Exploring the Planets

Orbiter Science Instruments

Mars orbital spacecraft use many kinds of instruments to study different aspects of the planet.

The photo on the right shows the Mars Reconnaissance Orbiter during assembly. Reflecting foil for temperature control covers the spacecraft. The science instruments are mounted on the "science deck," which faces down toward Mars during normal operations.
NASA/JPL photo and diagrams

Mars Orbiter Diagrams

Charge-Coupled Device (CCD)
Like your own personal digital camera, a spacecraft camera records images using a CCD — an array of tiny detectors whose combined measurements of light form a picture. With the use of special filters, images can reveal the chemistry of a planet's surface. This CCD is identical to the one used by the Mars Reconnaissance Orbiter's HiRISE camera.

Charge-Coupled Device (CCD)
A series of mirrors in the HiRISE camera direct light to its CCD.

HiRISE Diagram

Lasers and Radar
Visible and infrared observations of Mars record reflected sunlight, but some instruments must provide their own source of energy. Radar sensors like MARSIS (on the Mars Express) and SHARAD (on the Mars Reconnaissance Orbiter) transmit a radio signal and measure the faint reflected echoes that return from underground geologic layers. Laser altimeters like MOLA (on the Mars Global Surveyor) create detailed topographic maps by sending out a narrow light beam and measuring how long it takes to reflect back from the surface.

Measuring Unseen Fields
Measuring a planet's gravity and magnetic properties offers clues to interior structure and processes. Magnetometers reveal magnetic field variations left behind in Martian rocks billions of years ago. And by tracking subtle changes in a spacecraft's velocity as it orbits Mars, scientists can create maps of density differences in the crust due to giant impacts and the growth of great volcanoes.


Deep Space Network Antenna
Spacecraft return data to Earth mainly in the form of radio signals, which are collected by an array of large dish antennas called the Deep Space Network. The antenna is 70 meters (220 feet) across. Three antennas are located around the Earth to allow 24-hour coverage of missions anywhere in the solar system. At greater distances, the amount of data a radio signal can carry in a given time declines, limiting the amount of information a spacecraft can send back. New communication techniques using lasers may allow much higher data rates over long distances.

Front View of the 70m antenna at Goldstone, California