Alice Occultation - Gladstone

This animation shows how the count rate observed by New Horizons’ Alice instrument decreases as Pluto’s atmosphere passes in front of the sun. The decreasing count rate is due to the ultraviolet sunlight having to pass through progressively larger amounts of the atmosphere as the spacecraft line of sight gets closer to Pluto. The observed count rates are compared with predictions based on two plausible models of Pluto’s atmosphere: a “turbulent” case, where the expected count rate is relatively large, due