NASA decided to make maximum use of the spaceship designated for this purpose, Mariner 10. During the transit near Venus, its research instruments surveyed and measured Venus and also the comet Kohotek
introduction
The fourth planet that NASA aspired to reach is Mercury. This planet can be reached in two ways. One way is a direct flight and the other way is via a transit flight near Venus. The second way was chosen. The reason for this lies in the shorter flight time. When a spacecraft approaches Venus its speed increases due to the effect of its gravity. The spacecraft flies at its designed speed and as it approaches Venus its speed increases due to the acceleration added to it as it passes by the planet. To make such a flight, the spacecraft must be launched at certain times suitable for this. The appropriate dates for the launch were 1970 and 1973. The date chosen was November 3, 1973. The appropriate time frame for a launch in 1973 was late October to early November.
NASA decided to make maximum use of the spaceship designated for this purpose, Mariner 10. While passing by Venus, its research instruments surveyed and measured Venus and also Comet Kohotek, (which from the end of November and during the month of December 1973 to mid-January 1974, when it is 120 million km from the earth, it could be observed with the naked eye).
The transit distance from Venus is 5,280 km and from the planet Hama 1,016 km.
The structure of the spaceship
The spacecraft weighs 528 kg and includes 78 kg of research instruments. The proximity of Hema's planet to the Sun necessitated the appropriate installation of heat shields. Rotational movement of the solar shelves and keeping them away from the sunlight in this way allows a maximum temperature of 100 degrees. From the moment of launch until the approach of the spacecraft to the planet Hema, the solar panels are tilted until a tilting angle of 76 degrees is reached. Immediately after launch, the heat shield was deployed around the spacecraft.
The spacecraft has an octahedral structure and has eight electronic cells. In the center, there is a spherical fuel tank for track repairs. The exhaust nozzle of the main engine protrudes through the sun visor in the center of the spacecraft. The spaceship has 12 navigation engines including three pairs of engines at the end of each shelf. The length of the low praise antenna is 2.85 meters. The magnetometer carrier is 6 meters long. The length of a sun shelf is 2.7 meters.
spacecraft instruments
1. Two TV cameras - the clarity of the images is like those obtained by terrestrial TV cameras that film the moon. The cameras must detect the surface of the planet Hema and Venus if possible because it is covered with clouds, determine the direction of the axis of rotation of the planet Hema and photograph the clouds of Venus and the clouds in ultraviolet. The resolution of the cameras during the transit near the planet Hama is 1.6 km. The cameras had to photograph both Comet Kohotek and the Earth and the Moon, once at a distance of 400,000 km from the Earth and a second time at a distance of 150,000 km from the Moon.
The cameras are located on a coverage plate and are designed to provide accurate targets from any part of the planet. Each camera is capable of transmitting at small and large angles. Each site is photographed, coded and transmitted as it is captured by the cameras. It was also recorded on film on the spacecraft and later broadcast in greater resolution. In total, the cameras must transmit 8,000 images to Israel.
2. An ultraviolet spectrometer to test the existence of an atmosphere on the planet Hema and its components. This is done when Mercury is between the Sun and the spacecraft.
3. Radio transmitter - transmitting signals from the two stars, Venus and Mercury, to measure the atmosphere, ionosphere, mass and radius of the two planets and their surface.
4. A device for detecting high-energy particles - how particles from the wind encounter the atmosphere and surface of the planet Hema and the examination of the solar flares during the passage near the planet Hema.
5. Infrared radio - measure the temperature of Venus above the cloud cover and on the dark side and find gaps in the cloud cover.
6. Two magnetometers - devices for measuring the amount of ions and electrons in defined energy ranges. It is possible to learn from this what is the influence of the planets on the solar wind and to conclude from this the electromagnetic properties of the two planets.
7. Electrostatic tester for testing the plasma in space during the flight.
8. An experimental device for transmitting X-wave transmissions.
track corrections
The nature of the flight requires the greatest precision. The deviation of Venus by 1.6 km would have resulted in a deviation of 1,600 km from the planet Mercury. For this reason, four route corrections were planned during the flight. The first flight correction was planned for the tenth day after launch and was designed to offset launch deviations. The second amendment came two weeks later. At this time the Sun's gravity is stronger than that of Venus and it may divert the spacecraft so that it crosses the orbit of the planet Mercury and it misses it. The third correction comes four days after the transit near Venus and this is to avoid unknown effects of the transit itself. The last correction was made four weeks before the transit near the planet Hema. After the encounter, the spacecraft enters an orbit around the sun that brings it together once again with the planet Mercury on September 22, 1974, and it photographs it once more. All this is done on the assumption that the spacecraft's systems are not damaged until then.
The photography technique
The spacecraft photos before being processed on the computer are blurry and uninformative. The brightening of the images is done with a special technique in which they are transmitted in a "broken" form that presents a very rich specification. Shortly after the exposure of the photograph, it is divided into 700 horizontal lines, each of which has 832 samples. The 592,400 units of information receive numerical values for the purpose of transferring them to national reception stations. At the control center, the photographs are reassembled and enlarged as soon as they are received from the spacecraft. When receiving the photographs, a selective review of the previous photographs and parts of the photographs is done to obtain greater detail from exhibits with special characteristics. For various reasons the "live" photographs are dark, distorted and the details of the ground are not clear. Noise during transmissions sometimes caused complete lines to be omitted and it was necessary to extrapolate from nearby lines to get a complete picture. As each photograph is finished developing, it is highlighted to remove the gray tones that appear in most photographs to more precisely define the black and white contrasts.
flight characterization
The course of the flight can be divided into three stages:
A. The flight phase to Venus begins on November 3, 1973 and ends on February 5, 1974.
B. The transit near Venus and its measurement on February 5, 1974.
third. Flight towards the planet Hema and its measurement. Begins on February 5, 1974 and ends on March 29, 1974
Dispatch and security of information
The launch was done on time with the Atlas Centaur launcher. Seven days after the launch, the spacecraft's computer was programmed for the encounter with Venus to ensure the receipt of the most information in the event that contact with the spacecraft is lost for any reason. A similar procedure is carried out two days after the transit by Venus in preparation for the encounter with the planet Mercury. The measurement of Venus begins three days before the transit and its photographing continues for 17 days afterwards. The duration of the shooting of the planet Hama is planned for 19 days.
Phase I - from November 3, 1973 to February 5, 1974
November 3 - Shortly after the launch it became clear that three small heat protectors of the cameras did not come into operation and the temperature dropped to 30 degrees below zero. There was a fear that the cameras would go out of action. The inspection of the photographs that was done later showed that no defect was found in their quality. Three hours after the launch the spacecraft systems were checked and they started their work. The Earth was photographed five times and the Moon was photographed six times. Earth's cloud cover looks similar to that of Venus and the moon's rough, shapeless surface resembles that of the planet Mercury (until this launch some photographs of the planet had been obtained from Earth, albeit of poor quality). The researchers wanted to check the exposure time needed for the cameras in space conditions and tap from that for the future photographs of Venus and the planet Hema.
November 13 - first correction of the flight path. The flight speed was increased to a greater extent than planned to 7.8 meters per second instead of 4.5 meters per second.
December 11 - Mariner 10 discovered strong radiation from a brown nebula 9 times higher than that of the Sun. They hoped that the emission of hydrogen from the nebula would help to better understand the formation of the universe.
January 10, 1974 - the main power system malfunctioned and the secondary power system came into operation instead.
January 18 - second correction in the flight path.
January 19 - Kohotek comet photo. This shoot is more than just checking the cameras. The field of view of the cameras is small and they can photograph bright objects, while for photographing comets it is necessary to use cameras with a wide angle of reception and they must be powerful because the intensity of the brightness of the comets is low. The comet was photographed to check if it has the presence of noble gases such as helium and argon.
January 30 - A malfunction in the gyroscope caused the loss of 20% of the spacecraft's fuel supply. The nitrogen gas that regulates the gyro stabilizers. There was a fear that the information that the spacecraft collected and will collect would be lost and that it would miss the planet Hema.
A small but not serious malfunction that accompanied the spacecraft throughout its flight was the heating of the batteries. Other faults were in the particle detection facility and the automatic activation mechanism of the information system.
In the particle detection facility, one of the lids is half-opened, allowing charged particles moving in space to not be absorbed by the measuring devices. The caps were designed so that they would only be opened during the flight itself and not during the launch, and this to prevent contamination of the device. Losing half of the experiment is not critical since the explosion of the particles emitted from the sun is equal in all directions. The second sensor can do all the work by itself.
The malfunction related to the information system occurred while the spacecraft was preparing for ultraviolet observation maneuvers. At a distance of 21.6 million km from the Earth, the spacecraft mysteriously disconnected itself from the main power system - the solar panels, and activated the secondary system - a battery. The malfunctions forced the researchers to reprogram the spacecraft's computer in a different and shorter series of operations than the original for the transit near Venus. All this to maintain strength for the measurement of Hema's planet.
Phase B – February 5, 1974
A transit near Venus will be described in a separate article
Phase III - from February 5 to March 29, 1974
March 16 - correction of the flight path.
The control of the spacecraft in its axis of rotation has weakened due to particles that apparently hit the spacecraft and peeled off flakes of paint from the solar shelves and the high praise antenna and they inject light into the sensing device of the planet Canopus. The flight engineers were able to control the spacecraft by deploying the solar panels in different directions. The pressure of the solar radiation on the shelves is enough to allow control of the spacecraft. It was not known how this problem would affect the transit near Mercury. Since the mission was fully successful, it was decided to make another transit flight.
The findings of the transit flight
The photographing of the planet Hema began on March 23 from a distance of 6 million km. The duration of the photographs was planned for 19 days. Due to a short in the electrical system, it was decided to temporarily stop the operation of the spacecraft's systems. The pass by the star was made as planned on March 29 and at a distance of 750 km from it. All photographs were of high quality. The operation of the spacecraft was stopped on April 3 due to overheating in some of the spacecraft's systems. Mariner 10's engineers wanted to keep several sensors in place for the second flyby in September. Due to the premature shutdown of the spacecraft's cameras and systems, only 1,000 photographs were taken.
The most surprising findings were the reality of a magnetic field and an atmosphere. The strength of the magnetic field is 1% of that of the Earth. The Earth's magnetic field is explained by the existence of liquid iron in the core of the sphere. The speed of the rotation of the planet Hema around itself is too slow to give such dynamic effects, so two explanations for the phenomenon have been put forward:
A. The magnetic field is created by a strong and constant bombardment of charged particles into the atmosphere from the sun.
b The magnetic field is a remnant of a stronger field when the axial velocity of the planet Hema was greater.
The planet Hema has its own atmosphere, although its density is less than 0.1% of the density of the Earth's atmosphere. The atmosphere is very thin and contains argon and neon with some hydrogen and helium on the dark side. The source of the helium is probably from the decay of sediments rich in radioactive materials in the star's crust. This discovery was a complete surprise due to the close proximity of the planet Hema to the Sun and its size, which on its surface do not allow an atmospheric presence.
Two hypotheses were put forward to explain the phenomenon:
A. A certain amount of gases from the sun's particles has been trapped in the planet.
B. A certain amount of gases was ejected from the star's interior due to the slow decay of radioactive elements.
Like the Moon, Mercury is full of craters, but these are thinner and more delicate and their rims are wider. The diameter of the craters is 160 km. The diameter of the smallest observed crater is 8 km. It is evident that some kind of erosive process took place here. Most of the craters were created by meteorites and a minority due to volcanic eruptions. They formed immediately after the formation of the planet 4.5 billion years ago. In the 40 km diameter crater there is evidence of a meteorite impact. Around the crater is seen material in the shape of horns that was thrown out of it by a collision. The rays reach up to a distance of 96 km from the crater.
In one of the photographs you see a crater similar to the craters of the moon and next to it are signs indicating an earthquake or volcanic eruptions. In the photographs we see a volcano bigger than any terrestrial volcano. One does not notice in the photographs mountains similar to those found on the moon. On the other hand, signs of slopes or rocks hundreds of kilometers long are visible. Particularly surprising is the presence of bumps, low hills and streams. Some of the streams are straight and others are meandering as if formed by water flow. One of the photographs shows a crater whose bottom was covered by a flow of material, probably lava. In other photographs you see a deep canyon. The planet Hema has large cracks created by the sun's heat, and the planes covering it are smaller than thought.
The color of the planet Hema is yellow and north of the equator there is a bright spot. There are considerable differences between the Northern Hemisphere and the Southern Hemisphere. The temperature on the light side is 500 degrees and on the dark side 200 degrees below zero.
The planet appears to have formed differently from Earth. Its specific gravity is greater than that of the Earth. 66% of the content of Mercury is iron. The iron was created first and was later covered with another material until the final product was obtained - the planet.
Mariner 10 discovered strong and mysterious radiation, near the star, from a body orbiting it. It has been hypothesized that the planet Hema has its own moon. Despite the problems created in the electrical system, the spacecraft's cameras were directed towards the source of the radiation, but nothing was found. At the same time, ultraviolet radiation from a distant star was also discovered. On March 29, the ultraviolet cameras were aimed at this body. Signs of a body with a diameter of 25.6 km were picked up. On April 11, an attempt was made to find another moon. Later it turned out that it is not a moon at all. Its relative speed to the planet Mercury (this movement was caused by the high speed of Mariner 10) misled the astronomers.
Phase 29 - from March 22 to September XNUMX, a flight in a solar orbit and a second transit flight
On May 9 and 10, route corrections were made. The repairs are designed to allow a transit flight from a distance of 47,300 km. The transit flight was designed to allow full coverage of the southern hemisphere, in particular of the illuminated side, which could not be done on the first transit flight. Initial photography of the South Pole and more advanced analyzes of high and sloping areas. The resolution of the cameras is 1 km per pixel. This flight path allows for another transit flight in the fifth stage, on March 16, 1975.
The possibility of performing another orbit correction in June or July was raised to reduce the distance of the passage to the dark side and to learn more about the magnetic field. During the flight some problems arose which were overcome. The guidance system instead of operating according to Canopus operated according to another planet. More fuel had to be used to restore the guidance system to its normal function. The large and unplanned use of fuel for the transit flight raised hopes that the amount of fuel would still be sufficient to carry out another transit flight in March 1975.
On the first transit flight, Mariner 10 photographed the planet Hema, moved to the side not visible from Earth and photographed it. The photos were stored in memory and later broadcast to Israel at the same time as additional photos were taken. This time the transmission of the photographs was done by a different method. A routine communication check revealed a fault in one of the recording tapes. As a result, the recording tape worked strangely. This malfunction did not raise any concerns regarding the transit flight on September 21. The only change is the direct transmission of the photographs as opposed to the method of transmission on the first transit flight. The transmission rate is one photo per 42 seconds. Paradoxically, the number of photographs is smaller. When the recording tape. Functioning properly, the photo frequency is greater than one photo per 42 seconds.
September 18 - The spacecraft's cameras were tested and found to be working.
September 20 - Mariner 10 began transmitting photographs from the planet Hama.
September 22 - two series of photographs were taken with a difference of a few hours between one series of photographs and the other. A total of 500 photographs were broadcast, the photographs were broadcast with a difference of 42 seconds between each photograph. A total of 38% of the face of the star was covered in the two transit flights. Places photographed on the first transit flight were photographed this time from a better angle. In this flyby, only two instruments were activated to measure the planet Hema, the television camera and the ultraviolet spectrometer. The instruments for investigating particles and magnetic fields continued to collect interstellar information. Mariner 10 passed within 50,000 km of the bright side of the southern hemisphere. A total of 1,800 photographs were broadcast.
Findings of the second transit flight
The photographs resemble the surface of the moon. "Crooked" ridges can be noticed. The center of the planet Hema collapsed inward into the star itself when it was young. At that time, high rocks were formed from the surface and thousands of kilometers long. The giant craters were left from the impact of large meteorites before and after the final stages of the "maturation" of the planet Hema. 3.5 billion years ago, a meteorite hit the planet Hema which created a crater with a diameter of 1,300 km, this is the Caloris basin.
Phase 22 - from September 1974, 16 to March 1975, XNUMX, a flight in a solar orbit and a third transit flight
March 15 - Mariner 10's instability did not allow her to lock onto Canopus. Additional difficulties in directing the spacecraft arose due to the simultaneous use of Space Network Deep, to track the German spacecraft Helios and to track the two spacecraft Pioneer 10 and Pioneer 11 on their way to Jupiter. It was feared that Mariner 10 would crash into the surface of Mercury. The Helios tracking team agreed to give priority to Mariner 10. Most of the spacecraft's instruments were not working and the amount of fuel in its tanks was minimal.
March 16 - today the third transit flight was performed at a distance of 288 km from the ground and at a flight speed of 46,000 km/h. The minimum distance between the spacecraft and the ground was on the dark side of Mercury. No filming was done at that time. The transit flight lasted four hours. The spacecraft passed over the North Pole, transmitted 300 photographs and measured the magnetic field of Mercury. The photos are sharp and of excellent quality.
Before the launch of Mariner 10, it was hypothesized that there was a correlation between the axial velocity of the planet Hema and its magnetic field. A high axial speed gives a strong magnetic field and vice versa. It was estimated that the planet Mercury has a very weak magnetic field, if any. The first transit flight of the spacecraft showed that this is not the case. Mercury has a relatively strong magnetic field. The role of the spacecraft on the third flyby was to measure this difference. Therefore she aimed at the dark side of the planet Mercury. An area where the planet Hema is protected from solar disturbances. The spacecraft's instruments measured the speed of the solar wind.
The North Pole was re-photographed since photographs taken earlier were oblique. The last picture was directed towards the Kaloris Basin. This is the largest basin imaged in the three flybys. So that the photographs would not be lost, they were broadcast to Israel every 42 seconds.
Findings of the third transit flight
The planet Mercury has an internal and natural magnetic field similar to that of the Earth.
Summary of findings
Nomenclature (names of places)
Two important ridges received the name Dursa (in Latin avenues). They are named after the astronomers Schiapirelli and Antoniaidi. Valleys are named after the Goldstone and Wallis radio telescopes in the Mojave Desert and the Arecibo Wallis in Puerto Rico.
As Mariner is far from the planet Mercury, the first feature that appeared in the photographs was a particularly bright area, although its shape is not defined. The space at the center of this area is named after Professor Gerard Kuyper.
Another crater with a diameter of 1.5 km was named Hun-Kal, the number 20 in the Mayan language. The crater marks exactly the 20th latitude on the new map of Mercury and is intended to serve as a reference point similar to Greenwich. Among the most interesting formations, a large number of giant curved cliffs, some of which extend for hundreds of kilometers as they "pass" over the sides of craters and their bottoms rise to a height of 3 kilometers or more. These received the name Rupes (cliffs in Latin). And their names are derived from the names of the ships of famous explorers such as Captain Cook's Endeavor and Discovery and Columbus's Santa Maria.
Geology
The planet Hema probably has a developed crust tens of kilometers thick. The cliffs are pushback replicas. It was assumed that they were formed as a result of pressing processes in the surface of the planet. These cliffs are probably different from the cliffs on the surface of Mars and the Moon in that they were formed following the collapse of two plates from the face of the planet Mercury that were moving towards each other while its core was shrinking. Unlike them, the replicas on the face of Mars and the Moon were created due to a stretching process when parts of the interior of the sphere separated from each other.
Since the specific mass of the planet Mercury is close to that of the Earth, they concluded that the iron core occupies more than 50% of the volume. It is possible that the face compression originates from a strong gravitational pressure on the crust. This view of the crust implies that Mercury is most similar to the Moon on the outside, but more like the Earth on the inside. This comparison is supported by evidence that the face of the planet Mercury is layered everywhere with a layer of insulating dust - a porous material that is compacted like the soil of the moon.
The largest formations of the planet Hema are the basins, at least 18 of which are larger than 190 km in diameter. Like the moon's basins, many of them are filled with lava flows. The most prominent of them is the Kaloris Basin. Its bottom is cracked and divided by cliffs. The name of the basin derived from the Latin word "chlor" (heat) comes from the fact that the basin is close to one of the two hot poles of the planet Mercury.
Since the planet Mercury moves in a relatively elliptical orbit with an unusual combination of the speeds of its rotation around itself and the speed of its movement around the Sun, the relative motion of the Sun in the star's sky is strange. At the perihelion the sun stops, goes back upwards, more than one degree and sets off again. This "dance" lasted a week. At the same time, the area under the midday sun "bakes" for a longer time. Therefore it is called "the warm pole". Two places, one of them near Kaloris share these temperatures in their perihelions.
