a lot of lessons from Mariner 4.
Unlike that first flight, these two Mariners were not tasked with performing scientific investigations during their cruise to Mars. Their specific goal was to begin—and end—their primary operations at Mars encounter. The space age was maturing. They were to fly over the equator and southern hemisphere of Mars, respectively.
Each craft was just under one thousand pounds in mass (or about double the mass of Mariner 4), and measured ten feet tall and about nineteen feet wide when in cruise mode. As before, there was an analog tape recorder for image storage and retransmission. There was also a digital recorder for science data storage. And, like Mariner 4, internal temperature control of the spacecraft, critical to successful operation, was governed by an ingenious system of slatted louvers, like Venetian blinds, on the sides of the boxy main body.
One stunning difference was the amount of data that could be sent back to Earth. The designers of Mariner 4 had been very conservative, so concerned were they that things be kept simple to ensure mission success. With these new spacecraft, there was an intense effort to maximize the data return and speed with new techniques; but this was not implemented without conflict. Conservative engineers sparred with the more aggressive science team in a running battle over data rates. Ultimately, the newer system was couched as an “engineering experiment,” which would have provided political cover in case of a failure. But the net result was that its data transmission was about two thousand times that of its predecessor. While a stunning success, this would not be the last time unmanned space exploration would suffer internal squabbles over political concerns.
Launched a month apart, the twin spacecraft arrived at Mars separated by only five days. Mariner 6 entered the vicinity of Mars on July 29, 1969. The probe was flying via inertial guidance as opposed to relying on the problematic Canopus sensor. This had caused much drama on Mariner 4. And on this flight, when the explosive retainers of Mariner 6's scan platform were ignited to release the cameras and instruments into their postlaunch science-gathering configuration, they blew a small cloud of detritus into the craft's immediate vicinity. Of course, being in midflight, the particles kept right on traveling with the spacecraft, and the Canopus star sensor began trying to lock on these small, brightly lit particles instead of the proper guide star. So rather than track bits of paint and ash as they flew past Mars (and possibly end up imaging the black of space instead of the planet), they relied on the internal guidance system to orient the craft.
Fifty hours prior to flyby, the instruments were activated. Two hours later, the “bomb run” began, and for the next forty-one hours, forty-nine images were snapped of the approach to Mars via the narrow-angle (or close-up) camera. On July 31, the close encounter began, and another twenty-six close-ups were captured.The craft sped past Mars at a distance of about two thousand miles, or less than half that of Mariner 4. As it left Martian space, it sent home the data and images it had acquired, then began a limited set of observations of the outer solar system and the Milky Way's galactic edge.
The only equipment failure on Mariner 6 was insufficient cooling of the infrared spectrometer at Mars encounter, limiting its usefulness. Overall, though, the mission was a crowning success. Shortly it would be Mariner 7's turn to barrel its way past Mars.
Despite the early navigation and communication problems, Mariner 7 behaved very politely as it neared its target. Reaching Martian space on August 2, 1969, the craft captured ninety-three images of Mars as it closed on the planet. After fifty-seven hours of approach, the close flyby began. The craft was taking a more southerly trajectory than originally planned, due to early analysis of Mariner 6 images.
Unlike that first flight, these two Mariners were not tasked with performing scientific investigations during their cruise to Mars. Their specific goal was to begin—and end—their primary operations at Mars encounter. The space age was maturing. They were to fly over the equator and southern hemisphere of Mars, respectively.
Each craft was just under one thousand pounds in mass (or about double the mass of Mariner 4), and measured ten feet tall and about nineteen feet wide when in cruise mode. As before, there was an analog tape recorder for image storage and retransmission. There was also a digital recorder for science data storage. And, like Mariner 4, internal temperature control of the spacecraft, critical to successful operation, was governed by an ingenious system of slatted louvers, like Venetian blinds, on the sides of the boxy main body.
One stunning difference was the amount of data that could be sent back to Earth. The designers of Mariner 4 had been very conservative, so concerned were they that things be kept simple to ensure mission success. With these new spacecraft, there was an intense effort to maximize the data return and speed with new techniques; but this was not implemented without conflict. Conservative engineers sparred with the more aggressive science team in a running battle over data rates. Ultimately, the newer system was couched as an “engineering experiment,” which would have provided political cover in case of a failure. But the net result was that its data transmission was about two thousand times that of its predecessor. While a stunning success, this would not be the last time unmanned space exploration would suffer internal squabbles over political concerns.
Launched a month apart, the twin spacecraft arrived at Mars separated by only five days. Mariner 6 entered the vicinity of Mars on July 29, 1969. The probe was flying via inertial guidance as opposed to relying on the problematic Canopus sensor. This had caused much drama on Mariner 4. And on this flight, when the explosive retainers of Mariner 6's scan platform were ignited to release the cameras and instruments into their postlaunch science-gathering configuration, they blew a small cloud of detritus into the craft's immediate vicinity. Of course, being in midflight, the particles kept right on traveling with the spacecraft, and the Canopus star sensor began trying to lock on these small, brightly lit particles instead of the proper guide star. So rather than track bits of paint and ash as they flew past Mars (and possibly end up imaging the black of space instead of the planet), they relied on the internal guidance system to orient the craft.
Fifty hours prior to flyby, the instruments were activated. Two hours later, the “bomb run” began, and for the next forty-one hours, forty-nine images were snapped of the approach to Mars via the narrow-angle (or close-up) camera. On July 31, the close encounter began, and another twenty-six close-ups were captured.The craft sped past Mars at a distance of about two thousand miles, or less than half that of Mariner 4. As it left Martian space, it sent home the data and images it had acquired, then began a limited set of observations of the outer solar system and the Milky Way's galactic edge.
The only equipment failure on Mariner 6 was insufficient cooling of the infrared spectrometer at Mars encounter, limiting its usefulness. Overall, though, the mission was a crowning success. Shortly it would be Mariner 7's turn to barrel its way past Mars.
Despite the early navigation and communication problems, Mariner 7 behaved very politely as it neared its target. Reaching Martian space on August 2, 1969, the craft captured ninety-three images of Mars as it closed on the planet. After fifty-seven hours of approach, the close flyby began. The craft was taking a more southerly trajectory than originally planned, due to early analysis of Mariner 6 images.
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