “windows” that do transmit well.