Destination Mars by Rod Pyle Read Free Book Online Page A

sophisticated guesswork to interpret, but they showed a Mars that astronomers had scarcely imagined for all their years at the eyepieces of their mighty telescopes. For what those marvelous instruments could not reveal was the truth that emerged from the Mariner images: Mars was a desert, a place of craters and windswept stone, and vast fields of oxidized sand. It was, in short, an apparently dead world.
    The mission was not an easy one. Launched with its twin, Mariner 3, only Mariner 4 made the full journey. Both craft departed Earth in November 1964, with Mariner 3 failing to fully jettison its protective shroud in Earth orbit. Unable to extend its solar-power panels, it soon died of battery starvation and now resides, mummified, in a lazy orbit around the sun.
    Mariner 4 fared better, following the planned trajectory to Mars. It is worth relating that after observing the failure of the fiberglass shroud to release Mariner 3, technicians descended tothe cape and, within a matter of a few weeks, designed a new nose cone from metal with an improved release mechanism. This quick fix was indicative of those rough-and-ready early days of space exploration, and the new design worked perfectly. Mariner 4 left Earth orbit without incident in December and headed off for the long voyage to Mars, fifty-four million miles distant—if one could fly in a straight line. But one could not, and the distance traveled would be far longer.
    This was NASA's first success with Mars and only the second time a still-operating robotic probe flew by another planet (the Soviet Union had attempted as much, but all its machines failed before executing their primary missions). Mariner 2, launched in August 1962, had performed a successful flyby of Venus later that year (Mariner 1, true to form, was destroyed shortly after launch). 1
    Mariner 4 arrived at Mars in mid-July 1965, returning twenty-one good images and part of a twenty-second as it sped past the planet just over five thousand miles distant. The craft was crude by today's standards, but in 1964 terms it was a miracle of engineering for the unknown. In total, the basic instrumentation on the ship would send home twenty-three million scientific measurements. Not all of these were specific to Mars; many were measures of dust in space en route, attempts to measure both Earth's and Mars's magnetic fields, and many others.
    Imaging was a paramount goal. The twelve-pound TV camera's images were stored to an onboard tape recorder and relayed back to Earth—twice to reduce the likelihood of errors—beginning a few hours after it left the Martian system. A primitive onboard computer converted the images to radio code to be relayed back to JPL via a global network of huge tracking dishes. Each of the twenty-one images, which were only 200 lines in resolution (the high-definition TV of today is 1,080 lines) took almost nine hours to download.
    The operation of this camera was intended to be completely automated. There was a long delay between ground-sent commands,reception by Mariner, and a return confirmation, due to the extreme distance from Earth, so various sensors were installed to enable the system to operate autonomously. These were basic light-measuring systems that would sense when Mars was close enough to illuminate a photosensitive element to a certain level, then trigger the various parts of the imaging system as the craft swung by Mars. It was a one-shot deal, and any error could negate the entire trip. The cameras had to eject a lens-cap (controllers, concerned about a failure at this step, had accomplished this through a “cheat” in operations months prior). They then had to warm up and begin the picture-taking sequence right on time. Then, as Mariner 4 disappeared behind Mars after the flyby, the automated tape recorder (with three hundred feet of tape) would turn on and off in bursts to record the images for playback later, as the Earth was, for now, out of sight from Mariner's