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"Voyager spacecraft" redirects here. For the fictional starship from the television show Star Trek: Voyager, see USS Voyager (Star Trek)
This article is about the deep-space probes. The fictional ''Intrepid''-class Starship USS Voyager is the primary setting of the Science fiction Television series For the planned series of missions to Mars by the same name, see Voyager program (Mars)
For all other uses see Voyager. The Voyager Mars Program was a planned series of unmanned NASA probes to the planet Mars.
The trajectories that enabled Voyager spacecraft to visit the outer planets and achieve velocity to escape our solar system
The trajectories that enabled Voyager spacecraft to visit the outer planets and achieve velocity to escape our solar system

The Voyager program consists of a pair of unmanned scientific probes, Voyager 1 and Voyager 2. A space probe is a scientific Space exploration mission in which a Robotic spacecraft leaves the Gravity well of Earth and approaches the The Voyager 1 spacecraft is a 722-kilogram robotic Space probe of the outer Solar system and beyond launched September 5, Voyager 2 is an unmanned Interplanetary Spacecraft launched on August 20, 1977. 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 continue their mission into the outer solar system. The Solar System consists of the Sun and those celestial objects bound to it by Gravity. They have since continued out and will one day exit the solar system. These probes were built at JPL and were funded by NASA. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program

Both missions have gathered large amounts of data about the gas giants of the solar system, of which little was previously known. A gas giant (sometimes also known as a Jovian planet after the planet Jupiter, or giant planet) is a large Planet that is not primarily The Solar System consists of the Sun and those celestial objects bound to it by Gravity. In addition, the spacecraft trajectories have been used to place limits on the existence of a hypothetical post-Plutonian Planet X.

Contents

History

The Voyager probes were originally conceived as part of the Mariner program, and designated Mariner 11 and Mariner 12, respectively. The Mariner program was a program conducted by the American space agency NASA that launched a series of robotic interplanetary probes The Voyager 1 spacecraft is a 722-kilogram robotic Space probe of the outer Solar system and beyond launched September 5, Voyager 2 is an unmanned Interplanetary Spacecraft launched on August 20, 1977. They were then moved into a separate program named Mariner Jupiter-Saturn, later retitled Voyager because it was more appealing and romantic. Voyager is a scaled-back version of the Grand Tour program of the late 1960s and early 1970s. The Planetary Grand Tour was an ambitious plan to send unmanned probes to the outermost planets of the solar system The Grand Tour's plan was to send a pair of probes to fly by all the outer planets; it was scaled back because of budget cuts. However, in the end, Voyager fulfilled all the Grand Tour flyby objectives except for Pluto, which at the time was considered a planet by the IAU.

Voyager 1 is thought to have penetrated the termination shock in late 2004
Voyager 1 is thought to have penetrated the termination shock in late 2004

In the 1990s, Voyager 1 overtook the slower travelling Pioneer 10 to become the most distant human made artifact in space. The heliosphere is a bubble in space "blown" into the Interstellar medium (the hydrogen and helium gas that permeates the Galaxy) by the Pioneer 10 ( Pioneer-F) was the first Spacecraft to travel through the Asteroid belt, which it entered on July 15, 1972 It will keep that record for at least several decades; even the fast (at launch) New Horizons probe will not catch up with it since its final speed will be less than Voyager 1's. New Horizons is a Robotic spacecraft mission by NASA currently underway Voyager 1 and Pioneer 10 are also the most widely-separated man made objects in the Universe because they are travelling in roughly opposite directions from the sun.

Periodic contact has been maintained with both probes to monitor conditions in the outer expanses of the solar system. The crafts' radioactive power sources are still producing electrical energy, fuelling hopes of locating the solar system's heliopause. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. The heliosphere is a bubble in space "blown" into the Interstellar medium (the hydrogen and helium gas that permeates the Galaxy) by the In late 2003, Voyager 1 began sending data that seemed to indicate it had crossed the termination shock, but interpretations of this data are in dispute. The Voyager 1 spacecraft is a 722-kilogram robotic Space probe of the outer Solar system and beyond launched September 5, The heliosphere is a bubble in space "blown" into the Interstellar medium (the hydrogen and helium gas that permeates the Galaxy) by the It is now believed that the termination shock was crossed in December 2004, with the heliopause an unknown distance ahead.

Due to budget cuts prompted by President George W. Bush's Vision for Space Exploration, it was rumored that the probes were to be deactivated and abandoned[1] as early as October 2005, before they would have observed the heliopause. George Walker Bush ( born July 6 1946 is the forty-third and current President of the United States. The Vision for Space Exploration is the United States space policy announced on January 14, 2004 by U The heliosphere is a bubble in space "blown" into the Interstellar medium (the hydrogen and helium gas that permeates the Galaxy) by the However, the program continues to be funded into 2007.

Location and trajectories of Pioneer and Voyager spacecraft as of April 4, 2007
Location and trajectories of Pioneer and Voyager spacecraft as of April 4, 2007

As of April 4, 2007, Voyager 1 is over 15. Events 1581 - Francis Drake completes a circumnavigation of the world and is knighted by Elizabeth I. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. 18 terameters (15. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International 18×1012 meters, or 15. 18×109 km, 101. 4 AU, or 9. The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the 4 billion miles) from the Sun, and has thus entered the heliosheath, the termination shock region between the solar system and interstellar space, a vast area where the Sun's influence gives way to the other bodies in the galaxy. The heliosphere is a bubble in space "blown" into the Interstellar medium (the hydrogen and helium gas that permeates the Galaxy) by the The heliosphere is a bubble in space "blown" into the Interstellar medium (the hydrogen and helium gas that permeates the Galaxy) by the

As of September 2006, Voyager 2 is at a distance of around 80. 5 AU (approximately 12 terameters) from the Sun, deep in the scattered disc, and traveling outward at roughly 3. The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the TERA is a shielded Twisted pair connector for use with Category 7 twisted-pair data cables developed by The Siemon Company and standardized in 2003 by The Sun (Sol is the Star at the center of the Solar System. The scattered disc (or scattered disk) is a distant region of the Solar System that is sparsely populated by icy Minor planets known as scattered 3 AU a year. It is more than twice the distance from the Sun as Pluto. On December 10, 2007, instruments on board Voyager 2 sent data back to Earth indicating that the Solar System is asymmetrical (i. e. , bent). It has reached the termination shock, about 10 billion miles from where Voyager 1 first crossed.

Spacecraft design

Voyager 2 passing Saturn (Image generated with Celestia)
Voyager 2 passing Saturn (Image generated with Celestia)

The identical Voyager spacecraft are three-axis stabilized systems that use celestial or gyro referenced attitude control to maintain pointing of the high-gain antennas toward Earth. Celestia is a 3-D Astronomy program created by Chris Laurel The program is based on the Hipparcos Catalogue (HIP and allows users to travel through an extensive In Mathematics and its applications a coordinate system is a system for assigning an n - Tuple of Numbers or scalars to each point Celestial navigation, also known as astronavigation, is a Position fixing technique that was devised to help sailors cross the featureless oceans without having to A gyroscope is a device for measuring or maintaining orientation, based on the principles of Angular momentum. The attitude of a body is its orientation as perceived in a certain Frame of reference; providing a vector along which a spacecraft is pointing is a description of its attitude The high-gain antenna (HGA is an antenna with a focused narrow radiowave beam width EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 The prime mission science payload consisted of 10 instruments (11 investigations including radio science). Radio astronomy is a subfield of Astronomy that studies celestial objects at radio frequencies. Only five investigator teams are still supported, though data is collected for two additional instruments. [2] The Flight Data Subsystem (FDS) and a single eight-track digital tape recorder (DTR) provide the data handling functions. Magnetic tape is a medium for Magnetic recording generally consisting of a thin magnetizable coating on a long and narrow strip of Plastic. The FDS configures each instrument and controls instrument operations. It also collects engineering and science data and formats the data for transmission. Data transmission is the transfer of Data from point-to-point often represented as an Electro-magnetic Signal over a physical point-to-point or point-to-multipoint The DTR is used to record high-rate Plasma Wave Subsystem (PWS) data. In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound The data is played back every six months.

The Imaging Science Subsystem, made up of a wide angle and a narrow angle camera, is a modified version of the slow scan vidicon camera designs that were used in the earlier Mariner flights. In older Video cameras before the mid to late 1980s a video camera tube or pickup tube was used instead of a Charge-coupled device (CCD The Imaging Science Subsystem consists of two television-type cameras, each with 8 filters in a commandable Filter Wheel mounted in front of the vidicons. One has a low resolution 200 mm wide-angle lens with an aperture of f/3 (Wide Angle Camera), while the other uses a higher resolution 1500 mm narrow-angle f/8. 5 lens (Narrow Angle Camera).

Unlike the other onboard instruments, operation of the cameras is not autonomous, but is controlled by an imaging parameter table residing in one of the spacecraft computers, the Flight Data Subsystem (FDS).

The computer command subsystem (CCS) provides sequencing and control functions. The CCS contains fixed routines such as command decoding and fault detection and corrective routines, antenna pointing information, and spacecraft sequencing information. The Voyager spacecraft have three RCA 1802 CPUs running at 6. The RCA (CDP1802 (aka RCA COSMAC * COSMAC 1802) is an 8-bit CMOS Microprocessor (µP introduced by RCA in early 4 MHz. These CPUs sent to space were operating at full military specification temperatures (-55 to +125 °C).

The Attitude and Articulation Control Subsystem (AACS) controls the spacecraft orientation, maintains the pointing of the high-gain antenna towards Earth, controls attitude maneuvers, and positions the scan platform.

Uplink communications is via S band (16-bit/s command rate) while an X band transmitter provides downlink telemetry at 160 bit/s normally and 1. Uplink An uplink (UL or U/L is the portion of a communications link used for the transmission of signals from an Earth terminal The S band ranges from 2 to 4  GHz, crossing the (artificial boundary between UHF and SHF at 3 In Telecommunications and Computing, bitrate (sometimes written bit rate, data rate or as a Variable R or f b The X band is part of the Microwave region of the Electromagnetic spectrum. 4 kbit/s for playback of high-rate plasma wave data. All data is transmitted from and received at the spacecraft via the 3. 7-meter high-gain antenna.

Power

Radioisotope thermoelectric generators for the Voyager program.
Radioisotope thermoelectric generators for the Voyager program.

Electrical power is supplied by three radioisotope thermoelectric generators (RTGs). Electric power is defined as the rate at which Electrical energy is transferred by an Electric circuit. A radioisotope thermoelectric generator ( RTG, RITEG) is an Electrical generator which obtains its power from Radioactive decay. They are powered by plutonium-238 (distinct from the Pu-239 isotope used in nuclear weapons) and provided approximately 470 W at 30 volts DC when the spacecraft was launched. Plutonium-239 is an Isotope of Plutonium. Plutonium-239 is the primary Fissile isotope used for the production of Nuclear weapons although The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second. The volt (symbol V) is the SI derived unit of electric Potential difference or Electromotive force. Direct current ( DC) is the unidirectional flow of Electric charge. Plutonium-238 decays with a half-life of 87. Half-Life (computer-game page here It's already listed in the disambiguation page 74 years, [3] so RTGs using Pu-238 will lose a factor of 1 − 0. 51 / 87. 74 = 0. 78% of their power output per year. In 2006, 29 years after launch, such an RTG would produce only 470 W × 2-(29/87. 74) ~= 373 W — or about 79. 5% — of its initial power. However, the bi-metallic thermocouples that convert heat into electricity also degrade, so the actual power will be even lower. In Electrical engineering and industry thermocouples are a widely used type of temperature sensor and can also be used as a means to convert thermal Potential In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature As of August 11 2006, the power generated by Voyager 1 and Voyager 2 had dropped to 290 W and 291 W respectively, about 60% of the power at launch. Events 2492 BC - Traditional date of the defeat of Bel by Hayk, progenitor and founder of the Armenian nation This is better than the pre-launch predictions based on a conservative thermocouple degradation model. As the electrical power decreases, spacecraft loads must be turned off, eliminating some spacecraft capabilities.

Powering down

As of the present date, the Voyager 2 and Voyager 1 scan platforms, including all of the platform instruments, have been powered down. The ultraviolet spectrometer (UVS)[4] on Voyager 1 was active until 2003, when it too was deactivated. Gyro operations will end in 2010 for Voyager 2 and 2011 for Voyager 1. Gyro operations are used to rotate the probe 360 degrees six times a year to measure the magnetic field of the spacecraft, which is then subtracted from the magnetometer science data. In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges A magnetometer is a scientific instrument used to measure the strength and/or direction of the Magnetic field in the vicinity of the instrument

The two Voyager spacecraft continue to operate, with some loss in subsystem redundancy, but retain the capability of returning scientific data from a full complement of VIM science instruments. Both spacecraft also have adequate electrical power and attitude control propellant to continue operating until around 2020, when the available electrical power will no longer support science instrument operation. At that time, science data return and spacecraft operations will cease.

Voyager Interstellar Mission

The Voyager primary mission was completed in 1989 with the close flyby of Neptune by the Voyager 2 spacecraft. The Voyager Interstellar Mission (VIM) is a mission extension which began when the two spacecraft had already been in flight for over 12 years. [5] The Heliophysics Division of the NASA Science Mission Directorate conducted a Heliophysics Senior Review in 2008. The panel found that the VIM, "is a mission that is absolutely imperative to continue" and that VIM "funding near the optimal level and increased DSN support is warranted. "[6]

Voyager Golden Record

Main article: Voyager Golden Record

Voyager 1 and 2 both carry with them a golden record that contains pictures and sounds of Earth, along with symbolic directions for playing the record and data detailing the location of Earth. The Voyager Golden Record is a Phonograph record included in the two Voyager Spacecraft launched in 1977 The record is intended as a combination time capsule and interstellar message to any civilization, alien or far-future human, that recovers either of the Voyager craft. The contents of this record were selected by a committee chaired by Carl Sagan. Carl Edward Sagan ( November 9 1934 &ndash December 20 1996) was an American Astronomer, astrochemist, author

Fiction and popular culture

The Voyager launches occurred just before the dawn of the media-savvy 1980s, and the program's discoveries during the primary phase of its mission, including striking never-before-seen close up color photos of the major planets, were regularly documented by both print and electronic media outlets. As a result, the Voyager program, especially at the high points of its mission, has seen significant public limelight. As a result, there are a number of references to the Voyager program or to the particular probes themselves within popular culture.

Notes and references

  1. ^ "Voyager probes in funding crisis", BBC, March 10, 2005.  
  2. ^ -Nasa Website Voyager
  3. ^ The Actinide Research Quarterly: Summer 1997
  4. ^ Ultraviolet Spectrometer. Voyager: The Interstellar Mission. NASA JPL. Retrieved on 2006-06-11. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 1184 BC - Trojan War: Troy is sacked and burned according to the calculations of Eratosthenes.
  5. ^ Interstellar Mission. NASA.
  6. ^ [http://www.igpp.ucla.edu/public/THEMIS/SCI/Pubs/Proposals%20and%20Reports/Senior%20Review%202008%20Report%20Final.pdf Senior Review 2008 of the Mission Operations and Data Analysis Program for the Heliophysics Operating Missions] p. 7. NASA.

External links

See also

External links

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