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Diagram of SWEAP, SPC subinstrument
Diagram of SWEAP, SPAN-A subinstrument
SPAN-B

SWEAP (Solar Wind Electrons Alphas and Protons) is an instrument on the unmanned space probe to the Sun, the Parker Solar Probe.[1] The spacecraft with SWEAP on board was launched by a Delta IV Heavy on 12 August 2018 from Cape Canaveral, Florida.[2] SWEAP includes two types of instruments, the Solar Probe Cup (SPC) and Solar Probe Analyzers (SPAN).[3] SWEAP has four sensors overall, and is designed to take measurements of the Solar wind including electrons and ions of hydrogen (protons) and helium (these are the main components of the Solar wind and coronal plasma).[4]

Background[edit]

Scientists studying emissions spectra from the Sun's corona, the bright halo surrounding it, taken during total solar eclipses, had thought they pointed to the presence of a new element they called "coronium". In the late 1930s, Walter Grotrian and Bengt Edlén postulated instead that they were from highly ionized known elements, particularly iron. Since the levels of ionization they proposed required temperatures in the millions of Kelvins, they were not initially accepted as those temperatures were far hotter than the actual surface of the Sun, which was thought impossible as the corona, without any apparent heat source of its own, should be cooler than the Sun. But later measurements of the corona's temperature by other means suggested this was correct. Why this apparent disparity, now called the coronal heating problem, exists is still not known for certain.[5][6]

Some theories suggest interactions between the various atomic particles in the plasma of the corona could account for the extra heat. To test those theories it would be useful to collect data from the corona itself. NASA thus commissioned the Solar Probe Plus for a 2018 launch (it was renamed the Parker Solar Probe (PSP), after Eugene Parker, who predicted the existence of the later-proven solar wind in the 1950s, the first time NASA had ever named a space mission after a then-living person[7][a]). Following a gravity assist from Earth and Mars, it uses further gravity assists from Venus to make ever-closer orbits to the Sun.[9]

Design[edit]

SWEAP consists of the Solar Probe Cup (SPC), a faraday cup which faces the Sun and is designed to measure electrons and ions in the space environment near the Sun; the Solar Probe Analyzers (SPAN-A and SPAN-B);[10][11] and the SWEAP electronics module (SWEM).

The Solar Probe Cup is a Sun facing instrument directly exposed to the Sun, and had to be designed to handle the high temperature conditions at 9-10 Solar radii from the Sun, that are planned for the mission.[12] In operation it peeks out from the probes Sun shield, and is made entirely of refractory materials to endure these conditions. The hottest portion, the grid in front of the cup, can be heated to 3,000 °F (1,650 °C)[13] and is made of tungsten. The wiring connecting to the electronics is made of niobium with sapphire insulators.

SPAN-A and B are behind the heat shield, oriented forward ("ram side") and backward along the spacecraft's orbit, and take electron and ion measurements overs a wide field of view.[14] SPAN-A measure ions and electrons and SPAN-B measures electrons.[15]

Summary:[16]

  • Solar Probe Cup (SPC): Outside solar shield directly exposed to the Sun
  • Solar Probe Analyzers (SPAN)
    • SPAN-Ai: ion electrostatic analyzer (ESA) on the ram side
    • SPAN-Ae: electron electrostatic analyzer on the ram side
    • SPAN-B: electron electrostatic analyzer on the anti-ram side
  • SWEAP Electronics Module (SWEM)

Operations[edit]

By September 2018, SWEAP had been turned on and first light data was returned.[17]

Location[edit]

Ram-side view, SPAN-A marked

See also[edit]

Notes[edit]

  1. ^ Parker died in 2022.[8]

References[edit]

  1. ^ Kasper, Justin C. "The SWEAP Investigation for Parker Solar Probe". www.cfa.harvard.edu. Retrieved 2018-10-07.
  2. ^ Brown, Geoffrey; Brown, Dwayne; Fox, Karen (12 August 2018). "Parker Solar Probe Launches on Historic Journey to Touch the Sun". Johns Hopkins University Applied Physics Laboratory. Retrieved 13 August 2018.
  3. ^ Kasper, Justin C. "The SWEAP Investigation for Parker Solar Probe". www.cfa.harvard.edu. Retrieved 2018-10-07.
  4. ^ Kasper, Justin C.; Abiad, Robert; Austin, Gerry; Balat-Pichelin, Marianne; Bale, Stuart D.; Belcher, John W.; Berg, Peter; Bergner, Henry; Berthomier, Matthieu (2015-10-29). "Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus". Space Science Reviews. 204 (1–4): 131–186. doi:10.1007/s11214-015-0206-3. hdl:11603/31312. ISSN 0038-6308.
  5. ^ Klimchuk, James (September 6–9, 2004). How Do We Solve the Coronal Heating Problem?. SOHO 15 Conference – Solar Heating. St Andrews, Scotland: European Space Agency. p. 355. Bibcode:2004ESASP.575....2K. ESA SP-575.
  6. ^ Cham, Jorge (December 14, 2021). "To Touch the Sun". Physics. 14. American Physical Society: 178. Bibcode:2021PhyOJ..14..178.. doi:10.1103/Physics.14.178. ISSN 1943-2879. OCLC 819219406. Retrieved January 16, 2024.
  7. ^ Chang, Kenneth (August 10, 2018). "NASA's Parker Solar Probe Is Named for Him. 60 Years Ago, No One Believed His Ideas About the Sun". The New York Times. Archived from the original on August 11, 2018. Retrieved January 16, 2024. It is the Parker Solar Probe, named after Dr. Parker, now 91 years old. It is the first time that NASA has named a mission for a living person.
  8. ^ Chang, Kenneth (March 17, 2022). "Eugene N. Parker, 94, Dies; Predicted the Existence of Solar Wind". The New York Times. Retrieved January 20, 2024.
  9. ^ Schirber, Michael (December 14, 2021). "How to Survive Flying Too Close to the Sun". Physics. 14. American Physical Society: 176. Bibcode:2021PhyOJ..14..176S. doi:10.1103/Physics.14.176. ISSN 1943-2879. OCLC 819219406. Retrieved January 15, 2024.
  10. ^ Kasper, Justin C. "The SWEAP Investigation for Parker Solar Probe". www.cfa.harvard.edu. Retrieved 2018-10-07.
  11. ^ Kasper, Justin C.; Abiad, Robert; Austin, Gerry; Balat-Pichelin, Marianne; Bale, Stuart D.; Belcher, John W.; Berg, Peter; Bergner, Henry; Berthomier, Matthieu (2015-10-29). "Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus". Space Science Reviews. 204 (1–4): 131–186. Bibcode:2016SSRv..204..131K. doi:10.1007/s11214-015-0206-3. hdl:1721.1/107474. ISSN 0038-6308.
  12. ^ Kasper, Justin C.; Abiad, Robert; Austin, Gerry; Balat-Pichelin, Marianne; Bale, Stuart D.; Belcher, John W.; Berg, Peter; Bergner, Henry; Berthomier, Matthieu; Bookbinder, Jay; Brodu, Etienne; Caldwell, David; Case, Anthony W.; Chandran, Benjamin D. G.; Cheimets, Peter; Cirtain, Jonathan W.; Cranmer, Steven R.; Curtis, David W.; Daigneau, Peter; Dalton, Greg; Dasgupta, Brahmananda; Detomaso, David; Diaz-Aguado, Millan; Djordjevic, Blagoje; Donaskowski, Bill; Effinger, Michael; Florinski, Vladimir; Fox, Nichola; Freeman, Mark; et al. (2016). "Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus". Space Science Reviews. 204 (1–4): 131–186. Bibcode:2016SSRv..204..131K. doi:10.1007/s11214-015-0206-3. hdl:11603/31312.
  13. ^ Garner, Rob (2018-07-12). "Parker Solar Probe Instruments". NASA. Retrieved 2018-10-07.
  14. ^ Garner, Rob (2018-07-12). "Parker Solar Probe Instruments". NASA. Retrieved 2018-10-07.
  15. ^ Garner, Rob (2018-07-12). "Parker Solar Probe Instruments". NASA. Retrieved 2018-10-07.
  16. ^ Kasper, Justin C.; Abiad, Robert; Austin, Gerry; Balat-Pichelin, Marianne; Bale, Stuart D.; Belcher, John W.; Berg, Peter; Bergner, Henry; Berthomier, Matthieu (2015-10-29). "Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus". Space Science Reviews. 204 (1–4): 131–186. doi:10.1007/s11214-015-0206-3. hdl:11603/31312. ISSN 0038-6308.
  17. ^ "Illuminating First Light Data from Parker Solar Probe – Parker Solar Probe". blogs.nasa.gov. 19 September 2018. Retrieved 2018-12-23.
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