page_title: Alice (spacecraft instrument)
hierarchical_section_title: Alice (spacecraft instrument)
caption_attribution_description: English: This figure shows how the Alice instrument count rate changed over time during the sunset and sunrise observations. The count rate is largest when the line of sight to the sun is outside of the atmosphere at the start and end times. Molecular nitrogen (N2) starts absorbing sunlight in the upper reaches of Pluto's atmosphere, decreasing as the spacecraft approaches the planet's shadow. As the occultation progresses, atmospheric methane and hydrocarbons can also absorb the sunlight and further decrease the count rate. When the spacecraft is totally in Pluto's shadow the count rate goes to zero. As the spacecraft emerges from Pluto's shadow into sunrise, the process is reversed. By plotting the observed count rate in the reverse time direction, it is seen that the atmospheres on opposite sides of Pluto are nearly identical. The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, designed, built, and operates the New Horizons spacecraft, and manages the mission for NASA's Science Mission Directorate. The Southwest Research Institute, based in San Antonio, leads the science team, payload operations and encounter science planning. New Horizons is part of the New Frontiers Program managed by NASA's Marshall Space Flight Center in Huntsville, Alabama.
context_page_description: Alice is an ultraviolet imaging spectrometer for spacecraft, with one used on the New Horizons spacecraft, and another on the Rosetta spacecraft. Alice is a small telescope with spectrograph and a special detector with 32 pixels each with 1024 spectral channels detecting ultraviolet light.
  Alice has an off-axis telescope which sends light to a Rowland-circle spectrograph, and the instrument has a field of view of 6 degrees. It is designed to capture airglow and solar occultation at the same time, and has two inputs to allow this.
context_section_description: Alice is an ultraviolet imaging spectrometer for spacecraft, with one used on the New Horizons spacecraft, and another on the Rosetta spacecraft. Alice is a small telescope with spectrograph and a special detector with 32 pixels each with 1024 spectral channels detecting ultraviolet light.
  Alice has an off-axis telescope which sends light to a Rowland-circle spectrograph, and the instrument has a field of view of 6 degrees. It is designed to capture airglow and solar occultation at the same time, and has two inputs to allow this.
caption: Infrographic of Alice data from its 2015 encounter with Pluto on New Horizons
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