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Solar Maximum Mission
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<h2 id="instruments">Instruments</h2> Experiments on board the Solar Maximum Mission<table><tbody><tr><th>Name</th><th>Target</th><th>Principal Investigator</th></tr><tr><td><a href="/facts/Coronagraph/ggUUrlYY">Coronagraph</a>/Polarimeter: 446.5–658.3 nm, 1.5- 6 sq.solar radii <a href="/facts/Field_of_view/Xp1G4CXF">fov</a>, 6.4 arcsec res.</td><td>Solar corona, prominences, and flares</td><td>House, Lewis L., <a href="/facts/High_Altitude_Observatory/WxdUqcjA">High Altitude Observatory</a></td></tr><tr><td>Ultraviolet Spectrometer and polarimeter 175.0–360.0 nm raster imager, 0.004 nm sp.res.</td><td>Solar UV, <a href="/facts/Earth/HLLmDfj0">Earth</a>'s <a href="/facts/Atmosphere/oUpLaGRF">atmosphere</a></td><td><a href="/facts/Einar_Tandberg-Hanssen/aMRXvlAJ">Tandberg-Hanssen, Einar A.</a>, <a href="/facts/NASA/TIMCV0yV">NASA</a> <a href="/facts/Marshall_Space_Flight_Center/Q5XqseqT">Marshall Space Flight Center</a></td></tr><tr><td>Soft X-ray Polychromator: raster imager, crystal spectrom. in parts of 0.14–2.25 nm</td><td>Solar flares, active solar regions</td><td><a href="/facts/Loren_Acton/GDypS7KL">Acton, Loren W.</a>, <a href="/facts/Lockheed_Corporation/FymLE6jf">Lockheed Palo Alto</a>, Culhane, J <a href="/facts/University_College,_London/7dmHhCf5">University College, London</a>, Leonard, Gabriel, Alan-Henri, <a href="/facts/Rutherford_Appleton_Laboratory/LuHVhXIE">Rutherford Appleton Laboratory</a></td></tr><tr><td>Hard X-ray Imaging Spectrometer: <a href="/facts/Field_of_view/Xp1G4CXF">fov</a> 6.4 arcmin, 8 or 32 arcsec res, 3.5–30 keV</td><td>Solar active regions and flares</td><td><a href="/facts/Cornelis_de_Jager/NPCx8tlJ">de Jager, Cornelis</a>, <a href="/facts/University_of_Utrecht/SfvqmD0l">University of Utrecht</a></td></tr><tr><td>Hard X-ray Burst Spectrometer: CsI(Na), 15 energy channels covering 20–260 keV</td><td>Solar flares and active regions</td><td><a href="/facts/Kenneth_John_Frost/NQz326lR">Frost, Kenneth J.</a>, <a href="/facts/NASA_Goddard_Space_Flight_Center/WfoEKknM">NASA Goddard Space Flight Center</a></td></tr><tr><td>Gamma-ray Spectrometer: NaI(T1),0.01-100 MeV in 476 channels, 16.4 s per spectrum</td><td>solar gamma-rays</td><td>Chupp, Edward L, <a href="/facts/University_of_New_Hampshire/RDqRkwTA">University of New Hampshire</a></td></tr><tr><td>Active Cavity Radiometer Irradiance Monitor: 0.001-1000 micrometer solar flux</td><td>solar irradiance</td><td>Willson, Richard C, <a href="/facts/NASA_Jet_Propulsion_Laboratory/zPXnxRBf">NASA Jet Propulsion Laboratory</a></td></tr></tbody></table> <h2 id="failure-and-repair">Failure and repair</h2> <p>The white-light coronagraph/polarimeter (C/P) took coronal images for about six months from March 1980 before suffering an electronics failure in September that prevented operation.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> </p><p>In November 1980, the second of four fuses in SMM's <a href="/facts/Spacecraft_attitude_control/hE6aMu26">attitude control</a> system failed, causing it to rely on its <a href="/facts/Magnetorquers/oNkUX0wf">magnetorquers</a> in order to maintain attitude. In this mode, only three of the seven instruments on board were usable, as the others required the satellite to be accurately pointed at the Sun. The use of the satellite's magnetorquers prevented the satellite from being used in a stable position and caused it to "wobble" around its nominally sun-pointed attitude.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> SMM was left in standby mode for 3 years.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p><p>The first orbiting, uncrewed satellite to be repaired in space, SMM was notable in that its useful life compared with similar <a href="/facts/Spacecraft/YQqQaUw0">spacecraft</a> was significantly increased by the direct intervention of a crewed space mission. During <a href="/facts/STS-41-C/9CydS6Rc">STS-41-C</a> in April 1984, the <a href="/facts/Space_Shuttle_Challenger/K4dGtVCC">Space Shuttle <i>Challenger</i></a> rendezvoused with the SMM, astronauts <a href="/facts/James_van_Hoften/cfBJWd7V">James van Hoften</a> and <a href="/facts/George_Nelson_(astronaut)/r17u6X7G">George Nelson</a> attempted to use the <a href="/facts/Manned_Maneuvering_Unit/TgFMp6FV">Manned Maneuvering Unit</a> to capture the satellite and to bring it into the orbiter's payload bay for repairs and servicing. The plan was to use an astronaut-piloted Maneuvering Unit to grapple the satellite with the Trunnion Pin Attachment Device (TPAD) mounted between the hand controllers of the Maneuvering Unit, null its rotation rates, and allow the Shuttle to bring it into the Shuttle's payload bay for stowage. Three attempts to grapple the satellite using the TPAD failed. The TPAD jaws could not lock onto Solar Max because of an obstructing grommet on the satellite not included in its blueprints. </p><p>This led to an improvised plan which nearly ended the satellite's mission. The improvisation had the astronaut use his hands to grab hold of a solar array and null the rotation with a push from the Maneuvering Unit's thrusters. Instead, this attempt induced higher rates and in multiple axes; the satellite was tumbling out of control and quickly losing battery life. SMM Operations Control Center engineers shut down all non-essential satellite subsystems and with a bit of luck were able to recover the satellite minutes before total failure. The ground support engineers then stabilized the satellite and nulled its rotation rates for capture with the <a href="/facts/SRMS/zzemGb81">Shuttle's robotic arm</a>. This proved to be a much better plan. The satellite had been fitted with one of the arm's <a href="/facts/Grapple_fixture/rt33fQEq">grapple fixtures</a> so that the robotic arm was able to capture and maneuver it into the shuttle's payload bay for repairs.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p><p>During the mission, the SMM's entire attitude control system module and the electronics module for the coronagraph/polarimeter instrument were replaced, and a gas cover was installed over the X-ray polychromator.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> Their successful work added five more years to the lifespan of the satellite. The mission was depicted in the 1985 <a href="/facts/IMAX/ox5Y9EsB">IMAX</a> movie <i><a href="/facts/The_Dream_Is_Alive/5hqDq7oN">The Dream Is Alive</a></i>. </p> <h2 id="discovery-of-comets">Discovery of comets</h2> <p>10 comets were discovered in images from the SMM, all of which are members of the <a href="/facts/Kreutz_sungrazer/DS5MAJ9l">Kreutz sungrazer</a> group.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a><a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p> <table><tbody><tr><th>Designation</th><th>Alternate</th><th>Observation date</th><th>Discoverer</th><th>Ref</th></tr><tr><td>C/1987 T2 (SMM-1)</td><td>-</td><td>1987-Oct-05</td><td>O. C. St. Cyr</td><td><a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a></td></tr><tr><td>C/1987 U4 (SMM-2)</td><td>-</td><td>1987-Oct-17</td><td>O. C. St. Cyr</td><td><a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a></td></tr><tr><td>C/1988 M1 (SMM-3)</td><td>1988l</td><td>1988-Jun-27</td><td>O. C. St. Cyr</td><td><a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a></td></tr><tr><td>C/1988 Q1 (SMM-4)</td><td>1988m</td><td>1988-Aug-21</td><td>D. KobeC. Waugh</td><td><a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a></td></tr><tr><td>C/1988 T1 (SMM-5)</td><td>1988n</td><td>1988-Oct-11</td><td>O.C. St. Cyr</td><td><a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a><a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a></td></tr><tr><td>C/1988 U1 (SMM-7)</td><td>1988q</td><td>1988-Oct-24</td><td>A. L. Stanger</td><td><a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a><a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a></td></tr><tr><td>C/1988 W1 (SMM-6)</td><td>1988p</td><td>1988-Nov-18</td><td>O.C. St. Cyr</td><td><a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a><a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a></td></tr><tr><td>C/1989 L1 (SMM-8)</td><td>1989m</td><td>1989-Jun-02</td><td>O.C. St. CyrD. L. Kobe</td><td><a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a><a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a></td></tr><tr><td>C/1989 N3 (SMM-9)</td><td>1989q</td><td>1989-Jul-08</td><td>O.C. St. Cyr</td><td><a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a><a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a></td></tr><tr><td>C/1989 S1 (SMM-10)</td><td>1989x</td><td>1989-Sep-28</td><td>O.C. St. Cyr</td><td><a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a><a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a></td></tr></tbody></table> <h2 id="findings">Findings</h2> <p>Significantly, the SMM's ACRIM instrument package showed that contrary to expectations, the Sun is actually brighter during the <a href="/facts/Sunspot/7E8cWSGl">sunspot</a> cycle maximum (when the greatest number of dark 'sunspots' appear). This is because sunspots are surrounded by bright features called <a href="/facts/Solar_facula/gABrlqBC">faculae</a>, which more than cancel the darkening effect of the sunspot. </p><p>The major scientific findings from the SMM are presented in several review articles in a monograph.<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a> </p> <h2 id="end-of-mission">End of mission</h2> <p>SMM's orbit slowly decayed due to atmospheric drag taking it down into denser regions. The <a href="/facts/March_1989_geomagnetic_storm/9UTmIHXS">March 1989 geomagnetic storm</a> was reported to have led to SMM dropping half a kilometre at the start of the storm and 5 kilometres over the whole period.<a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> The satellite eventually lost attitude control on November 17, 1989, and re-entry and burn-up occurred on December 2, 1989, over the Indian Ocean.<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> </p> <h2 id="see-also">See also</h2> <ul> <li>Spaceflight portal</li></ul> <ul><li><a href="/facts/List_of_heliophysics_missions/cBreIYaY">List of heliophysics missions</a> <ul><li><a href="/facts/Advanced_Composition_Explorer/LyrvNMgF">Advanced Composition Explorer</a></li> <li><a href="/facts/Parker_Solar_Probe/MDCAJsnl">Parker Solar Probe</a></li> <li><a href="/facts/Solar_and_Heliospheric_Observatory/vxkoDFAh">Solar and Heliospheric Observatory</a></li> <li><a href="/facts/Solar_Dynamics_Observatory/2vgpPzEt">Solar Dynamics Observatory</a></li> <li><a href="/facts/Solar_Orbiter/CQJEtpI0">Solar Orbiter</a></li> <li><a href="/facts/WIND_(spacecraft)/4zulP4LK">WIND (spacecraft)</a></li></ul></li> <li><a href="/facts/Charles_Hyder/gRMnEzNu">Charles Hyder</a></li></ul> <h2 id="external-links">External links</h2> Wikimedia Commons has media related to Solar Maximum Mission. <ul><li><a href="https://heasarc.gsfc.nasa.gov/docs/heasarc/missions/solarmax.html">HEASARC</a>, SMM</li> <li><a href="https://solarscience.msfc.nasa.gov/SMM.shtml">Marshall Space Flight Center</a> <a href="https://web.archive.org/web/20070524133217/http://solarscience.msfc.nasa.gov/SMM.shtml">Archived</a> 2007-05-24 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a>, SMM</li> <li><a href="https://web.archive.org/web/20080704071440/http://smm.hao.ucar.edu/smm/smmcp_cme.html">SMM C/P Coronal Mass Ejections</a></li> <li><a href="http://www.acrim.com">Total Solar Irradiance</a> <a href="https://web.archive.org/web/20170611210135/http://www.acrim.com/">Archived</a> 2017-06-11 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a> ACRIM</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>M. Suzuki (11 February 1999). "TOPEX/Poseidon – Description of Mission". University of Texas. Archived from the original on 20 November 2013. Retrieved 9 July 2013. <a href="https://web.archive.org/web/20131120234120/http://www.tsgc.utexas.edu/spacecraft/topex/mms.html" target="_blank">https://web.archive.org/web/20131120234120/http://www.tsgc.utexas.edu/spacecraft/topex/mms.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"Solar Maximum Mission (SMM)". hao.ucar.edu. National Center for Atmospheric Research. Retrieved 13 November 2024. <a href="https://www2.hao.ucar.edu/mlso/solar-maximum-mission" target="_blank">https://www2.hao.ucar.edu/mlso/solar-maximum-mission</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"Solar Maximum Mission (SMM)". hao.ucar.edu. National Center for Atmospheric Research. Retrieved 13 November 2024. <a href="https://www2.hao.ucar.edu/mlso/solar-maximum-mission" target="_blank">https://www2.hao.ucar.edu/mlso/solar-maximum-mission</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>"STS-41-C Press Kit" (PDF). NASA. March 1984. Retrieved 9 July 2013. <a href="https://www.nasa.gov/wp-content/uploads/2023/05/sts-41c-press-kit.pdf?emrc=b712fa" target="_blank">https://www.nasa.gov/wp-content/uploads/2023/05/sts-41c-press-kit.pdf?emrc=b712fa</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>"Solar Maximum Mission (SMM)". hao.ucar.edu. National Center for Atmospheric Research. Retrieved 13 November 2024. <a href="https://www2.hao.ucar.edu/mlso/solar-maximum-mission" target="_blank">https://www2.hao.ucar.edu/mlso/solar-maximum-mission</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>"STS-41-C Press Kit" (PDF). NASA. March 1984. Retrieved 9 July 2013. <a href="https://www.nasa.gov/wp-content/uploads/2023/05/sts-41c-press-kit.pdf?emrc=b712fa" target="_blank">https://www.nasa.gov/wp-content/uploads/2023/05/sts-41c-press-kit.pdf?emrc=b712fa</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>"STS-41-C Press Kit" (PDF). NASA. March 1984. Retrieved 9 July 2013. <a href="https://www.nasa.gov/wp-content/uploads/2023/05/sts-41c-press-kit.pdf?emrc=b712fa" target="_blank">https://www.nasa.gov/wp-content/uploads/2023/05/sts-41c-press-kit.pdf?emrc=b712fa</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>G. W. Kronk. "The Sungrazing Comets: SMM Sungrazers". Cometography.com. Retrieved 14 November 2024. <a href="https://cometography.com/sungrazers/sungrazersmm.html" target="_blank">https://cometography.com/sungrazers/sungrazersmm.html</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>R. M. MacQueen; O. C. St. Cyr (1991). "Sungrazing comets observed by the solar maximum mission coronagraph". Icarus. 90 (1): 96–106. doi:10.1016/0019-1035(91)90071-Z. ISSN 0019-1035. <a href="/wiki/Icarus_(journal)" target="_blank">/wiki/Icarus_(journal)</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>"C/1987 T2 (SMM) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 14 November 2024. <a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1987T2" target="_blank">https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1987T2</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>"C/1987 U4 (SMM) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 14 November 2024. <a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1987U4" target="_blank">https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1987U4</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>"C/1988 M1 (SMM) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 14 November 2024. <a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1988M1" target="_blank">https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1988M1</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>"C/1988 Q1 (SMM) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 14 November 2024. <a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1988Q1" target="_blank">https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1988Q1</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>D. W. Green (25 October 1988). "Comet 1988n (SMM 5)". Central Bureau for Astronomical Telegrams. 4668. Bibcode:1988IAUC.4668....1S. <a href="http://www.cbat.eps.harvard.edu/iauc/04600/04668.html" target="_blank">http://www.cbat.eps.harvard.edu/iauc/04600/04668.html</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>"C/1988 T1 (SMM) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 14 November 2024. <a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1988T1" target="_blank">https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1988T1</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>D. W. Green (17 December 1988). "Comet 1988q (SMM-7)". Central Bureau for Astronomical Telegrams. 4692. Bibcode:1988IAUC.4692....1S. <a href="http://www.cbat.eps.harvard.edu/iauc/04600/04692.html" target="_blank">http://www.cbat.eps.harvard.edu/iauc/04600/04692.html</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>"C/1988 U1 (SMM) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 14 November 2024. <a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1988U1" target="_blank">https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1988U1</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>D. W. Green (3 December 1988). "Comet 1988p (SMM 6)". Central Bureau for Astronomical Telegrams. 4684. Bibcode:1988IAUC.4684....1S. <a href="http://www.cbat.eps.harvard.edu/iauc/04600/04684.html" target="_blank">http://www.cbat.eps.harvard.edu/iauc/04600/04684.html</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>"C/1988 W1 (SMM) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 14 November 2024. <a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1988W1" target="_blank">https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1988W1</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>D. W. Green (7 June 1989). "Comet 1989m (SMM 8)". Central Bureau for Astronomical Telegrams. 4793. <a href="http://www.cbat.eps.harvard.edu/iauc/04700/04793.html" target="_blank">http://www.cbat.eps.harvard.edu/iauc/04700/04793.html</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>"C/1989 L1 (SMM) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. 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Green (25 October 1989). "Comet 1989x (SMM 10)". Central Bureau for Astronomical Telegrams. 4884. Bibcode:1989IAUC.4884....1S. <a href="http://www.cbat.eps.harvard.edu/iauc/04800/04884.html" target="_blank">http://www.cbat.eps.harvard.edu/iauc/04800/04884.html</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>"C/1989 S1 (SMM) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 14 November 2024. <a href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1989S1" target="_blank">https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1989S1</a> <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> <li id="fn:26"><p>K. T. Strong; J. L. R. Saba; B. M. Haisch; J. T. Schmelz (1999). The Many Faces of the Sun: A Summary of the Results from Nasa's Solar Maximum Mission. New York, USA: Springer. Bibcode:1999mfs..conf.....S. 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