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

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and transition region. The spacecraft consists of a

satellite bus A satellite bus (or spacecraft bus) is the main body and structural component of a satellite or spacecraft, in which the payload and all scientific instruments are held. Bus-derived satellites are less customized than specially-produced satelli ...

and

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

built by the

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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 imaging spectrometer, providing one image per second at 0.3-

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

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, tailed bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding ...

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 Sun's outermost atmospheric layer, the Stellar corona, corona. This Plasma (physics), plasma mostly consists of electrons, protons and alpha particles with kinetic energy betwee ...

. 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 radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

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 a ...

(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 graphics, raster image, or the smallest addressable element in a dot matrix display device. In most digital display devices, p ...

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 angle, angular extent of the observable world that is visual perception, 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 elec ...

(FoV) of 120 arcseconds. The far-ultraviolet channel covers 133.2-135.8 nm and 139.0-140.6 nm with an 0.04 nm resolution and an effective area of . The near-ultraviolet channel covers 278.5-283.5 nm with an 0.08 nm resolution and an effective area of . Slit-jaw imaging has four

passband A passband is the range of frequency, frequencies or wavelengths that can pass through a Filter (signal processing), filter. For example, a radio receiver contains a bandpass filter to select the frequency of the desired radio signal out of all t ...

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 multi ...

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

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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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* NASA

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* Space Sciences Laboratory,

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* Sydney Institute for Astronomy,

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* Center for Plasma Astrophysics,

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* Rutherford Appleton Laboratory *

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* National Astronomical Observatory of Japan *

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References

External links

Official website
at NASA Science
Official website
at NASA Goddard Space Flight Center
Official website
at Lockheed Martin Solar and Astrophysics Laboratory * 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