ICESat-2 By the Numbers: 300 Trillion

The video explains how the Atlas instrument emits a pulse of photons that travel through the atmosphere, reflect off the Earth's surface, and return to the instrument. Only a small number of photons are received back, and this precise reception is crucial for accurately calculating elevation.

What happens to photons as they travel through the atmosphere after being emitted by the Atlas instrument?

• They increase in number.

• They disappear completely.

• They are absorbed by the atmosphere.

• They scatter in all directions.

How many photons does the Atlas instrument typically receive back?

• Thousands of photons

• None

• Hundreds of photons

• Just about a dozen photons

What is the role of the Atlas instrument in photon reflection?

• It captures only photons that reflect straight back.

• It increases the number of photons.

• It captures photons that reflect in all directions.

• It absorbs all photons.

Why is it important for the window of received photons to be very small?

• To increase the number of photons received

• To reduce the timing error

• To capture photons from different directions

• To make the instrument more powerful

What allows scientists to calculate elevation very precisely?

• The large number of photons received

• The small window of received photons

• The speed of the photons

• The high power of the Atlas instrument