Forty years ago today, the United States launched the Mariner 9 spacecraft on a mission to Mars.  Among other achievements, Mariner 9 would become the first terrestrial spacecraft to orbit another planet other than Earth.

The Mariner Program was a NASA project whose goal was to investigate the planets Mars, Venus and Mercury from space.  A total of ten (10) Mariner spacecraft were launched between 1962 and 1973.  Seven (7) of these pioneering missions were considered successful.  The first interplanetary flyby, the first orbiting of another planet and the first gravity assist maneuver were all accomplished by Mariner spacecraft.

Each Mariner was built around a central bus or housing that was either hexagonal or octagonal in shape.   All spacecraft guidance, navigation, propulsion, communication, power and instrumentation systems were contained within or attached to this central bus.  Mariner spacecraft were typically configured with a set of four (4) solar panels for power.  However, Mariner’s 1, 2 and 10 used just two (2).  Cameras were carried by all Mariner space probes with the exception of Mission’s 1, 2 and 5.

Mariner 9 carried a scientific instrumentation package that consisted principally of an imaging system, ultraviolet spectrometer, infrared spectrometer and infrared radiometer.  Fully deployed, each pair of solar panels measured 22.6-feet across.  These panels provided 800 watts of power at Earth and 500 watts at Mars.  Power was stored in a 20-amp-hour nickel-cadmium battery.

Mariner 9 lift-off mass was 2,196 lbs.  Propellant useage during the flyout to Mars resulted in a spacecraft mass of 1,232 lbs in Martian orbit. Scientific instrumentation accounted for 139-lbs of the on-rbit mass. Spacecraft propulsion for mid-course corrections and orbital insertion was provided by a 300-lb thrust liquid rocket motor burning monomethyl hydrazine and nitrogen tetroxide.  Mariner 9’s 3.28-foot diameter antenna telemetered data back to Earth at rates of 1, 2, 4, 8 or 16 kilobits/second using dual S-band 10 watt and 20 watt transmitters.

Mariner 9 was launched from Cape Canaveral’s LC-36B at 22:23:00 UTC on Sunday, 30 May 1971.  An Atlas-Centaur SLV-3C launch vehicle provided the propulsive energy required to climb out of the Earth’s gravity well and send the probe on its way to Mars.  It would take Mariner 9 roughly 167 Earth days to travel a distance of 214.85 million nautical miles to the Red Planet.

Mariner 9 entered Mars orbit at 00:18:00 UTC on Sunday, 14 November 1971.  This marked the first time that a terrestrial spacecraft had achieved orbit about another planet in our Solar System other than Earth.   Initial orbital parameters included an apoapsis of 9,672-nm and a periapsis of 755-nm at an inclination of 64.3 degrees.   Interestingly, Mariner 9 arrived ahead of the Soviet Mars 2 space probe despite the latter’s eleven (11) day head start.

A planet-wide dust storm greeted Mariner 9 upon its arrival in Mars orbit.  Hence, imaging of the planetary surface did not begin in earnest until late November.  However, it was not until mid-January 1972 that the storm had subsided to the point that high quality images could be obtained from orbit.

Mariner 9 ultimately took 7,329 images which covered 100% of the Martian surface.  The photos revealed a fascinating planetary topology that featured river beds, craters, extinct volcanoes, mountains and canyons.  Mariner 9 discovered Olympus Mons, the largest known extinct volcano in the Solar System.  Valles Marineris, a system of Martian canyons measuring 2,170-nm in length, was named after Mariner 9 in tribute to the probe’s significant space exploration accomplishments.  Photographed as well were the diminutive Martian moons of Phobos and Deimos.

Upon depletion of its attitude control system propellant supply, Mariner 9’s mission was officially terminated when the spacecraft’s systems were turned-off on Friday, 27 October 1972.  Total time spent investigating the Martian environment from orbit was 349-days.  Though long silent, the craft remains in orbit around the Red Planet.  It is expected to continue to do so through approximately the year 2022.