..by Anura Guruge
Just a couple of weeks ago, I was writing about ‘Mariner 2‘ in what hopefully and with luck might be my next book; my 12th (not counting those that I have co-authored or edited). Given that this book is meant to be the first book I have written specifically as an eBook (i.e., Kindle, iPad, Google etc.), I am not that concerned about copyright because I fully appreciate that eBook content is readily ‘shareable‘ — which is why I have refrained from making all my books eBooks.
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In December 14, 1962, the 447 lbs U.S. ‘Mariner 2’, became the first successful interplanetary space probe when it passed, as planned, within 21,648 miles of Venus following an incident-prone 108-day voyage from Earth. It had a pyramidal structure, consisting of a solid base topped off by a skeletal mast that culminated in a cylindrical housing. Much of probe’s seven scientific instruments were contained within the mast structure; the total weight permitted for these instruments capped at 40 lbs. The base 41” across was hexagonal in shape, and was made up of six magnesium compartments. It had a total height of 12’. For comparison, Dawn, when launched, was six times heavier and its base over one-and-a-half times longer.
The six compartments in the base housed: a small rocket engine for course-correction, the required propellant, a bottle of nitrogen gas for altitude adjustments, most of the electronics, all of the communications equipment, a 1000 Watt-hour sealed silver-zinc battery and a battery charger. The only radio transmitter on-board had a 3 Watt transmission power, this being comparable to that of a contemporary car phone and about one-third that of a modern cell phone. Three huge steerable antennas, one in California, the other in Australia and the third in South Africa, had to be used to capture the weak radio signal from the probe, the geographic separation of the three compensating for Earth’s unceasing rotation around its axis. One of the key objectives of the mission was to explore the limits of long-range, extraterrestrial communications, particularly as it related to spacecraft command and control.
There were two solar cell wings, one 6’ x 2.5’ the other a foot shorter; a large directional dish antenna was mounted off the bottom of the base unit, a cylindrical omnidirectional antenna sat at the top of the mast while two smaller antennas for command and control were embedded into the solar panels. When deployed the two solar panel wings had a total span of 16.5’. The solar panels were extended within 45 minutes of launch. With the solar panels deployed Dawn has a wingspan of 64.75’.
The seven scientific instruments borne aloft by ‘Mariner 2’ consisted of: two radiometers (one microwave and the other infrared) for measuring Venusian atmospheric and terrestrial radiation [in particular temperature]; a fluxgate magnetometer to monitor and measure magnetic fields; an a Geiger counter equipped ionization chamber to determine high-energy cosmic radiation; a particle detector [i.e., a modified Geiger counter] to establish the presence of lower-energy radiation particularly the x-ray and ultraviolet range; a cosmic dust detector and a solar plasma spectrometer to study the solar wind. No cameras were included since Venus was known to be shrouded by a dense, amorphous cloud blanket.
‘Mariner 2’ was launched from the Cape Canaveral Air Force Station, on Florida’s eastern seaboard, around 2 a.m. local time, on August 27, 1962. It was launched atop a two-stage ‘Atlas-Agena’ rocket, the first-stage ‘Atlas’ part derived from the United States’ first intercontinental ballistic missile (ICBM) system, the ‘SM-65 Atlas’; the first of which was produced in 1959. The Atlas burn lasted just five minutes, the first-stage then separating from the Agena-Mariner section. Two burns of the upper-stage ‘RM-81 Agena’ followed, prior to its separation. Earth orbit escape resulted 26 minutes and 3 seconds after liftoff.
On July 22, 1962, NASA launched ‘Mariner 1’, a twin of ‘Mariner 2’, its first foray into robotic interplanetary probes. Within five minutes of launch, due to erroneous guidance, the ‘Atlas-Agena’ launch vehicle had veered off-course and had to be destroyed. Thirty-four days later, the Soviets launched ‘Venera 2 MV-1 No.1’ [‘Sputnik 19’] with the intent of it becoming the first man made object to land on another planet.
Mariner 2 never let those on Earth forget that most of its technology was still in the experimental stage and that it was boldly blazing into truly uncharted territory. Its journey, as was to be expected, was not without incident. In those early days launch accuracy was still a bit iffy, mandating a need for midcourse corrections. Thus, a week after launch a midcourse correction maneuver sequence was initiated using the onboard rocket engine and gas jets. Eleven days into the flight, ‘Mariner 2’ unexpectedly switched off its navigational gyroscopes and lost orientation [i.e., ‘attitude’] control. Mariner 2, however, managed to automatically recover from this glitch. Three weeks later there was a similar loss of orientation, again Mariner being able to quickly recover from it without any intervention from home. Just over a month later, the output from the smaller solar panel abruptly dropped.
On December 14, 1962, Mariner reached its expected target distance from Venus. The goal had always been to flyby rather than getting too close and running the risk if getting yanked in by Venus’ gravitational field. During the flyby Mariner’s radiometers, magnetometer and Geiger counters made repeated scans, back-and-forth, across both the dark and light sides of the planet – the radiometer readings for surface temperature involving three separate scans over a thirty-five minute period. The results indicated that the Venusian surface was extremely hot, its thick carbon dioxide heavy atmosphere causing rampant greenhouse effect heating.
The last radio transmission from Mariner 2 was received on Earth on January 3, 1963, twenty days post the Venus flyby. This groundbreaking mission to that point had lasted 129 days. It is thought that Mariner 2 entered heliocentric orbit soon after that and has remained so since.