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Sailing Messenger to a Mercury Encounter

Who would have thought the planet Mercury would prove so useful in explaining how solar sails work? The Messenger spacecraft’s recent course adjustment maneuvers have proven unnecessary because controllers have been able to use its solar panels creatively, harnessing solar radiation pressure (SRP). And what better place to shake out such methods but on your way to a Sun-drenched planet that moves in an environment where SRP can be eleven times higher than that near Earth?

It may come as a surprise that we are already using solar sailing techniques on operational missions, but Messenger is not the first. In fact, we can go back to another Mercury mission, Mariner 10, which took advantage of the effect of solar photons on its twin solar panels, each about nine feet in length and three feet in width, a highly usable 55 square feet that not only generated power but got the spacecraft out of serious trouble. Launched in 1973, Mariner 10 ran into problems with its stabilizing gyroscopes and, later, with flaking paint on its high-gain antenna. The latter confused the spacecraft’s navigational sensors and caused it to lose its lock on the guide star Canopus.

The result: On March 6, 1974, Mariner 10’s troubled star-tracker induced a roll that lasted forty minutes, using up vital attitude control gases as the spacecraft tried to stabilize itself. Here’s what happened next, as told in the mission report:

On 11 March the spacecraft was not oriented in roll on the star Canopus as it went out of the star sensor’s view early in the morning due to the distraction of stray bright particles. However, the spacecraft was stable in its roll attitude because the tilt of Mariner’s solar panels is such that solar pressure on the panels created a torque counter to the natural drift in roll of the spacecraft. This stable condition was the result of skilled testing over the weekend to develop various combinations of panel tilt angles. One panel is at 66 deg and the other at 66½ degrees. The Mariner 10 roll attitude can be controlled by judicious tilting of the spacecraft solar panels.

So there you are, solar sailing at work, or at least, solar attitude correction made possible by the transfer of momentum from solar photons hitting those big solar panels. Messenger has done Mariner 10 one better by tilting its solar panels to adjust its trajectory, ensuring that the spacecraft would meet the 200-kilometer Mercury flyby point (it missed by a mere 1.4 kilometers), a targeting feat that Jim McAdams (Johns Hopkins Applied Physics Laboratory) describes as ‘spectacular.’

Look for more of the same on Messenger’s second Mercury flyby as controllers continue to use solar radiation pressure to control trajectory. In this case, the combination of spacecraft attitude and solar array orientation should continue to reduce the need for trajectory correction maneuvers using more traditional thrusters. By the time Messenger goes into orbit around Mercury in 2011 following gravity assist flybys of Earth, Venus (twice) and Mercury itself (three times), the use of solar radiation pressure should be better understood in a critical operational environment.

Image: Artist’s impression of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft in orbit at Mercury. MESSENGER launched on Aug. 3, 2004, and will begin a year-long orbital study of Mercury in March 2011, materially aided by solar sailing techniques. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

We’re closing on the second Mercury flyby, which takes place on October 6. The vehicle is now 90.04 million kilometers from the Sun and 140.9 million kilometers from Earth. All of the practical information we can learn about solar sailing from such encounters points to the need to get a working sail into near-Earth space for rigorous testing. With NanoSail-D’s duplicate ready to go, let’s hope a dedicated space sail can find a ride to orbit to extend the hard won experience of the Messenger mission.

Comments on this entry are closed.

  • FrankH September 10, 2008, 15:39

    Mariner 4 used small “sails” (solar pressure vanes) at the end of its solar panels as well, so the practice dates back to the very beginning of unmanned space exploration.

  • forrest noble September 11, 2008, 15:50

    Pretty cool stuff. Future spacecraft will be designed with this knowledge of solar panel manipulation capabilities for navigation purposed.

  • Darnell Clayton September 11, 2008, 23:53

    Forget Mars! (half joking here)

    Lets go to Mercury instead! We could take advantage of the solar wind to launch items towards Earth (and beyond).

    Unfortunately until we are able to develop some type of magnetic shield/field, taking advantage of Mercury’s position will only exist on paper. :-(

  • ljk October 9, 2008, 20:14

    NASA MESSENGER Sets Record for Accuracy of Planetary Flyby


    “By using solar sailing – rotating the spacecraft and tilting its solar
    panels to use the very small pressure from sunlight to alter the
    spacecraft’s trajectory – MESSENGER navigators have achieved
    a new record for the smallest miss distance between the intended
    and actual closest approach distance during a flyby of a planet
    other than Earth.”

  • ljk May 1, 2009, 9:50

    April 30, 2009

    New Mysteries Unveiled on Mercury

    Written by Nancy Atkinson

    Even though Mercury looks like the Moon at first glance, scientists from the MESSENGER mission say it’s becoming apparent that Mercury is an amazingly dynamic planet, and is actually more like Mars.

    For example, before this mission, scientists weren’t sure if volcanism even existed on Mercury, but from the spacecraft’s two flybys, they now know it is a very important part of the planet’s history.

    Additional new findings from the second flyby of Mercury in October 2008 show that the planet’s atmosphere, magnetosphere, and geological past are all characterized by much greater levels of activity than scientists first suspected.

    And by the way, isn’t this a stunning picture of an impact basin? It’s one of the new discoveries from MESSENGER.

    Full article here:


  • ljk July 6, 2009, 9:50

    Unknown Dark Material on Mercury


    Explanation: What is that strange material on Mercury? When flying by Mercury last October, the robotic MESSENGER spacecraft imaged much of the solar system’s innermost planet in unprecedented detail.

    As common in science, new data bring new mysteries. Pictured above on the lower right, a large crater — about 100 kilometers across — has unusual dark material of unknown composition near its center. The material’s darkness does not appear to be caused by shadows, as the Sun was near zenith when the image was taken.

    One origin hypothesis is that the dark material was uncovered from beneath Mercury’s surface during the impact that created the surrounding crater. If so, the composition of the dark mound might be similar to the composition of some mysterious dark rings also recently discovered on Mercury.

    Alternatively, the dark material could be related to an unusual composition of the impacting rock. MESSENGER will buzz past Mercury again later this year before entering orbit in 2011.


  • ljk October 8, 2009, 20:46

    October 5, 2009

    Massive Mosaic of Mercury

    Written by Nancy Atkinson

    If you want to REALLY see Mercury up close and personal, take a look at this absolutely HUGE mosaic of the planet. It was put together by Jason Perry, who actually works with the Cassini mission but in his spare time stitched together 66 images from the MDIS narrow angle camera from the MESSENGER mission’s second flyby of Mercury in October 2008, along with some data from the Mariner 10 mission in the 1970s.

    The full file is 20 MB, with a resolution of 0.6 kilometers (0.37 miles) per pixel. What fun! —for us, that is. It took Perry four days just to set up his software, according to Emily Lakdawalla at the Planetary Society Blog.


    Full article and mosaic here:


  • ljk October 9, 2009, 21:45

    Mercury’s geochronology revised by applying Model Production Functions to Mariner 10 data: geological implications

    Authors: M. Massironi (1), G. Cremonese (2), S. Marchi (1), M. Martellato (3), M. Mottola (4), R.J. Wagner (4) ((1) Padova University; (2) INAF-Padova; (3) CISAS-Padova; (4) DLR-Berlin)

    (Submitted on 8 Oct 2009)

    Abstract: Model Production Function chronology uses dynamic models of the Main Belt Asteroids (MBAs) and Near Earth Objects (NEOs) to derive the impactor flux to a target body. This is converted into the crater size-frequency-distribution for a specific planetary surface, and calibrated using the radiometric ages of different regions of the Moon’s surface.

    This new approach has been applied to the crater counts on Mariner 10 images of the highlands and of several large impact basins on Mercury. MPF estimates for the plains show younger ages than those of previous chronologies. Assuming a variable uppermost layering of the Hermean crust, the age of the Caloris interior plains may be as young as 3.59 Ga, in agreement with MESSENGER results that imply that long-term volcanism overcame contractional tectonics.

    The MPF chronology also suggests a variable projectile flux through time, coherent with the MBAs for ancient periods and then gradually comparable also to the NEOs.

    Comments: Accepted by Journal Geophysical Research Letters

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

    Cite as: arXiv:0910.1399v1 [astro-ph.EP]

    Submission history

    From: Simone Marchi [view email]

    [v1] Thu, 8 Oct 2009 15:04:08 GMT (129kb)


  • ljk February 25, 2011, 23:05