Mariner IV - First Flyby of Mars
Some personal experiences
© Copyright 1996-2006. All rights reserved.
This is the story of Mariner IV, the world's first mission to the planet Mars. Among many important discoveries, it consigned the "canal" theory to limbo. A description of the mission and spacecraft is augmented by the author's personal experiences while associated with this historic undertaking. (illustrated)
Early Observations and Theories
Ancient astronomers noticed "wandering stars" which moved differently from others in the sky. Today we know them as planets (Greek for "wanderers") which, along with Earth, orbit our Sun. Sky gazers had been fascinated by one particular planet for ages. From its blood-red color, the Greeks dubbed it Ares, god of war, whereas the Romans named it Mars. Its changing aspect was often viewed as a harbinger of doom.
In 350 B.C. Aristotle, "knowing" that the Universe is "naturally" perfect, with Earth at its center, attempted to explain the movements of the stars and planets by assuming that they moved on concentric crystalline spheres. Unfortunately, this did not agree with observation, so he added a number of spheres, ending up with a total of 55! In 200 B.C. Aristarchus of Samos found that this system could be vastly simplified by assuming that the Sun, not Earth, was at the center. Aristotle's views were firmly entrenched, and he was generally ignored. However, his concept did not allow for "retrograde motion" (As Earth, moving faster, catches up to and passes Mars, it appears to move backwards for a while before resuming its forward motion). In 150 A.D. Claudius Ptolemy neatly cleared this up by showing that this motion could be explained by having planets moving not on the spherical shells, but on circles attached to them called "epicycles". In his final model epicycles were placed on epicycles. The Catholic Church accepted this system as dogma. Anyone who disagreed was branded a heretic and subject to be burned at the stake. Thus the Ptolemaic-Aristotelean system was firmly entrenched for the next 2000 years.
In 1513 Polish astronomer Nicolai Copernicus proposed a heliocentric (Sun-centered) solar system. in which Earth traveled around the Sun, but he still assumed circular orbits. To adjust his concept he was forced to retain epicycles, although the system was much simplified. In the late 15th century Danish astronomer Tycho Brahe made a great number of celestial observations, concentrating on Mars. In 1600 he hired an assistant, Johannes Kepler to work with the data. Kepler found that the only simple model that would account for Mars' motion was that its orbit was not a circle but an ellipse! Thus was the modern age of astronomy begun. Fortunately Keppler had concentrated on Mars, whose orbit is more elliptical than any other planet, or he might not have come to that conclusion. (The orbital eccentricity of Mars is .0934. Two planets have higher values, Pluto at .2488 and Mercury at .2056. In Keppler's time Pluto had not yet been discovered and Mercury was too close to the Sun for precise measurements.)
Life on Mars?
Although readily seen with the naked eye, it remained for the invention of the telescope circa 1600 to allow scrutiny of its surface. With this instrument in 1659 Christiaan Huygens identified a dark patch on the surface (known today as Syrtis Major) which led to discover that Mars rotates on its axis much as the Earth does. As time passed, a variety of surface features could be observed, and what's more, apparently changed with the seasons. The north white polar cap, warmed by the summer sun, shrank in size. Simultaneously, a "wave of darkening" spread from the north pole towards the equator. This led to speculation that martian plants, brown in winter, turned green as water from the polar caps nourished them.
In 1877, during a close approach to Earth, and at a time of exceptional clarity in both planets' atmospheres, Giovanni Schiaparelli observed light and dark markings, which he assumed to be continents and seas. He also noted what appeared to be straight lines, and dubbed them "canali", "channels" or "grooves" in Italian. Probably fueled by recent canal building on Earth (the Suez had just been completed, and Panama planned) this was translated into "canals" in English, fueling speculation that martian beings had dug a vast network of waterways to bring water from melting ice caps to nourish their agriculture. In a series of experiments in 1913 E. Walter Maunder showed that at the limit of vision, the human eye interprets a series of dots as a straight line. His findings were generally ignored as far as Mars was concerned.
Lowell's map of Mars
Percival Lowell, captivated by the idea, dedicated his life to further study of this subject, constructing Lowell Observatory in Flagstaff, Arizona, with its 24-inch telescope for that purpose. Believing that intelligent beings existed on Mars, over the years he developed a well-developed map of the supposed canals, with "oases" at their intersections. A puzzling observation was "gemination", when some of the canals appeared to double. Not all astronomers agreed with Lowell, however. Many never saw any sign of canals at all.
However, this fueled speculation that there was sentient life on Mars, resulting in a spate of science fiction stories, one of which was War of the Worlds, written in 1895 by H. G. Wells. On Halloween night, 1938, the story was relocated from England to New Jersey, and broadcast as a realistic pseudo-news radio show by Orson Welles' "Mercury Theater". Many listeners, having tuned in late, missed hearing the disclaimer that it was only a show, and mass panic ensued, with people all across the United States believing they were in reality being invaded by Martians.
Observations from Earth showed that a Mars day was similar in length to Earth's, that it had north and south white polar caps, a year twice as long as Earth's, a very thin atmosphere, was much colder than Earth (being farther from the Sun), with gravity about 1/3 that of Earth, and had markings which changed with the seasons. In short, a cold, inhospitable place for life to exist. Or was it? And then, there were those canals, still a mystery in the 1960s.
There was only one way to answer those puzzling questions .... go there and find out!
The Mariner and Ranger Missions
In 1936 a group of Cal Tech (California Institute of Technology) students formed the Guggenheim Aeronautical Laboratory for the purpose of conducting rocket research. In the late 1930s, with war raging in Europe, they were awarded a contract from the US Army to develop rocket assisted takeoff devices for airplanes. In 1944 it was renamed Jet Propulsion Laboratory, (referred to as "JPL" or, familiarly, "The Lab") and in 1958 became responsible for planning NASA's space missions. It went on to become the World's leading space science laboratory.
Whereas the Ranger series of missions explored the Earth's Moon, Mariner was designed to fly by or orbit Venus and Mars (see Appendix A). The first, Mariner I, failed shortly after launch, but Mariner II performed the first successful encounter with another planet when it flew by Venus.
I joined the Lab in 1962, qualifying the then-new integrated circuits for space missions. Even though they passed all tests, it was decided to use conventional discrete components. At that time the academic atmosphere of CalTech suffused JPL. However, as time went by, NASA got its greedy claws deeper and deeper into "overseeing" all activities regarding space exploration, the result of which was a giant pyramid of administration, with a few dedicated technicians and engineers actually trying to get something accomplished.
"Society in every state is a blessing, but Government, even in its best state, is but a necessary evil; in its worst state, an intolerable one."
- Thomas Paine, Common Sense (1776)
With its penchant for outrageously expensive, bloated and overly-managed pork-barrel programs, NASA can be likened to the hidebound U.S. Navy admirals prior to World War II who kept insisting that battleships were indispensable, and aircraft would never amount to anything despite overwhelming evidence to the contrary. Much time, talent and money was wasted by designing heavyweight spacecraft only to find they had to be redesigned when the launch vehicle they were to use was not ready at launch time.
In the days of the Johnson administration, "Lady Bird" set her eyes on beautifying America, and we were given $250,000 for landscaping. In vain we protested against this waste, begging to use the funds for a quick and dirty Venus mission. No, it was not allocated for that use, so we got the $^&*% reflecting pools and olive trees instead. But I digress ....
Mariners III and IV were identical, designed to fly by Mars, collecting scientific data along the way, and then pass by the red planet to obtain images of the surface. Besides Mariners III and IV, there was a third, the PT/M (Proof Test Model) which remained on the ground for testing and simulation purposes. Mariner IV was launched successfully, proceeding to perform flawlessly (well, almost flawlessly, as we shall see), returning the first close-up images of the planet's surface.
Mariner IV (click to enlarge). The rocket motor nozzle points toward you from the bus. On either side of the nozzle are adjustable temperature control louvers. The high gain antenna dish is at top, under the low gain antenna mast which also holds the magnetometer sensor .
Mariners III and IV were designed around an octagonal structure called the "bus". Each of the eight sections was a "bay". Mechanical components were of magnesium to save weight; individual chasses were hogged out of magnesium blocks. Four solar panels were attached to the bus to furnish power to the Spacecraft (abbreviated "S/C"). Spacecraft subsystems were located as follows:
|Bay I||Power subsystem, which distributed electricity to other components.|
|Bay II||Propulsion, which included a small rocket motor for mid-course correction.|
|Bay III||Some scientific instruments, and DAS (Data Automation System) for organizing data.|
|Bay IV||Data Encoder and Command, organizing data and interpreting ground commands.|
|Bay V||Radio Frequency communications and video tape recorder.|
|Bay VI||Radio Transmitter and Receiver.|
|Bay VII||Attitude control and gas supply.|
|Bay VIII||Power Regulator and battery.|
In addition, some scientific instruments and the low gain radio antenna were placed on a mast situated on top of the bus. Below the bus was the TV camera and sensors, mounted on the scan platform, which pointed the TV camera at the planet. Power used by all these complex electronics was less than that of two 100-watt light bulbs!
As the Earth rotated, the spacecraft appeared to move across the sky. To keep radio contact around the clock, three tracking stations were located approximately equidistantly around the Earth: Goldstone, California; Johannesburg, South Africa; and Woomera, Australia.
Spanning millions of miles, the 10-watt transmitter beamed its information to Earth, where the feeble signal was captured by 200-foot antennas. Initially, data rate was 33-1/3 bits per second, decreasing to 8-1/3 bps later in the mission. Communication was two-way, "downlink" referring to data sent from the spacecraft, and "uplink" for commands sent from the Earth.
As well as data feeds from the stations, we had teletype and voice circuits. One night a message issued from Australia, "Sorry, we can't track the spacecraft, (they pronounced it "Spice-Crahft) the Galahs (an aggressive local parakeet) have eaten the radome (antenna cover)".
One Christmas eve our teletype started chattering, spewing out what looked like random Os and Xs. It was the image of six kangaroos pulling Santa's sled!
GMT (Greenwich Mean Time) was used to standardize operations across various time zones, also known as "zulu" time. Station operators at the South African station ("Joburg") took exception to this, claiming that it was denigrating to some native tribes. A memo was passed around to refer to "GMT" in communications with that station.
Of primary importance during the mission was keeping the solar panels oriented so as to receive maximum sunlight, which was accomplished by the attitude control system. Two points of reference were used, in conjunction with the appropriate sensors - the Sun and the star Canopus. If these sensors indicated drift away from the nominal position, small puffs of gas were ejected from nozzles located at the ends of the solar panels. Any unequal pressure from sunlight on various parts of the S/C which might affect its orbit was corrected by adjustable vanes mounted on the ends of the solar panels. In the event a mid-course maneuver was required, the rocket motor nozzle, which was fixed, had to be aimed by changing the S/C attitude. In this event, attitude control was temporarily switched over to a gyro system.
An extremely important subsystem was the CC&S (Central Computer and Sequencer). This device was similar in function to a washing machine timer, but far more sophisticated. It issued commands to the various other subsystems at preset times during the mission. Thus the spacecraft could be completely autonomous, fulfilling its mission without any guidance from Earth. However, the stored commands could be modified from Earth. Its memory consisted (honestly!) of ferromagnetic "doughnuts" strung on wires.
The Scan Subsystem
left to right:
1. Technician Jack Collier performing a system test. At left, Mars optical simulator, sensor (center front), drive motor (center, rear), electronics and power supply.
2. Power supply.
3. Sensor subassembly.
4. Electronics chassis. Note discrete components; integrated circuits were not known to be reliable enough at that time. Each component was "qualified", tested exhaustively for high reliability.
Since it would not be known exactly where the spacecraft would be as it passed Mars, the TV camera was mounted on the scan platform. A few hours before it reached the planet, power was applied, and the platform bobbed up and down. When the planet came in view of the wide-angle (40 degree field of view) sensor, the platform driving motor switched from scanning to tracking mode, which kept the scan sensor, and hence the TV camera, pointed directly at the planet. When the planet came in view of the TV camera with a narrow field of view (one degree), it started taking a series of pictures as the S/C swept across the planetary surface.
I was assigned as co-Engineer for the scan subsystem. I noted that the circuitry, which had already been designed, seemed overly complicated. There was plenty of testing and overseeing construction, however. Some of the subassemblies were constructed "in house", those subcontracted were referred to as "off lab" (we couldn't really call them "outhouse"). We were mystified by the erratic operation of our power supplies, until I noticed a white film on the components. I took a trip out to the subcontractor and went through their manufacturing processes. The last operation was cleaning them of any debris, solder flux, etc. I asked them to show me what they used for a cleaning solution. One of their techs disappeared into the men's room and returned with a five-gallon container of green soap! Dipping the probes of an ohmmeter in the solution showed that it was extremely conductive.
Another manufacturer built our preamplifier on a small sub-chassis which included the sensor and lens assemblies. One of the tests involved shaking each subassembly on a vibrating table, to simulate conditions during launch, during which the boards on our preamp were shaking loose from the chassis. Another visit to the assembler. The boards were bonded to the chassis with epoxy, and components soldered on. Inspecting this operation revealed that the solderer placed the chassis in a vise and tightened it up, deforming the chassis and popping the board loose!
The lens assembly focused the image of Mars onto the detector, which consisted of a circular 1-1/4 inch silicon wafer (basically a solar cell). Two orthogonal lines were scribed through the active surface down to the substrate, dividing it into four quadrants. This was an exacting process, and not all wafers made it successfully through the procedure.
Somehow we got through these and other trials and tribulations, and it was time for acceptance testing. First was the "shake test", where the unit was subjected to the sorts of vibrations it would encounter during launch atop a large rocket. Then followed hours in a vacuum chamber where it was subjected to cycles of heat and cold. During the test, performance had to be monitored 24 hours a day. A rack full of test equipment, mounted outside the chamber, monitored signals from the unit under test. Three of us took turns keeping watch over our "baby". One night a frantic operator (who shall be nameless) woke me out of a sound sleep, saying that the whole system had failed. I grabbed my clothes and hurried to the testing facility. Sure enough, the oscilloscope showed there was power to the unit ... but .... it was wired into the circuit ahead of the power on switch. "Problem" solved.
Mariner IV blasts off to Mars atop an Atlas/Agena D launch vehicle Nov. 28, 1964
Two spacecraft were to be launched from Cape Canaveral, Mariner III and Mariner IV. Most of our Space Science crew went to attend the launch, yet the S/C data had to be monitored 24 hours a day from JPL. I was one of the two left behind at the lab, working 12 hours on, 12 off, 7 days a week, for a month. Although this was a grueling schedule, my overtime pay allowed me to purchase a brand new maroon Jaguar convertible!
A nosecone of new design was fitted over Mariner III (Mariners I and II were Venus probes) to protect it from debris and heating effects of the atmosphere during launch. Unfortunately Mariner III used a new construction method for the nose cone. It was fabricated of an aluminum honeycomb with fiberglass laminations. It had been tested for thermal stress, and high vacuum, but never both at once. Upon launch, gas in the nose cone cells exploded inwards and wrapped the shroud about the space craft structure, so that even though the explosive bolts were fired, the nose cone could not detach. This meant that the solar panels could not be deployed, and the battery soon discharged.
Mariner IV was equipped with the proven design nosecone, and on Nov. 28, 1964 the Spacecraft, mounted atop a 100-foot high two stage liquid-fueled Atlas/Agena D, blasted off without incident.
The sun sensor locked on the Sun, and the solar panels were getting full sunlight. The next step was to give the spacecraft a slight roll for the Canopus sensor to lock onto that star and stop the roll. However, it first acquired Markab, hunted again, but locked on Aldermarin instead. Trying again, it picked out Regulus and finally locked on Canopus after three more tries.
The rest of the crew returned to the Lab, and we settled down to a steady routine of monitoring data from "our baby" rapidly receding from Earth.
Monitoring spacecraft data was accomplished in the Space Flight Operations Facility (SFOF, pronounced "ESS-fof"), a large room in one of the buildings. There were stations manned by representatives of each spacecraft subsystem: Space Science (us), Power, Pyro (pyrotechnics, responsible for firing explosive squibs to initiate irreversible, one-time events, such as extending the solar panels, popping the cover off the TV camera, etc.), Attitude Control, and so forth.
To minimize personnel meandering about, each station consisted of a desk equipped with a telephone system, TV monitor and TV camera with which we could send diagrams, equations, etc. We also had access to TV cameras located throughout the building, some with tilt and pan controls. A favorite pastime was to train the camera on the front door, and when a particularly attractive female entered, to follow her on her walk through the building. With these comm facilities, we could communicate amongst ourselves while staying at our assigned post. Overseeing the operation was the "Bus Chief", and I, monitoring science data (while on my shift), was "Space Chief". It took some getting used to, picking up the telephone and saying "Bus Chief, this is Space Chief" without breaking into laughter. (No, we didn't wear funny hats). As it turned out, there were more stations than room on the main floor, so some of the monitoring stations were dispersed about a gallery, which overlooked it. There was one slight problem - no one had thought to install a communication link between the main floor and the balcony. We solved this neatly by rigging up two pulleys, some clothesline and a basket, by which we could pass messages back and forth!
Proceed to Page 2, Cruise Mode, Encounter, Results from Mariner and other missions.
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