NASA to Send a Probe Into the Sun


NASA recently announced its choices for the experiments to fly aboard the Solar Probe Plus spacecraft, which is slated to launch no later than 2018. This spacecraft will perform the unprecedented task of flying into the Sun’s atmosphere – or corona – to take measurements of the plasma, magnetic fields and dust that surround our nearest star. It will be the first human-made satellite to approach the Sun at such a close proximity.

The previous record-holder for a spacecraft that approached the Sun was Helios 2, which came within 27 million miles (43.5 million kilometers) of the Sun in 1976. Solar Probe Plus will shatter that record, flying to 3.7 million miles (5.9 million kilometers) of the Sun’s surface at its closest approach. In flying so close to the Sun, the spacecraft will be able to get amazingly detailed data on the structure of the atmosphere that surrounds the Sun.

As you can imagine, it gets a little toasty as one gets that close to the Sun. Solar Probe Plus will utilize a special heat shield made of an 8-foot (2.4 m), 4.5 inch (11 cm)-thick special carbon-composite foam plate that will protect the craft from temperatures of up to 2600 degrees Fahrenheit (1400 degrees Celsius) and intense solar radiation. The heat shield is a modified version of that which was used in the MESSENGER mission to Mercury.

NASA has chosen five science projects out of the thirteen that were proposed since 2009. The selected proposals are, according to the press release:

— Solar Wind Electrons Alphas and Protons Investigation: principal investigator, Justin C. Kasper, Smithsonian Astrophysical Observatory in Cambridge, Mass. This investigation will specifically count the most abundant particles in the solar wind — electrons, protons and helium ions — and measure their properties. The investigation also is designed to catch some of the particles in a special cup for direct analysis.
— Wide-field Imager: principal investigator, Russell Howard, Naval Research Laboratory in Washington. This telescope will make 3-D images of the sun’s corona, or atmosphere. The experiment actually will see the solar wind and provide 3-D images of clouds and shocks as they approach and pass the spacecraft. This investigation complements instruments on the spacecraft providing direct measurements by imaging the plasma the other instruments sample.
— Fields Experiment: principal investigator, Stuart Bale, University of California Space Sciences Laboratory in Berkeley, Calif. This investigation will make direct measurements of electric and magnetic fields, radio emissions, and shock waves that course through the sun’s atmospheric plasma. The experiment also serves as a giant dust detector, registering voltage signatures when specks of space dust hit the spacecraft’s antenna.
— Integrated Science Investigation of the Sun:principal investigator, David McComas of the Southwest Research Institute in San Antonio. This investigation consists of two instruments that will take an inventory of elements in the sun’s atmosphere using a mass spectrometer to weigh and sort ions in the vicinity of the spacecraft.
— Heliospheric Origins with Solar Probe Plus: principal investigator, Marco Velli of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Velli is the mission’s observatory scientist, responsible for serving as a senior scientist on the science working group. He will provide an independent assessment of scientific performance and act as a community advocate for the mission.

Two important questions that the mission hopes to answer is the perplexing mystery of why the Sun’s atmosphere is hotter than its surface, and the mechanism for the solar wind that emanates from the Sun into the Solar System. The spacecraft will have a front-row seat to watch the solar wind speed up from subsonic to supersonic speed.

Because of the conservation of momentum, it takes a lot of slowing down to send a spacecraft towards the Sun. The Earth and objects on the Earth are traveling around the Sun at an average of 30 kilometers per second (67,000 miles per hour). So, to slow the spacecraft down enough to get it close to the Sun, it will have to fly around Venus seven times! This is the opposite of a gravity assist, or “slingshot”, in which a satellite gains energy by flying by a planet. In the case of Solar Probe Plus, as well as that of MESSENGER, multiple flybys of Venus imparts some of the craft’s energy to Venus, thereby slowing down the spacecraft.

The Solar Probe Plus mission is part of NASA’s “Living With a Star Program”, of which the Solar Dynamics Observatory is also a mission. This program is designed to study the impact our Sun has on the space environment of the Solar System, and acquire data to better equip future space missions.

Source: NASA press release, APL mission site

13 Replies to “NASA to Send a Probe Into the Sun”

  1. Interesting to note that original plans for a dedicated solar probe mission envisioned a solar polar orbit with a gravity assist from Jupiter (similar to Ulysses) and one or two flybys at perihelion distances of ~4 solar radii. (from the NASA webpage)-

    “In contrast, Solar Probe Plus remains nearly in the ecliptic plane and makes many near-Sun passes at increasingly lower perihelia.”

    The baseline mission provides for 24 perihelion passes inside 0.16 AU (35 RS[solar radii]), with 19 passes occurring within 20 RS of the Sun. The first near-Sun pass occurs 3 months after launch, at a
    heliocentric distance of 35 RS. Over the next several years successive Venus gravity assist (VGA) maneuvers gradually lower the perihelia to ~9.5 RS, by far the closest any spacecraft has ever come to the Sun. The spacecraft completes it nominal mission with three passes, separated by 88 days, at this distance.”

    While an equatorial mission will meet the stated goals, a polar orbit would enable a ‘3D’ view of the solar environment.

  2. Don’t worry about the probe burning up. The plan calls for a night landing.

    Couldn’t resist, sorry.

  3. I’m really liking this mission and expect some serendipitous or unplanned science to come out of it!

  4. Two important questions that the mission hopes to answer is the perplexing mystery of why the Sun’s atmosphere is hotter than its surface, and the mechanism for the solar wind that emanates from the Sun into the Solar System.

    Actually, there is no “perplexing mystery” as to why the Sun’s corona is hotter than its surface; that’s just propaganda from the “Electric Sun” proponents. This is from an ESA/NASA — “Solar Mystery Nears Solution with Data from SOHO Spacecraft” — November 5, 1997, press release:

    “We now have direct evidence for the upward transfer of magnetic energy from the Sun’s surface toward the corona above. There is more than enough energy coming up from the loops of the ‘magnetic carpet’ to heat the corona to its known temperature,” said Dr. Alan Title of the Stanford-Lockheed Institute for Space Research, Lockheed Martin Advanced Technology Center, Palo Alto, CA, who led the research. “Each one of these loops carries as much energy as a large hydroelectric plant, such as the Hoover dam, generates in about a million years!”

    Therefore, the purpose of the Solar Probe Plus spacecraft is to confirm that theory and gather additional data while there.

  5. I think the probe will also discover that the sun is not completely made out of iron and a thin layer of hydrogen and helium hiding the iron core as the “Electric Sun” proponents would make you believe.

  6. The issue of the Sun’s atmosphere being hotter than its surface has been solved. Quoting from here“They discovered that waves of magnetic plasma, initiated in large ‘bright point’ structures on the Sun, are energetic enough to heat the corona…”

  7. The heliosphere or corona is heated by oscillations in the solar magnetic field that wiggle the ions in the gas. These ions are spiralling around the magnetic field lines and dragged along if they wiggle. Hence some of these spirallying particles acquire energy by the change in the magnetic field, Think of the changing magnetic field as inducing (induction) a changing electric field which pushes the charged particles and gives them more energy. This wiggling converts some of that energy into thermal energy of these charged species. The ionized gas builds up this thermal energy, which turns out to be quite large.

    I figured right away there would have to be a lot of gravity braking to get a craft into an orbt that close. That is a lot of “delta-vee” needed, which will take 7 orbital passes with Venus to accomplish this.


  8. The nice thing about gravity assists is that you get to study the planet providing the assist as a bonus, on top of the primary mission goals. And you get to do it with instruments you wouldn’t use on a dedicated mission to that planet.

  9. “Only the Sun knows what we really need to know, only the Sun has the secrets”

    – Bradbury, I think from the “The Golden Apples of the Sun”

  10. VANKA wrote:

    “Actually, there is no “perplexing mystery” as to why the Sun’s corona is hotter than its surface; that’s just propaganda from the “Electric Sun” proponents… ”

    BOOOOOOOOOOO!!!!!!!!!!!!!!!!!!! why do you inist on trolling tis topic EVERY FEW DAYS?

  11. The corona heating mechanism has a good theoretical basis and some observational evidence backing it, but like always, there are plenty of details to mop up…

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