 The IRIS satellite with solar arrays in deployed configuration and telescope front door closed | |
| Names | Explorer 94 IRIS SMEX-12 |
|---|---|
| Mission type | Heliophysics |
| Operator | NASA /Lockheed Martin |
| COSPAR ID | 2013-033A |
| SATCATno. | 39197 |
| Mission duration | 2 years (planned) 12 years, 7 months, 21 days(in progress) |
| Spacecraft properties | |
| Spacecraft | Explorer XCIV |
| Spacecraft type | Interface Region Imaging Spectrograph |
| Bus | IRIS |
| Manufacturer | Lockheed Martin |
| Launch mass | 200 kg (440 lb) |
| Start of mission | |
| Launch date | 28 June 2013, 02:27:46UTC |
| Rocket | Pegasus-XL (F42) |
| Launch site | Vandenberg,Stargazer |
| Contractor | Orbital Sciences Corporation |
| Orbital parameters | |
| Reference system | Geocentric orbit |
| Regime | Sun-synchronous orbit |
| Perigee altitude | 623 km (387 mi) |
| Apogee altitude | 665 km (413 mi) |
| Inclination | 97.90° |
| Period | 97.47 minutes |
| Instruments | |
| Interface Region Imaging Spectrograph (IRIS) | |
Explorer program | |
Interface Region Imaging Spectrograph (IRIS),[1] also calledExplorer 94 andSMEX-12,[2] is aNASA solar observation satellite. The mission was funded through theSmall Explorer program to investigate the physical conditions of the solar limb, particularly the interface region made up of thechromosphere andtransition region. The spacecraft consists of asatellite bus andspectrometer built by theLockheed Martin Solar and Astrophysics Laboratory (LMSAL), and a telescope provided by theSmithsonian Astrophysical Observatory (SAO). IRIS is operated by LMSAL and NASA'sAmes Research Center.
The satellite's instrument is a high-frame-rate ultravioletimaging spectrometer, providing one image per second at 0.3-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,[3] along with theGravity and Extreme Magnetism (GEMS) space observatory.[4]
IRIS is intended to advance Sun-Earth connection studies by tracing the flow of energy and plasma into the corona andheliosphere 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 thecorona and thesolar 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.[1]
The spacecraft arrived atVandenberg Air Force Base,California, on 16 April 2013 and was successfully deployed from anOrbital L-1011 carrier aircraft flying over the Pacific Ocean at an altitude of 12,000 m (39,000 ft), roughly 160 km (99 mi) 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 aPegasus-XL launch vehicle.[5][6][1]
The IRIS instrument is a multi-channel imaging spectrograph with a 19 cm (7.5 in)ultraviolet telescope. IRIS obtains a spectra along a slit (1/3 arcsecond wide), and slit-jaw images. Thecharge-coupled device (CCD) detectors has 1/6 arcsecondpixels. IRIS will have an effectivespatial resolution between 0.33 and 0.40 arcsecond and a maximumfield of view (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 2.8 cm2 (0.43 sq in). The near-ultraviolet channel covers 278.5-283.5 nm with an 0.08 nm resolution and an effective area of 0.3 cm2 (0.047 sq in).[7] Slit-jaw imaging has fourpassbands: 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 (0.7Mbit/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.[8]
IRIS achievedfirst light on 17 July 2013.[9] 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".[9] On 31 October 2013, calibrated IRIS data and images were released on the project website.[10] An open-access article describing the satellite and initial data was published in the journalSolar Physics.[11]
Data collected from the IRIS spacecraft has shown that the interface region of theSun 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.[12]
In 2019, IRIS detected tadpole like jets coming out from the Sun according to NASA.[13]
Science and engineering team members include:[10]
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