ALICE (Rosetta)
ALICE is an ultraviolet imaging spectrograph that was part of the payload of the European Space Agency's Rosetta mission. This instrument was designed to study the composition, structure, and dynamics of cometary atmospheres, with a special focus on the 67P/Churyumov-Gerasimenko comet. Here are some key details about ALICE:
- Launch and Mission: ALICE was launched aboard Rosetta on March 2, 2004, from the Guiana Space Centre in Kourou, French Guiana. The primary objective of Rosetta was to perform detailed studies of comet 67P/Churyumov-Gerasimenko, and ALICE played a crucial role in this endeavor.
- Instrument Design: ALICE operates in the extreme and far ultraviolet (EUV and FUV) range, specifically from 70 to 205 nanometers. It uses a concave holographic grating to disperse UV light onto a microchannel plate detector, which then converts the UV photons into electrons. These electrons are amplified and detected to produce a spectrum.
- Scientific Goals:
- To analyze the composition of the coma (the cloud of gases and dust surrounding the comet's nucleus) by identifying the presence of various molecules like water, carbon monoxide, carbon dioxide, and other gases.
- To study the spatial distribution and variability of these gases over time, providing insights into the comet's outgassing behavior as it approaches the Sun.
- To investigate the interaction between the solar wind and the comet's atmosphere, known as the coma.
- Key Discoveries:
- ALICE was instrumental in detecting the presence of argon in the coma of 67P/Churyumov-Gerasimenko, which was a significant finding as argon is a noble gas and its presence can help understand the comet's formation environment in the early solar system.
- It also contributed to the understanding of the comet's water production rate and the overall outgassing behavior, which varied significantly as the comet approached and then receded from the Sun.
- Operational Challenges: Operating an ultraviolet spectrometer in space presents several challenges, including the need for calibration due to the degradation of optical components over time and the sensitivity of UV detectors to solar radiation.
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