Low energy charged particle instrument LECP 3. Cosmic ray instrument CRS 4. Plasma instrument PLS 5. Plasma wave instrument PWS. One other instrument is collecting data but does not have official science investigation associated with it:. Both spacecraft are now exploring the Heliosheath. The heliosphere is a bubble around the sun created by the outward flow of the solar wind from the sun and the opposing inward flow of the interstellar wind. That heliosphere is the region influenced by the dynamic properties of the sun that are carried in the solar wind--such as magnetic fields, energetic particles and solar wind plasma.
The heliopause marks the end of the heliosphere and the beginning of interstellar space. Excerpts from that passage follow: "One was from a few scientists who worried that we hadn't corrected for the speed of Earth in space in launching the message.
He wrote with great anxiety that he felt it was very hazardous to reveal our existence and location to the galaxy. For all we know, any creatures out there were malevolent or hungry, and once they knew of us, the might come to attack or eat us Many other less knowledgeable people had the same concerns. There is a sphere of radio transmission about thirty light years thick expanding outward at the speed of light, announcing to every star it envelops that the earth is full of people.
Our television programs flood space with signals detectable at enormous distances by instruments not much greater than our own. It is a sobering thought that the first news of us may be the outcome of the Super Bowl. Whether or not Sir Martin Ryle is justified in his anxieties about revealing the location of our civilization is of course a debatable subject.
Even so, it is too late to worry about it, so we might as well try to be friendly". There are so many. Voyager is probably the most scientifically productive mission ever.
It was only the second mission to visit Jupiter and Saturn and the only one to visit Uranus and Neptune. Voyager 1 and 2 obtained the first detailed profiles of the atmospheres of Saturn, Uranus and Neptune and improved our understanding of the characteristics of the atmosphere of Jupiter. The Voyager spacecraft revealed the enormous amount of detail in the rings of Saturn, discovered the rings of Jupiter and provided the first detailed images of the rings of Uranus and Neptune.
Voyager imaged Earth's moon and discovered twenty-three new moons at the outer planets. Voyager made significant improvements in the measurements of the magnetospheres at Jupiter and Saturn and provided the first measurements of the magnetospheres at Uranus and Neptune. The significance of the Voyager is the vast amount of new knowledge about our outer solar system it provided and the interest in further exploration it generated.
That interest has resulted in the Galileo mission to Jupiter and the Cassini mission to Saturn as well as the discovery of three new satellites at Saturn using Earth-based instruments. Discovery of active volcanism on Io, a satellite of Jupiter, was probably the greatest surprise. It was the first time active volcanoes had been seen on another body in the solar system.
It appears that activity on Io affects the entire Jovian system. The Voyager spacecraft weight, including hydrazine, at launch was kg or about pounds. It was almost the weight and size of a sub-compact car. The current approximate weight of Voyager 1 is kg and Voyager 2 is kg.
The difference is in the amount of hydrazine remaining. Hydrazine is being used to control the spacecrafts' attitude. The spacecraft, without the various booms could fit inside a cube that is about 4 meters on each side. The approximate measurements of the different structures follow - please refer to the spacecraft picture at the above web site. The high gain antenna is 3. The Radioisotope Thermoelectric Generator boom is 3.
The Bus Housing Electronics is about 1. The spacecraft height - from the top of the reflector structure in the middle of the high gain antenna to the bottom of the triangular feet below the bus housing electronics - is about 3. There are messages on the Voyagers in the form of a phonograph record and drawings on the cover that protects the record.
There are three different computer types on the Voyager spacecraft and there are two of each kind. Total number of words among the six computers is about 32K. Computer Command System CCS - bit word, interrupt type processors 2 with words each of plated wire, non-volatile memory.
According to my calculations, that's a total of about 68KB, or small potatoes compared to today's microprocessors. We probably could perform all functions with one of today's boards and still have room for solid state data storage and much more fault detection software. We would still need a second unit for redundancy. Today's microprocessors are also much faster than the chips used on Voyager and a comparative system would use less electrical power.
On the other hand, software might be more complicated as opposed to that used in an interrupt type system, but it would be much more capable and more flexible.
Let's look closer at the CCS. The CCS has two main functions: to carry out instructions from the ground to operate the spacecraft, and to be alert for a problem or malfunction and respond to it. Two identical word memories contain both fixed routines about words and a variable section about words for changing science sequences.
The CCS issues commands to the AACS for movement of the scan platform or spacecraft maneuvers; to the FDS for changes in instrument configurations or telemetry rates and to numerous other subsystems within the spacecraft for specific actions. The FDS also keeps the spacecraft "time" and provides frequency references to the instruments and other spacecraft subsystems. The Voyager spacecraft computers are interrupt driven computer, similar to processors used in general purpose computers with a few special instructions for increased efficiency.
The Voyager system is one of the most sophisticated ever designed for a deep-space probe. There are seven top-level fault protection routines, each capable of covering a multitude of possible failures. The spacecraft can place itself in a safe state in a matter of only seconds or minutes, an ability that is critical for its survival when round-trip communication times for Earth stretch to several hours as the spacecraft journeys to the remote outer solar system.
Both Voyagers were specifically designed and protected to withstand the large radiation dosage during the Jupiter swing-by. This was accomplished by selecting radiation-hardened parts and by shielding very sensitive parts.
An unprotected human passenger riding aboard Voyager 1 during its Jupiter encounter would have received a radiation dose equal to one thousand times the lethal level. The Voyager spacecraft can point its scientific instruments on the scan platform to an accuracy of better than one-tenth of a degree. This is comparable to bowling strike-after-strike ad infinitum, assuming that you must hit within one inch of the strike pocket every time.
Such precision is necessary to properly center the narrow-angle picture whose square field-of-view would be equivalent to the width of a bowling pin.
To avoid smearing in Voyager's television pictures, spacecraft angular rates must be extremely small to hold the cameras as steady as possible during the exposure time.
Each spacecraft is so steady that angular rates are typically 15 times slower than the motion of a clock's hour hand. But even this was not steady enough at Neptune, where light levels are times fainter than those on Earth. Spacecraft engineers devised ways to make Voyager 30 times steadier than the hour hand on a clock.
The electronics and heaters aboard each nearly one-ton Voyager spacecraft can operate on only watts of power, or roughly one-fourth that used by an average residential home in the western United States.
A set of small thrusters provides Voyager with the capability for attitude control and trajectory correction. Each of these tiny assemblies has a thrust of only three ounces. The Voyager scan platform can be moved about two axes of rotation. A thumb-sized motor in the gear train drive assembly which turns revolutions for each single revolution of the scan platform will have rotated five million revolutions from launch through the Neptune encounter.
This is equivalent to the number of automobile crankshaft revolutions during a trip of km mi , about the distance from Boston,MA to Dallas,TX. The Voyager gyroscopes can detect spacecraft angular motion as little as one ten-thousandth of a degree.
The Sun's apparent motion in our sky moves over 40 times that amount in just one second. A twin probe, Voyager 2, saw the same thing in Last year, Voyager 1 witnessed another exit sign. But not until Voyager feels the magnetic field lines flip will astronomers know that the craft has escaped the heliosphere.
If Voyager 1 does manage to leave the heliosphere before it runs out of power around , the spacecraft will probe the Local Cloud, a wisp of interstellar flotsam absorbing traces of light from nearby stars.
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