Mars Global Surveyor

Mars Global Surveyor was a highly successful NASA mission that operated in orbit around Mars for nearly a decade. Launched in 1996, it served as a pivotal Mars orbiter that fundamentally reshaped scientific understanding of the Red Planet. The mission achieved its primary goal of mapping the entire Martian surface and provided critical data that guided subsequent missions like the Mars Exploration Rover program. Its extended operational life yielded a wealth of discoveries concerning the planet's geology, climate, and potential for past water on Mars.

Spacecraft Design and Construction

The spacecraft bus was built by Lockheed Martin based on a design heritage from the Mars Observer mission. Its structure featured a hexagonal shape with deployable components, including a single solar panel and a high-gain antenna. The design emphasized reliability for its long-duration mission in the harsh environment of interplanetary space. Key systems included reaction wheels for precise attitude control and a robust radioisotope heater unit system to protect components from extreme cold.

Mission Objectives and Orbit

The primary mission objective was to complete a global map of Mars over one full Martian year. To achieve this, mission planners at the Jet Propulsion Laboratory utilized an innovative technique called aerobraking to circularize its initial elliptical capture orbit. This process, which used friction with the upper atmosphere of Mars, saved a significant amount of propellant. The final operational orbit was a nearly circular, Sun-synchronous orbit that allowed for consistent lighting conditions for surface imaging, passing over the same local time each Martian day.

Scientific Instruments

The spacecraft carried a suite of six primary instruments. The Mars Orbiter Camera system, managed by Malin Space Science Systems, provided high-resolution grayscale and wide-angle color images. The Mars Orbiter Laser Altimeter constructed precise topographic maps by measuring the time for laser pulses to reflect off the surface. Other instruments included a Thermal Emission Spectrometer for mineralogical analysis, a Magnetometer and Electron Reflectometer to study remnant magnetic fields, an Ultraviolet Spectrometer for atmospheric composition, and the Doppler tracking system for analyzing the planet's gravity field.

Mission Timeline and Operations

Launched on a Delta II rocket from Cape Canaveral Air Force Station in November 1996, the spacecraft entered Martian orbit in September 1997. The aerobraking phase, complicated by a partially deployed solar panel, lasted over a year before mapping operations began in March 1999. The primary mission concluded in January 2001, but NASA granted several extensions due to the spacecraft's excellent health and continued data return. Communications were suddenly lost in November 2006, and subsequent investigations by the Mars Reconnaissance Orbiter team suggested a battery failure triggered by a software error.

Scientific Discoveries and Legacy

The mission revolutionized understanding of Martian history. MOLA data revealed the planet's northern lowlands and southern highlands in unprecedented detail, including evidence for an ancient Oceanus Borealis. The Magnetometer discovered remnant, localized crustal magnetic fields, indicating Mars once had a global magnetic field like Earth. Imagery from the Mars Orbiter Camera provided strong evidence for recent gullies and seepage features suggesting occasional liquid water flow. Its data served as the foundational base map for planning landing sites for Spirit, Opportunity, Phoenix, and Curiosity, cementing its legacy as one of NASA's most productive planetary missions.

Category:NASA probes Category:Mars orbiters Category:Spacecraft launched in 1996 Category:Missions to Mars