Ionospheric Connection Explorer
Artist's concept of ICON
|Mission type||Earth observation|
|Operator||UC Berkeley SSL / NASA|
|Mission duration||Planned: 2 years|
Elapsed: 1 year, 1 month, 13 days
|Manufacturer||UC Berkeley / Northrop Grumman|
|Launch mass||287 kg (633 lb)|
|Dimensions||Height: 193 cm x 106 cm diameter|
solar panel: 254 cm x 84 cm
|Start of mission|
|Launch date||11 October 2019 UTC|
|Launch site||Stargazer |
Cape Canaveral Skid Strip
|Perigee altitude||575 km (357 mi)|
The Ionospheric Connection Explorer (ICON) is a satellite designed to investigate changes in the Earth's ionosphere, 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, 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's Explorers program and is operated by UC Berkeley'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 rocket. 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 11 October 2019 (UTC).
ICON will perform a two-year mission to observe conditions in both the thermosphere and ionosphere. ICON is equipped with four instruments: a Michelson interferometer, built by the United States Naval Research Laboratory, measures the winds and temperatures in the thermosphere; an ion drift meter, built by UT Dallas, measures the motion of charged particles in the ionosphere; and two ultraviolet imagers built at UC Berkeley, observe the airglow 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 (ISS), fly through the ionosphere and can be affected by its changing electric and magnetic fields. The ionosphere also acts as a conduit for many communications signals, such as radio waves and the signals that make GPS systems work. The ionosphere is where space weather 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.
Upon initial completion and delivery of the ICON observatory in 2016, launch plans centered around the launch range at Kwajalein Atoll in the Pacific Ocean. ICON was originally scheduled to launch in June 2017, but was repeatedly delayed because of problems with its Pegasus XL rocket. The rocket was mated to its air-launch aircraft Stargazer 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 October 11, 2019 [UTC]. After an approximately month-long commissioning period, ICON will begin sending back its first science data in November.
The launch system has a good track record launching small science payloads for NASA, and had a successful launch in December 2016. The launch system has placed more than 80 satellites in low orbit since its first in 1990.
- 2017, Kwajalein Atoll, Pacific Ocean - delayed for investigation of separation systems
- June 2018, Kwajalein Atoll - delayed for noise in avionics systems
- October 2018, Cape Canaveral, FL - scrubbed for noise in avionics systems
- October 2019, Cape Canaveral, FL - successfully launched
Northrop Grumman's Pegasus XL rocket is carried aloft by the Stargazer aircraft to approximately 40,000 feet over the open ocean, where it is released and free-falls five seconds before igniting its first-stage rocket motor. The aircraft can also ferry the launch vehicle to different sites.
The launch was delayed multiple times after its original planned launch date in June 2017. The launch took place 11 October 2019 (UTC).
ICON carries four scientific instruments designed to image even the faintest plasma or airglow to build up a picture of the ionosphere's density, composition and structure. The complete instrument payload has a mass of 130 kg (290 lb) and are listed below:
- Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI)
- Ion Velocity Meter (IVM) is an ion drift meter
- Extreme Ultra-Violet (EUV), an imager
- Far Ultra-Violet (FUV), an imager
MIGHTI was developed at the United States Naval Research Laboratory, IVM at the University of Texas, and EUV and FUV were developed at the University of California. MIGHTI measures wind speed and temperature between 90 and 300 km in altitude. The velocity measurements are gathered by observing the Doppler shift in the red and green lines of atomic oxygen. 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 10 mph, even though the spacecraft would be traveling at over 14,000 mph (to stay in orbit).
IVM collects in situ data about ions in the local environment around the spacecraft, whereas EUV and FUV are cameras. EUV is designed to observe height and density of the daytime ionosphere, and detect the glow of oxygen.
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 UC Berkeley. The UCB MOC currently operates seven NASA satellites. ICON was placed into a 27-degree inclination orbit, and communications are through TDRSS, the orbiting NASA communications network. Ground contacts with ICON are performed mainly from the Berkeley Ground Station, an 11-meter dish, with backup contacts out of Wallops and Santiago.
- "ICON: Exploring where Earth's Weather meets Space Weather" (PDF). University of California, Berekeley. Retrieved 4 February 2018.
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- Englert, Christoph R.; Harlander, John M.; Brown, Charles M.; Marr, Kenneth D.; Miller, Ian J.; Stump, J. Eloise; Hancock, Jed; Peterson, James Q.; Kumler, Jay (20 April 2017). "Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI): Instrument Design and Calibration". Space Science Reviews. 212 (1–2): 553–584. doi:10.1007/s11214-017-0358-4. ISSN 0038-6308. PMC 6042234. PMID 30008488.
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Media related to Ionospheric Connection Explorer at Wikimedia Commons