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General: VOYAGER 1 VOYAGER 2 ENCOUNTER WITH SATURN (ISRAEL) CONFIRMS RELATIVITY THEORY
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Science: Encounter with Saturn confirms relativity theory
By Marcus Chown
WHEN THE spaceprobe Voyager 1 flew past Saturn in 1980, it not only
observed the planet and its moons but also provided scientists with data
that confirms Einstein’s general theory of relativity. In 1915, Einstein
predicted that light loses energy climbing out of the ‘gravitational well’
of a massive body, such as a planet. The effect is known as the gravitational
red shift, because as light loses energy its frequency is reduced, making
it appear redder.
Voyager 1 was able to test the red shift effect when it flew past Saturn,
using radio signals sent back to Earth by a transmitter locked at a very
precise frequency. The spaceprobe was equipped with an ultrastable crystal
oscillator, known as the USO. This acted as a very precise standard, varying
its frequency by less than 5 parts in 1012. Electronic equipment on board
multiplied the frequency of the oscillator by 120 times, to provide the
frequency of the spaceprobe’s radio transmitter – 2.3 gigahertz. These signals
were then picked up by the radio telescopes of NASA’s Deep Space Network,
which was used to track and control both Voyager spaceprobes.
Now, long after the event, Timothy Krisher and his colleagues at the
Jet Propulsion Laboratory in Pasadena, California, have examined the record
of the signal from Voyager 1. The spaceprobe flew within 180 000 kilometres
of Saturn on 12 November 1980. They find that as the spaceprobe moved in
and out of the gravitational field of Saturn, its transmitter’s frequency
dipped. The dip was no more than a few hertz, but it was within 1 per cent
of the prediction of general relativity for a frequency of 2.3 gigahertz.
Fluctuations in the frequency of the transmitter – though very small – nevertheless
prevented the theory from being tested even more severely (Physical Review
Letters, vol 64, p 1322).
Krisher and his colleagues have yet to determine whether data from the
transmitter on board Voyager 2 can help them to test general relativity
further. It was badly affected by intense radiation as it passed by Jupiter
on its way to Saturn and so its data may not be as reliable as the data
from its predecessor. The current results may, however, rule out some alternatives
to Einstein’s theory.
https://www.newscientist.com/article/mg12517102-600-science-encounter-with-saturn-confirms-relativity-theory/ |
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Voyager program
 A poster of the planets and moons visited during the Voyager program.
The Voyager program is an American scientific program that employs two interstellar probes, Voyager 1 and Voyager 2. They were launched in 1977 to take advantage of a favorable planetary alignment to explore the two gas giants Jupiter and Saturn and potentially also the ice giants, Uranus and Neptune - to fly near them while collecting data for transmission back to Earth. After Voyager 1 successfully completed its flyby of Saturn and its moon Titan, it was decided to send Voyager 2 on flybys of Uranus and Neptune.[1]
After the planetary flybys were complete, decisions were made to keep the probes in operation to explore interstellar space and the outer regions of the solar system. On 25 August 2012, data from Voyager 1 indicated that it had entered interstellar space.[2] On 5 November 2019, data from Voyager 2 indicated that it also had entered interstellar space.[3] On 4 November 2019, scientists reported that on 5 November 2018, the Voyager 2 probe had officially reached the interstellar medium (ISM), a region of outer space beyond the influence of the solar wind, as did Voyager 1 in 2012.[4][5][6] In August 2018, NASA confirmed, based on results by the New Horizons spacecraft, the existence of a "hydrogen wall" at the outer edges of the Solar System that was first detected in 1992 by the two Voyager spacecraft.[7][8][9]
As of 2024, the Voyagers are still in operation beyond the outer boundary of the heliosphere in interstellar space. Voyager 1 is moving with a velocity of 61,198 kilometers per hour (38,027 mph), or 17 km/s, (10.5 miles/second) relative to the Sun, and is 24,475,900,000 kilometers (1.52086×1010 mi) from the Sun[10] reaching a distance of 162 AU (24.2 billion km; 15.1 billion mi) from Earth as of May 25, 2024.[11] As of 2024, Voyager 2 is moving with a velocity of 55,347 kilometers per hour (34,391 mph), or 15 km/s, relative to the Sun, and is 20,439,100,000 kilometers (1.27003×1010 mi) from the Sun[12] reaching a distance of 136.627 AU (20.4 billion km; 12.7 billion mi) from Earth as of May 25, 2024.[11]
The two Voyagers are the only human-made objects to date that have passed into interstellar space — a record they will hold until at least the 2040s — and Voyager 1 is the farthest human-made object from Earth.[13]
https://en.wikipedia.org/wiki/Voyager_program
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Voyager 1: 'The Spacecraft That Could' Hits New Milestone
Aug. 15, 2006
Voyager 1, already the most distant human-made object in the cosmos, reaches 100 astronomical units from the sun on Tuesday, August 15 at 5:13 p.m. Eastern time (2:13 p.m. Pacific time).
Voyager 1, already the most distant human-made object in the cosmos, reaches 100 astronomical units from the sun on Tuesday, August 15 at 5:13 p.m. Eastern time (2:13 p.m. Pacific time). That means the spacecraft, which launched nearly three decades ago, will be 100 times more distant from the sun than Earth is.
In more common terms, Voyager 1 will be about 15 billion kilometers (9.3 billion miles) from the sun. Dr. Ed Stone, Voyager project scientist and the former director of NASA's Jet Propulsion Laboratory in Pasadena, Calif., says the Voyager team always predicted that the spacecraft would have enough power to last this long.
"But what you can't predict is that the spacecraft isn’t going to wear out or break. Voyager 1 and 2 run 24 hours a day, seven days a week, but they were built to last," Stone said. The spacecraft have really been put to the test during their nearly 30 years of space travel, flying by the outer planets, and enduring such challenges as the harsh radiation environment around Jupiter.
The spacecraft are traveling at a distance where the sun is but a bright point of light and solar energy is not an option for electrical power. The Voyagers owe their longevity to their nuclear power sources, called radioisotope thermoelectric generators, provided by the Department of Energy.
Voyager 1 is now at the outer edge of our solar system, in an area called the heliosheath, the zone where the sun's influence wanes. This region is the outer layer of the 'bubble' surrounding the sun, and no one knows how big this bubble actually is. Voyager 1 is literally venturing into the great unknown and is approaching interstellar space. Traveling at a speed of about one million miles per day, Voyager 1 could cross into interstellar space within the next 10 years.
"Interstellar space is filled with material ejected by explosions of nearby stars," Stone said. "Voyager 1 will be the first human-made object to cross into it."
Voyager Project Manager Ed Massey of JPL says the survival of the two spacecraft is a credit to the robust design of the spacecraft, and to the flight team, which is now down to only 10 people. "But it’s these 10 people who are keeping these spacecraft alive. They’re very dedicated. This is sort of a testament to them, that we could get all this done."
Between them, the two Voyagers have explored Jupiter, Uranus, Saturn and Neptune, along with dozens of their moons. In addition, they have been studying the solar wind, the stream of charged particles spewing from the sun at nearly a million miles per hour.
https://www.jpl.nasa.gov/news/voyager-1-the-spacecraft-that-could-hits-new-milestone/
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