Ionospheric Connection Explorer

Ionospheric Connection Explorer
ICON (Explorer 96) satellite
NamesExplorer 96
ICON
Mission typeIonospheric research
OperatorUC Berkeley SSL / NASA
COSPAR ID2019-068A Edit this at Wikidata
SATCAT no.44628
Websiteicon.ssl.berkeley.edu
Mission duration2 years (planned)
5 years, 20 days
Spacecraft properties
SpacecraftExplorer XCVI
Spacecraft typeIonospheric Connection Explorer
BusLEOStar-2[1]
ManufacturerUniversity of California, Berkeley / Northrop Grumman
Launch mass288 kg (635 lb) [2]
DimensionsHeight: 193 cm (76 in) and 106 cm (42 in) of diameter [3]
Solar panel: 254 × 84 cm (100 × 33 in)
Power780 watts
Start of mission
Launch date11 October 2019, 02:00 UTC[4]
RocketPegasus XL (F44)
Launch siteCape Canaveral Skid Strip, Stargazer [5]
ContractorNorthrop Grumman
Entered serviceNovember 2019
End of mission
Last contact24 July 2024
Orbital parameters
Reference systemGeocentric orbit
RegimeLow Earth orbit
Perigee altitude575 km (357 mi)
Apogee altitude603 km (375 mi)
Inclination27.00°
Period97.00 minutes
Explorer program
← TESS (Explorer 95)
IXPE (Explorer 97) →

Ionospheric Connection Explorer (ICON)[6] was a satellite designed to investigate changes in the ionosphere of Earth, the dynamic region high in the 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.[6][7] It is part of NASA's Explorer program and is operated by University of California, Berkeley's Space Sciences Laboratory.[8] In July of 2024, the mission was declared lost after a loss of contact. [9]

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,[10] excluding launch costs.[11] The principal investigator of ICON is Thomas Immel at the University of California, Berkeley.[10][12]

ICON was originally scheduled to launch in June 2017 and was repeatedly delayed because of problems with its Pegasus XL 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.[13] ICON was successfully launched on 11 October 2019, at 02:00 UTC.[4]

Overview

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ICON's observational geometry, showing both in-situ and remote sensing of the ionosphere-thermosphere system.

ICON will perform a two-year mission to observe conditions in both the thermosphere and ionosphere.[10] ICON is equipped with four instruments: a Michelson interferometer, built by the United States Naval Research Laboratory (NRL), measures the winds and temperatures in the thermosphere; an ion drift meter, built by University of Texas at Dallas, measures the motion of charged particles in the ionosphere; and two ultraviolet imagers built at University of California, 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.[3] Improved understanding of this environment can help predict such events and improve satellite safety and design.[3]

Launch planning

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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.[14][15] ICON was originally scheduled to launch in June 2017, but was repeatedly delayed because of problems with its Pegasus XL launch vehicle. The launch vehicle was mated to its air-launch aircraft Stargazer for a launch attempt in June 2018.[5] 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.[14] The October 2018 launch from Florida was scheduled after an initial review of the avionics issues.[14] 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

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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:[16][17]

  • 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 (NRL), IVM at the University of Texas, and EUV and FUV were developed at the University of California, Berkeley.[16] MIGHTI measures wind speed and temperature between 90 km (56 mi) and 300 km (190 mi) in altitude.[18] 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.[18] The temperature measurements are done by photometeric observations with a CCD.[18] MIGHTI is designed to detect wind speeds as low as 16 km/h (9.9 mph), even though the spacecraft is traveling at over 23,000 km/h (14,000 mph) (to stay in orbit).[19]

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 [19]

The solar panel produces 780 watts,[2] but the observatory's power consumption ranges between 209 and 265 watts when in science mode.[3]

Mission Operations

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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.[20] The UCB MOC currently operates seven NASA satellites. ICON was placed into a 27.00° inclination orbit, and communications are through Tracking and Data Relay Satellite System (TDRSS), the orbiting NASA communications network. Ground contacts with ICON are performed mainly from the Berkeley Ground Station, an 11 m (36 ft) dish, with backup contacts out of Wallops Flight Facility (WFF), Virginia and Santiago, Chile.

Loss of Contact

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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.[21] On July 24, 2024, NASA declared the mission had ended. [22]

See also

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References

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  1. ^ "ICON: Exploring where Earth's Weather meets Space Weather" (PDF). University of California, Berkeley. Retrieved 4 February 2018.
  2. ^ a b ICON Factsheet Archived 24 October 2018 at the Wayback Machine, Northrop Grumman, Accessed: 24 October 2018
  3. ^ a b c d ICON, October 2018, NASA Public Domain This article incorporates text from this source, which is in the public domain.
  4. ^ a b NASA Launches Long-Delayed ICON Space Weather Satellite to Study Earth's Ionosphere, Amy Thompson, Space.com, 11 October 2019
  5. ^ a b Granath, Bob (21 September 2018). "NASA's ICON launch now targeted for October 26 - ICON Mission". NASA. Retrieved 21 September 2018. Public Domain This article incorporates text from this source, which is in the public domain.
  6. ^ a b "Ionospheric Connection Explorer". University of California, Berkeley.
  7. ^ "ICON Mission Overview". NASA. 31 March 2016. Archived from the original on 6 November 2017. Retrieved 4 February 2018. Public Domain This article incorporates text from this source, which is in the public domain.
  8. ^ Sanders, Robert (16 April 2013). "UC Berkeley selected to build NASA's next space weather satellite". Berkeley News. Retrieved 19 January 2016.
  9. ^ https://science.nasa.gov/science-research/heliophysics/nasas-icon-mission-ends-with-several-ionospheric-breakthroughs/
  10. ^ a b c Harrington, J. D. (5 April 2013). "NASA Selects Explorer Investigations for Formulation". NASA. Retrieved 6 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  11. ^ Leone, Dan (20 October 2015). "Heliophysics Small Explorer Solicitation Set for First Half of 2016". SpaceNews. Retrieved 21 October 2015.
  12. ^ "ICON Project Management". University of California, Berkeley. Retrieved 14 October 2017.
  13. ^ Bartels, Meghan (23 October 2018). "ICON of Delay? NASA, Northrop Grumman Postpone Earth Satellite Mission Yet Again". SPACE.com. Retrieved 9 March 2019.
  14. ^ a b c Gebhardt, Chris (5 October 2018). "Northrop Grumman Innovation Systems updates ICON launch status". NASASpaceFlight.com. Retrieved 26 October 2018.
  15. ^ Clark, Stephen (10 November 2017). "Launch of NASA ionospheric probe delayed to examine rocket issue". Spaceflight Now. Retrieved 26 October 2018.
  16. ^ a b "Ionospheric Connection Explorer (ICON) Satellite". Aerospace Technology. Retrieved 11 October 2018.
  17. ^ "ICON (Ionospheric Connection Explorer) - Satellite Missions". directory.eoportal.org. Archived from the original on 4 August 2019. Retrieved 11 October 2018.
  18. ^ a b c 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. Bibcode:2017SSRv..212..553E. doi:10.1007/s11214-017-0358-4. ISSN 0038-6308. PMC 6042234. PMID 30008488.
  19. ^ a b Frazier, Sarah (18 October 2018). "Counting Down to the Ionospheric Connection Explorer (ICON) Launch". SciTechDaily. Retrieved 26 October 2018.
  20. ^ Simon, Matt (17 October 2019). "UC Berkeley Was About to Launch a Satellite. Then PG&E Said It Was Cutting Power". Wired (San Francisco, Calif.). Wired. ISSN 1059-1028. Retrieved 19 October 2019.
  21. ^ "ICON Mission Out of Contact – ICON Mission". blogs.nasa.gov. 7 December 2022. Retrieved 9 December 2022.
  22. ^ https://science.nasa.gov/science-research/heliophysics/nasas-icon-mission-ends-with-several-ionospheric-breakthroughs/
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