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Mariner 4: the story on HearLore | HearLore
— Ch. 1 · Octagonal Frame And Star Navigation —
Mariner 4.
~7 min read · Ch. 1 of 6
The Mariner 4 spacecraft consisted of an octagonal magnesium frame, four feet across a diagonal and three feet high. Four solar panels were attached to the top of the frame with an end-to-end span of twelve feet, including solar pressure vanes which extended from the ends. A six-foot elliptical high-gain parabolic antenna was mounted at the top of the frame as well. An omnidirectional low-gain antenna was mounted on a ten-foot tall mast next to the high-gain antenna. The overall height of the spacecraft was fourteen feet.
The scientific instruments included a helium magnetometer, mounted on the waveguide leading to the omnidirectional antenna, to measure the magnitude and other characteristics of the interplanetary and planetary magnetic fields. An ionization chamber Geiger counter, mounted on the waveguide leading to the omnidirectional antenna nearer the body of the spacecraft, measured charged-particle intensity and distribution in interplanetary space and in the vicinity of Mars. A trapped radiation detector, mounted on the body with counter-axes pointing seventy degrees and one hundred thirty-five degrees from the solar direction, measured the intensity and direction of low-energy particles.
A cosmic ray telescope, mounted inside the body pointing in anti-solar direction, measured the direction and energy spectrum of protons and alpha particles. A solar plasma probe, mounted on the body pointing ten degrees from the solar direction, measured the very low energy charged particle flux from the Sun. A cosmic dust detector, mounted on the body with microphone plate approximately perpendicular to the plane of orbit, measured the momentum, distribution, density, and direction of cosmic dust. A television camera, mounted on a scan platform at the bottom center of the spacecraft, obtained closeup pictures of the surface of Mars.
Launch Sequence And Star Lock
Mariner 3 had been a total loss due to failure of the payload shroud to jettison. JPL engineers suggested there had been a malfunction during separation of the metal fairing exterior from the Fiberglas inner lining. Pressure differential between the inner and outer part of the shroud could have caused the spring-loaded separation mechanism to become tangled and thus fail to detach properly. Testing at JPL confirmed this failure mode and an effort was made to develop a new, all-metal fairing. The downside of this was that the new fairing would be significantly heavier and reduce the Atlas-Agena's lift capacity.
After launch from Cape Canaveral Air Force Station Launch Complex 12, the protective shroud covering Mariner 4 was jettisoned and the Agena-D/Mariner 4 combination separated from the Atlas-D booster at fourteen hours twenty-seven minutes twenty-three seconds UTC on the 28th of November 1964. The Agena's first burn took place from fourteen hours twenty-eight minutes fourteen seconds to fourteen hours thirty minutes thirty-eight seconds. The initial burn put the spacecraft into an Earth parking orbit and the second burn from fifteen hours two minutes fifty-three seconds to fifteen hours four minutes twenty-eight seconds injected the craft into a Mars transfer orbit.
After Sun acquisition, the Canopus star tracker went searching for Canopus. The star tracker was set to respond to any object more than one-eighth as bright as Canopus, and less than eight times as bright as Canopus. Including Canopus, there were seven such objects visible to the sensor. It took more than a day of star-hopping to find Canopus, as the sensor locked on to other stars instead: a stray light pattern from the near Earth, Alderamin, Regulus, Naos, and Gamma Velorum were acquired before Canopus.
What were the physical dimensions of the Mariner 4 spacecraft?
The Mariner 4 spacecraft had an octagonal magnesium frame four feet across a diagonal and three feet high. The overall height including solar panels was fourteen feet with an end-to-end span of twelve feet.
When did the Mariner 4 mission launch from Cape Canaveral Air Force Station Launch Complex 12?
Mariner 4 launched on the 28th of November 1964 at fourteen hours twenty-seven minutes twenty-three seconds UTC. The Agena-D/Mariner 4 combination separated from the Atlas-D booster at that time before entering Earth parking orbit.
How many photographs did the Mariner 4 television camera take during its flyby of Mars?
The Mariner 4 television camera took twenty-one pictures using alternate red and green filters plus twenty-one lines of a twenty-second picture. These images covered about one percent of the planet's surface starting near forty degrees North and ending at fifty degrees South.
What scientific instruments failed or malfunctioned during the Mariner 4 mission to Mars?
The Geiger-Müller tube part of the ionization chamber failed in February 1965 while the plasma probe suffered performance degradation due to a resistor failure on the 8th of December 1964. All other instruments operated successfully despite these specific component issues.
Why was the Mariner 3 mission considered a total loss compared to Mariner 4?
Mariner 3 failed because the payload shroud jettison mechanism became tangled preventing separation of the metal fairing exterior from the Fiberglas inner lining. This malfunction caused pressure differential issues that prevented the spacecraft from deploying properly after launch.
The Mariner 4 spacecraft flew by Mars on July 14 and 15, 1965. Its closest approach was twelve thousand miles from the Martian surface at zero-one hours zero-zero minutes fifty-seven seconds UT the 15th of July 1965. The distance to Earth was forty-six million miles, its speed was three point nine miles per second relative to Mars, and five point six miles per second relative to Earth. Planetary science mode was turned on at fifteen hours forty-one minutes forty-nine seconds UTC on July 14.
The camera sequence started at zero-zero hours eighteen minutes thirty-six seconds UT on July 15 (seven hours eighteen minutes forty-nine seconds p.m. EST on July 14) and twenty-one pictures using alternate red and green filters, plus twenty-one lines of a twenty-second picture were taken. The images covered a discontinuous swath of Mars starting near forty degrees North, one hundred seventy degrees East, down to about thirty-five degrees South, two hundred degrees East, and then across to the terminator at fifty degrees South, two hundred fifty-five degrees East, representing about one percent of the planet's surface. The images taken during the flyby were stored in the on-board tape recorder.
At zero-two hours nineteen minutes eleven seconds UTC, Mariner 4 passed behind Mars as seen from Earth and the radio signal ceased. The signal was reacquired at zero-three hours thirteen minutes four seconds UTC when the spacecraft reappeared. Cruise mode was then re-established. Transmission of the taped images to Earth began about eight and a half hours after signal reacquisition and continued until August 3. All images were transmitted twice to ensure no data was missing or corrupt. Each individual photograph took approximately six hours to be transmitted back to Earth.
Hand-Colored Pixels And Verification
The on-board tape recorder used on Mariner 4 was a spare, not originally intended for the Mariner 4 flight. Between the failure of Mariner 3, the fact that the Mariner 4 recorder was a spare, and some error readings suggesting an issue with the tape recorder, it was determined that the team would test the camera function definitively. This eventually led to the first digital image being painted. While waiting for the image data to be computer processed, the team used a pastel set from an art supply store to hand-color paint-by-numbers style a numerical printout of the raw pixels.
The resulting image provided early verification that the camera was functioning. The hand-drawn image compared favorably with the final, computer-processed one. The total data returned by the mission was five point two million bits, about six hundred thirty-four kilobytes. All instruments operated successfully with the exception of a part of the ionization chamber, namely the Geiger-Müller tube, which failed in February 1965. In addition, the plasma probe had its performance degraded by a resistor failure on the 8th of December 1964, but experimenters were able to recalibrate the instrument and still interpret the data.
Cratered Surface And Scientific Shift
The images returned showed a Moon-like cratered terrain, which scientists did not expect, although amateur astronomer Donald Cyr had predicted craters. Later missions showed that the craters were not typical for Mars, but only for the more ancient region imaged by Mariner 4. A surface atmospheric pressure of ten millibars and daytime temperatures of minus eighty degrees Celsius were estimated. No magnetic field or Martian radiation belts or, again surprisingly, surface water was detected.
Bruce C. Murray used photographs from Mariner 4 to elucidate Mars's geologic history. Images of craters and measurements of a thin atmosphere, much thinner than expected, indicating a relatively inactive planet exposed to the harshness of space, generally dissipated hopes of finding intelligent life on Mars. Life on Mars had been the subject of speculation and science fiction for centuries. If there was life on Mars, after Mariner 4 most concluded it would probably be smaller, simpler forms. Others concluded that a search for life on Earth at kilometer resolution, using several thousand photographs, did not reveal a sign of life on the vast majority of these photographs; thus, based on the twenty-two photographs taken by Mariner 4, one could not conclude there was no intelligent life on Mars.
Micrometeoroid Hits And Final Silence
Data acquisition resumed in late 1967. The cosmic dust detector registered seventeen hits in a fifteen-minute span on September 15, part of an apparent micrometeoroid shower that temporarily changed the spacecraft attitude and probably slightly damaged its thermal shield. Later it was speculated that Mariner 4 passed through debris of comet D/1895 Q1 Swift, and even made a flyby of that comet's possibly shattered nucleus at three million miles.
On December 7 the gas supply in the attitude control system was exhausted, and between December 10 and 11, a total of eighty-three micrometeoroid hits were recorded which caused perturbation of the spacecraft's attitude and degradation of the signal strength. On the 21st of December 1967, communications with Mariner 4 were terminated. The spacecraft is now derelict in an superior heliocentric orbit. The total cost of the Mariner 4 mission is estimated at eight hundred thirty-two million dollars. Total research, development, launch, and support costs for the Mariner series of spacecraft, Mariners 1 through 10, was approximately five hundred fifty-four million dollars.