Cosmic Ray Subsystem

File:HD.6B.155 (10727124456).jpg or cloud chamber, which can show the tracks certain particles make as they travel because they trigger little bubbles despite being of atomic size.]]

Areas of original study for this investigation:{{Cite web|url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1977-076A-08|title=NASA - NSSDCA - Experiment - Details|website=nssdc.gsfc.nasa.gov|access-date=2017-01-13}}

• origin and acceleration process, life history, and dynamic contribution of interstellar cosmic rays,
• nucleosynthesis of elements in cosmic-ray sources
• behavior of cosmic rays in the interplanetary medium
• trapped planetary energetic particle environment.

High-Energy Telescope System:

• 6 and 500 MeV/nucleon for atomic numbers from 1 through 30
• Electrons from 3 and 100 MeV

Low-Energy Telescope System:{{Cite web|url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1977-084A-08|title=NASA - NSSDCA - Experiment - Details|website=nssdc.gsfc.nasa.gov|access-date=2017-01-13}}

• 0.15 and 30 MeV/nucleon for atomic numbers from 1 to 30.
• Measures anisotropies of electrons and nuclei.

Electron Telescope (TET):

• The TET measures the energy spectrum of electrons from 3 to 110 MeV.

The TET consists of eight solid state detectors with different thicknesses of tungsten between each detector.{{Cite web|url=http://voyager.gsfc.nasa.gov/instruments.html#HET|title=INSTRUMENTS|last=Team|first=Voyager Cosmic Ray Subsystem|website=voyager.gsfc.nasa.gov|language=en|access-date=2017-02-02}} The detectors and tungsten layers are stacked one on top of each other. The tungsten layers range from 0.56 mm to 2.34 mm thick and function as absorbers. Each TET solid state detector has an area of 4.5 cm² and is 3 mm thick.{{Cite web|url=http://voyager.gsfc.nasa.gov/heliopause/vim/electrons/voyager2/index.html|title=Voyager Cosmic Ray Subsystem|last=Team|first=Voyager Cosmic Ray Subsystem|website=voyager.gsfc.nasa.gov|language=en|access-date=2017-02-11|archive-url=https://web.archive.org/web/20170212090909/http://voyager.gsfc.nasa.gov/heliopause/vim/electrons/voyager2/index.html|archive-date=2017-02-12|url-status=dead}}

Principal investigators: Rochus Eugen Vogt, Edward C. Stone, Alan C. Cummings{{Cite web|url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1977-084A-08|title=NASA - NSSDCA - Experiment - Details|website=nssdc.gsfc.nasa.gov|access-date=2017-02-02}}

The CRS was tested to operate down to a temperature of minus 49 degrees F (minus 59 degrees C) during its development in the 1970s.

During its development the CRS was rated to operate down to a temperature of minus 49 degrees F (minus 45 degrees C). Up until 2019 the instrument was operating on both Voyager 1 and Voyager 2, however in the summer of 2019 there was need to save some power on Voyager 2. The heater for the CRS was turned off at this time, which caused a lowering of the CRS temperature to drop below its lowest rated operating temperature. The device cooled down to minus 74 degrees Fahrenheit (minus 59 degrees Celsius) but it still continued to operate at this temperature.

File:Cosmic Rays at Voyager 1.png

File:Transitional regions.jpg as discovered by Voyager as of June 2013]]

File:PIA22924-Voyager2LeavesTheSolarSystem-20181105.jpg |accessdate=December 10, 2018 }}]]

In 1977 the spectra of helium, carbon, nitrogen, oxygen, and neon during the solar minimum was measured using the CRS instrument on the Voyagers that year.{{cite journal|url=http://authors.library.caltech.edu/44774/|title=Evidence that the anomalous cosmic-ray component is singly ionized|pages=L99–L103|first1=Cummings, A.|last1=C.|first2=Stone, E.|last2=C.|first3=Webber, W.|last3=R.|date=15 December 1984|journal=Astrophysical Journal Letters|volume=287|bibcode=1984ApJ...287L..99C|doi=10.1086/184407|access-date=11 February 2017|archive-date=11 February 2017|archive-url=https://web.archive.org/web/20170211235618/http://authors.library.caltech.edu/44774/|url-status=dead}} The solar minimum of 1977 occurred towards the end of year, and it was possible to observe both interplanetary, galactic, and anomalous energy spectra.

In the early 1980s, the CRS detected charged particles around Saturn.{{Cite book|url=https://books.google.com/books?id=tJnsCAAAQBAJ&pg=PA343|title=Astronomy and Astrophysics Abstracts: Literature 1982|last1=Böhme|first1=S.|last2=Fricke|first2=W.|last3=Hefele|first3=H.|last4=Heinrich|first4=I.|last5=Hofmann|first5=W.|last6=Krahn|first6=D.|last7=Matas|first7=V. R.|last8=Schmadel|first8=L. D.|last9=Zech|first9=G.|date=2013|publisher=Springer Science & Business Media|isbn=978-3-662-12334-8|page=343}} It detected a 0.43 million volt flux of protons as it traveled through Saturn's magnetosphere. In the 1980s the CRS data from both Voyagers was used to determine the abundances of energetic particles from the Sun and additional information.{{Cite book|url=https://books.google.com/books?id=I0b1CAAAQBAJ&pg=PA380|title=Literature 1985|last1=Böhme|first1=S.|last2=Esser|first2=U.|last3=Fricke|first3=W.|last4=Hefele|first4=H.|last5=Heinrich|first5=I.|last6=Hofmann|first6=W.|last7=Krahn|first7=D.|last8=Matas|first8=V. R.|last9=Schmadel|first9=L. D.|date=2013|publisher=Springer Science & Business Media|isbn=978-3-662-11178-9|page=380}} Another area studied in the 1980s using CRS data was variation in galactic cosmic rays in the outer Heliosphere{{cite journal|title=Variations of Galactic Cosmic Rays with Heliolatitude in the Outer Heliosphere|journal = International Cosmic Ray Conference|volume = 3|pages = 393|bibcode = 1987ICRC....3..393M|last1 = McDonald|first1 = F. B.|last2 = Lal|first2 = N.|year = 1987}}

CRS helped predict that Voyager 1 and 2 would cross the Solar System's termination shock in 2003.{{cite web |title=cosmic-ray subsystem |url=https://www.oxfordreference.com/view/10.1093/oi/authority.20110803095641369 |website=Oxford Reference |publisher=Oxford University Press |archive-url=https://web.archive.org/web/20220419093036/https://www.oxfordreference.com/view/10.1093/oi/authority.20110803095641369 |archive-date=19 April 2022 |url-status=live}} This helped support the later conclusion that Voyager 1 crossed the termination shock in December 2004 and that Voyager 2 crossed it in August 2007.{{cite journal|title=Voyager's long goodbye|first=Ron|last=Cowen|date=5 September 2012|journal=Nature|volume=489|issue=7414|pages=20–21|doi=10.1038/489020a|pmid=22962703 |bibcode=2012Natur.489...20C|doi-access=free}}

In 2011, CRS data along with the Voyager Magnetometer discovered an area where the solar wind was not going in either direction.{{cite web|url=https://gizmodo.com/5865196/voyager-discovers-cosmic-purgatory|title=Voyager Discovers Cosmic Purgatory|first=Jesus|last=Diaz|date=5 December 2011 |publisher=}} The area was identified as a sort of charged particle doldrums, where the particles from the Solar System are pushed back by cosmic forces. At a distance of 17 light-hours Voyager 1 was commanded to rotate several times (in the other direction then its spinning), to make detection in other directions.

It was determined that in 2012 Voyager 1 entered interstellar space, that is it entered the interstellar medium between the stars.{{cite web|url=http://www.jpl.nasa.gov/news/news.php?release=2013-278|title=How Do We Know When Voyager Reaches Interstellar Space?|website=NASA/JPL}} One of the reasons this was recognized was a significant increase in galactic cosmic rays.{{Cite web|url=http://www.jpl.nasa.gov/news/news.php?release=2013-278|title=How Do We Know When Voyager Reaches Interstellar Space?|website=NASA/JPL|access-date=2017-02-11}}

In 2013 CRS data lead some to propose that Voyager 1 had entered a "transition zone" as it leaves the heliosphere.{{Cite journal|last=Cowen|first=Ron|title=So, has Voyager 1 left the Solar System? Scientists face off|url=http://www.nature.com/news/so-has-voyager-1-left-the-solar-system-scientists-face-off-1.12662|journal=Nature|doi=10.1038/nature.2013.12662|year=2013|s2cid=124689125 |url-access=subscription}} There was some changes in the amounts and type of detections that triggered deeper analysis.{{Cite journal|last=Cowen|first=Ron|title=So, has Voyager 1 left the Solar System? Scientists face off|url=http://www.nature.com/news/so-has-voyager-1-left-the-solar-system-scientists-face-off-1.12662|journal=Nature|language=en|doi=10.1038/nature.2013.12662|year=2013|s2cid=124689125 |url-access=subscription}} The results from the magnetometer muddied the waters of interpretation.{{Cite news|url=https://blogs.scientificamerican.com/basic-space/voyager-is-in-a-new-region-of-space-and-now-that-place-has-a-name/|title=Voyager is in a new region of space, and now that place has a name|last=Oakes|first=Kelly|newspaper=Scientific American Blog Network|access-date=2017-02-11|language=en}}

{{quote|First I don't think any of us on the CRS [Cosmic Ray Subsystem, an instrument on Voyager] team will ever forget watching on the computer monitors, even on an hourly basis, in one case, as some particle intensities dropped precipitously, and others increased simultaneously on several occasions in July and August, 2012.|{{cite web|url=https://blogs.scientificamerican.com/basic-space/voyager-is-in-a-new-region-of-space-and-now-that-place-has-a-name/|title=Voyager is in a new region of space, and now that place has a name|first=Kelly|last=Oakes|publisher=}}}}

Other scientists proposed that this indicated a departure from the Solar System in the sense that it had left the Sun's heliosphere. The issue was the interpretation of the drop in cosmic rays, which happened at 123 AU from the Sun for Voyager 2 that year. The many revelations and restructured understandings as the Voyagers head out, as influenced by data from the CRS and other active instruments, was called by Nature publication as the "long goodbye".

The CRS on Voyager 2, helped identify that spacecraft's departure from the Sun's heliosphere in 2018.

File:Voyager diagram.jpg

{{clear}}

• Cosmic-ray observatory
• New Horizons (see plasma and high-energy particle spectrometer suite)
• Local Interstellar Cloud

{{reflist}}

• [http://adsabs.harvard.edu/full/1977SSRv...21..355S Cosmic ray investigation for the Voyager missions: Energetic particle studies in the outer heliosphere – and beyond, Stone, et al]
• [https://web.archive.org/web/19981203103703/http://helios.gsfc.nasa.gov/cosmic.html NASA – Cosmic Rays] (general overview of CR)
• [http://voyager.gsfc.nasa.gov/objectives.html Objective of CRS]
• [http://voyager.jpl.nasa.gov/science/bibliography_crs.html Papers by decade from CRS]
• [http://voyager.gsfc.nasa.gov/ CRS]
• [http://voyager.jpl.nasa.gov/spacecraft/instruments_crs.html Voyager Instruments – Cosmic Ray Subsystem]
• [https://web.archive.org/web/20170118161706/http://voyager.gsfc.nasa.gov/heliopause/v2la1.html CRS – Graphs]
• [https://web.archive.org/web/20170212090909/http://voyager.gsfc.nasa.gov/heliopause/vim/electrons/voyager2/index.html TET info]
• [https://www.jpl.nasa.gov/news/news.php?feature=7446 A New Plan for Keeping NASA's Oldest Explorers Going (July 2019)]

{{Voyager program}}

Category:Voyager program

Category:Spacecraft instruments