MESSENGER mission to Mercury

[Rick]

MESSENGER Navigates Second Hot Season, Executes Third Orbit-Correction Maneuver

MESSENGER Mission News
September 7, 2011

Today the MESSENGER spacecraft emerged unscathed from the second of four"hot seasons" expected to occur during its one-year primary mission in orbit around Mercury. Hours later, mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., successfully executed a maneuver to adjust the spacecraft's trajectory.

This hot season began on August 9 and lasted nearly one month. During that time, the closest approach of the spacecraft to Mercury was on the sunlit side of the planet. MESSENGER's sunshade reached temperatures as high as 350°C during this season, and its solar panels had to be turned off the Sun for short periods during each orbit to protect them from overheating.

More: http://messenger.jhuapl.edu/news_room/details.php?id=181

[Rick]

MESSENGER Finds New Evidence for Water Ice at Mercury's Poles

New observations by the MESSENGER spacecraft provide compelling support for the long-held hypothesis that Mercury harbors abundant water ice and other frozen volatile materials in its permanently shadowed polar craters.

Three independent lines of evidence support this conclusion: the first measurements of excess hydrogen at Mercury's north pole with MESSENGER's Neutron Spectrometer, the first measurements of the reflectance of Mercury's polar deposits at near-infrared wavelengths with the Mercury Laser Altimeter (MLA), and the first detailed models of the surface and near-surface temperatures of Mercury's north polar regions that utilize the actual topography of Mercury's surface measured by the MLA. These findings are presented in three papers published online today in Science Express.

More: http://www.nasa.gov/mission_pages/messenger/media/PressConf20121129.html

[Rick]

MESSENGER Completes Its First Extended Mission at Mercury

On March 17, 2013, MESSENGER successfully completed its year-long first extended mission in orbit about Mercury, building on the groundbreaking scientific results from its earlier primary mission. Today the team is poised to embark on a second extended mission that promises to provide new observations of Mercury's surface and interior at unprecedented spatial resolution and of the planet's dynamic magnetosphere and exosphere at high time resolution during the peak and declining phase of the current solar cycle.

More: http://messenger.jhuapl.edu/news_room/details.php?id=237

[Rick]

MESSENGER's First Images of Comets Encke and ISON

As the new comet C/2012 S1 (ISON) and the well-known short-period comet 2P/Encke both approach their closest distances to the Sun later this month, they are also passing close to the MESSENGER spacecraft now orbiting the innermost planet Mercury. Just this week, both comets have brightened sufficiently to be captured in images by MESSENGER's wide-angle camera.

More: http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=1296

(Link tested on all the systems and browsers I have available, and works fine on all. If you're having trouble with it, please put details in this thread in Updates and Upsets.)

[Rick]

A Tale of Two Comets: MESSENGER Captures Images of Encke and ISON

n November 18, NASA's Mercury-orbiting MESSENGER spacecraft pointed its Mercury Dual Imaging System (MDIS) at 2P/Encke and captured this image of the comet as it sped within 2.3 million miles (3.7 million kilometers) of Mercury's surface. The next day, the probe captured this companion image of C/2012 S1 (ISON), as it cruised by Mercury at a distance of 22.5 million miles (36.2 million kilometers) on its way to its late-November closest approach to the Sun.

MESSENGER's cameras have been acquiring targeted observations of Encke since October 28 and ISON since October 26, although the first faint detections didn't come until early November. During the closest approach of each comet to Mercury, the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) and X-Ray Spectrometer (XRS) instruments also targeted the comets. Observations of ISON conclude on November 26, when the comet passes too close to the Sun, but MESSENGER will continue to monitor Encke with both the imagers and spectrometers through early December.

The spacecraft has a view of the comets very different from that of Earth-based observers. "MESSENGER imaged Encke only a few days before its perihelion when it was at its brightest," explains Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory, who is leading MESSENGER's comet-observation campaign. "That we are so close to the comet at this time offers a chance to make important observations that could shed light on its asymmetric behavior about perihelion."

More: http://messenger.jhuapl.edu/news_room/details.php?id=246
APOD: http://apod.nasa.gov/apod/ap131123.html

[Rick]

Mercury's Contraction Much Greater Than Thought

New global imaging and topographic data from MESSENGER show that the innermost planet has contracted far more than previous estimates. The results are based on a global study of more than 5,900 geological landforms, such as curving cliff-like scarps and wrinkle ridges, that have resulted from the planet's contraction as Mercury cooled. The findings, published online today in Nature Geoscience, are key to understanding the planet's thermal, tectonic, and volcanic history, and the structure of its unusually large metallic core.

Unlike Earth, with its numerous tectonic plates, Mercury has a single rigid, top rocky layer. Prior to the MESSENGER mission only about 45% of Mercury's surface had been imaged by spacecraft. Old estimates, based on this non-global coverage, suggested that the planet had contracted radially by about 1/2 to 2 miles (0.8 to 3 kilometers), substantially less than that indicated by models of the planet's thermal history. Those models predicted a radial contraction of about 3 to 6 miles (5 to 10 kilometers) starting from the late heavy bombardment of the Solar System, which ended about 3.8 billion years ago.

The new results, which are based on the first comprehensive survey of the planet's surface, show that Mercury contracted radially by as much as 4.4 miles (7 kilometers) -- substantially more than the old estimates, but in agreement with the thermal models. Mercury's modern radius is 1,516 miles (2,440 kilometers).

More: http://messenger.jhuapl.edu/news_room/details.php?id=254

[Rick]

MESSENGER Modifies Orbit to Prepare for Low-Altitude Campaign

MESSENGER successfully completed the first orbit-correction maneuver of its Second Extended Mission this morning to raise its minimum altitude above Mercury from 113.9 kilometers (70.8 miles) to 155.1 kilometers (96.4 miles). This maneuver is the first of four designed to modify the spacecraft's orbit around Mercury so as to delay the spacecraft's inevitable impact onto Mercury's surface and allow scientists to continue to gather novel information about the innermost planet.

During the primary phase of the MESSENGER mission, the spacecraft's orbit around Mercury was highly eccentric, drifting between 200 and 500 kilometers (124 to 311 miles) above Mercury's surface at closest approach, and between 15,200 and 14,900 kilometers (9,445 to 9,258 miles) above the surface at its farthest point, and completing an orbit every 12 hours. Spacecraft operators at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, conducted several spacecraft maneuvers to counter the perturbing forces that caused MESSENGER's lowest orbital altitude to drift upward, away from its preferred observing geometry, and early in MESSENGER's First Extended Mission conducted a pair of maneuvers to reduce the orbital period to eight hours.

"In this final phase of the mission, the opposite effect is happening," explained the mission trajectory lead Jim McAdams of APL. "To extend the mission, we need to raise the minimum altitude by increasing the Mercury-relative speed of the spacecraft when it is farthest from Mercury."

More: http://messenger.jhuapl.edu/news_room/details.php?id=257

[Rick]

MESSENGER and STEREO Measurements Open New Window Into High-Energy Processes on the Sun

Understanding the Sun from afar isn't easy. How do you figure out what powers solar flares -- the intense bursts of radiation coming from the release of magnetic energy associated with sunspots -- when you must rely on observing only the light and particles that make their way to Earth's orbit? One answer: you get closer.

NASA's MESSENGER spacecraft -- which orbits Mercury, and so is as close as 28 million miles from the Sun versus Earth's 93 million miles -- is close enough to the Sun to detect solar neutrons that are created in solar flares. The average lifetime for one of these neutrons is only 15 minutes. How far they travel into space depends on their speed, and slower neutrons don't travel far enough to be seen by particle detectors in orbit around Earth.

More: http://messenger.jhuapl.edu/news_room/details.php?id=258

[Rick]

MESSENGER Gets Closer to Mercury than Ever Before

On July 25, MESSENGER moved closer to Mercury than any spacecraft has before, dropping to an altitude at closest approach of only 100 kilometers (62 miles) above the planet's surface.

"The science team is implementing a remarkable campaign that takes full advantage of MESSENGER's orbital geometry, and the spacecraft continues to execute its command sequences flawlessly as the 14th Mercury year of the orbit phase comes to a close," said MESSENGER Mission Operations Manager Andy Calloway, of the Johns Hopkins University Applied Physics Laboratory (APL).

More: http://messenger.jhuapl.edu/news_room/details.php?id=259

[Rick]

MESSENGER Provides First Optical Images of Ice Near Mercury's North Pole

NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has provided the first optical images of ice and other frozen volatile materials within permanently shadowed craters near Mercury's north pole. The images not only reveal the morphology of the frozen volatiles, but they also provide insight into when the ices were trapped and how they've evolved, according to an article published today in the journal, Geology.

Two decades ago, Earth-based radar images of Mercury revealed the polar deposits, postulated to consist of water ice. That hypothesis was later confirmed by MESSENGER through a combination of neutron spectrometry, thermal modeling, and infrared reflectometry. "But along with confirming the earlier idea, there is a lot new to be learned by seeing the deposits," said lead author Nancy Chabot, the Instrument Scientist for MESSENGER's Mercury Dual Imaging System (MDIS) and a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.

Beginning with MESSENGER's first extended mission in 2012, scientists launched an imaging campaign with the broadband clear filter of MDIS's wide-angle camera (WAC). Although the polar deposits are in permanent shadow, through many refinements in the imaging, the WAC was able to obtain images of the surfaces of the deposits by leveraging very low levels of light scattered from illuminated crater walls. "It worked in spectacular fashion," said Chabot.

The team zeroed in on Prokofiev, the largest crater in Mercury's north polar region found to host radar-bright material. "Those images show extensive regions with distinctive reflectance properties," Chabot said. "A location interpreted as hosting widespread surface water ice exhibits a cratered texture indicating that the ice was emplaced more recently than any of the underlying craters."

More: http://messenger.jhuapl.edu/news_room/details.php?id=266

[Rick]

Third of Four Planned Maneuvers Extends MESSENGER Orbital Operations

MESSENGER mission controllers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., conducted the third of four maneuvers today to raise the spacecraft's minimum altitude sufficiently to extend orbital operations and delay the probe's inevitable impact onto Mercury's surface until early next spring.

More: http://messenger.jhuapl.edu/news_room/details.php?id=267

[Rick]

Maneuver Successfully Delays MESSENGER's Impact, Extends Orbital Operations

MESSENGER mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., successfully conducted a maneuver today designed to raise the spacecraft's minimum altitude sufficiently to extend orbital operations and delay the probe's inevitable impact onto Mercury's surface until early next spring.

The immediately previous maneuver, completed on October 24, 2014, raised MESSENGER to an altitude at closest approach from 25.4 kilometers (15.8 miles) to 184.4 kilometers (114.6 miles) above the planet's surface. Because of progressive changes to the orbit over time, the spacecraft's minimum altitude continued to decrease.

At the time of this most recent maneuver, MESSENGER was in an orbit with a closest approach of 25.7 kilometers (16.0 miles) above the surface of Mercury. With a velocity change of 9.67 meters per second (21.62 miles per hour), the spacecraft's four largest monopropellant thrusters (with a small contribution from four of the 12 smallest monopropellant thrusters) nudged the spacecraft to an orbit with a closest approach altitude of 105.1 km (65.3 miles).

More: http://messenger.jhuapl.edu/news_room/details.php?id=271

[Rick]

New MESSENGER Maps of Mercury's Surface Chemistry Provide Clues to the Planet's History

The MESSENGER mission was designed to answer several key scientific questions, including the nature of Mercury's geological history. Remote sensing of the surface's chemical composition has a strong bearing on this and other questions. Since MESSENGER was inserted into orbit about Mercury in March 2011, data from the spacecraft's X-Ray Spectrometer (XRS) and Gamma-Ray Spectrometer (GRS) have provided information on the concentrations of potassium, thorium, uranium, sodium, chlorine, and silicon, as well as ratios relative to silicon of magnesium, aluminum, sulfur, calcium, and iron.

Map: http://messenger.jhuapl.edu/news_room/images/magnesium-silicon.jpg

More: http://messenger.jhuapl.edu/news_room/details.php?id=273

[Rick]

Best views yet of Mercury's ice-filled craters

Scientists have obtained the most detailed views yet of ice deposits inside the permanently shadowed craters at Mercury's north pole.

The pictures were taken by Nasa's Mercury Messenger spacecraft, which has been orbiting just tens of kilometres from the planet's surface.

More: http://www.bbc.co.uk/news/science-environment-31917308

[Rick]

MESSENGER's Endgame: Hover Campaign Promises Bird's-Eye View of Mercury's Surface

MESSENGER will not go gentle into that good night. The mission will end sometime this spring, when the spacecraft runs out of propellant and the force of solar gravity causes it to impact the surface of Mercury. But the team initiated a "hover" observation campaign designed to gather scientific data from the planet at ultra-low altitudes until the last possible moment. Engineers have devised a series of orbit-correction maneuvers (OCMs) over the next five weeks -- the first of which was carried out today -- designed to delay the inevitable impact a bit longer.

A highly accurate OCM executed on January 21 targeting a 15-kilometer periapsis altitude -- the lowest to date -- set the stage for the hover campaign, in a short extension of the Second Extended Mission termed XM2-Prime (XM2'). The top science goals for XM2' will be carried out with the Magnetometer (MAG) and the Neutron Spectrometer (NS), and each instrument will target different objectives in different regions, explained MESSENGER Deputy Project Scientist Haje Korth, of The Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md.

"With MAG, we will look for crustal magnetic anomalies," he said. "For instance, we have seen hints of crustal magnetization at higher altitudes (~70 kilometers) over the northern rise in Mercury's northern smooth plains. We will revisit this region at lower altitudes during XM2'. There may be other regions where such signals can be observed, and we will be looking for them."

"With NS, scientists will hone in on shadowed craters at northern high latitudes to search for water ice," Korth said. "We have found such evidence previously in the mission, but we hope to find more at low altitudes and spatially resolve the distribution within individual craters if we are lucky."

More: http://messenger.jhuapl.edu/news_room/details.php?id=276