International Cometary Explorer
Encyclopedia
The International Cometary Explorer (ICE) spacecraft
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....

 was originally known as International Sun/Earth Explorer 3 (ISEE-3) satellite, launched August 12, 1978. It was part of the ISEE (International Sun-Earth Explorer) international cooperative program between NASA
NASA
The 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...

 and ESRO
ESRO
The European Space Research Organization was an international organisation founded by 10 European nations with the intention of jointly pursuing scientific research in space. It was founded in 1964...

/ESA
European Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...

 to study the interaction between the Earth's magnetic field
Earth's magnetic field
Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...

 and the solar wind
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 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...

. The program used three spacecraft, a mother/daughter pair (ISEE 1 and ISEE 2 and a heliocentric spacecraft (ISEE 3, later renamed ICE).

ISEE 3 was the first spacecraft to be placed in a halo orbit
Halo orbit
A halo orbit is a periodic, three-dimensional orbit near the , , or Lagrange points in the three-body problem of orbital mechanics. A spacecraft in a halo orbit does not technically orbit the Lagrange point itself , but travels in a closed, repeating path near the Lagrange point...

 at one of Earth-Sun Lagrangian point
Lagrangian point
The Lagrangian points are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects...

s (L1). It was later (as ICE) sent to visit Comet Giacobini-Zinner
21P/Giacobini-Zinner
Comet Giacobini–Zinner is a periodic comet in our solar system.It was discovered by Michel Giacobini from , who observed the comet in the constellation of Aquarius on December 20, 1900...

 and became the first spacecraft to do so by flying through a comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...

's tail passing the nucleus at a distance of approximately 7800 km. ICE was not equipped with cameras.

Original mission: International Sun/Earth Explorer 3 (ISEE-3)

ISEE-3 originally operated in a halo orbit
Halo orbit
A halo orbit is a periodic, three-dimensional orbit near the , , or Lagrange points in the three-body problem of orbital mechanics. A spacecraft in a halo orbit does not technically orbit the Lagrange point itself , but travels in a closed, repeating path near the Lagrange point...

 about the Sun
Sun
The 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...

-Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 Lagrangian point
Lagrangian point
The Lagrangian points are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects...

, 235 Earth radii above the surface (about 1.5 million km, or 924,000 miles). It was the first artificial object placed at a so-called "libration point", proving that such a suspension between gravitational fields was possible.

The purposes of the mission were:
  • to investigate solar-terrestrial relationships at the outermost boundaries of the Earth's magnetosphere;
  • to examine in detail the structure of the solar wind near the Earth and the shock wave that forms the interface between the solar wind and Earth's magnetosphere;
  • to investigate motions of and mechanisms operating in the plasma sheets; and,
  • to continue the investigation of cosmic rays and solar flare emissions in the interplanetary region near 1 AU.


ISEE-3 was spun at 20 rpm, with a rotational axis in line with the ecliptic
Ecliptic
The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...

, to keep it properly oriented for its experiments and solar power generation.

Second mission: International Cometary Explorer

On June 10, 1982, after completing its original mission, ISEE-3 was repurposed. It was renamed the International Cometary Explorer (ICE). The primary scientific objective of ICE was to study the interaction between the solar wind and a cometary atmosphere. After a successful thruster burn to knock it loose from its halo orbit on September 1 of that year, it used the instability of the Earth/Moon and Earth/Sun Lagrange points
Lagrangian point
The Lagrangian points are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects...

, making a series of lunar orbits over the next 15 months. Its last and closest pass over the Moon, on December 22, 1983, was a mere 119.4 km above the moon's surface. By the beginning of 1984, ICE was in heliocentric orbit
Heliocentric orbit
A 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...

.

Giacobini-Zinner encounter

After ejection out of the Earth-Moon system, ICE entered a heliocentric orbit ahead of the Earth on a trajectory intercepting that of Comet Giacobini-Zinner
21P/Giacobini-Zinner
Comet Giacobini–Zinner is a periodic comet in our solar system.It was discovered by Michel Giacobini from , who observed the comet in the constellation of Aquarius on December 20, 1900...

.
On 11 September 1985, the craft passed through the plasma tail of Comet Giacobini-Zinner
21P/Giacobini-Zinner
Comet Giacobini–Zinner is a periodic comet in our solar system.It was discovered by Michel Giacobini from , who observed the comet in the constellation of Aquarius on December 20, 1900...

. Due to the nature of its original mission, ICE carried no cameras. It instead carried instruments for measurements of energetic particles, waves, plasmas, and fields.

Halley encounter

ICE transited between the Sun and Comet Halley in late March 1986, when other spacecraft (Giotto
Giotto mission
Giotto was a European robotic spacecraft mission from the European Space Agency, intended to fly by and study Halley's Comet. On 13 March 1986, the mission succeeded in approaching Halley's nucleus at a distance of 596 kilometers....

, Vega 1 and 2
Vega program
The Vega program was a series of Venus missions which also took advantage of the appearance of Comet Halley in 1986. Vega 1 and Vega 2 were unmanned spacecraft launched in a cooperative effort among the Soviet Union and Austria, Bulgaria, Hungary, the German Democratic Republic, Poland,...

, Suisei
Suisei probe
Suisei , originally known as Planet-A, was an unmanned space probe developed by the Institute of Space and Astronautical Science ....

 and Sakigake
Sakigake
Sakigake , pre-launch codename MS-T5, was Japan's first interplanetary spacecraft, and the first deep space probe to be launched by any country other than the USA or the Soviet Union...

) were in the vicinity of Comet Halley
Comet Halley
Halley's Comet or Comet Halley is the best-known of the short-period comets, and is visible from Earth every 75 to 76 years. Halley is the only short-period comet that is clearly visible to the naked eye from Earth, and thus the only naked-eye comet that might appear twice in a human lifetime...

 on their early March comet rendezvous missions (see Halley Armada
Halley Armada
The Halley Armada is the generally accepted and popularly used name of five space probes sent to examine Halley's Comet during its 1986 sojourn through the inner solar system, connected with apparition "1P/1982 U1"...

). ICE flew through the tail and its minimum distance to the comet nucleus was 28 million km (for comparison the Earth's minimum distance to Comet Halley in 1910 was 20.8 million km).

Heliospheric mission

An update to the ICE mission was approved by NASA in 1991. It defines a Heliospheric mission for ICE consisting of investigations of coronal mass ejections in coordination with ground-based observations, continued cosmic ray
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...

 studies, and the Ulysses probe
Ulysses probe
Ulysses is a decommissioned robotic space probe that was designed to study the Sun as a joint venture of NASA and the European Space Agency . The spacecraft was originally named Odysseus, because of its lengthy and indirect trajectory to near Solar distance...

. By May 1995 ICE was being operated with only a low duty cycle, with some support being provided by the Ulysses project for data analysis.

End of mission

On 1997-05-05, NASA ended the ICE mission, and ordered the probe shut down, with only a carrier signal left operating.

The ISEE-3/ICE downlink bit rate was nominally 2048 bit/s during the early part of the mission, and 1024 bit/s during the Giacobini-Zinner comet encounter. The bit rate then successively dropped to 512 bit/s (on 1985-12-09), 256 bit/s (on 1987-01-05), 128 bit/s (on 1989-01-24) and finally to 64 bit/s (on 1991-12-27).

As of January 1990, ICE was in a 355-day heliocentric orbit
Heliocentric orbit
A 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...

 with an aphelion of 1.03 AU, a perihelion of 0.93 AU and an inclination of 0.1 degree. It may be possible to capture the spacecraft in 2014, when it again makes a close approach to Earth. If the craft is recovered, it has already been donated by NASA to the Smithsonian Institution
Smithsonian Institution
The Smithsonian Institution is an educational and research institute and associated museum complex, administered and funded by the government of the United States and by funds from its endowment, contributions, and profits from its retail operations, concessions, licensing activities, and magazines...

.

Reactivation

In 1999, NASA made brief contact with ICE to verify its carrier signal.

On 2008-09-18, NASA, with the help of KinetX
KinetX
KinetX, Inc. is a privately held Tempe, Arizona based engineering, technology, software development and business consulting firm specializing in aerospace systems...

, successfully located and reactivated ICE using the Deep Space Network
Deep Space Network
The Deep Space Network, or DSN, is a world-wide network of large antennas and communication facilities that supports interplanetary spacecraft missions. It also performs radio and radar astronomy observations for the exploration of the solar system and the universe, and supports selected...

. A status check revealed that all but one of its 13 experiments were still functioning, and it still has enough propellant for 150 m/s of ΔV
Delta-v
In astrodynamics a Δv or delta-v is a scalar which takes units of speed. It is a measure of the amount of "effort" that is needed to change from one trajectory to another by making an orbital maneuver....

. NASA scientists are considering reusing the probe to observe additional comets in 2017 or 2018. Such a mission, however, would delay any attempt to capture the spacecraft until the 2040s
2040s
The 2040s decade will begin on January 1, 2040 and will end on December 31, 2049. It is the fifth decade of the 21st century and the 3rd millennium.- Notable predictions and known events :* Possible manned mission by NASA to Jupiter's moon, Callisto...

.

ISEE 1 and ISEE 2

ISEE 1 and ISEE 2 were launched on October 22, 1977 from Cape Canaveral by a Delta rocket, and both re-entered on September 26, 1987. ISEE 2, NSSDC ID: 1977-102B

External links

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