Voyager 1

Voyager 1
Model of the Voyager spacecraft, a small-bodied spacecraft with a large, central dish and many arms and antennas extending from it
Model of the Voyager spacecraft design
Mission typeOuter planetary, heliosphere, and interstellar medium exploration
OperatorNASA / Jet Propulsion Laboratory
COSPAR ID1977-084A[1]
no.10321[2]
Websitevoyager.jpl.nasa.gov
Mission duration
  • 42 years, 5 months, 11 days elapsed
  • Planetary mission: 3 years, 3 months, 9 days
  • Interstellar mission: 39 years, 2 months, 2 days elapsed
Spacecraft properties
Spacecraft typeMariner Jupiter-Saturn
ManufacturerJet Propulsion Laboratory
Launch mass825.5 kg (1,820 lb)
Power470 watts (at launch)
Start of mission
Launch dateSeptember 5, 1977, 12:56:00 (1977-09-05UTC12:56Z) UTC
RocketTitan IIIE
Launch siteCape Canaveral Launch Complex 41
Flyby of Jupiter
Closest approachMarch 5, 1979
Distance349,000 km (217,000 mi)
Flyby of Saturn
Closest approachNovember 12, 1980
Distance124,000 km (77,000 mi)
Flyby of Titan (atmosphere study)
Closest approachNovember 12, 1980
Distance6,490 km (4,030 mi)
 

Voyager 1 is a space probe launched by NASA on September 5, 1977. Part of the Voyager program to study the outer Solar System, Voyager 1 was launched 16 days after its twin, Voyager 2. Having operated for 42 years, 5 months and 11 days as of February 16, 2020, the spacecraft still communicates with the Deep Space Network to receive routine commands and to transmit data to Earth. Real-time distance and velocity data is provided[3] by NASA and JPL. At a distance of 148.67 AU (22.2 billion km; 13.8 billion mi) from Earth as of January 19, 2020[4] it is the most distant man-made object from Earth.[5]

The probe's objectives included flybys of Jupiter, Saturn, and Saturn's largest moon, Titan. Although the spacecraft's course could have been altered to include a Pluto encounter by forgoing the Titan flyby, exploration of the moon took priority because it was known to have a substantial atmosphere.[6][7][8] Voyager 1 studied the weather, magnetic fields, and rings of the two planets and was the first probe to provide detailed images of their moons.

After completing its primary mission with the flyby of Saturn on November 12, 1980, Voyager 1 became the third of five artificial objects to achieve the escape velocity required to leave the Solar System.[citation needed] On August 25, 2012, Voyager 1 became the first spacecraft to cross the heliopause and enter the interstellar medium.[9]

In a further testament to the robustness of Voyager 1, the Voyager team completed a successful test of the spacecraft's trajectory correction maneuver (TCM) thrusters in late 2017 (the first time these thrusters were fired since 1980), a project enabling the mission to be extended by two to three years.[10]

Voyager 1's extended mission is expected to continue until about 2025 when its radioisotope thermoelectric generators will no longer supply enough electric power to operate its scientific instruments.

Mission background

History

In the 1960s, a Grand Tour to study the outer planets was proposed which prompted NASA to begin work on a mission in the early 1970s.[11] Information gathered by the Pioneer 10 spacecraft helped Voyager's engineers design Voyager to cope more effectively with the intense radiation environment around Jupiter.[12] However, shortly before launch, strips of kitchen-grade aluminum foil were applied to certain cabling to further enhance radiation shielding.[13]

Initially, Voyager 1 was planned as "Mariner 11" of the Mariner program. Due to budget cuts, the mission was scaled back to be a flyby of Jupiter and Saturn and renamed the Mariner Jupiter-Saturn probes. As the program progressed, the name was later changed to Voyager, since the probe designs began to differ greatly from previous Mariner missions.[14]

Spacecraft components

The 3.7 m (12 ft) diameter high gain dish antenna used on the Voyager craft

Voyager 1 was constructed by the Jet Propulsion Laboratory.[15][16][17] It has 16 hydrazine thrusters, three-axis stabilization gyroscopes, and referencing instruments to keep the probe's radio antenna pointed toward Earth. Collectively, these instruments are part of the Attitude and Articulation Control Subsystem (AACS), along with redundant units of most instruments and 8 backup thrusters. The spacecraft also included 11 scientific instruments to study celestial objects such as planets as it travels through space.[18]

Communication system

The radio communication system of Voyager 1 was designed to be used up to and beyond the limits of the Solar System. The communication system includes a 3.7-meter (12 ft) diameter high gain Cassegrain antenna to send and receive radio waves via the three Deep Space Network stations on the Earth.[19] The craft normally transmits data to Earth over Deep Space Network Channel 18, using a frequency of either 2.3 GHz or 8.4 GHz, while signals from Earth to Voyager are transmitted at 2.1 GHz.[20]

When Voyager 1 is unable to communicate directly with the Earth, its digital tape recorder (DTR) can record about 67 megabytes of data for transmission at another time.[21] Signals from Voyager 1 take over 20 hours to reach Earth.[4]

Power

Voyager 1 has three radioisotope thermoelectric generators (RTGs) mounted on a boom. Each MHW-RTG contains 24 pressed plutonium-238 oxide spheres.[22] The RTGs generated about 470 W of electric power at the time of launch, with the remainder being dissipated as waste heat.[23] The power output of the RTGs declines over time (due to the 87.7-year half-life of the fuel and degradation of the thermocouples), but the craft's RTGs will continue to support some of its operations until 2025.[18][22]

As of February 16, 2020, Voyager 1 has 71.5% of the plutonium-238 that it had at launch. By 2050, it will have 56.5% left.

Computers

Unlike the other onboard 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). Since the 1990s, most space probes have had completely autonomous cameras.[24]

The computer command subsystem (CCS) controls 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 1970s Viking orbiters.[25] The hardware in both custom-built CCS subsystems in the Voyagers is identical. There is only a minor software modification: one of them has a scientific subsystem that the other lacks.[citation needed]

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 the scan platform. The custom-built AACS systems on both Voyagers are the same.[26][27]

Scientific instruments

Instrument name Abr. Description
Imaging Science System
(disabled)
ISS Utilized a two-camera system (narrow-angle/wide-angle) to provide images of Jupiter, Saturn and other objects along the trajectory. More
Filters
Narrow-angle camera[28]
Name Wavelength Spectrum Sensitivity
Clear 280–640 nm
Voyager - Filters - Clear.png
UV 280–370 nm
Voyager - Filters - UV.png
Violet 350–450 nm
Voyager - Filters - Violet.png
Blue 430–530 nm
Voyager - Filters - Blue.png
?
Green 530–640 nm
Voyager - Filters - Green.png
?
Orange 590–640 nm
Voyager - Filters - Orange.png
?
Wide-angle camera[29]
Name Wavelength Spectrum Sensitivity
Clear 280–640 nm
Voyager - Filters - Clear.png
?
Violet 350–450 nm
Voyager - Filters - Violet.png
Blue 430–530 nm
Voyager - Filters - Blue.png
CH4-U 536–546 nm
Voyager - Filters - CH4U.png
Green 530–640 nm
Voyager - Filters - Green.png
Na-D 588–590 nm
Voyager - Filters - NaD.png
Orange 590–640 nm
Voyager - Filters - Orange.png
CH4-JST 614–624 nm
Voyager - Filters - CH4JST.png
  • Principal investigator: Bradford Smith / University of Arizona (PDS/PRN website)
  • Data: PDS/PDI data catalog, PDS/PRN data catalog
Radio Science System
(disabled)
RSS Utilized the telecommunications system of the Voyager spacecraft to determine the physical properties of planets and satellites (ionospheres, atmospheres, masses, gravity fields, densities) and the amount and size distribution of material in Saturn's rings and the ring dimensions. More
  • Principal investigator: G. Tyler / Stanford University PDS/PRN overview
  • Data: PDS/PPI data catalog, PDS/PRN data catalog (VG_2803), NSSDC data archive
Infrared Interferometer Spectrometer
(disabled)
IRIS Investigates both global and local energy balance and atmospheric composition. Vertical temperature profiles are also obtained from the planets and satellites as well as the composition, thermal properties, and size of particles in More
  • Principal investigator: Rudolf Hanel / NASA Goddard Space Flight Center (PDS/PRN website)
  • Data: PDS/PRN data catalog, PDS/PRN expanded data catalog (VGIRIS_0001, VGIRIS_002), NSSDC Jupiter data archive
Ultraviolet Spectrometer
(disabled)
UVS Designed to measure atmospheric properties, and to measure radiation. More
  • Principal investigator: A. Broadfoot / University of Southern California (PDS/PRN website)
  • Data: PDS/PRN data catalog
Triaxial Fluxgate Magnetometer
(active)
MAG Designed to investigate the magnetic fields of Jupiter and Saturn, the interaction of the solar wind with the magnetospheres of these planets, and the magnetic field of interplanetary space out to the boundary between the solar wind and the magnetic field of More
  • Principal investigator: Norman F. Ness / NASA Goddard Space Flight Center (website)
  • Data: PDS/PPI data catalog, NSSDC data archive
Plasma Spectrometer
(defective)
PLS Investigates the microscopic properties of the plasma ions and measures electrons in the energy range from 5 eV to 1 keV. More
  • Principal investigator: John Richardson / MIT (website)
  • Data: PDS/PPI data catalog, NSSDC data archive
Low Energy Charged Particle Instrument
(active)
LECP Measures the differential in energy fluxes and angular distributions of ions, electrons and the differential in energy ion composition. More
  • Principal investigator: Stamatios Krimigis / JHU / APL / University of Maryland (JHU/APL website / UMD website / KU website)
  • Data: UMD data plotting, PDS/PPI data catalog, NSSDC data archive
Cosmic Ray System
(active)
CRS Determines the origin and acceleration process, life history, and dynamic contribution of interstellar cosmic rays, the nucleosynthesis of elements in cosmic-ray sources, the behavior of cosmic rays in the More
  • Principal investigator: Edward Stone / Caltech / NASA Goddard Space Flight Center (website)
  • Data: PDS/PPI data catalog, NSSDC data archive
Planetary Radio Astronomy Investigation
(disabled)
PRA Utilizes a sweep-frequency radio receiver to study the radio-emission signals from Jupiter and Saturn. More
  • Principal investigator: James Warwick / University of Colorado
  • Data: PDS/PPI data catalog, NSSDC data archive
Photopolarimeter System
(defective)
PPS Utilized a telescope with a More
  • Principal investigator: Arthur Lane / JPL (PDS/PRN website)
  • Data: PDS/PRN data catalog
Plasma Wave Subsystem
(active)
PWS Provides continuous, sheath-independent measurements of the electron-density profiles at Jupiter and Saturn as well as basic information on local wave–particle interaction, useful in studying the magnetospheres. More
  • Principal investigator: Donald Gurnett / University of Iowa (website)
  • Data: PDS/PPI data catalog

For more details on the Voyager space probes' identical instrument packages, see the separate article on the overall Voyager Program.

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