What are the marked absorption structures in sunlight called?
[Answer]
What causes these absorption structures?
[Answer]
Why do these structures make ground station observations of trace gases in the atmosphere difficult?
[Answer]
Because of this ground station observations initially concentrated on the measurement of strong absorbers in the atmosphere. What species is the principal example of a strong atmospheric absorber?
[Answer]
In what decade were the first ground station measurements of nitrogen dioxide concentrations made?
[Answer]
Given the defects of solar radiation as a light source, what was the key problem for ground station measurements?
[Answer]
What was the main technique used in ground station observations to try to solve this problem?
[Answer]
Satellite-borne spectrometers can measure spectra from three light paths. What are these light paths?
[Answer]
Which of these light paths provides a reference spectrum?
[Answer]