NASA MESSENGER Instruments Take Aim

Status Report From: Johns Hopkins University
Posted: Sunday, January 13, 2008


MESSENGER's engineering and operations teams convened at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., early this morning to confirm the health and readiness of the spacecraft.

At 7:56 a.m. EST the last bits of data from the spacecraft were received as it transitioned from high-gain downlink to beacon-only operations, turning the Mercury Dual Imaging System (MDIS) instrument toward the planet to start the approach color movie sequence. For the next 24 hours or so, the spacecraft will take three color frames of the planet every 20 minutes. When MESSENGER approaches within 39,000 kilometers (24,233.5 miles) of Mercury, the Mercury Atmospheric and Surface Composition Spectrometer instrument will start interleaving sweeps of the planet's anti-sunward tail at ultraviolet and visible wavelengths.

"The spacecraft is now on autopilot, executing the more than 5,000-line on-board command sequence and dutifully capturing the data from this historic flyby," said APL's Eric Finnegan, the MESSENGER Systems Engineer. "The operations team and the radio science team are now preparing for the post-occultation period, where operators at the Deep Space Network in Goldstone, Calif., will test their skill at capturing the spacecraft's radio signal, just minutes before closet approach with the planet, providing critical measurements for determining the mass distribution within Mercury."

MESSENGER Has Mercury in Its Sights!

With just one day until MESSENGER's historic flyby of Mercury, MESSENGER has Mercury clearly in its sights. The Narrow Angle Camera, part of the MDIS instrument, took this image on January 12, 2008, when MESSENGER was about 1.2 million kilometers (750,000 miles) away from Mercury. Mercury has a diameter of about 4,880 kilometers (3,030 miles), and this image has a resolution of about 31 kilometers/pixel (19 miles/pixel).

As the spacecraft continues toward closest approach, additional information and features will be available online at, so check back frequently. Following the flyby, be sure to check for the latest released images and science results!

On the Eve

MESSENGER Project Scientist Ralph McNutt, Jr., a member of the MESSENGER team since the mission was first proposed to NASA in 1996, reflects on the significance of the spacecraft's first flight past Mercury.

MESSENGER - in many ways, the little spacecraft that could - will soon make its first flyby of the innermost planet of our solar system. The science team is poised to convert the downlinked data stream of binary bits into the first close-up images of this puzzling world in almost 33 years. Technological advances made over the last three decades, built into a suite of miniaturized electronic instruments, will yield other types of measurements, many of which could not have been made at the time of Mariner 10.

MESSENGER is so nearly perfectly on course that two backup trajectory-correction maneuvers were not needed, and solar pressure from the looming Sun is helping to ease the probe toward threading its final needle - a point in mathematical and physical space at 200 kilometers (124 miles) above Mercury's rocky surface. Tomorrow's flyby - whose primary purpose is to continue to slow the spacecraft for eventual propulsive insertion into orbit about Mercury in March 2011 - will allow unprecedented views of about half of the side of the planet not seen by Mariner 10.

In a week's time, the entire Caloris basin - an impact structure more than 1,300 kilometers (about 800 miles) in diameter - will have been revealed in all its glory. Many other such impact features on Mercury - signatures of the late heavy bombardment of the inner solar system that produced the Imbrium basin on the Moon and the Hellas basin on Mars, among others - may be imaged at close range for the first time.

The flyby observations and their scientific implications should be spectacular. But in an electronic world of special effects and the global village, connected by cell phones and the Internet, mythical exploration can be confused with the real thing. It should not surprise planetary scientists that a public used to seeing Captain Jean-Luc Picard navigating the Enterprise from the Earth past Saturn in less than 10 seconds on a television trailer might be confused that the actual journey to Mercury is such a long one.

Sci-Fi Channel viewers are more likely to be familiar with Stargate Atlantis than with the likes of Admiral Fabian Gottlieb von Bellingshausen, Captain Nathaniel Palmer, Captain John Davis, and those who subsequently followed to explore Antarctica. The omnipresence of sophisticated entertainment imparts an ever-increasing need for the technical community to engage their non-technical counterparts not just in education but also simply in continuing conversation.

Driven by the economic bonanza and unfettered national ambitions of the spice trade, the Era of European Exploration yielded widespread new understanding of our planet for the first time. Later explorers sought in vain for northeast and northwest passages, uncovering still more about Earth and its environs. Antarctica had its own heroic age of exploration. Through two world wars, expeditions to these farthest reaches of the Earth were small and privately financed, but the small budgets yielded significant discoveries.

That world changed in 1947 with "Operation Highjump," the U.S. Naval expedition to Antarctica. New national rivalries fueled explorations of the planet's last unknown real estate. And then something wonderful happened. A world on the precipice of the Cold War agreed to global scientific cooperation as part of the International Geophysical Year (1957-58), which established the framework for the current era of Antarctic exploration founded on the Antarctic Treaty. At the same time, a new U.S. agency, the National Aeronautics and Space Administration (NASA), was formed.

Fifty years later, the explorers have changed, and their horizons have broadened. The national political imperatives have changed as well, but exploration and new discoveries continue. The Cold War and the Space Race have taken humanity to the Moon - for a short time, but surely not the last - yet space exploration has also taught us how to work together in a truly international enterprise. Like the signing of the Antarctic Treaty, this cooperation has been no small feat.

Robotic emissaries now in orbit about Saturn, Mars, Venus, and our Moon have been enabled and are now operated by thousands of engineers, scientists, and space agency staffers from several continents and many nations. The twin Voyager spacecraft are nearing the interstellar void, and New Horizons is en route to the first views of Pluto and other Kuiper Belt objects beyond the orbit of Neptune. Everyone on this planet continues by proxy to feel the push of Robert Browning: "Ah, a man's reach should exceed his grasp, Or what's a heaven for?"

MESSENGER will soon return images and other observations from regions unseen and of phenomena unsuspected. We scientists will scurry to analyze, quantify, and make sense of it all. Journalists will scamper to report the news, and many citizens will turn avidly to their Web browsers to view the latest findings.

Those are the trees. But there is also a forest. This is exploration and discovery in its most real sense, not some electronic-game designer's newest effort. The exploration paradigm is shifting, and we can and should all take the new path together. Doing so will not be not easy or cheap. And we must balance our finite resources with the need to preserve what we have here on our own planet. Life always presents us with choices and balances. But the message from MESSENGER and our other far-flung emissaries is that exploring the unknown is part of the best in us all.

No need to beam me up, Scotty. There is intelligent life here.

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.

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