Helios-A and
Helios-B (also known as
and
), were a pair of probes launched into
heliocentric orbitA heliocentric orbit is an orbit around the Sun. All planets, comets, and asteroids in our Solar System are in such orbits, as are many artificial probes and pieces of debris. The moons of planets in the Solar System, by contrast, are not in heliocentric orbits as they orbit their respective planet...
for the purpose of studying
solarThe Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
processes. A joint venture of the
Federal Republic of GermanyWest Germany is the common English, but not official, name for the Federal Republic of Germany or FRG in the period between its creation in May 1949 to German reunification on 3 October 1990....
(
West GermanyWest Germany is the common English, but not official, name for the Federal Republic of Germany or FRG in the period between its creation in May 1949 to German reunification on 3 October 1990....
) and
NASAThe National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
, the probes were launched from the John F. Kennedy Space Center at
Cape Canaveral, FloridaCape Canaveral is a city in Brevard County, Florida, United States. The population was 8,829 at the 2000 census. As of 2008, the estimated population according to the U.S. Census Bureau was 10,147...
, on Dec. 10, 1974, and Jan. 15, 1976, respectively.
The probes are notable for having set a maximum speed record among spacecraft at 252,792 km/h (157,078 mi/h or 43.63 mi/s or 70.22 km/s or 0.000234
cThe speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...
). Helios 2 flew three million kilometers closer to the Sun than Helios 1, achieving perihelion on 17 April 1976 at a record distance of 0.29 AU (or 43.432 million kilometers), slightly inside the orbit of
MercuryMercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
. Helios 2 was sent into orbit 13 months after the launch of Helios 1. The Helios space probes completed their primary missions by the early 1980s, but they continued to send data up to 1985. The probes are no longer functional but still remain in their elliptical orbit around the Sun.
Scientific instruments
{| class="wikitable"
|-
! scope="col" width="135" | Instrument Name
! Description
|-
|
PlasmaIn physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
Experiment Investigation
Helios-A and
Helios-B (also known as
and
), were a pair of probes launched into
heliocentric orbitA heliocentric orbit is an orbit around the Sun. All planets, comets, and asteroids in our Solar System are in such orbits, as are many artificial probes and pieces of debris. The moons of planets in the Solar System, by contrast, are not in heliocentric orbits as they orbit their respective planet...
for the purpose of studying
solarThe Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
processes. A joint venture of the
Federal Republic of GermanyWest Germany is the common English, but not official, name for the Federal Republic of Germany or FRG in the period between its creation in May 1949 to German reunification on 3 October 1990....
(
West GermanyWest Germany is the common English, but not official, name for the Federal Republic of Germany or FRG in the period between its creation in May 1949 to German reunification on 3 October 1990....
) and
NASAThe National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
, the probes were launched from the John F. Kennedy Space Center at
Cape Canaveral, FloridaCape Canaveral is a city in Brevard County, Florida, United States. The population was 8,829 at the 2000 census. As of 2008, the estimated population according to the U.S. Census Bureau was 10,147...
, on Dec. 10, 1974, and Jan. 15, 1976, respectively.
The probes are notable for having set a maximum speed record among spacecraft at 252,792 km/h (157,078 mi/h or 43.63 mi/s or 70.22 km/s or 0.000234
cThe speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...
). Helios 2 flew three million kilometers closer to the Sun than Helios 1, achieving perihelion on 17 April 1976 at a record distance of 0.29 AU (or 43.432 million kilometers), slightly inside the orbit of
MercuryMercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
. Helios 2 was sent into orbit 13 months after the launch of Helios 1. The Helios space probes completed their primary missions by the early 1980s, but they continued to send data up to 1985. The probes are no longer functional but still remain in their elliptical orbit around the Sun.
Scientific instruments
{| class="wikitable"
|-
! scope="col" width="135" | Instrument Name
! Description
|-
|
PlasmaIn physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
Experiment Investigation
Helios-A and
Helios-B (also known as
and
), were a pair of probes launched into
heliocentric orbitA heliocentric orbit is an orbit around the Sun. All planets, comets, and asteroids in our Solar System are in such orbits, as are many artificial probes and pieces of debris. The moons of planets in the Solar System, by contrast, are not in heliocentric orbits as they orbit their respective planet...
for the purpose of studying
solarThe Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
processes. A joint venture of the
Federal Republic of GermanyWest Germany is the common English, but not official, name for the Federal Republic of Germany or FRG in the period between its creation in May 1949 to German reunification on 3 October 1990....
(
West GermanyWest Germany is the common English, but not official, name for the Federal Republic of Germany or FRG in the period between its creation in May 1949 to German reunification on 3 October 1990....
) and
NASAThe National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
, the probes were launched from the John F. Kennedy Space Center at
Cape Canaveral, FloridaCape Canaveral is a city in Brevard County, Florida, United States. The population was 8,829 at the 2000 census. As of 2008, the estimated population according to the U.S. Census Bureau was 10,147...
, on Dec. 10, 1974, and Jan. 15, 1976, respectively.
The probes are notable for having set a maximum speed record among spacecraft at 252,792 km/h (157,078 mi/h or 43.63 mi/s or 70.22 km/s or 0.000234
cThe speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...
). Helios 2 flew three million kilometers closer to the Sun than Helios 1, achieving perihelion on 17 April 1976 at a record distance of 0.29 AU (or 43.432 million kilometers), slightly inside the orbit of
MercuryMercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
. Helios 2 was sent into orbit 13 months after the launch of Helios 1. The Helios space probes completed their primary missions by the early 1980s, but they continued to send data up to 1985. The probes are no longer functional but still remain in their elliptical orbit around the Sun.
Scientific instruments
{| class="wikitable"
|-
! scope="col" width="135" | Instrument Name
! Description
|-
|
PlasmaIn physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
Experiment Investigation
| Measures the velocity and distribution of the solar wind plasma.
|-
|
Flux-gate MagnetometerA magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature...
| Measures the field strength and direction of low frequency magnetic fields in the Sun’s environment.
|-
|
Search Coil MagnetometerA magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature...
| Compliments the Flux-Gate Magnetometer by measuring the magnetic fields between 0 and 3 kHz.
|-
|
PlasmaIn physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
Wave Investigation
|
|-
|
Cosmic Radiation Investigation
| Measures protons, electrons and x-rays to determine the distribution of cosmic rays.
|-
|
Low-Energy Electron and Ion Spectrometer
| Investigates the higher energy portion of the crossover region between the solar wind particles and the cosmic rays.
|-
|
Zodiacal Light Photometer
| Measures the scattering of sunlight by interplanetary dust particles.
|-
|
Micrometeoroid Analyser
| Investigates the composition, charge, mass, velocity and direction of interplanetary dust particles.
|}
Mission profile
Launch and trajectory
{|
|
|}
Timeline of travel
{| class="wikitable"
! scope="col" width="100" | Date
! Event
|-
|
1974-11-10
| Launch of
Helios-A
|-
|
1976-01-15
| Launch of
Helios-B
|-
|
1976-04-17
| Closest flyby of the
SunThe Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
of any spacecraft, performed by
Helios II.
|}