Interface Region Imaging Spectrograph (IRIS), also called Explorer 94 and SMEX-12, is a

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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 A chromosphere ("sphere of color") is the second layer of a star's atmosphere, located above the photosphere and below the solar transition region and corona. The term usually refers to the Sun's chromosphere, but not exclusively. In the S ...

and transition region. The spacecraft consists of a

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and

spectrometer A spectrometer () is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where th ...

built by the Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), and a telescope provided by the

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(SAO). IRIS is operated by LMSAL and NASA's

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. The satellite's instrument is a high-frame-rate ultraviolet

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, providing one image per second at 0.3

arcsecond A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

angular resolution and sub-

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spectral resolution. NASA announced, on 19 June 2009, that IRIS was selected from six Small Explorer mission candidates for further study, along with the Gravity and Extreme Magnetism (GEMS) space observatory.

Mission

IRIS is intended to advance Sun-Earth connection studies by tracing the flow of energy and plasma into the corona and

heliosphere The heliosphere is the magnetosphere, astrosphere and outermost atmospheric layer of the Sun. It takes the shape of a vast, bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interst ...

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 corona and the

solar wind The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the ...

. 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. File:IRIS observatory overview.png File:IRIS spectrograph assembly.png

Launch

The spacecraft arrived at

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, on 16 April 2013 and was successfully deployed from an Orbital L-1011 carrier aircraft flying over the Pacific Ocean at an altitude of , roughly 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 Pegasus-XL launch vehicle.

Experiment

Interface Region Imaging Spectrograph (IRIS)

The IRIS instrument is a multi-channel imaging spectrograph with a

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 radiati ...

telescope. IRIS obtains a spectra along a slit (1/3 arcsecond wide), and slit-jaw images. The

charge-coupled device A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are ...

(CCD) detectors has 1/6 arcsecond

pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the s ...

s. IRIS will have an effective

spatial resolution In physics and geosciences, the term spatial resolution refers to distance between independent measurements, or the physical dimension that represents a pixel of the image. While in some instruments, like cameras and telescopes, spatial resoluti ...

between 0.33 and 0.40 arcsecond and a maximum

field of view The field of view (FoV) is the extent of the observable world that is seen at any given moment. In the case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation. Humans a ...

(FoV) of 120 arcseconds. The far-ultraviolet channel covers 133.2-135.8 nm and 139.0-140.6 nm with a 4 nm resolution and an effective area of . The near-ultraviolet channel covers 278.5-283.5 nm with a 8 nm resolution and an effective area of . Slit-jaw imaging has four

passband A passband is the range of frequencies or wavelengths that can pass through a filter. For example, a radio receiver contains a bandpass filter to select the frequency of the desired radio signal out of all the radio waves picked up by its anten ...

s: 133.5 nm and 140.0 nm with a 4 nm bandpass each; and 279.6 nm and 283.1 nm with a 0.4 nm bandpass each. IRIS has a high data rate (0.7

Mbit/s In telecommunications, data-transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mul ...

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.

Science results

IRIS achieved first light on 17 July 2013. 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". On 31 October 2013, calibrated IRIS data and images were released on the project website. An open-access article describing the satellite and initial data was published in the journal ''Solar Physics''. 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. In 2019, IRIS detected tadpole like jets coming out from the Sun according to NASA. 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

IRIS team

Science and engineering team members include: * Lockheed Martin Solar and Astrophysics Laboratory * Lockheed Martin Sensing and Exploration Systems *

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* Institute for Theoretical Astrophysics,

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* High Altitude Observatory,

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* Stanford University * NASA

* NASA

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* Sydney Institute for Astronomy,

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* Center for Plasma Astrophysics, Catholic University of Leuven * Mullard Space Science Laboratory *

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* Max Planck Institute for Solar System Research *

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References

External links

IRIS website
by NASA
IRIS website
by NASA Goddard Space Flight Center
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 {{2013 in space Explorers Program Missions to the Sun Spectrographs Spacecraft launched in 2013 Solar space observatories Ultraviolet telescopes Articles containing video clips Spacecraft launched by Pegasus rockets