Spacecraft design is a critical part of any mission. For each kilogram of the spacecraft, many kilograms of rocket fuel are needed to reach escape velocity. So engineers and scientists have worked to keep the spacecraft mass (including structure, engines and fuel for orbital maneuvers, instruments, and power generation, navigation and communication equipment) at an absolute minimum. MESSENGER's propulsion system is integrated into the spacecraft structure to make the most economical use of mass. The miniaturized instruments are located on a science deck that will face Mercury, while a lightweight thermal shade shields the spacecraft from the blistering light of the nearby Sun. Most of the instruments are fixed rigidly to the body of the probe, so coverage of Mercury is achieved by spacecraft motion over the planet. The imaging system uses a miniature scanning mirror so it can quickly collect image mosaics.
Learn about the Onboard Instruments of MESSENGER