The eight instruments aboard MESSENGER, described below, have been carefully chosen to answer the key scientific questions of the mission.
This instrument consists of two cameras that will map landforms, track variations in surface spectra and gather topographic information. A scanning mirror will help point it in whatever direction is chosen. The two instruments will enable MESSENGER to “see” depth much like our two eyes do.
This instrument will detect gamma rays and neutrons that are emitted by radioactive elements on Mercury's surface, or by surface elements that have been stimulated by cosmic rays. It will be used to map the relative abundances of different elements, and will help to determine if there is ice at Mercury’s poles, which are never exposed to direct sunlight.
This instrument will map Mercury's magnetic field, and will search for regions of magnetized rocks in the crust.
The Mercury Laser Altimeter contains a laser that will send light to the planet’s surface, and a sensor that will gather the laser light after it has been reflected back from the surface. Together they will measure the amount of time for light to make a round-trip to the surface and back. Recording variations in this distance will produce highly accurate descriptions of Mercury’s topography.
Energetic Particle and Plasma Spectrometer (EPPS)
Gamma rays and high energy x-rays from the Sun, striking Mercury's surface, can cause the surface elements to emit low-energy x-rays. XRS will detect these emitted x-rays to measure the abundances of various elements in the materials of Mercury's crust.
Radio Science (RS)
RS will use the doppler effect to measure very slight changes in the spacecraft's velocity as it orbits Mercury. This will allow scientists to study Mercury's mass distribution, including variations in the thickness of its crust.
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