View source for Interface Region Imaging Spectrograph

{{Short description|NASA satellite of the Explorer program}}
{{Distinguish|text=[[Infrared Astronomical Satellite]] (IRAS)}}
{{Use American English|date=December 2021}}
{{Use dmy dates|date=January 2018}}
{{Infobox spaceflight
| name              = Interface Region Imaging Spectrograph
| names_list        = Explorer 94<br />IRIS<br />SMEX-12
| image             = IRIS spacecraft model.png
| image_caption     = Interface Region Imaging Spectrograph (Explorer 94) satellite
| image_size        = 300px

| mission_type      = [[Heliophysics]]
| operator          = [[NASA]] / [[Lockheed Martin]]
| COSPAR_ID         = 2013-033A
| SATCAT            = 39197
| website           = 
| mission_duration  = 2 years (planned)<br />{{time interval|27 June 2013 02:27:46|show=ymd|sep=,}} ''(in progress)''

| spacecraft        = Explorer XCIV
| spacecraft_type   = Interface Region Imaging Spectrograph
| spacecraft_bus    = IRIS
| manufacturer      = [[Lockheed Martin]]
| launch_mass       = {{cvt|200|kg}}
| dimensions        = 
| power             =

| launch_date       = 28 June 2013, 02:27:46 [[Coordinated Universal Time|UTC]]
| launch_rocket     = [[Northrop Grumman Pegasus|Pegasus-XL]] (F42)
| launch_site       = [[Vandenberg Space Force Base|Vandenberg]], ''[[Stargazer (aircraft)|Stargazer]]''
| launch_contractor = [[Orbital Sciences Corporation]]

| entered_service   = 
| deactivated       = 
| last_contact      = 
| decay_date        =

| orbit_reference   = [[Geocentric orbit]]
| orbit_regime      = [[Sun-synchronous orbit]]
| orbit_periapsis   = {{cvt|623|km}}
| orbit_apoapsis    = {{cvt|665|km}}
| orbit_inclination = 97.90°
| orbit_period      = 97.47 minutes
| apsis             = gee

| instruments       = Interface Region Imaging Spectrograph (IRIS)

| programme         = '''Explorer program'''
| previous_mission  = [[NuSTAR]] (Explorer 93)
| next_mission      = [[Gravity and Extreme Magnetism Small Explorer|GEMS]] (Explorer)
}}

'''Interface Region Imaging Spectrograph''' ('''IRIS'''),<ref name="Display"/> also called '''Explorer 94''' and '''SMEX-12''',<ref name=Explorer-satellites>{{cite web |url=https://nssdc.gsfc.nasa.gov/multi/explorer.html|title=NASA's Explorer Program Satellites|publisher=NASA|date=22 July 2019|access-date=12 December 2021}} {{PD-notice}}</ref> is a [[NASA]] solar observation satellite. The mission was funded through the [[Small Explorer program]] to investigate the physical conditions of the solar limb, particularly the interface region made up of the [[chromosphere]] and [[solar transition region|transition region]]. The spacecraft consists of a [[satellite bus]] and [[spectrometer]] built by the [[Lockheed Martin]] Solar and Astrophysics Laboratory (LMSAL), and a telescope provided by the [[Smithsonian Astrophysical Observatory]] (SAO). IRIS is operated by LMSAL and NASA's [[Ames Research Center]].

The satellite's instrument is a high-frame-rate ultraviolet [[imaging spectrometer]], providing one image per second at 0.3 [[Minute and second of arc|arcsecond]] angular resolution and sub-[[ångström]] spectral resolution.

NASA announced, on 19 June 2009, that IRIS was selected from six Small Explorer mission candidates for further study,<ref name="nasa20080529"/> along with the [[Gravity and Extreme Magnetism]] (GEMS) space observatory.<ref name="nasa20090619"/>

== Mission ==
IRIS is intended to advance Sun-Earth connection studies by tracing the flow of energy and plasma into the corona and [[heliosphere]] for which no suitable observations exist. To achieve this IRIS obtains a high-resolution UV spectra and images of the Sun's chromosphere, specifically on the non-thermal energy that creates the [[Stellar corona|corona]] and the [[solar wind]]. IRIS seeks to determine: (1) the types of non-thermal energy which dominate in the chromosphere and beyond; (2) the means by which the chromosphere regulates mass and energy supply to the corona and heliosphere; and, (3) how magnetic flux and matter rise through the lower solar atmosphere, and the role played by flux emergence in flares and mass ejections. To answer these questions, IRIS utilize a single instrument, a multi-channel imaging spectrograph.<ref name="Display">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2013-033A|title=Display: IRIS (Explorer 94) 2013-033A |publisher=NASA|date=28 October 2021|access-date=12 December 2021}} {{PD-notice}}</ref>

<gallery mode=packed heights=200px>
File:IRIS observatory overview.png
File:IRIS spectrograph assembly.png
</gallery>

== Launch ==
The spacecraft arrived at [[Vandenberg Space Force Base|Vandenberg Air Force Base]], [[California]], on 16 April 2013 and was successfully deployed from an [[Lockheed L-1011 TriStar|Orbital L-1011]] carrier aircraft flying over the Pacific Ocean at an altitude of {{cvt|12000|m}}, roughly {{cvt|160|km}} northwest of Vandenberg. The launch vehicle was dropped at 02:27:46 UTC on 28 June 2013 (7:27 p.m. PDT on 27 June 2013) by a [[Northrop Grumman Pegasus|Pegasus-XL]] launch vehicle.<ref name="nasa20130417"/><ref name="nasa20130628"/><ref name="Display"/>

== Experiment ==
=== Interface Region Imaging Spectrograph (IRIS) ===
The IRIS instrument is a multi-channel imaging spectrograph with a {{cvt|19|cm}} [[ultraviolet]] telescope. IRIS obtains a spectra along a slit (1/3 arcsecond wide), and slit-jaw images. The [[charge-coupled device]] (CCD) detectors has 1/6 arcsecond [[pixel]]s. IRIS will have an effective [[spatial resolution]] between 0.33 and 0.40 arcsecond and a maximum [[field of view]] (FoV) of 120 arcseconds. The far-ultraviolet channel covers 133.2-135.8&nbsp;nm and 139.0-140.6&nbsp;nm with an 0.04&nbsp;nm resolution and an effective area of {{cvt|2.8|cm2}}. The near-ultraviolet channel covers 278.5-283.5&nbsp;nm with an 0.08&nbsp;nm resolution and an effective area of {{cvt|0.3|cm2}}.<ref name="foo">{{cite web|url=https://iris.lmsal.com/documents/iris_csr_instrument.pdf|title=Interface Region Imaging Spectrograph (IRIS) Concept Study Report (CSR)|publisher=LMSAL|date=16 December 2008|access-date=20 April 2024}}</ref> Slit-jaw imaging has four [[passband]]s: 133.5&nbsp;nm and 140.0&nbsp;nm with a 4&nbsp;nm bandpass each; and 279.6&nbsp;nm and 283.1&nbsp;nm with a 0.4&nbsp;nm bandpass each. IRIS has a high data rate (0.7 [[Data-rate units|Mbit/s]] on average) so that the baseline cadence is 5 seconds for slit-jaw images and 1 second for six spectral windows, including rapid rastering to map solar regions.<ref name="Experiment1">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=2013-033A-01|title=Experiment: Interface Region Imaging Spectrograph (IRIS)|publisher=NASA|date=28 October 2021|access-date=12 December 2021}} {{PD-notice}}</ref>

== Science results ==

IRIS achieved [[first light (astronomy)|first light]] on 17 July 2013.<ref name="firstlight"/> NASA noted that "IRIS's first images showed a multitude of thin, fibril-like structures that have never been seen before, revealing enormous contrasts in density and temperature occur throughout this region even between neighboring loops that are only a few hundred miles apart".<ref name="firstlight"/> On 31 October 2013, calibrated IRIS data and images were released on the project website.<ref name="lmsal"/> An open-access article describing the satellite and initial data was published in the journal ''Solar Physics''.<ref name="DePontieu2014a"/>

Data collected from the IRIS spacecraft has shown that the interface region of the [[Sun]] is significantly more complex than previously thought. This includes features described as solar heat bombs, high-speed plasma jets, nano-flares, and mini-tornadoes. These features are an important step in understanding the transfer of heat to the corona.<ref name="DePontieu2014b"/>

In 2019, IRIS detected tadpole like jets coming out from the Sun according to NASA.<ref>{{cite web|url=http://www.nasa.gov/feature/goddard/2019/solar-tadpole-like-jets-seen-with-nasa-s-iris-add-new-clue-to-age-old-mystery|title=Tadpole-Like Jets From Sun Add New Clue to Age-Old Mystery|publisher=NASA|date=2019-02-19|access-date=2019-04-10}} {{PD-notice}}</ref>

<gallery mode="packed" heights="200">
A Slice of Light How IRIS Observes the Sun.webm|Video of IRIS data from a solar flare on 11 March 2015
Iris-sdo-x1.6-20140910.jpg|X-class solar flare on Sept. 10, 2014
Iris 20150428 100823 0.gif|IRIS captured several large solar prominences on the edge of the Sun
IRIS Image of Sun dec 2013.jpg|IRIS view above the Sun's surface extending well out into the solar atmosphere
</gallery>

== IRIS team ==
Science and engineering team members include:<ref name="lmsal"/>
* [[Lockheed Martin Solar and Astrophysics Laboratory]]
* Lockheed Martin Sensing and Exploration Systems
* [[Smithsonian Astrophysical Observatory]]
* [[Montana State University]]
* Institute for Theoretical Astrophysics, [[University of Oslo]]
* High Altitude Observatory, [[National Center for Atmospheric Research]]
* [[Stanford University]]
* NASA [[Ames Research Center]]
* NASA [[Goddard Space Flight Center]]
* [[National Solar Observatory]]
* [[Space Sciences Laboratory]], [[University of California, Berkeley]]
* [[Princeton Plasma Physics Laboratory]]
* Sydney Institute for Astronomy, [[University of Sydney]]
* Center for Plasma Astrophysics, [[Katholieke Universiteit Leuven|Catholic University of Leuven]]
* [[Mullard Space Science Laboratory]]
* [[Rutherford Appleton Laboratory]]
* [[European Space Agency]]
* [[Max Planck Institute for Solar System Research]]
* [[National Astronomical Observatory of Japan]]
* [[Niels Bohr Institute]], [[University of Copenhagen]]

== See also ==
{{Portal|Spaceflight}}
* [[Explorer program]]

== References ==
{{Reflist|refs=

<ref name="nasa20080529">{{cite news|url=http://www.nasa.gov/home/hqnews/2008/may/HQ_C08029_SMEX_Awards.html|title=NASA Selects Small Explorer Investigations for Concept Studies|publisher=NASA|first=J. D. |last=Harrington|date=29 May 2008}} {{PD-notice}}</ref>

<ref name="nasa20090619">{{cite news|url=http://www.nasa.gov/home/hqnews/2009/jun/HQ_09-141_SMEX_Selections.html|title=NASA Awards Two Small Explorer Development Contracts|publisher=NASA|first=J. D. |last=Harrington|date=19 June 2009}} {{PD-notice}}</ref>

<ref name="nasa20130417">{{cite news|url=http://www.nasa.gov/mission_pages/iris/news/arrives-vafb.html|title=NASA'S Newest Solar Satellite Arrives at Vandenberg AFB for Launch|publisher=NASA|first1=Susan|last1=Hendrix|first2=George|last2=Diller|date=17 April 2013|access-date=18 April 2013|archive-date=3 July 2013|archive-url=https://web.archive.org/web/20130703025340/http://www.nasa.gov/mission_pages/iris/news/arrives-vafb.html|url-status=dead}} {{PD-notice}}</ref>

<ref name="nasa20130628">{{cite web|url=http://www.nasa.gov/content/iris-solar-observatory-launches-begins-mission/|title=IRIS Solar Observatory Launches, Begins Mission|publisher=NASA|date=28 June 2013}} {{PD-notice}}</ref>

<ref name="firstlight">{{cite news|url=http://www.nasa.gov/content/goddard/iris-telescope-first-glimpse-of-suns-mysterious-atmosphere/index.html|title=NASA's IRIS Telescope Offers First Glimpse of Sun's Mysterious Atmosphere|publisher=NASA|first=Karen C.|last=Fox|date=25 July 2013|access-date=29 July 2013|archive-date=10 September 2015|archive-url=https://web.archive.org/web/20150910093524/http://www.nasa.gov/content/goddard/iris-telescope-first-glimpse-of-suns-mysterious-atmosphere/index.html|url-status=dead}} {{PD-notice}}</ref>

<ref name="lmsal">{{cite web|url=http://iris.lmsal.com/|title=Interface Region Imaging Spectrograph|publisher=Lockheed Martin Solar and Astrophysics Laboratory}}</ref>

<ref name="DePontieu2014a">{{cite journal|title=The Interface Region Imaging Spectrograph (IRIS)|journal=Solar Physics |first1=B.|last1=De Pontieu|first2=A. M.|last2=Title|first3=J.|last3=Lemen |first4=G. D.|last4=Kushner|first5=D. J.|last5=Akin|first6=B.|last6=Allard|first7=T.|last7=Berger|first8=P.|last8=Boerner|first9=M.|last9=Cheung|first10=C.|last10=Chou|last11=Drake|first11=J. F.|last12=Duncan |first12=D. W.|last13=Freeland|first13=S.|last14=Heyman|first14=G. F.|last15=Hoffman|first15=C.|last16=Hurlburt|first16=N. E.|last17=Lindgren|first17=R. W.|last18=Mathur|first18=D.|last19=Rehse|first19=R. |last20=Sabolish|first20=D.|last21=Seguin|first21=R.|last22=Schrijver|first22=C. J.|last23=Tarbell|first23=T. D.|last24=Wülser|first24=J.-P.|last25=Wolfson|first25=C. J.|last26=Yanari|first26=C.|last27=Mudge |first27=J.|last28=Nguyen-Phuc|first28=N.|last29=Timmons|first29=R.|last30=van Bezooijen|first30=R.|display-authors=5|volume=289|issue=7|pages=2733–2779|date=July 2014|arxiv=1401.2491 |bibcode=2014SoPh..289.2733D|doi=10.1007/s11207-014-0485-y|s2cid=53596913}}</ref>

<ref name="DePontieu2014b">{{cite journal|title=On the prevalence of small-scale twist in the solar chromosphere and transition region|journal=Science |first1=B.|last1=De Pontieu|first2=L. |last2=Rouppe van der Voort|first3=S. W.|last3=McIntosh|first4=T. M. D.|last4=Pereira|first5=M.|last5=Carlsson|first6=V.|last6=Hansteen|first7=H.|last7=Skogsrud|first8=J.|last8=Lemen|first9=A. M.|last9=Title |first10=P.|last10=Boerner|first11=N.|last11=Hurlburt|first12=T. D.|last12=Tarbell|first13=J. P.|last13=Wuelser|first14=E. E.|last14=De Luca|first15=L.|last15=Golub|first16=S.|last16=McKillop|first17=K. |last17=Reeves|first18=S.|last18=Saar|first19=P.|last19=Testa|first20=H.|last20=Tian|first21=C.|last21=Kankelborg|first22=S.|last22=Jaeggli|first23=L.|last23=Kleint|first24=J.|last24=Martinez-Sykora|display-authors=5|volume=346|issue=6207|page=1255732|date=October 2014|arxiv=1410.6862|bibcode=2014Sci...346D.315D|doi=10.1126/science.1255732|pmid=25324398|s2cid=51601695}}</ref>
}}

== External links ==
{{Commons category|IRIS (satellite)}}

* [https://www.nasa.gov/iris IRIS website] by NASA
* [https://iris.gsfc.nasa.gov/ IRIS website] by NASA Goddard Space Flight Center
* [http://iris.lmsal.com/ IRIS website] by Lockheed Martin
* De Pontieu, B., Title, A.M., Lemen, J.R. et al. The Interface Region Imaging Spectrograph (IRIS) ''Sol Phys'' 289, 2733–2779 (2014) https://doi.org/10.1007/s11207-014-0485-y
* De Pontieu, B., Polito, V., Hansteen, V. et al. A New View of the Solar Interface Region from the Interface Region Imaging Spectrograph (IRIS) ''Sol Phys'' 296, 84 (2021) https://doi.org/10.1007/s11207-021-01826-0

{{Explorer program}}
{{Sun spacecraft}}
{{Space observatories}}
{{Orbital launches in 2013}}
{{2013 in space}}

[[Category:Explorers Program]]
[[Category:Missions to the Sun]]
[[Category:Spectrographs]]
[[Category:Spacecraft launched in 2013]]
[[Category:Solar space observatories]]
[[Category:Ultraviolet telescopes]]
[[Category:Articles containing video clips]]
[[Category:Spacecraft launched by Pegasus rockets]]