Misplaced Pages

#223776

56-717: The Pioneer Venus project was part of the Pioneer program consisting of two spacecraft, the Pioneer Venus Orbiter and the Pioneer Venus Multiprobe , launched to Venus in 1978. The program was managed by NASA 's Ames Research Center . The Pioneer Venus Orbiter entered orbit around Venus on December 4, 1978, and performed observations to characterize the atmosphere and surface of Venus. It continued to transmit data until October 1992. The Pioneer Venus Multiprobe deployed four small probes into

112-614: A Titan flyby, while JSX served as a contingency plan. JST focused on a Titan flyby, while JSX provided a flexible mission plan. If JST succeeded, JSX could proceed with the Grand Tour, but in case of failure, JSX could be redirected for a separate Titan flyby, forfeiting the Grand Tour opportunity. The second probe, now Voyager 2 , followed the JSX trajectory, granting it the option to continue on to Uranus and Neptune. Upon Voyager 1 completing its main objectives at Saturn, Voyager 2 received

168-496: A 290 kg bus which carried one large (315 kg) and three small atmospheric probes. The large probe was released on November 16, 1978 and the three small probes on November 20. All four probes entered the Venus atmosphere on December 9, followed by the bus. The Pioneer Venus large probe was about 1.5 m in diameter and equipped with 7 science experiments. After deceleration from initial atmospheric entry at about 11.5 km/s,

224-411: A JST or JSX trajectory. After completing their flybys, the probes would communicate with Earth, relaying vital data using their magnetometers , spectrometers , and other instruments to detect interstellar , solar , and cosmic radiation . Their radioisotope thermoelectric generators (RTGs) would limit the maximum communication time with the probes to roughly a decade . Following their primary missions,

280-472: A commandable filter wheel mounted in front of the vidicons. One has a low resolution 200 mm (7.9 in) focal length wide-angle lens with an aperture of f/3 (the wide-angle camera), while the other uses a higher resolution 1,500 mm (59 in) narrow-angle f/8.5 lens (the narrow-angle camera). Three spacecraft were built, Voyager 1 (VGR 77-1), Voyager 2 (VGR 77-3), and test spare model (VGR 77-2). There are three different computer types on

336-535: A dense atmosphere. This encounter sent Voyager 1 out of the plane of the ecliptic, ending its planetary science mission. Had Voyager 1 been unable to perform the Titan flyby, the trajectory of Voyager 2 could have been altered to explore Titan, forgoing any visit to Uranus and Neptune. Voyager 1 was not launched on a trajectory that would have allowed it to continue to Uranus and Neptune, but could have continued from Saturn to Pluto without exploring Titan. During

392-490: A mission extension, enabling it to proceed to Uranus and Neptune. This allowed Voyager 2 to diverge from the originally planned JST trajectory. The probes would be launched in August or September 1977, with their main objective being to compare the characteristics of Jupiter and Saturn, such as their atmospheres , magnetic fields , particle environments, ring systems , and moons . They would fly by planets and moons in either

448-531: A new interplanetary space weather network: Pioneer 6 and Pioneer 9 are in solar orbits with 0.8 AU distance to the Sun. Their orbital periods are therefore slightly shorter than Earth's. Pioneer 7 and Pioneer 8 are in solar orbits with 1.1 AU distance to the Sun. Their orbital periods are therefore slightly longer than Earth's. Since the probes' orbital periods differ from that of the Earth, from time to time, they face

504-399: A parachute was deployed at 47 km altitude. The probe stopped broadcasting when it impacted the surface. The science experiments were: The three small probes were identical to each other, 0.8 m in diameter and 90 kg each small probe. The small probes were each targeted at different parts of the planet; They had no parachutes and the aeroshells did not separate from the probe. Two of

560-581: A region of outer space beyond the influence of the solar wind , as did Voyager 1 in 2012. 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. As of 2024, the Voyagers are still in operation beyond the outer boundary of

616-554: A revised power management plan was implemented to better manage the two probes' dwindling power supply. The Voyager spacecraft each weighed 815 kilograms (1,797 pounds) at launch, but after fuel usage are now about 733 kilograms (1,616 pounds). Of this weight, each spacecraft carries 105 kilograms (231 pounds) of scientific instruments. The identical Voyager spacecraft use three-axis-stabilized guidance systems that use gyroscopic and accelerometer inputs to their attitude control computers to point their high-gain antennas towards

SECTION 10

#1732772926224

672-423: A scientific subsystem that the other lacks. According to Guinness Book of Records, CCS holds record of "longest period of continual operation for a computer". It has been running continuously since 20 August 1977. The Attitude and Articulation Control Subsystem (AACS) controls the spacecraft orientation (its attitude). It keeps the high-gain antenna pointing towards the Earth, controls attitude changes, and points

728-516: A separate program named Mariner Jupiter-Saturn (also Mariner Jupiter-Saturn-Uranus , MJS , or MJSU ), part of the Mariner program , later renamed because it was thought that the design of the two space probes had progressed sufficiently beyond that of the Mariner family to merit a separate name. On March 4, 1977, NASA announced a competition to rename the mission, believing the existing name

784-437: A side of the Sun that cannot be seen from Earth. The probes can sense parts of the Sun several days before the Sun's rotation reveals it to ground-based Earth orbiting observatories. 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

840-620: Is attached to one of the bus sides. The angled square panel to the right is the optical calibration target and excess heat radiator. The three radioisotope thermoelectric generators (RTGs) are mounted end-to-end on the lower boom. The scan platform comprises: the Infrared Interferometer Spectrometer (IRIS) (largest camera at top right); the Ultraviolet Spectrometer (UVS) just above the IRIS;

896-459: 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 × 10  mi) from the Sun reaching a distance of 136.627  AU (20.4  billion   km ; 12.7 billion  mi ) from Earth as of May 25, 2024. 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

952-639: Is two 16-bit word machines with modular memories and 8198 words each. The Attitude and Articulation Control System (AACS) is two 18-bit word machines with 4096 words each. Unlike the other on-board instruments, the operation of the cameras for visible light is not autonomous, but rather it is controlled by an imaging parameter table contained in one of the on-board digital computers , the Flight Data Subsystem (FDS). More recent space probes, since about 1990, usually have completely autonomous cameras. The computer command subsystem (CCS) controls

1008-496: The Deep Space Network were increased from 64 to 70 m (210 to 230 ft) dramatically increasing their areas for gathering weak microwave signals. Whilst the craft were between Saturn and Uranus the onboard software was upgraded to do a degree of image compression and to use a more efficient Reed-Solomon error-correcting encoding . Then between 1986 and 1989, new techniques were brought into play to combine

1064-657: The heliopause on 25 August 2012, making it the first spacecraft to enter interstellar space. In December 2018, NASA announced that Voyager 2 had crossed the heliopause on 5 November 2018, making it the second spacecraft to enter interstellar space. As of 2017 Voyager 1 and Voyager 2 continue to monitor conditions in the outer expanses of the Solar System. The Voyager spacecraft are expected to be able to operate science instruments through 2020, when limited power will require instruments to be deactivated one by one. Sometime around 2025, there will no longer be sufficient power to operate any science instruments. In July 2019,

1120-412: 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 × 10  mi) from the Sun reaching a distance of 162  AU (24.2  billion   km ; 15.1 billion  mi ) from Earth as of May 25, 2024. As of 2024 , Voyager 2

1176-421: The 1990s, Voyager 1 overtook the slower deep-space probes Pioneer 10 and Pioneer 11 to become the most distant human-made object from Earth, a record that it will keep for the foreseeable future. The New Horizons probe, which had a higher launch velocity than Voyager 1 , is travelling more slowly due to the extra speed Voyager 1 gained from its flybys of Jupiter and Saturn. Voyager 1 and Pioneer 10 are

SECTION 20

#1732772926224

1232-495: The 2040's—and Voyager 1 is the farthest human-made object from Earth. Voyager did things no one predicted, found scenes no one expected, and promises to outlive its inventors. Like a great painting or an abiding institution, it has acquired an existence of its own, a destiny beyond the grasp of its handlers. The two Voyager space probes were originally conceived as part of the Planetary Grand Tour planned during

1288-458: The Earth and their scientific instruments towards their targets, sometimes with the help of a movable instrument platform for the smaller instruments and the electronic photography system. The diagram shows the high-gain antenna (HGA) with a 3.7 m (12 ft) diameter dish attached to the hollow decagonal electronics container. There is also a spherical tank that contains the hydrazine monopropellant fuel. The Voyager Golden Record

1344-513: The Venusian atmosphere on December 9, 1978. All four probes transmitted data throughout their descent to the surface. One probe survived the landing and transmitted data from the surface for over an hour. The Pioneer mission consisted of two components, launched separately: an orbiter and a multiprobe. The orbiter was launched on May 20, 1978 on an Atlas-Centaur rocket. The orbiter's mass was 517 kg (1,140 lb). The Pioneer Venus Orbiter

1400-484: The Voyager spacecraft, two of each kind, sometimes used for redundancy. They are proprietary, custom-built computers built from CMOS and TTL medium-scale CMOS integrated circuits and discrete components, mostly from the 7400 series of Texas Instruments . Total number of words among the six computers is about 32K. Voyager 1 and Voyager 2 have identical computer systems. The Computer Command System (CCS),

1456-475: The cameras. The CCS contains fixed computer programs such as command decoding, fault detection, and correction routines, antenna-pointing routines, and spacecraft sequencing routines. This computer is an improved version of the one that was used in the Viking orbiter . The hardware in both custom-built CCS subsystems in the Voyagers is identical. There is only a minor software modification for one of them that has

1512-477: The central controller of the spacecraft, has two 18-bit word, interrupt-type processors with 4096 words each of non-volatile plated-wire memory . During most of the Voyager mission the two CCS computers on each spacecraft were used non-redundantly to increase the command and processing capability of the spacecraft. The CCS is nearly identical to the system flown on the Viking spacecraft. The Flight Data System (FDS)

1568-428: The data for transmission . The DTR is used to record high-rate Plasma Wave Subsystem (PWS) data, which 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. The Imaging Science Subsystem consists of two television-type cameras, each with eight filters in

1624-399: The farther that they get from the Earth. For example, the data rate used from Jupiter was about 115,000 bits per second. That was halved at the distance of Saturn, and it has gone down continually since then. Some measures were taken on the ground along the way to reduce the effects of the inverse-square law. In between 1982 and 1985, the diameters of the three main parabolic dish antennas of

1680-493: The first probe has been attributed to Stephen A. Saliga, who had been assigned to the Air Force Orientation Group, Wright-Patterson AFB, as chief designer of Air Force exhibits. While he was at a briefing, the spacecraft was described to him, as, a "lunar-orbiting vehicle, with an infrared scanning device." Saliga thought the title too long, and lacked theme for an exhibit design. He suggested, "Pioneer", as

1736-612: The flyby missions to Jupiter and Saturn . While successful, the missions returned much poorer images than the Voyager program probes would five years later. In 1978, the end of the program saw a return to the inner Solar System, with the Pioneer Venus Orbiter and Multiprobe , this time using orbital insertion rather than flyby missions. The new missions were numbered beginning with Pioneer 6 (alternate names in parentheses). The spacecraft in Pioneer missions 6, 7, 8, and 9 comprised

Pioneer Venus project - Misplaced Pages Continue

1792-523: The heliopause boundary has allowed both spacecraft to make measurements of the interstellar fields, particles and waves unaffected by the solar wind . Two significant findings so far have been the discovery of a region of magnetic bubbles and no indication of an expected shift in the Solar magnetic field. The entire Voyager 2 scan platform, including all of the platform instruments, was switched off in 1998. All platform instruments on Voyager 1 , except for

1848-435: The heliosheath is not smooth, but filled with giant magnetic bubbles, theorized to form when the magnetic field of the Sun becomes warped at the edge of the Solar System. In June 2012, Scientists at NASA reported that Voyager 1 was very close to entering interstellar space, indicated by a sharp rise in high-energy particles from outside the Solar System. In September 2013, NASA announced that Voyager 1 had crossed

1904-606: The late 1960s and early 70s that aimed to explore Jupiter , Saturn , Saturn's moon , Titan , Uranus , Neptune , and Pluto . The mission originated from the Grand Tour program , conceptualized by Gary Flandro , an aerospace engineer at the Jet Propulsion Laboratory, in 1964, which leveraged a rare planetary alignment occurring once every 175 years. This alignment allowed a craft to reach all outer planets using gravitational assists . The mission

1960-493: The most widely separated human-made objects anywhere since they are travelling in roughly opposite directions from the Solar System . In December 2004, Voyager 1 crossed the termination shock , where the solar wind is slowed to subsonic speed, and entered the heliosheath , where the solar wind is compressed and made turbulent due to interactions with the interstellar medium . On 10 December 2007, Voyager 2 also reached

2016-617: The name of the probe, since "the Army had already launched and orbited the Explorer satellite, and their Public Information Office was identifying the Army, as, 'Pioneers in Space,'" and, by adopting the name, the Air Force would "make a 'quantum jump' as to who, really, [were] the 'Pioneers' in space.'" The earliest missions were attempts to achieve Earth's escape velocity , simply to show it

2072-473: The optimal level and increased DSN ( Deep Space Network ) support is warranted." The main objective of the VIM was to extend the exploration of the Solar System beyond the outer planets to the heliopause (the farthest extent at which the Sun's radiation predominates over interstellar winds) and if possible even beyond. Voyager 1 crossed the heliopause boundary in 2012, followed by Voyager 2 in 2018. Passing through

2128-448: The power generated by Voyager 1 and Voyager 2 had dropped to 267.9 W and 269.2 W respectively, about 57% of the power at launch. The level of power output was better than pre-launch predictions based on a conservative thermocouple degradation model. As the electrical power decreases, spacecraft loads must be turned off, eliminating some capabilities. There may be insufficient power for communications by 2032. The Voyager primary mission

2184-431: 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. On 5 November 2019, data from Voyager 2 indicated that it also had entered interstellar space. On 4 November 2019, scientists reported that on 5 November 2018, the Voyager 2 probe had officially reached the interstellar medium (ISM),

2240-399: The probes would continue to drift into interstellar space. Voyager 2 was the first to be launched. Its trajectory was designed to allow flybys of Jupiter, Saturn, Uranus, and Neptune. Voyager 1 was launched after Voyager 2 , but along a shorter and faster trajectory that was designed to provide an optimal flyby of Saturn's moon Titan , which was known to be quite large and to possess

2296-564: The scan platform. The custom-built AACS systems on both craft are identical. It has been erroneously reported on the Internet that the Voyager space probes were controlled by a version of the RCA ;1802 (RCA CDP1802 "COSMAC" microprocessor ), but such claims are not supported by the primary design documents. The CDP1802 microprocessor was used later in the Galileo space probe , which

Pioneer Venus project - Misplaced Pages Continue

2352-751: The signals from multiple antennas on the ground into one, more powerful signal, in a kind of an antenna array . This was done at Goldstone, California , Canberra (Australia) , and Madrid (Spain) using the additional dish antennas available there. Also, in Australia, the Parkes Radio Telescope was brought into the array in time for the fly-by of Neptune in 1989. In the United States, the Very Large Array in New Mexico

2408-470: The small probes reached the surface, and one of these, the day probe, continued to broadcast for 67 minutes and 37 seconds after reaching the surface. The Pioneer Venus bus also carried two experiments, a neutral mass spectrometer and an ion mass spectrometer to study the composition of the atmosphere. With no heat shield or parachute, the bus made measurements only to about 110 km altitude before burning up. Pioneer program Credit for naming

2464-484: The spacecraft was launched. Plutonium-238 decays with a half-life of 87.74 years, so RTGs using Pu-238 will lose a factor of 1−0.5 = 0.79% of their power output per year. In 2011, 34 years after launch, the thermal power generated by such an RTG would be reduced to (1/2) ≈ 76% of its initial power. The RTG thermocouples , which convert thermal power into electricity, also degrade over time reducing available electric power below this calculated level. By 7 October 2011

2520-403: The termination shock, about 1.6 billion kilometres (1 billion miles) closer to the Sun than from where Voyager 1 first crossed it, indicating that the Solar System is asymmetrical . In 2010 Voyager 1 reported that the outward velocity of the solar wind had dropped to zero, and scientists predicted it was nearing interstellar space . In 2011, data from the Voyagers determined that

2576-674: The two Imaging Science Subsystem (ISS) vidicon cameras to the left of the UVS; and the Photopolarimeter System (PPS) under the ISS. Only five investigation teams are still supported, though data is collected for two additional instruments. The Flight Data Subsystem (FDS) and a single eight-track digital tape recorder (DTR) provide the data handling functions. The FDS configures each instrument and controls instrument operations. It also collects engineering and science data and formats

2632-400: The two Voyagers have been carried out using their 3.7-meter (12 ft) high-gain antennas. The high-gain antenna has a beamwidth of 0.5° for X-band, and 2.3° for S-band. (The low-gain antenna has a 7 dB gain and 60° beamwidth.) Because of the inverse-square law in radio communications , the digital data rates used in the downlinks from the Voyagers have been continually decreasing

2688-401: 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 . After the planetary flybys were complete, decisions were made to keep

2744-440: The ultraviolet spectrometer (UVS) have also been switched off. The Voyager 1 scan platform was scheduled to go off-line in late 2000 but has been left on to investigate UV emission from the upwind direction. UVS data are still captured but scans are no longer possible. Gyro operations ended in 2016 for Voyager 2 and in 2017 for Voyager 1 . Gyro operations are used to rotate the probe 360 degrees six times per year to measure

2800-597: Was brought into temporary use along with the antennas of the Deep Space Network at Goldstone. Using this new technology of antenna arrays helped to compensate for the immense radio distance from Neptune to the Earth. Electrical power is supplied by three MHW-RTG radioisotope thermoelectric generators (RTGs). 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

2856-531: Was completed in 1989, with the close flyby of Neptune by Voyager 2 . The Voyager Interstellar Mission (VIM) is a mission extension, which began when the two spacecraft had already been in flight for over 12 years. 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

SECTION 50

#1732772926224

2912-420: Was designed and built years later. The digital control electronics of the Voyagers were not based on a microprocessor integrated-circuit chip. The uplink communications are executed via S-band microwave communications . The downlink communications are carried out by an X-band microwave transmitter on board the spacecraft, with an S-band transmitter as a back-up. All long-range communications to and from

2968-550: Was feasible and to study the Moon . This included the first launch by NASA which was formed from the old NACA . These missions were carried out by the Air Force Ballistic Missile Division , Army , and NASA. Five years after the early Able space probe missions ended, NASA Ames Research Center used the Pioneer name for a new series of missions, initially aimed at the inner Solar System , before

3024-449: Was inserted into an elliptical orbit around Venus on December 4, 1978. It carried 17 experiments (with a total mass of 45 kg): In May 1992 the orbiter began the final phase of its mission, in which the periapsis was held between 150 and 250 km until the fuel ran out and atmospheric entry destroyed the spacecraft in August 1992. The Pioneer Venus Multiprobe was launched on August 8, 1978 on an Atlas-Centaur rocket. It consisted of

3080-482: Was not appropriate as the mission had differed significantly from previous Mariner missions. Voyager was chosen as the new name, referencing an earlier suggestion by William Pickering , who had proposed the name Navigator . Due to the name change occurring close to launch, the probes were still occasionally referred to as Mariner 11 and Mariner 12, or even Voyager 11 and Voyager 12. Two mission trajectories were established: JST aimed at Jupiter, Saturn, and enhancing

3136-839: Was to send several pairs of probes and gained momentum in 1966 when it was endorsed by NASA 's Jet Propulsion Laboratory . However, in December 1971, the Grand Tour mission was canceled when funding was redirected to the Space Shuttle program . In 1972, a scaled-down (four planets, two identical spacecraft) mission was proposed, utilizing a spacecraft derived from the Mariner series, initially intended to be Mariner 11 and Mariner 12 . The gravity-assist technique, successfully demonstrated by Mariner 10 , would be used to achieve significant velocity changes by maneuvering through an intermediate planet's gravitational field to minimize time towards Saturn. The spacecrafts were then moved into

#223776