Panaramic Camera (Pancam) - The most advanced color imaging system ever sent to another planet, Pancam will use twin cameras mounted on a mast to survey the Martian terrain. The high-resolution system can rotate in a complete circle and can swing up to 180 degrees up or down. A collection of about 14 filters will allow observations across the light spectrum.

Microsopic Imager (MI) - Located at the end of the rover arm, MI is a one part microscope and one part CCD camera. It should provide close-up, black and white images of rock surfaces and interiors exposed by the rock abrasion tool.

The rovers will also use a trio of spectrometers to make observations across the light spectrum:

Miniature Thermal Emissions Spectrometer (Mini-TES) - Located near the Pancam atop the rover mast, this instrument will determine the mineralogy of rocks and soil from hundreds of meters away. Mini-Tes will help researchers identify targets for the rover to move toward.

Mössbauer Spectrometer (MB) - This sensor for this spectrometer is located on the robotic arm, and will allow researchers to study iron-bearing minerals and the magnetic properties of surface materials.

Alpha Particle X-Ray Spectrometer (APXS) - The APXS will determine the chemistry of objects studied by the rover arm by observing their alpha particle and x-ray emissions. Most observations will be taken at night, and can take up to 10 hours to take.

A grinding tool at the end of each rover's arm will eat into specific rocks to expose interior stone untouched by the effects of weather on Mars. It can create a hole 2 inches wide (45 millimeters) and one-fifth of an inch (5 millimeters) deep. Once exposed, other tools on the rover arm can analyze the rock.

The MER robots carry three sets of magnets each, one pair of magnets on the robotic arm and another pair on the vehicle's front end and a stronger single magnet on the rover deck. Each set varies in strength and should study magnetic minerals in Martian dust and the planet's geologic history.