The MVACS package is designed to conduct a series of key experiments that will provide new answers to the questions outlined in the previous pages. The payload consists of four instruments. The Surface Stereo Imager (SSI) will take panoramic images of the area around the landing site. These images will be used to study the geology and to derive atmospheric dust and water levels. The SSI also serves as eyes for the scientists as they operate the other instruments. The Meteorology Package (MET) will measure atmospheric pressure, wind, temperature, and humidity near the surface. The Thermal and Evolved Gas Analyzer (TEGA) will determine the concentrations of ice, adsorbed volatiles, and volatile-bearing minerals in samples acquired by the Robotic Arm (RA). It will dig trenches into the surface to search for ground ice and fine-scale layering. It also serves as a hand that can deliver samples to the TEGA. The camera on its wrist is capable of imaging the surface and samples in microscopic detail. By determining the amounts of water contained in ice, adsorbed in the regolith, trapped in water-bearing minerals, and present as vapor, the MVACS instruments will help answer how water is presently distributed and how it behaves seasonally. By measuring the quantity of adsorbed carbon dioxide, they will help define the role of this carbon dioxide reservoir in long term climate change. The MVACS instruments are described in detail in the instruments section of this site.