Ionospheric Connection Explorer (ICON) is a satellite designed to investigate changes in the

ionosphere The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays ...

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

, the dynamic region high in our atmosphere where terrestrial weather from below meets space weather from above. ICON studies the interaction between Earth's weather systems and space weather driven by the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

, and how this interaction drives turbulence in the upper atmosphere. It is hoped that a better understanding of this dynamic will mitigate its effects on communications, GPS signals, and technology in general. It is part of

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...

Explorer program The Explorers program is a NASA exploration program that provides flight opportunities for physics, geophysics, heliophysics, and astrophysics investigations from space. Launched in 1958, Explorer 1 was the first spacecraft of the United Stat ...

and is operated by

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant un ...

's Space Sciences Laboratory. On 12 April 2013, NASA announced that ICON, along with Global-scale Observations of the Limb and Disk (GOLD), had been selected for development with the cost capped at US$200 million, excluding launch costs. The principal investigator of ICON is Thomas Immel at the University of California, Berkeley. ICON was originally scheduled to launch in June 2017 and was repeatedly delayed because of problems with its

Pegasus XL Pegasus is an Air launch to orbit, air-launched launch vehicle developed by Orbital Sciences Corporation (OSC) and now built and launched by Northrop Grumman. Capable of carrying small payloads of up to into low Earth orbit, Pegasus first fl ...

launch vehicle. It was next due to launch on 26 October 2018 but the launch was rescheduled to 7 November 2018, and postponed again just 28 minutes before launch. ICON was successfully launched on 11 October 2019, at 02:00 UTC.

Overview

ICON will perform a two-year mission to observe conditions in both the

thermosphere The thermosphere is the layer in the Earth's atmosphere directly above the mesosphere and below the exosphere. Within this layer of the atmosphere, ultraviolet radiation causes photoionization/photodissociation of molecules, creating ions; the ...

and

. ICON is equipped with four instruments: a

Michelson interferometer The Michelson interferometer is a common configuration for optical interferometry and was invented by the 19/20th-century American physicist Albert Abraham Michelson. Using a beam splitter, a light source is split into two arms. Each of those ...

, built by the

United States Naval Research Laboratory The United States Naval Research Laboratory (NRL) is the corporate research laboratory for the United States Navy and the United States Marine Corps. It was founded in 1923 and conducts basic scientific research, applied research, technological ...

(NRL), measures the winds and temperatures in the thermosphere; an

ion drift meter An ion drift meter is a device used to measure the velocity of individual ions in the area of a spacecraft. This information can then be used to calculate the ion drift in the space surrounding the instrument as well as the strength of an electric f ...

, built by

University of Texas at Dallas The University of Texas at Dallas (UTD or UT Dallas) is a public research university in Richardson, Texas. It is one of the largest public universities in the Dallas area and the northernmost institution of the University of Texas system. It w ...

, measures the motion of

charged particle In physics, a charged particle is a particle with an electric charge. It may be an ion, such as a molecule or atom with a surplus or deficit of electrons relative to protons. It can also be an electron or a proton, or another elementary pa ...

s in the ionosphere; and two

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...

imagers built at

, observe the

airglow Airglow (also called nightglow) is a faint emission of light by a planetary atmosphere. In the case of Earth's atmosphere, this optical phenomenon causes the night sky never to be completely dark, even after the effects of starlight and diffu ...

layers in the upper atmosphere in order to determine both ionospheric and thermospheric density and composition. Many low-Earth orbiting satellites, including the

International Space Station The International Space Station (ISS) is the largest Modular design, modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos ( ...

(ISS), fly through the ionosphere and can be affected by its changing electric and

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

s. The ionosphere also acts as a conduit for many communications signals, such as

radio wave Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz ( GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (sho ...

s and the signals that make GPS systems work. The ionosphere is where

space weather Space weather is a branch of space physics and aeronomy, or heliophysics, concerned with the time varying conditions within the Solar System, including the solar wind, emphasizing the space surrounding the Earth, including conditions in the ...

manifests, creating unexpected conditions; electric currents can cause electrical charging of satellites, changing density can affect satellite orbits, and shifting magnetic fields can induce current in power systems, causing strain, disrupting communications and navigation or even triggering blackouts. Improved understanding of this environment can help predict such events and improve satellite safety and design.

Launch planning

Upon initial completion and delivery of the ICON observatory in 2016, launch plans centered around the launch range at

Kwajalein Atoll Kwajalein Atoll (; Marshallese: ) is part of the Republic of the Marshall Islands (RMI). The southernmost and largest island in the atoll is named Kwajalein Island, which its majority English-speaking residents (about 1,000 mostly U.S. civilia ...

in the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...

. ICON was originally scheduled to launch in June 2017, but was repeatedly delayed because of problems with its

launch vehicle. The launch vehicle was mated to its air-launch aircraft

Stargazer Stargazer may refer to: * an observational astronomer, particularly an amateur Aerospace * Stargazer (aircraft), a Lockheed L-1011 airliner used to launch the Pegasus rocket * Orbiting Astronomical Observatory 2, nicknamed Stargazer, the first ...

for a launch attempt in June 2018. This launch was cancelled days before because the rocket showed issues on the first leg of the ferry flight to Kwajalein. Given the availability of the launch range in Cape Canaveral, and a review of the suitability of this site, it was adopted as the ICON launch site. The October 2018 launch from Florida was scheduled after an initial review of the avionics issues. Whereas the delays in 2017 were due to concerns with rocket-payload and fairing separation systems, the 2018 delays were due to noise in the rocket avionics systems. The issues resulted finally in the 2018 Cape Canaveral launch being scrubbed minutes before the scheduled launch. These issues were ultimately resolved and ICON launched from Cape Canaveral on 11 October 2019 at 02:00 UTC. After an approximately month-long commissioning period, ICON began sending back its first science data in November 2019.

Science payload

''ICON'' carries four scientific instruments designed to image even the faintest plasma or

to build up a picture of the ionosphere's density, composition and structure. The complete instrument payload has a mass of and are listed below: *

Michelson Interferometer The Michelson interferometer is a common configuration for optical interferometry and was invented by the 19/20th-century American physicist Albert Abraham Michelson. Using a beam splitter, a light source is split into two arms. Each of those ...

for Global High-Resolution Thermospheric Imaging (MIGHTI) * Ion Velocity Meter (IVM) is an

* Extreme Ultra-Violet (EUV), an imager * Far Ultra-Violet (FUV), an imager MIGHTI was developed at the

(NRL), IVM at the

University of Texas The University of Texas at Austin (UT Austin, UT, or Texas) is a public research university in Austin, Texas. It was founded in 1883 and is the oldest institution in the University of Texas System. With 40,916 undergraduate students, 11,075 ...

, and EUV and FUV were developed at the

. MIGHTI measures wind speed and temperature between and in

altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...

. The velocity measurements are gathered by observing the

Doppler shift The Doppler effect or Doppler shift (or simply Doppler, when in context) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who ...

in the red and green lines of

atomic oxygen There are several known allotropes of oxygen. The most familiar is molecular oxygen (O2), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (O3). Others are ...

. This is done with the Doppler Asymmetric Spatial Heterodyne (DASH) which uses échelle gratings. The temperature measurements are done by photometeric observations with a CCD. MIGHTI is designed to detect wind speeds as low as , even though the spacecraft is traveling at over (to stay in orbit). IVM collects ''in situ'' data about ions in the local environment around the spacecraft, whereas EUV and FUV are spectrographic imagers. EUV is a 1-dimension limb imager designed to observe height and density of the daytime ionosphere by detecting the glow of oxygen ions and other species at wavelengths between 55 and 85 nm. FUV is a 2-dimension imager that observes the limb and below at 135 and 155 nm, where bright emissions of atomic oxygen and molecular nitrogen are found The solar panel produces 780

watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...

s, but the observatory's power consumption ranges between 209 and 265 watts when in science mode.

Mission Operations

Once launched, and for the duration of its two-year science mission, the ICON observatory is controlled and operated by the Mission Operations Center (MOC) at the Space Sciences Laboratory at University of California, Berkeley. The UCB MOC currently operates seven NASA satellites. ICON was placed into a 27.00°

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Ea ...

orbit, and communications are through

Tracking and Data Relay Satellite System The U.S. Tracking and Data Relay Satellite System (TDRSS) is a network of American communications satellites (each called a tracking and data relay satellite, TDRS) and ground stations used by NASA for space communications. The system was desig ...

(TDRSS), the orbiting NASA communications network. Ground contacts with ICON are performed mainly from the Berkeley Ground Station, an dish, with backup contacts out of

Wallops Flight Facility Wallops Flight Facility (WFF) is a rocket launch site on Wallops Island on the Eastern Shore of Virginia, United States, just east of the Delmarva Peninsula and approximately north-northeast of Norfolk. The facility is operated by the Godda ...

(WFF),

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth are ...

and

Santiago Santiago (, ; ), also known as Santiago de Chile, is the capital and largest city of Chile as well as one of the largest cities in the Americas. It is the center of Chile's most densely populated region, the Santiago Metropolitan Region, whos ...

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...

Loss of Contact

The NASA ICON team lost contact with the ICON spacecraft on 25 November 2022. A fail-safe system designed to reset the spacecraft computer after 8 days with no receipt of commands from the ground failed to restore communications after it elapsed on 5 December 2022.

References

External links

ICON website
by NASA
ICON website
by University of California, Berkeley {{Orbital launches in 2019 Spacecraft launched in 2019 Explorers Program NASA satellites orbiting Earth 2019 in the United States Earth observation satellites of the United States Spacecraft launched by Pegasus rockets Geospace monitoring satellites