The Pioneer anomaly or Pioneer effect is the observed deviation from predicted trajectories A trajectory is the path a moving object follows through space as a function of time. The object might be a projectile or a satellite, for example. It thus includes the meaning of orbit—the path of a planet, an asteroid or a comet as it travels around a central mass. A trajectory can be described mathematically either by the geometry of the path, and velocities In physics, velocity is the rate of change of displacement . It is a vector physical quantity; both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is speed, a quantity that is measured in meters per second (m/s or ms−1) when using the SI (metric) system of various unmanned spacecraft A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some visiting the outer solar system The Solar System[a] consists of the Sun and those celestial objects bound to it by gravity, all of which were formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. Of the many objects that orbit the Sun, most of the mass is contained within eight relatively solitary planets[e] whose orbits are almost circular and, most notably Pioneer 10 Pioneer 10 was the first spacecraft to travel through the asteroid belt, on July 15, 1972, and to make direct observations of Jupiter, which it passed by on December 3, 1973. It was launched from Cape Canaveral Air Force Station's Launch Complex 36A on March 2, 1972 at 01:49:00 UTC. Pioneer 10 is heading in the direction of Aldebaran, located in and Pioneer 11 Pioneer 11 was the second mission of the Pioneer program (after its sister probe Pioneer 10) to investigate Jupiter and the outer solar system, and the first to explore Saturn and its main rings. Pioneer 11 used Jupiter's mass in a gravity assist to alter its trajectory toward Saturn. The unmanned spacecraft was developed by NASA Ames Research.
Both Pioneer spacecraft are escaping from the solar system, and are slowing down under the influence of the Sun's gravity. Upon very close examination, however, they are slowing down slightly more than expected. The effect can be modeled as a slight additional acceleration towards the Sun.
The anomaly has no universally accepted explanation. The explanation may be mundane, such as measurement error, thrust Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a proportional but opposite force on that system from gas leakage or uneven radiation In physics, radiation describes a process in which energetic particles or waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing. The word radiation is commonly used in reference to ionizing radiation only , but it may also refer to non-ionizing radiation (e.g., radio waves or visible light) of heat In physics and thermodynamics, heat is the process of energy transfer from one body or system to another due to thermal contact, which in turn is defined as an energy transfer to a body in any other way than due to work performed on the body. However, it is also possible that current physical theory does not correctly explain the behaviour of the craft relative to the sun.
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Initial indications
Pioneer 10 and 11 were sent on missions to Jupiter and Jupiter/Saturn respectively. Relatively simple, the spacecraft were spin-stabilised Spin-stabilisation is the method of stabilizing a satellite by means of spin. For most satellite applications this approach has been superseded by three-axis stabilisation. It is also used in non-satellite applications such as rifle and artillery in order to keep their main antennas pointed towards Earth using gyroscopic forces. Although the spacecraft included thrusters, these were left unused after their primary encounters, leaving them on a long "cruise" phase through the outer solar system. During this period, both spacecraft were repeatedly contacted to obtain various measurements on their physical environment, providing valuable information long after their initial missions were complete.
Since the spacecraft were flying without additional stabilization thrusts during their "cruise", it is possible to characterize the density of the solar medium by its effect on the spacecraft's motion. In the outer solar system this effect would be easily calculable, based on ground-based measurements of the deep space environment. However, when these effects were taken into account, along with all other known effects, the calculated position of the Pioneers did not agree with measurements based on timing the return of the radio signals being sent back from the spacecraft. These consistently showed that both spacecraft were closer to the inner solar system than they should be, by thousands of kilometres - small compared to their distance from the Sun, but still statistically significant. This apparent discrepancy grew over time as the measurements were repeated, suggesting that whatever was causing the anomaly was still acting on the spacecraft.
As the anomaly was growing, it appeared that the spacecraft were moving more slowly than expected. Direct measurements of the spacecraft's speed using the Doppler effect The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. The received frequency is higher (compared to demonstrated the same thing: the Pioneers were slowing down more than expected.
When all known forces acting on the spacecraft are taken into consideration, a very small but unexplained force remains. It appears to cause a constant sunward The Sun is the star at the center of the Solar System. It has a diameter of about 1,392,000 kilometers , about 109 times that of Earth, and its mass (about 2 × 1030 kilograms, 330,000 times that of Earth) accounts for about 99.86% of the total mass of the Solar System. About three quarters of the Sun's mass consists of hydrogen, while the rest is acceleration of (8.74 ± 1.33) × 10−10 m/s2 for both spacecraft. If the positions of the spacecraft are predicted one year in advance based on measured velocity and known forces (mostly gravity), they are actually found to be some 400 km closer to the sun at the end of the year. The magnitude of the Pioneer effect is numerically quite close to the product of the speed of light The speed of light, usually denoted by c, is a physical constant important in many areas of physics. Light and all other electromagnetic radiation always travel at this speed in empty space , regardless of the motion of the source or the inertial frame of the observer. Its value is exactly 299,792,458 metres per second (approximately 186,282 miles and the Hubble constant Hubble's law describes the observation in physical cosmology that the velocity at which various galaxies are receding from the Earth is proportional to their distance from us. The law was first derived from the General Relativity equations by Georges Lemaître in 1927. Edwin Hubble derived it empirically in 1929 after nearly a decade of, but the significance of this, if any, is unknown. Gravitationally bound objects such as the solar system, or even the galaxy, do not partake of the expansion of the universe It is an intrinsic expansion—that is, it is defined by the relative separation of parts of the universe and not by motion "outward" into preexisting space. — this is known both from theory[1] and by direct measurement.[2]
Other indications
The Pioneers were uniquely suited to discover the effect because they have been flying for long periods of time without additional course corrections. Most deep-space probes launched after the Pioneers either stopped at one of the planets, or alternately used thrusting throughout their mission.
The Voyagers The Voyager program is a series of U.S. unmanned space missions that consists of a pair of unmanned scientific probes, Voyager 1 and Voyager 2. They were launched in 1977 to take advantage of a favorable planetary alignment of the late 1970s. Although they were officially designated to study just Jupiter and Saturn, the two probes were able to flew a mission profile similar to the Pioneers, but were not spin stabilized. Instead, they required frequent firings of their thrusters A monopropellant rocket is a rocket that uses a single chemical as its power source and propellant. Usually the propellant is admitted to a decomposition chamber that contains a silver or platinum sponge catalyst. The most commonly used monopropellant is hydrazine (N2H4), a chemical which is characterized as "strongly reducing" (sic) for attitude control Attitude dynamics is the modeling of the changing position and orientation of a vehicle, due to external forces acting on the body. Attitude control is the purposeful manipulation of controllable external forces to establish a desired attitude, whereas attitude determination is the utilization of vehicle sensors to ascertain the current vehicle to stay aligned with Earth. Spacecraft like the Voyagers acquire small and unpredictable changes in speed as a side effect of the frequent attitude control firings. This 'noise' makes it impractical to measure small accelerations such as the Pioneer effect.
Newer spacecraft have used spin stabilization for some or all of their mission, including both the Galileo Galileo was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. Named after the astronomer and Renaissance pioneer Galileo Galilei, it was launched on October 18, 1989 by the Space Shuttle Atlantis on the STS-34 mission. It arrived at Jupiter on December 7, 1995, a little more than six years later, via gravitational and Ulysses Ulysses was a robotic space probe designed to study the Sun. The spacecraft, named for the Latin translation of "Odysseus" after Dante's Inferno, was launched October 6, 1990 from the Space Shuttle Discovery as a joint venture of NASA and the European Space Agency. It was originally scheduled for launch in 1986 aboard the Space Shuttle. These spacecraft indicate a similar effect, although for various reasons (such as their relative proximity to the Sun) firm conclusions cannot be drawn from these sources.
The Cassini mission has reaction wheels A reaction wheel is a type of flywheel used primarily by spacecraft to change their angular momentum without using fuel for rockets or other reaction devices as well as thrusters for attitude control, and during cruise could rely for long periods on the reaction wheels alone, thus enabling precision measurements. However, it also had radioisotope thermoelectric generators A radioisotope thermoelectric generator is an electrical generator which obtains its power from radioactive decay. In such a device, the heat released by the decay of a suitable radioactive material is converted into electricity by the Seebeck effect using an array of thermocouples (RTGs) mounted close to the spacecraft body, radiating kilowatts of heat in hard-to-predict directions. The measured value of unmodelled acceleration for Cassini is (26.7 ± 1.1) × 10−10 m/s2, roughly three times as large as the Pioneer acceleration. Unfortunately, the measured value is the sum of the uncertain thermal effects and the possible anomaly. Therefore the Cassini measurements neither conclusively confirm nor refute the existence of the anomaly.[3]
Proposed explanations
There have been a number of proposed explanations for acceleration towards the sun have been pursued. These are defined as the following: observational errors, an unaccounted for real deceleration, and explanations that would essentially be New Physics.
Observational errors
The possibility of observational errors, which include measurement and computational errors, has been advanced as the reason for Pioneer anomaly interpretation of data. This would be the cause of approximation and statistical errors.
Further analysis has determined that significant errors are not likely because seven independent analyses have shown the effect as of March 2010.[4]
Recording errors
The effect is so small that it could be a statistical anomaly caused by differences in the way data were collected over the lifetime of the probes. Numerous changes were made over this period, including changes in the receiving instruments, reception sites, data recording systems and recording formats.
The Planetary Society announced on 1 June 2006 that 30 years of Pioneer data had been saved. It announced on 28 March 2007 that analysis of the data was underway. On March 19, 2008, it announced that one source of acceleration, uneven thermal radiation, had been found to explain some of the deviation, but not all.[5][6][7]
The deceleration model
It has been viewed as possible that a real deceleration In physics, and more specifically kinematics, acceleration is the change in velocity over time. Because velocity is a vector, it can change in two ways: a change in magnitude and/or a change in direction. In one dimension, i.e. a line, acceleration is the rate at which something speeds up. However, as a vector quantity, acceleration is also the is not accounted for in the current model for several reasons.
First, it is possible that deceleration is caused by gravitational Gravitation, or gravity, is one of the four fundamental interactions of nature , in which objects with mass attract one another. In everyday life, gravitation is most familiar as the agent that gives weight to objects with mass and causes them to fall to the ground when dropped. Gravitation causes dispersed matter to coalesce, thus accounting for forces from unidentified sources such as the Kuiper belt The Kuiper belt , sometimes called the Edgeworth-Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune (at 30 AU) to approximately 55 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20–200 times as massive. Like the asteroid belt, it consists or dark matter In astronomy and cosmology, dark matter is matter that is inferred to exist from gravitational effects on visible matter and background radiation, but is undetectable by emitted or scattered electromagnetic radiation. Its existence was hypothesized to account for discrepancies between measurements of the mass of galaxies, clusters of galaxies and. However, this acceleration does not show up in the orbits of the outer planets, so any generic gravitational answer would need to violate the equivalence principle In the physics of general relativity, the equivalence principle refers to several related concepts dealing with the equivalence of gravitational and inertial mass, and to Albert Einstein's assertion that the gravitational "force" as experienced locally while standing on a massive body is actually the same as the pseudo-force experienced (see modified inertia below). Likewise, the anomaly does not appear in the orbits of Neptune's moons, challenging the possibility that the Pioneer anomaly may be an unconventional gravitational phenomenon based on range from the Sun.[8][9]
Second, the cause could be drag In fluid dynamics, drag refers to forces that oppose the relative motion of an object through a fluid (a liquid or gas). Drag forces act in a direction opposite to the oncoming flow velocity. Unlike other resistive forces such as dry friction, which is nearly independent of velocity, drag forces depend on velocity from the interplanetary medium The interplanetary medium is the material which fills the solar system and through which all the larger solar system bodies such as planets, asteroids and comets move, including dust Dust is a general name for solid particles with diameters less than 20 thou . Particles in the atmosphere arise from various sources such as soil dust lifted up by wind, volcanic eruptions, and pollution. Dust in homes, offices, and other human environments contains small amounts of plant pollen, human and animal hairs, textile fibers, paper, solar wind The solar wind is a stream of charged particles ejected from the upper atmosphere of the sun. It mostly consists of electrons and protons with energies usually between 10 and 100 eV. The stream of particles varies in temperature and speed over time. These particles can escape the sun's gravity because of their high kinetic energy and the high and cosmic rays Cosmic rays are energetic particles originating from outer space that impinge on Earth's atmosphere. About 89% of all the incoming cosmic ray particles are simple protons, with nearly 10% being helium nuclei , and slightly under 1% are heavier elements; electrons (beta particles) constitute about 1% of galactic cosmic rays. The term ray is a. However, the measured densities are too small to cause the effect.
Third, gas Gas is one of four classical states of matter. Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons are so energized that they leave their parent atoms leaks, including helium Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among the elements and it exists only as a gas except from the spacecrafts' radioisotope thermoelectric generators A radioisotope thermoelectric generator is an electrical generator that obtains its power from radioactive decay. In such a device, the heat released by the decay of a suitable radioactive material is converted into electricity by the Seebeck effect using an array of thermocouples (RTGs) has been viewed as possible causes.
Fourth, a real deceleration not accounted for in the current model could result from radiation pressure Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. If absorbed, the pressure is the power flux density divided by the speed of light. If the radiation is totally reflected, the radiation pressure is doubled. For example, the radiation of the Sun at the Earth has a power flux density of 1,370 W/m2, so of sunlight, the spacecraft's radio Radio is the transmission of signals by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. Information is carried by systematically changing some property of the radiated waves, such as transmissions, or asymmetrical thermal radiation Thermal radiation is electromagnetic radiation emitted from a material which is due to the heat of the material, the characteristics of which depend on its temperature. An example of thermal radiation is the infrared radiation emitted by a common household radiator or electric heater. A person near a raging bonfire will feel the radiated heat of of the heat from the spacecraft. Possibilities include the asymmetrical radiation of heat from the RTGs (See Radioisotope rocket The radioisotope rocket is a type of rocket engine that uses the heat generated by the decay of radioactive elements to heat a working fluid, which is then exhausted through a rocket nozzle to produce thrust. They are similar in nature to the nuclear thermal rockets such as NERVA, but are considerably simpler and often have no moving parts) or the spacecraft electronics. Additionally, even if the RTGs themselves radiate symmetrically, some of their radiation will reflect from the back of the spacecraft’s dish-like main antenna, causing a recoil like sunlight striking a solar sail.
However, the radiation pressure of sunlight is too small at this distance, and points into the wrong direction. The same applies to the spacecraft's radio emissions. The asymmetrical radiation of heat remains a prime suspect, as presented at the second ISSI meeting in Berne, Feb 2007. A presentation at the APS The American Physical Society is the world's second largest organization of physicists, behind the Deutsche Physikalische Gesellschaft. The Society publishes more than a dozen scientific journals, including the world renowned Physical Review and Physical Review Letters, and organizes more than twenty science meetings each year. It is also a member April 2008 meeting suggests that differential heating may account for as much of 1/3 rd of the observed acceleration.[10]
Finally, a real deceleration not accounted for in the current model could be from electromagnetic forces Electromagnetism is one of the four fundamental interactions of nature, along with strong interaction, weak interaction and gravitation. It is the force that causes the interaction between electrically charged particles; the areas in which this happens are called electromagnetic fields due to an electric charge Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields. The interaction between a moving charge and an electromagnetic field is the source of the electromagnetic force, which is one of the on the spacecraft.
Sun, 08 Aug 2010 03:40:44 GMT+00:00
Kansas City Star Most unsuspecting Americans call this anomaly capitalism, but reptilian cannibalism might be a better term. Unfortunately, all this injustice has been ...
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those conditions beta is equal to 45 degrees and point A is almost right radially aligned with B The two hyperspheres look like two hyperplanes and can be represented by the figure below Figure 2 Pioneer Radar Gun Experiment Looking into a few minutes in the past I hope nobody would be silly enough to consider that I wrote radar gun experiment on a non tongue in cheek
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abstract: this paper reports the results of an analysis of the doppler tracking data of . pioneer. probes which did show an . anomalous. behaviour. a software has been developed for the sake of performing a data analysis as independent as ...
