SOHO – 15 years today

Dr. Leif Svalgaard advises via email that today is the 15th anniversary of the SOHO(Solar and Heliospheric Observatory). Here’s a story to celebrate one of the most successful space missions ever, still going strong. – Anthony

SOHO Celebrates 15 Years (December 2, 2010)

(Design: Alex Lutkus)

Congratulations are in order for SOHO! It launched on Dec. 2, 1995 and is still going strong, even if two of its instruments have been superseded by ones on the Solar Dynamics Observatory. Not too many spacecraft achieve this remarkable record of longevity. And its contributions to the field of heliophysics cannot be exaggerated. Our admiration goes to the scientists who conceived, built, and operated the instruments, as well as those who’ve analyzed the data over the last fifteen years; the engineers, who planned and built this sturdy spacecraft and helped construct and test its instruments; and the mission operations team who have been controlling it all these years.

Here’s some background.

Solar Observation Mission Celebrates 15 Years

12.01.10

SOHO launching on the Atlas II-AS (AC-121) at Cape Canaveral Air Station on December 2, 1995.

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SOHO launching on the Atlas II-AS (AC-121) at Cape Canaveral Air Station on December 2, 1995. Credit: NASA

This coronal mass ejection, observed by SOHO's EIT 195 instrument on April 7, 1997, was the first visual image of such an ejection headed for Earth.

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This coronal mass ejection — observed by SOHO’s EIT 195 instrument on April 7, 1997 — was the first visual image of such an ejection headed for Earth. It appeared as the lead story on the national news. Credit: SOHO/ESA/NASA On December 2, 1995, the Solar and Heliospheric Observatory or SOHO was launched into space from Cape Canaveral aboard an Atlas IIAS rocket. The joint ESA/NASA project began its work observing the sun at a time when the term “solar weather” was almost never used.

Fifteen years later, SOHO has revolutionized what we know about the solar atmosphere and violent solar storms produced by the sun. SOHO has become an expert comet-hunter, nightly news leader and a workhorse that helped create the field of near-real-time space weather reporting as we know it –- but it started as a tool to answer three scientific questions about the sun.

“We were looking for answers to three long-standing problems in solar physics,” said Joe Gurman, “the solar neutrino problem, the coronal heating mystery, and the question of what causes solar wind acceleration.” Gurman works at NASA’s Goddard Space Flight Center in Greenbelt, Md., and has been the U.S. project scientist for SOHO since 1998.

Placed into orbit around the L1 Lagrangian point between Earth and the sun, SOHO was able to observe the sun continuously without Earth ever obstructing its view. With its uninterrupted observations, says Gurman, SOHO has significantly helped with all three original questions.

First, the so-called solar neutrino problem was a conflict between how many neutrinos were predicted by fusion and models of the solar interior versus how many were in fact detected. SOHO confirmed that the interior models were correct and helped show that, instead, the detectors were not finding all the neutrinos since they were changing after they left the sun. Second is the coronal heating mystery, so called because the Sun’s outermost atmosphere, or corona, is unexpectedly hundreds of times hotter than the sun’s surface. SOHO helped determine that the movement of the Sun’s small-scale magnetic fields themselves could contribute, in principle, sufficient energy to heat the corona. Third, SOHO observed that the acceleration of the solar wind appears to be powered by a special kind of waves that can accelerate certain particles preferentially.

SOHO is perhaps best known for its observations of coronal mass ejections, or CMEs. These blasts of gas and magnetic fields are a fundamental concern for those who track and attempt to forecast space weather. But when SOHO launched in 1995, there was disagreement over what a CME headed for earth looked like. The first ever videos of a CME wave in the lower corona in April of 1997, combined with SOHO’s white light coronagraph observations of the accompanying “halo” CME, changed all that.

Steele Hill, who leads public outreach for SOHO at Goddard, had then only been working for the SOHO team for six months. “It was the first time we had witnessed an event like that. We could track it, predict its direction, and say that in two to three days it will have some impact on Earth.” Hill pulled together some SOHO files and made a movie. . . and it was the first story on the national news that night in April 1997.

An unexpected destiny for SOHO is that it has become the greatest comet-finder of all time. With its data stream available publicly, anyone can be a comet hunter — and as of November 1, 2010, SOHO had spotted more than 1,940 of them. (A contest to predict the day on which the 2,000th will be spotted is here.)

Artist's concept of SOHO spacecraft observing the sun. > View larger

Artist’s Concept of SOHO spacecraft observing the sun. Credit: NASA/A. Lutkus/H. Zell

After a good 15-years, SOHO isn’t easing in to retirement yet. A long archive of data such as SOHO’s is necessary to spot some of the tiniest waves that propagate through the body of the sun. Known as buoyancy or gravity-mode waves, these waves only disturb the surface of the sun at a speed of a millimeter per second.

“That’s a pretty hard measurement to do,” says Gurman. “With 15 years of observations, we just might have a strong enough signal.”

In addition, SOHO is still our only solar observatory to have gathered images of the sun during a solar maximum. The last maximum was in 2000. As we move into the next peak in 2013, it will be SOHO’s legacy that allows scientists to compare and contrast what we see now in newer missions such as the Solar Dynamics Observatory (SDO) and the Solar TErrestrial RElations Observatory (STEREO) to what was seen then.

“Every mission stands on the shoulders of the missions that came before it,” says Gurman. “Without the success of SOHO we never would have had the opportunity to get even better measurements with STEREO, Hinode, and SDO.”

Karen C. Fox

NASA’s Goddard Space Flight Center

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15 thoughts on “SOHO – 15 years today

  1. If the 90’s and 00’s era crafts still transmit as long as the pioneer crafts have done I’ll be impressed, but until then, oh well.
    What they should’ve done, being all climatewise, was to SOHO linked to another sat pointed at earth to study what happened on earth when what happened on the old fart Sol.
    Of course I’m a simpleton so I’ll never understand the point at staring at something singular and not registering what’s going on and happening all around as well, just to see what the effect is from a potential cause. Who does that anymore with virtual and abused abacus-models any who.

  2. 1995 was before the domnation of NASA by post normal scientists I guess. This was the kind of stuff that I loved about NASA and the space programme. I suppose good translation programmes will allow me to follow future space exploration by China and India. Does Burt Rutan take donations?

  3. Long-term efforts are worth their weight in gold, and for a particular view of the sun that continues today in SDO & STEREO, the mission lives on. Not only that, but SOHO caught the Sun going into both a normal minimum and a deep one.

  4. Heh. I noticed that the SOHO website is working again just in time. The “real time” SOHO images have been stuck on Nov 16th for almost two weeks — but it’s back to real time today.

  5. Second is the coronal heating mystery, so called because the Sun’s outermost atmosphere, or corona, is unexpectedly hundreds of times hotter than the sun’s surface. SOHO helped determine that the movement of the Sun’s small-scale magnetic fields themselves could contribute, in principle, sufficient energy to heat the corona.

    How does that affect earth if at all?
    And what about earths magnetic field, how does that heat our atmosphere if at all?

  6. Love the project, love the 15 year celebration logo.
    Could serve very well as a logo for a posh looking night club, all decorated with pictures of the sun and Huble, another high light of NASA performance.
    Great environment to have a nice cool drink.

  7. One thing I like about WUWT is it generally, …….nuts asside, sticks to the issues at hand. The quality of the people offering their insights make it worth the time to read through the threads. I enjoy any thread that gets Leif in the game. I don’t think WUWT is a repository of paranoids who dream up a conspiracy theory against the Concensus of thousands of Scientists. Most of what I read here shows that the nearly all Warming factual theories are wrong or can be challenged. I do worry that this TSI
    issue is not getting proper thrift because of vested interests. It was Nicola Scarfetta that accused Leif of having ‘a dog in this hunt’ of AGW.
    In Leif’s remarks about Oliver…(no, not the Christmas one) in the Dragon Book Thread said:
    ‘……………….he isn’t a crackpot.
    That bit comes when you realize that he believes thousands of astrophysicists are part of a worldwide conspiracy to suppress and withhold data supporting hos theory, while at the same manufacturing false data in support for the ‘standard model’. Now, I grant you that many people believe the same about AGW………….’
    I guess If I had a question at the moment for Leif, hoping you read this thread, it would be, Where do you stand on the merits of the beliefs of the Skeptics here at WUWT???

  8. I’ve always likes the SoHo district in Manhattan and LOVED the SOHO science and tecnology. They ROCK!wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww

  9. Well there’s a thing. As we speak, from my controllers console at Tidbinbilla tracking station, I am currently downlinking data from the birthday girl. Soho is a girl, we know this because she can be a complete bitch on occasions.
    The MDI problem is fixed and the spacecraft is in good health, for an old girl anyway.
    Currently other activities include ranging and commanding, on this particular “pass”.
    SOHO will set at 10:22:28 utc but I will release it at 09:55:00 utc.
    Another day, another data dump.
    Ian
    Canberra

  10. Neat Of SOHO to close down with three sunspot groups visible and then re-open with two sunspot groups in the same postion and of the same size as two of the three 18 days ago. Nearly threw me.
    Will Lief S be able to update his graphs thru the interregnum – ie has he had some sort of backup data?

  11. TFN Johnson says:
    December 3, 2010 at 7:08 am
    Will Lief S be able to update his graphs thru the interregnum – ie has he had some sort of backup data?
    Don’t use SOHO for that [but, of course, for many other things], so no problem.

  12. Sorry for my last ridiculous post on this thread. This morning I had an important work meeting and the night before (when I made this post) I could not get to sleep so I took an Ambie*.
    Haha…..guess it works pretty well because out like a light in the middle of my post. LOL
    Chris

  13. johnnythelowery says:
    December 2, 2010 at 9:44 pm
    I guess If I had a question at the moment for Leif, hoping you read this thread, it would be, Where do you stand on the merits of the beliefs of the Skeptics here at WUWT???
    Many are as dogmatic as the AGW crowd, just with opposite sign. Neither faction can be reasoned with.

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