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The two STEREO spacecraft were launched at 0052 UTC on October 26, 2006 from Launch Pad 17B at the [[Cape Canaveral Air Force Station]] in Florida on a [[Delta II]] 7925-10L launcher into highly [[ellipse|elliptical]] [[geocentric orbit]]s. The [[apogee]] reached the Moon's orbit. On December 15, 2006, on the fifth orbit, the pair swung by the Moon for a [[gravitational slingshot]]. Because the two spacecraft were in slightly different orbits, the "ahead" (A) spacecraft was ejected to a [[heliocentric orbit]] inside Earth's orbit while the "behind" (B) spacecraft remained temporarily in a high earth orbit. The B spacecraft encountered the Moon again on the same orbital revolution on January 21, 2007, ejecting itself from earth orbit in the opposite direction from spacecraft A. Spacecraft B entered a heliocentric orbit outside the Earth's orbit. Spacecraft A will take 347 days to complete one revolution of the sun and Spacecraft B will take 387 days. The A spacecraft/sun/earth angle will increase at 21.650 deg/year. The B spacecraft/sun/earth angle will change -21.999 degrees per year. Their current locations are shown [http://stereo.gsfc.nasa.gov/where.shtml here]. |
The two STEREO spacecraft were launched at 0052 UTC on October 26, 2006 from Launch Pad 17B at the [[Cape Canaveral Air Force Station]] in Florida on a [[Delta II]] 7925-10L launcher into highly [[ellipse|elliptical]] [[geocentric orbit]]s. The [[apogee]] reached the Moon's orbit. On December 15, 2006, on the fifth orbit, the pair swung by the Moon for a [[gravitational slingshot]]. Because the two spacecraft were in slightly different orbits, the "ahead" (A) spacecraft was ejected to a [[heliocentric orbit]] inside Earth's orbit while the "behind" (B) spacecraft remained temporarily in a high earth orbit. The B spacecraft encountered the Moon again on the same orbital revolution on January 21, 2007, ejecting itself from earth orbit in the opposite direction from spacecraft A. Spacecraft B entered a heliocentric orbit outside the Earth's orbit. Spacecraft A will take 347 days to complete one revolution of the sun and Spacecraft B will take 387 days. The A spacecraft/sun/earth angle will increase at 21.650 deg/year. The B spacecraft/sun/earth angle will change -21.999 degrees per year. Their current locations are shown [http://stereo.gsfc.nasa.gov/where.shtml here]. |
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Over time, the STEREO spacecraft will continue to separate from each other at a combined rate of approximately 44 degrees per year. There are no ''final'' positions for the spacecraft. They achieved 90 degrees separation on January 24, 2009, a condition known as [[quadrature]]. This is of interest because the mass ejections seen from the side on the limb by one spacecraft can potentially be observed by the ''in situ'' particle experiments of the other spacecraft. As they passed through Earth's [[Lagrangian point]]s {{L4}} and {{L5}}, in late 2009, they searched for [[Trojan (astronomy)|Lagrangian (trojan) asteroids]]. On February 6, 2011, the two spacecraft were exactly 180 degrees apart from each other, allowing the entire Sun to be seen for the first time. |
Over time, the STEREO spacecraft will continue to separate from each other at a combined rate of approximately 44 degrees per year. There are no ''final'' positions for the spacecraft. They achieved 90 degrees separation on January 24, 2009, a condition known as [[quadrature]]. This is of interest because the mass ejections seen from the side on the limb by one spacecraft can potentially be observed by the ''in situ'' particle experiments of the other spacecraft. As they passed through Earth's [[Lagrangian point]]s {{L4}} and {{L5}}, in late 2009, they searched for [[Trojan (astronomy)|Lagrangian (trojan) asteroids]]. On February 6, 2011, the two spacecraft were exactly 180 degrees apart from each other, allowing the entire Sun to be seen for the first time. |
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Even as the angle increases, the addition of an Earth-based view, e.g. from the [[Solar Dynamics Observatory]], will still provide full-Sun observations for several years. In 2015, contact will be lost for several months when the spacecraft pass behind the Sun. |
Even as the angle increases, the addition of an Earth-based view, e.g. from the [[Solar Dynamics Observatory]], will still provide full-Sun observations for several years. In 2015, contact will be lost for several months when the STEREO spacecraft pass behind the Sun. |
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They will then start to approach Earth again, with closest approach sometime in 2023. They will not be recaptured into Earth orbit. |
They will then start to approach Earth again, with closest approach sometime in 2023. They will not be recaptured into Earth orbit. |
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==Mission benefits== |
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The principal benefit of the mission is [[stereoscopic]] images of the sun. In other words, because the satellite's are at a different point along the Earth's orbit than the Earth itself, they can photograph parts of the sun that are not visible from the sun. This permits NASA scientists to directly monitor the far side of the sun, instead of inferring the activity on the far side from data that can be gleaned from Earth's view of the sun. The STEREO satellites principally monitor the far side for [[coronal mass ejections]]—massive bursts of [[solar wind]], solar [[Plasma (physics)|plasma]], and magnetic fields that are sometimes ejected into space.<ref name=CBC>{{cite news|title=Sun bares all for twin space probes|url=http://www.cbc.ca/technology/story/2011/02/07/science-sun-nasa-stereo.html|accessdate=8 February 2011|newspaper=CBC News|date=February 7, 2011}}</ref> |
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Since the radiation from coronal mass ejections, or CMEs, can disrupt Earth's communications, airlines, power grids, and satellites, more accurate forecasting of CMEs has the potential to provide greater warning to operators of these services.<ref name=CBC /> Before STEREO, the development of the [[sunspot]]s that are associated with CMEs was invisible on the far side of the sun. Since the sun rotates every 25 days, the far side was invisible to Earth for about days at a time before STEREO. The period that the sun's far side was previously invisible was a principle reason for the STEREO mission.<ref>{{cite news|last=Lemonick|first=Michael|title=NASA Images the Entire Sun, Far Side and All|url=http://www.time.com/time/health/article/0,8599,2046569,00.html|accessdate=8 February 2011|newspaper=[[Time (magazine){{!}}TIME]]|date=February 6, 2011}}</ref> |
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STEREO program scientist Lika Guhathakurta expects "great advances" in theoretical [[solar physics]] and space weather forecasting with the advent of constant 360-degree views of the sun.<ref>{{cite news|last=Winter|first=Michael|title=Sun shines in twin probes' first 360-degree images|url=http://content.usatoday.com/communities/ondeadline/post/2011/02/sun-shines-in-twin-probes-first-360-degree-images/1|accessdate=8 February 2011|newspaper=USA Today|date=Feb 07, 2011}}</ref> STEREO's observations are already being incorporated into forecasts of solar activity for airlines, power companies, satellite operators, and others.<ref>{{cite news|title=Stereo satellites move either side of Sun|url=http://www.bbc.co.uk/news/science-environment-12365083|accessdate=8 February 2011|newspaper=BBC News|date=6 February 2011}}</ref> |
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==Science instrumentation== |
==Science instrumentation== |
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Image:Sun 3D anaglyph STEREO.jpg|A three-dimensional [[anaglyph]] taken by STEREO, released by NASA on April 23, 2007.{{3d glasses}} |
Image:Sun 3D anaglyph STEREO.jpg|A three-dimensional [[anaglyph]] taken by STEREO, released by NASA on April 23, 2007.{{3d glasses}} |
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Image:BLUE STEREO 3D Time for Space Wiggle.gif|A three-dimensional Time for Space Wiggle image taken by STEREO |
Image:BLUE STEREO 3D Time for Space Wiggle.gif|A three-dimensional Time for Space Wiggle image taken by STEREO |
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==See also== |
==See also== |
Revision as of 05:45, 8 February 2011
STEREO (Solar TErrestrial RElations Observatory) is a solar observation mission.[1] Two nearly identical spacecraft were launched into orbits that cause them to respectively pull further ahead of and fall gradually behind the Earth. This will enable stereoscopic imaging of the Sun and solar phenomena, such as coronal mass ejections.
Mission profile
The two STEREO spacecraft were launched at 0052 UTC on October 26, 2006 from Launch Pad 17B at the Cape Canaveral Air Force Station in Florida on a Delta II 7925-10L launcher into highly elliptical geocentric orbits. The apogee reached the Moon's orbit. On December 15, 2006, on the fifth orbit, the pair swung by the Moon for a gravitational slingshot. Because the two spacecraft were in slightly different orbits, the "ahead" (A) spacecraft was ejected to a heliocentric orbit inside Earth's orbit while the "behind" (B) spacecraft remained temporarily in a high earth orbit. The B spacecraft encountered the Moon again on the same orbital revolution on January 21, 2007, ejecting itself from earth orbit in the opposite direction from spacecraft A. Spacecraft B entered a heliocentric orbit outside the Earth's orbit. Spacecraft A will take 347 days to complete one revolution of the sun and Spacecraft B will take 387 days. The A spacecraft/sun/earth angle will increase at 21.650 deg/year. The B spacecraft/sun/earth angle will change -21.999 degrees per year. Their current locations are shown here.
Over time, the STEREO spacecraft will continue to separate from each other at a combined rate of approximately 44 degrees per year. There are no final positions for the spacecraft. They achieved 90 degrees separation on January 24, 2009, a condition known as quadrature. This is of interest because the mass ejections seen from the side on the limb by one spacecraft can potentially be observed by the in situ particle experiments of the other spacecraft. As they passed through Earth's Lagrangian points L4 and L5, in late 2009, they searched for Lagrangian (trojan) asteroids. On February 6, 2011, the two spacecraft were exactly 180 degrees apart from each other, allowing the entire Sun to be seen for the first time.
Even as the angle increases, the addition of an Earth-based view, e.g. from the Solar Dynamics Observatory, will still provide full-Sun observations for several years. In 2015, contact will be lost for several months when the STEREO spacecraft pass behind the Sun.
They will then start to approach Earth again, with closest approach sometime in 2023. They will not be recaptured into Earth orbit.
Mission benefits
The principal benefit of the mission is stereoscopic images of the sun. In other words, because the satellite's are at a different point along the Earth's orbit than the Earth itself, they can photograph parts of the sun that are not visible from the sun. This permits NASA scientists to directly monitor the far side of the sun, instead of inferring the activity on the far side from data that can be gleaned from Earth's view of the sun. The STEREO satellites principally monitor the far side for coronal mass ejections—massive bursts of solar wind, solar plasma, and magnetic fields that are sometimes ejected into space.[2]
Since the radiation from coronal mass ejections, or CMEs, can disrupt Earth's communications, airlines, power grids, and satellites, more accurate forecasting of CMEs has the potential to provide greater warning to operators of these services.[2] Before STEREO, the development of the sunspots that are associated with CMEs was invisible on the far side of the sun. Since the sun rotates every 25 days, the far side was invisible to Earth for about days at a time before STEREO. The period that the sun's far side was previously invisible was a principle reason for the STEREO mission.[3]
STEREO program scientist Lika Guhathakurta expects "great advances" in theoretical solar physics and space weather forecasting with the advent of constant 360-degree views of the sun.[4] STEREO's observations are already being incorporated into forecasts of solar activity for airlines, power companies, satellite operators, and others.[5]
Science instrumentation
Each of the spacecraft carries cameras, particle experiments and radio detectors in four instrument packages:
- Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) - SECCHI has five cameras: an extreme ultraviolet imager (EUVI) and two white-light coronagraphs (collectively known as the Sun Centered Instrument Package or SCIP), which image the solar disk and the inner and outer corona, plus two heliospheric imagers (called the HI), which image the space between Sun and Earth. The purpose of SECCHI is to study the 3-D evolution of Coronal Mass Ejections through their full journey from the Sun's surface through the corona and interplanetary medium to their impact at Earth.[6][7]
- In-situ Measurements of Particles and CME Transients (IMPACT) - IMPACT will study energetic particles, the three-dimensional distribution of solar wind electrons and interplanetary magnetic field.[6][8]
- PLAsma and SupraThermal Ion Composition (PLASTIC) - PLASTIC will study the plasma characteristics of protons, alpha particles and heavy ions.[6]
- STEREO/WAVES (SWAVES) - SWAVES is a radio burst tracker that will study radio disturbances traveling from the Sun to the orbit of Earth.[6]
Spacecraft subsystems
- Structure
Launch weight including propellants was 1364 pounds (620 kg).
- Propulsion and attitude control
3-axis control
- Attitude determination - Each STEREO spacecraft has a primary and a backup Miniature Inertial Measurement Unit (MIMU), provided by Honeywell, which measure changes to the spacecraft attitude.[9] Each MIMU is equipped with three ring laser gyroscopes to detect angular changes. Additional attitude information is provided by the Star Tracker and the SECCHI Guide Telescope.[10]
- Power
475 Watts from solar panels.
- Telecommunications
Data downlink: 720 kilobits per second.
- Flight computers
STEREO's onboard computer systems are based on the Integrated Electronics Module (IEM), a device that combines core avionics in a single box. Each single-string spacecraft carries two 25 megahertz RAD6000 CPUs: one for Command/Data-handling, and one for Guidance-and-Control. Both are radiation hardened RAD6000 processors, based on IBM POWER CPUs (predecessor of the PowerPC chip found in older Macintoshes). The computers, slow by current personal computer standards, are typical for the radiation requirements needed on the STEREO mission.
- Data handling
For data storage, each spacecraft carries a solid state recorder able to store up to one gigabyte each. Its main processor collects and stores on the recorder images and other data from STEREO's instruments, which can then be sent back to Earth.
Image gallery
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The STEREO Space Probes in a Goddard Center Cleanroom
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One of the first images of the Sun taken by STEREO
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The Moon passing in front of the Sun from STEREO-B, February 25, 2007 (See the movie of the transit)
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The Sun's South Pole. Material can be seen erupting off the sun in the lower right side of the image.
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A three-dimensional anaglyph taken by STEREO, released by NASA on April 23, 2007. 3D red cyan glasses are recommended to view this image correctly.
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A three-dimensional Time for Space Wiggle image taken by STEREO
See also
- SOHO, solar observatory launched in 1995, still operational.
- Ulysses probe, 1990 mission, decommissioned June 30, 2009.
- Advanced Composition Explorer (ACE), launched 1997, still operational.
- Transition Region and Coronal Explorer (TRACE), launched 1998, still operational.
- Triana, satellite intended for L1
References
- ^ "NASA Launch Schedule". NASA Missions. September 20, 2006. Retrieved September 20, 2006.
- ^ a b "Sun bares all for twin space probes". CBC News. February 7, 2011. Retrieved 8 February 2011.
- ^ Lemonick, Michael (February 6, 2011). "NASA Images the Entire Sun, Far Side and All". TIME. Retrieved 8 February 2011.
- ^ Winter, Michael (Feb 07, 2011). "Sun shines in twin probes' first 360-degree images". USA Today. Retrieved 8 February 2011.
{{cite news}}
: Check date values in:|date=
(help) - ^ "Stereo satellites move either side of Sun". BBC News. 6 February 2011. Retrieved 8 February 2011.
- ^ a b c d "STEREO Spacecraft & Instruments". NASA Missions. March 8, 2006. Retrieved May 30, 2006.
- ^ Howard R. A., Moses J. D., Socker D. G., Dere K. P., Cook J. W. (2002). "Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI)". Solar Variabilit and Solar Physics Missions Advances in Space Research. 29 (12): 2017–2026.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Luhmann J. G., Curtis D. W., Lin R. P., Larson D, Schroeder P., Cummings A., Mewaldt R. A., Stone E. C., Davis A., von Rosenvinge T., Acuna M. H., Rearnes D., Ng C., Ogilvie K., Mueller-Mellin R., Kunow H., Mason G. M., Wiedenbeck M., Sauvaud A., Aoustin C., Louarn P., Dandouras J., Korth A., Bothmer V., Vasyliunas V., Sanderson T., Marsden R. G., Russell C. T., Gosling J. T., Bougeret J. L., McComas D. J., Linker J. A., Riley P., Odstrcil D., Pizzo V. J., Gombosi T., DeZeeuw D., Gombosi T., DeZeeuw D., Kecskemety K. (2005). "IMPACT: Science goals and firsts with STEREO". Solar Encounter, Solar-B and Stereo Advances in Space Research. 36 (8): 1534–1543.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ "Honeywell To Provide Miniature Inertial Measurement Units For STEREO Spacecraft". Web. Honeywell International, Inc. Retrieved 2006-10-25. [dead link]
- ^ Driesman, A., Hynes S, and Cancro, G. (2008), The STEREO Observatory, Space Science Reviews, 136, 17-44
Further reading
- STEREO spacecraft to image solar blasts in glorious 3-D, New Scientist December 9, 2005
- NASA Orbit simulations
External links
- STEREO, official site
- STEREO, Applied Physics Laboratory version
- STEREO Mission Profile by NASA's Solar System Exploration
- SECCHI homepage
- U of M, UMNnews
- STEREO, UK version
- [1], Stereoscopic anaglyphs from STEREO original images