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MESSENGER Mission News
August 20, 2009
http://messenger.jhuapl.edu



Upcoming Mercury Encounter Presents New Opportunities for Magnetometer

On September 29, the MESSENGER spacecraft will pass by Mercury for the third time, flying 141.7 miles above the planet’s rocky surface for a final gravity assist that will enable it to enter orbit about Mercury in 2011. This encounter will also provide new observational opportunities for MESSENGER’s Magnetometer, designed to determine the structure and origin of Mercury's intrinsic magnetic field.

The comparison of magnetosphere observations from MESSENGER's first flyby in January 2008 with data from the probe's second pass in October 2008 provided key new insight into the nature of the planet’s internal magnetic field and revealed new features of Mercury’s magnetosphere, explains Brian Anderson, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.

“MESSENGER’s first flyby of Mercury and Mariner 10’s encounters with the planet provided data only from Mercury's eastern hemisphere,” says Anderson, MESSENGER’s Deputy Project Scientist. “The October 2008 flyby provided the first measurements from Mercury’s western hemisphere, and scientists learned that the planet's magnetic field is highly symmetric. This finding is significant for the planet’s internal field because it implies that the dipole is even more closely aligned with the planet's rotation axis than we could conclude before the second flyby.”

The probe’s third flyby of Mercury next month will take it again over the planet’s western hemisphere, and the observations will be used to refine the estimate of the planetary magnetic field, Anderson explains.

“The previous flybys yielded significant insight into the dynamics of Mercury’s magnetosphere and its boundaries,” Anderson says. “During the second flyby a plasmoid and a series of traveling compression regions were observed in Mercury’s magnetotail, and a large flux transfer event was observed at the dayside magnetopause. These observations proved that the solar wind interaction, under the right circumstances, can drive intense magnetic reconnection at rates 10 times the rates observed at Earth.”

The behavior during the second flyby was markedly different from that found in the first flyby, demonstrating the profound influence of the solar wind environment on Mercury’s magnetosphere. “The third flyby is the last opportunity to survey the magnetotail and magnetopause regions in the equatorial plane, and the contrast in the system’s structure under different solar wind conditions already observed make it likely that the third flyby will yield new insights and perhaps more surprises for the dynamics of this smallest and most highly variable of the solar system’s planetary magnetospheres,” Anderson says.

As with the previous two flybys, the Magnetometer will record the magnetic field at the highest available observation rate of 20 vector magnetic field samples per second for a period of twelve hours centered on the time of closest approach. “This observing plan guarantees the highest possible science return from the encounter and will provide key observations to guide the magnetic field investigation plan for the prime orbital phase of the mission,” Anderson says.



Berkel Leaves Its Mark

The crater in the lower left corner of this image is Berkel, recently named for Turkish painter and printmaker Sabri Berkel (1909-1993). The crater contains dark material in its center and in a ring immediately surrounding it. Moreover, Berkel is surrounded by a blanket of bright ejecta and a system of bright rays. Other craters on Mercury’s surface, such as Basho, also exhibit both bright rays and dark halos. In contrast, two neighboring craters in this image (indicated by white arrows) have bright rays but lack dark halos. Members of the MESSENGER Science Team are investigating why some craters contain dark material while others do not, and what that means for the nature and structure of Mercury's crust. To view other images released over the summer, go online to http://messenger.jhuapl.edu/gallery/sciencePhotos/index.php.


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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MESSENGER Mission News
September 16, 2009
http://messenger.jhuapl.edu



MESSENGER Team Prepares for Third Flyby, Rehearses for Orbital Operations

In less than two weeks, on September 29, MESSENGER will fly by Mercury for the third and final time, a maneuver key to placing the probe on a trajectory that will enable its March 2011 insertion into orbit about Mercury. Even as the team readies for this critical event, a parallel effort has long been underway to prepare MESSENGER for the main event.
Since January, the team has been staging orbital operations rehearsal tests, called week-in-the-life (WITL) tests, to try out the new procedures and software being developed for the Mercury orbital mission. Next month, they will wrap up the second such test, and the results of these exercises are proving pivotal to the team’s plan.
“Because no spacecraft has orbited the planet Mercury before, we do not have any direct experience planning and scheduling science observations in such an environment,” explains Alice Berman, MESSENGER’s Payload Operations Manager. “Therefore, a comprehensive orbital operations readiness plan is underway to ensure that the mission’s full science success criteria can be met by the time that the nominal mission ends on 17 March 2012. The WITL tests, meant to simulate several realistic weeks of orbital operations, are an integral part of this overall readiness plan.”
Between 2009 and 2010, the team will run at least seven WITLs covering different weeks and orbital conditions. “It’s critical to test as many different observing scenarios and orbital conditions that will occur during the orbital mission as possible,” Berman says.
The first WITL test ran from January to April. The team chose to rehearse the planning and scheduling for a week in mid-October 2011, when the level of instrument commanding is not extremely demanding. The focus of WITL-1 was primarily on new procedures and software that had recently been developed. “We wanted to walk through all the processing steps of preparing a weekly command load, with careful attention to the newly developing software tools,” Berman recounts.
At an all-day workshop in February, the instrument teams worked through the required steps for preparing and delivering their WITL-1 instrument sequences to the mission operations team. The mission operations team then built the spacecraft command load – adding the necessary spacecraft commanding (e.g., solar array commanding, spacecraft downlinks) – and ran it on the MESSENGER hardware simulator. With that done, the mission operations and science operations teams reviewed the results.
A debriefing meeting was held in April to review the success of the test and gather the issues to be addressed and lessons learned prior to starting the next rehearsal test. “We learned that we need to have an extremely easy and efficient process, because we must start a new command load each week,” Berman explains. “We need a way to automatically keep track of status and approvals and to notify team members when their attention or action is needed. We found a project management software called JIRA that will help us do all this. We learned a lot about what our current tools can do (and what they cannot), and we are prioritizing the required software fixes and enhancements now.”
The second WITL test began in July 2009 and will be completed in October. “In addition to testing the improved the orbital planning processes and software, WITL-2 is focusing on a different timeframe of the orbital mission, so that different instrument and spacecraft components will be tested,” Berman says. “Right now the mission operations team is building the WITL-2 integrated command load, and then it will be tested on the MESSENGER hardware simulator.”
The remaining WITL tests will be conducted in 2010, and the team is currently developing the schedule and scope of these tests. “In 2010, the WITL tests will overlap in time so that the teams can exercise the process of working on more than one weekly command load at one time,” Berman notes. “We will carefully assess what works well and what does not, and we will update our processes and software tools with the lessons learned from each WITL test.”
“Once in orbit, our near-term scheduling strategy will be to prepare and upload a new command load (containing both instrument and spacecraft instructions) once per week,” Berman adds. “This work will require the close coordination of both the science and mission operations teams. We believe that it will take approximately three weeks to prepare each command load, so the science and mission operations teams will be working on more than one command load at any given time.”



On Target for Mercury Flyby 3

The MESSENGER spacecraft will pass 228 kilometers (142 miles) above Mercury's surface on September 29 for the mission's third flyby of the Solar System's innermost planet. The MESSENGER team has been working on the flyby observation plans for months. Three of the highlights for MDIS include:
  • <LI style="mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l0 level1 lfo1" class=MsoNormal>NAC approach mosaic. This mosaic will provide the first close-up images of a portion of Mercury's surface by spacecraft. (That portion of the surface appears as a featureless white strip near the limb of the planet in the top image.) <LI style="COLOR: black; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l0 level1 lfo1" class=MsoNormal>WAC and MASCS targeted observations. Unlike the neatly arranged rows and columns of most MDIS mosaics, for these observations WAC images in 11 color filters will be acquired as MASCS collects high-quality spectral measurements of specific targets of interest. Visit this page to learn more about these targeted observations.
  • NAC departure high-resolution southern hemisphere mosaic. This large 15-column by 13-row mosaic will provide new detail for an area of Mercury's surface in the southern hemisphere and will be complementary to a high-resolution mosaic of the northern hemisphere obtained during Mercury flyby 2.
On September 23, NASA will host a media teleconference previewing the flyby. Details of that event will be posted online at http://messenger.jhuapl.edu/news_room/index.php.


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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Go MErcury Space, Space ENvironment, GEochemistry and Ranging, Go! :speakcool:


228 km is a nice one! Can't wait to see the close-ups.
 

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Dwayne Brown
Headquarters, Washington Sept. 21, 2009
202-358-1726
[email protected]

Paulette Campbell
Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
240-228-6792
[email protected]

MEDIA ADVISORY: M09-181

NASA TO PREVIEW MISSION'S THIRD FLIGHT PAST MERCURY

WASHINGTON -- NASA will host a media teleconference at 1 p.m. EDT on Wednesday, Sept. 23, to preview the third and final flyby of Mercury by the Mercury Surface, Space Environment, Geochemistry, and Ranging spacecraft known as MESSENGER.

On Sept. 29, the spacecraft will swing less than 142 miles above the planet's rocky surface for a final gravity assist that will enable it to enter orbit around Mercury in March 2011. With more than 90 percent of the planet's surface imaged after the spacecraft's second flyby, the team will focus instruments on questions raised by the earlier flybys to advance our understanding of the planet closest to the sun.

The briefing participants are:
- Anthony Carro, MESSENGER program executive, NASA Headquarters in Washington
- Eric J. Finnegan, mission systems engineer, Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
- Noam R. Izenberg, Mercury Atmospheric and Surface Composition Spectrometer instrument scientist, Johns Hopkins University Applied Physics Laboratory
- Sean C. Solomon, principal investigator, Carnegie Institution of Washington

To participate in the teleconference, reporters should e-mail Dwayne Brown at [email protected] for dial-in and passcode information.

Audio of the teleconference will be streamed live at:




At the beginning of the briefing, related images will be available at:


 

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For Immediate Release
September 23, 2009


Media Contact: Paulette Campbell
(240) 228-6792
[email protected]

MESSENGER Prepares for Final Pass by Mercury
On September 29, 2009, the MESSENGER spacecraft will fly by Mercury for the third and final time, passing 141.7 miles above the planet’s rocky surface for a final gravity assist that will enable it to enter orbit about Mercury in 2011. With more than 90 percent of the planet’s surface already imaged, the team will turn its instruments during this flyby to specific features to uncover more information about the planet closest to the Sun.
“The first two flybys of Mercury revealed nearly half of the planet in detail for the first time,” notes MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. “During this third encounter, the MESSENGER camera will again image areas never before seen at close range, and we will obtain color images of other regions at resolutions superior to those of previous observations. Our other instruments will target interesting areas of the surface, atmosphere, and magnetosphere for detailed measurements designed to address questions raised by observations made during the earlier flybys.”
Depending on the activity of the Sun, Solomon adds, MESSENGER might also view yet another distinct snapshot of how the planet interacts with conditions in interplanetary space driven by the behavior of our nearest star.
Peering through Mercury’s Exosphere
The first two flybys provided an unprecedented glimpse into the structure of the planet’s tenuous exosphere and the processes behind it. During this encounter, the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) will again make high-spectral- and high-spatial-resolution measurements of Mercury’s exosphere.
“Targeted scans of the planet’s comet-like tail by the MASCS Ultraviolet and Visible Spectrometer will permit a search for temporal variability in both the sodium and calcium components,” notes MASCS Instrument Scientist Noam Izenberg of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. “In addition, we will target the north- and south-polar regions for detailed observations of those species, and we will look for several new exospheric species.”
A Few New Pictures
The Mercury Dual Imaging System (MDIS) will capture 1,559 pictures of the planet. “Using all 11 filters of the wide-angle camera, we are going to collect high-resolution, color images of scientifically interesting targets that we identified from the second flyby, and at the same time MASCS will observe those same targets,” explains APL’s Ralph McNutt, MESSENGER Project Scientist.
As MESSENGER approaches Mercury, MDIS’s narrow-angle camera (NAC) will capture images of previously unseen terrain. Later, as the spacecraft departs, the NAC will take high-resolution images of the southern hemisphere that will be used to create a mosaic to complement the high-resolution, northern-hemisphere mosaic obtained during the second Mercury flyby.
Images captured eight days before and 21 days after the probe’s closest approach to Mercury will allow MESSENGER scientists to create detailed phase curves of Mercury at multiple wavelengths, and searches will be conducted for possible satellites of Mercury as small as 100 meters in diameter.
Combing the Surface
Determining the composition of Mercury's surface is a major goal of the orbital phase of the mission, and during this flyby the instruments focused on compositional measurements will have a third opportunity to observe Mercury.
The MASCS sensors – both UVVS and the Visible and Infrared Spectrograph – will spend about 30 seconds on each of 11 targets, two at locations also targeted for photometry, focusing on end-member compositional characteristics identified during the second flyby. The X-Ray Spectrometer will once again look for X-ray fluorescence from surface elements, depending on the level of solar activity, and the Gamma-Ray Spectrometer will acquire more counting data from approximately the same region that it surveyed during the second flyby.
The Neutron Spectrometer will use two spacecraft maneuvers to provide better Doppler filtering of encountered neutron fluxes, including a 180° spacecraft roll on the night side (inbound) and a 45° roll on the dayside (outbound). The nightside maneuver will provide more information on the composition on the side of the planet away from that sampled during the first flyby, and the combination of dayside and night-side measurements will enable a test of the influence of planetary surface temperature on the thermal neutron fluxes, data important for properly interpreting the neutron fluxes to be measured during the orbital phase of the mission.
MESSENGER’s third Mercury flyby will provide more data on the correlation between high-resolution topography and high-resolution images of Mercury. The Mercury Laser Altimeter (MLA) will range to Mercury's surface and make a topographic profile along the instrument ground track. A shift in the longitude of closest approach by 17° to the west and 3° north from the position of closest approach for the second flyby will allow the data from the third flyby to augment and complement those from the second flyby. In addition, the slower flyby speed (approximately 1.5 kilometers per second slower relative to the center of Mercury) will keep the trajectory closer to the planet longer.
“The data we gather will provide additional topography of surface features on Mercury for our ongoing studies of the morphology of craters and tectonic structures, such as thrust faults,” says MLA Instrument Scientist Olivier Barnouin-Jha of APL. “It will also extend our equatorial view of Mercury’s global shape and allow us to confirm the discovery made during the first and second flyby of MESSENGER that Mercury’s equatorial region possesses a slightly elliptical shape.”
Surprises about Mercury’s Magnetic Field
The third Mercury encounter could reveal surprises about the planet’s magnetic field, says MESSENGER Deputy Project Scientist Brian Anderson, of APL. “The first two flybys took the spacecraft over opposite sides of the planet – over the eastern hemisphere in January 2008 and the western side in October 2008,” Anderson notes. “The third flyby will take it again over the planet’s western hemisphere, and the observations will be used to refine the estimate of the planet’s internal magnetic field.”
Anderson says this flyby is the last opportunity to survey the magnetotail and magnetopause regions in the equatorial plane. “The contrast in the system’s structure under different solar wind conditions already observed make it likely that the third flyby will yield new insights and perhaps more surprises regarding the dynamics of this smallest and most highly variable of the solar system’s planetary magnetospheres,” he adds.
As with the previous two flybys, the Magnetometer will record the magnetic field at the highest available observation rate of 20 vector magnetic field samples per second for a period of twelve hours centered on the time of closest approach. “This observing plan guarantees the highest possible science return from the encounter and will provide key observations to guide the magnetic field investigation plan for the prime orbital phase of the mission,” Anderson says.
”This flyby will not only be our last close look at the equatorial regions of Mercury, it is our final planetary gravity assist, and it will be important for the entire encounter to be executed as planned,” summarizes Solomon. “As enticing as these flybys have been for discovering some of Mercury’s secrets, they are the hors d’oeurves to the mission’s main course, observing Mercury from orbit for an entire year.”



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.




---------- Post added at 19:54 ---------- Previous post was at 07:04 ----------

September 24, 2009

Media Contact: Paulette Campbell
240-228-6792
[email protected]

Media Invited to Join MESSENGER Team for Mercury Closest Approach

At 5:55 p.m. on September 29, MESSENGER will fly 142 miles above the cratered surface of Mercury for the third and final time. The goal of the flyby is to adjust MESSENGER’s orbit so that it more closely matches that of Mercury, which will allow the spacecraft to be inserted into orbit about the innermost planet on March 18, 2011. During this encounter MESSENGER will have nearly the same view of Mercury as it did during its second flyby on October 6, 2008, so the team is planning targeted observations that build on the discoveries of the first two flybys.

Reporters are invited to the MESSENGER Situation Room at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., 5:00 p.m. – 7:00 p.m. on Tuesday, September 29, 2009, to watch operators maneuver the spacecraft through closest approach. Members of the MESSENGER operations and science teams will be available to discuss the mission and Mercury flyby activities.

Space is limited, and registration is required. Reporters interested in attending should contact Paulette Campbell at (240) 778-6792 or [email protected] by September 28, 2009.

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 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. Visit http://messenger.jhuapl.edu/ for the latest images from Jupiter and mission status reports.



The Applied Physics Laboratory, a division of The Johns Hopkins University, meets critical national challenges through the innovative application of science and technology. For more information, visit www.jhuapl.edu.
 

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Here is a flyby scenario starting one hour out from the flyby. Watch the flyby in the right MFD, and watch MESSENGER's orbit shrink in the right MFD :speakcool:.
Code:
BEGIN_DESC
Fly a DG on the same trajectory as MESSENGER Flyby 3
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 55103.875671296
END_ENVIRONMENT

BEGIN_FOCUS
  Ship GL-01
END_FOCUS

BEGIN_CAMERA
  TARGET GL-01
  MODE Cockpit
  FOV 50.00
END_CAMERA

BEGIN_MFD Left
  TYPE Orbit
  PROJ Frame
  FRAME Ecliptic
  REF Sun
  TARGET Mercury
END_MFD

BEGIN_MFD Right
  TYPE Orbit
  PROJ Ship
  FRAME Equator
  ALT
  REF Mercury
END_MFD

BEGIN_SHIPS
GL-01:DeltaGlider
  STATUS Orbiting Mercury
  RPOS 13826760.367 -1616278.316 -4638416.175
  RVEL -3155.985 446.901 2071.858
  AROT 19.37 70.78 105.78
  PRPLEVEL 0:1.0 1:1.0
  NOSECONE 0 0.0000
  GEAR 0 0.0000
  AIRLOCK 0 0.0000
END
END_SHIPS
 

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MESSENGER Mission News
September 25, 2009
http://messenger.jhuapl.edu



Hello, Mercury!

With four days remaining until MESSENGER's third flyby of Mercury, the Mercury Dual Imaging System’s narrow-angle camera captured this image of the approaching planet. Mercury appears as a sunlit crescent, and the MESSENGER spacecraft is quickly approaching at a speed of approximately 3.3 kilometers/second (7,400 miles/hour)! View this animation to watch the many instrument observations planned for the upcoming encounter next week.



Hear a Replay of NASA’s Preview of MESSENGER Mercury Flyby 3

On September 23, NASA hosted a media teleconference previewing the flyby. To hear a replay of that teleconference, call 800-627-0199. The supporting images, including an updated press kit, are available online at: http://messenger.jhuapl.edu/news_room/telecon6.html.


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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MESSENGER Mission News
September 28, 2009
http://messenger.jhuapl.edu



One Day to Mercury Flyby 3!

MESSENGER’s engineering and operations teams convened at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., this morning to confirm the health and readiness of the spacecraft. “All spacecraft sub-systems and instruments reported nominal operations, indicating that MESSENGER was ready for its third encounter with Mercury,” said MESSENGER Systems Engineer Eric Finnegan of APL.

At 10:28 a.m. the last bits of data from the spacecraft were received as it transitioned from high-gain downlink to beacon-only operations, turning towards the planet to start the approach tail-sweep sequence with the Mercury Atmospheric and Surface Composition Spectrometerinstrument. This morning, the spacecraft returned this image, revealing some of the last areas of terrain not before seen at close range by spacecraft. Higher-resolution images of these areas will be obtained tomorrow when the spacecraft is closer to the planet.

For the next 30 hours, the spacecraft will take repetitive scans through Mercury’s comet-like anti-sunward tail, pausing now and then to take a color image and a high-resolution mosaic of Mercury with the Mercury Dual Imaging System instrument.

The operations team will now prepare for the period of time after the closest approach point [tomorrow at 5:54:56 p.m.], approximately eight minutes after which the spacecraft will pass behind the planet and lose contact with Earth for a period of 51 minutes. “We will reestablish a high-rate data link with the spacecraft on Tuesday evening at 9:34 p.m., followed by playback of the data stored in the solid-state recorder starting at 11:39 p.m.,” Finnegan adds.

“MESSENGER is now on its own to carry out the command sequence developed by the all of the dedicated engineers and scientist of the MESSENGER flight team,” Finnegan says. “I look forward to the future scientific discoveries to be found in this new dataset.”


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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I've realised that the time in the above scenario I posted was out by about 5 mins. Below is an updated scenario. Closest approach is 227.7 km at 2009-09-29 21:54:58 UTC (you will notice that the Orbiter clock will show the time of closest approach at 21:56:04, a difference of 66 seconds. For an explanation of why, see this thread).
Code:
BEGIN_DESC
Fly a DG on the same trajectory as MESSENGER Flyby 3
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 55103.872270648
END_ENVIRONMENT

BEGIN_FOCUS
  Ship GL-01
END_FOCUS

BEGIN_CAMERA
  TARGET GL-01
  MODE Cockpit
  FOV 50.00
END_CAMERA

BEGIN_MFD Left
  TYPE Orbit
  PROJ Frame
  FRAME Ecliptic
  REF Sun
  TARGET Mercury
END_MFD

BEGIN_MFD Right
  TYPE Orbit
  PROJ Ship
  FRAME Equator
  ALT
  REF Mercury
END_MFD

BEGIN_SHIPS
GL-01:DeltaGlider
  STATUS Orbiting Mercury
  RPOS 13826760.367 -1616278.316 -4638416.175
  RVEL -3155.985 446.901 2071.858
  AROT 19.37 70.78 105.78
  PRPLEVEL 0:1.0 1:1.0
  NOSECONE 0 0.0000
  GEAR 0 0.0000
  AIRLOCK 0 0.0000
END
END_SHIPS
 

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MESSENGER Mercury Flyby 3 countdown: 1 hour, 41 minutes to closest approach.

http://messenger.jhuapl.edu/

---------- Post added at 10:15 PM ---------- Previous post was at 08:12 PM ----------

Flyby completed!
 

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MESSENGER Mission News
September 30, 2009
http://messenger.jhuapl.edu



MESSENGER Gains Critical Gravity Assist for Mercury Orbital Observations

MESSENGER successfully flew by Mercury yesterday, gaining a critical gravity assist that will enable it to enter orbit about Mercury in 2011 and capturing images of five percent of the planet never before seen. With more than 90 percent of the planet’s surface already imaged, MESSENGER’s science team had drafted an ambitious observation campaign designed to tease out additional details from features uncovered during the first two flybys. But an unexpected signal loss prior to closest approach hampered those plans.

Atapproximately 5:55 p.m., the spacecraft passed by Mercury at an altitude of 142 miles and at a relative velocity of more than 12,000 miles per hour according to Doppler residual measurements logged just prior to the closet approach point. As the spacecraft approached the planet, MESSENGER’s Wide Angle Camera captured this striking view, which shows portions of Mercury's surface that had remained unseen by spacecraft even after the three flybys by Mariner 10 in 1974 and 1975 and MESSENGER’s two earlier flybys in 2008.

“This third and final flyby was MESSENGER’s last opportunity to use the gravity of Mercury to meet the demands of the cruise trajectory without using the probe’s limited supply of on-board propellant,” says MESSENGER Mission Systems Engineer Eric Finnegan of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

A portion of the complicated encounter was executed in eclipse, when the spacecraft is in Mercury’s shadow and the spacecraft – absent solar power – was to operate on its internal batteries for 18 minutes. Ten minutes after entering eclipse and four minutes prior to the closet approach point, the carrier signal from the spacecraft was lost, earlier than expected.

According to Finnegan, the spacecraft autonomously transitioned to a safe operating mode, which pauses the execution of the command load and "safes the instruments," while maintaining knowledge of its operational state and preserving all data on the solid-state recorder.

“We believe this mode transition was initiated by the on-board fault management system due to an unexpected configuration of the power system during eclipse,” Finnegan says. MESSENGER was returned to operational mode at 12:30 a.m. with all systems reporting nominal operations. All on-board stored data were returned to the ground by early morning and are being analyzed to confirm the full sequence of events.

“Although the events did not transpire as planned, the primary purpose of the flyby, the gravity assist, appears to be completely successful,” Finnegan adds. “Furthermore, all approach observing sequences have been captured, filling in additional area of previously unexplored terrain and further exploring the exosphere of Mercury.”

“MESSENGER’s mission operations and engineering teams deserve high commendation for their professional and efficient approach to last night’s spacecraft safe-mode transition,” says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. “They quickly diagnosed the initial problem, restored the spacecraft to its normal operating mode, and developed plans to recover as much of our post-encounter science observations as possible. Most importantly, we are on course to Mercury orbit insertion less than 18 months from now, so we know that we will be returning to Mercury and will be able to observe the innermost planet in exquisite detail.”

Additional information and features from this encounter will be available online at http://messenger.jhuapl.edu/mer_flyby3.html. Be sure to check back frequently to see the latest released images and science results!



New Images of Mercury Released

In this image, Mercury's northern horizon cuts a crisp line against the blackness of space. The surface in the lower right corner of the image is near Mercury's terminator, the line between the light dayside and dark night side of the planet. Looking toward the horizon, smooth plains extend for large distances, similar to volcanic plains seen nearby during MESSENGER's second flyby of Mercury.

This WAC image reveals approximately an additional five percent of the surface that had been previously unseen by spacecraft. Among the many newly imaged surface features are impact craters, smooth plains, and an intriguing double-ring basin approximately 260 kilometers (125 miles) in diameter. The outer diameter of the basin is approximately 260 kilometers (160 miles). It has a double-ring structure common to basins with diameters larger than 200 kilometers (about 125 miles). The floor of the basin consists of smooth plains material. Concentric troughs, formed by surface extension, are visible on the basin floor, similar to those seen in Raditladi basin. Such troughs are rare on Mercury, and the discovery of such features in this newly imaged basin is of great interest to members of the MESSENGER Science Team. Crater chains produced during ejecta emplacement also can be seen emanating from the basin.

Members of the MESSENGER Science Team are gathered today at the Johns Hopkins University Applied Physics Laboratory, discussing these high-resolution images in detail.



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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MESSENGER Mission News
October 1, 2009
http://messenger.jhuapl.edu



NEW MESSENGER MERCURY IMAGES

A Bright Spot in the Latest Imaging
Humans have now had three views of the bright area shown near the top center of this image. The first view was as a mere tiny bright spot seen in telescopic images of Mercury obtained from Earth by astronomer Ronald Dantowitz. The second view was obtained by the MESSENGER Narrow Angle Camera during the spacecraft's second Mercury flyby on October 6, 2008. At that time, the bright feature was just on the planet's limb (edge) as seen from MESSENGER. Now MESSENGER has provided a new, even better view. The geometry of MESSENGER's third Mercury flyby allows us to see the feature and its surroundings in greater detail, including the smooth plains in the foreground and the rim of a newly discovered impact basin at lower left. Surprisingly, at the center of the bright halo is an irregular depression, which may have formed through volcanic processes. Color images from MESSENGER's Wide Angle Camera reveal that the irregular depression and bright halo have distinctive color. This area will be of particular interest for further observation during MESSENGER's orbital operations starting in 2011.

Evening Shadows
These imageswere taken on approach to Mercury during the spacecraft’s second (left) and third (right) flybys. The image from the second flyby was featured in an earlier release. The image on the right was taken about 75 minutes before MESSENGER’s closest approach. The two images cover very nearly the same terrain, but for the right image the Sun’s illumination is more nearly grazing (local time is almost sunset) and the viewing perspective of the spacecraft is more nearly vertical. The large impact crater bisected with a prominent scarp or cliff is the same feature in both images. Because of Mercury’s rotation between the two encounters, the position of the crater in the right image is nearly at the terminator (the division between the dayside and night side of the planet), and thus the shadows are longer. The near-grazing illumination emphasizes the topography of the crater floor, including the relief of the wrinkle ridges on either side of the large scarp. To the west of the crater, the shadows and viewing angle show that the terrain is far more rugged than it appeared from the second flyby.

Seeing Double?
This image shows a double-ring impact basin, with another large impact crater on its south-southwestern side. Smaller, more recent impacts formed comparatively fresh craters across the entire surface visible in this image. The floor within the inner or peak ring appears to be smoother than the floor between the peak ring and the outer rim, possibly the result of lava flows that partially flooded the basin some time after impact. Double-ring basins are formed when a large meteoroid strikes the surface of a rocky planet.

Crater Ejecta and Chains of Secondary Impacts
This newly observed flat-floored crater was viewed at an oblique angle as MESSENGER approached Mercury for its third flyby, about two hours from closest approach. This crater is younger than nearby craters of similar size, indicated by the distinctive halo of small secondary craters that radiate outward from the central structure. Many of these secondaries are aligned in chain-like formations and some show characteristic “herringbone” features pointing back to the crater of origin. Crater chains are just one of many ejecta types observed on Mercury. Other ejecta features include distinct continuous ejecta and crater rays, which are composed of both ejecta and secondaries. Another ejecta feature of note in this mosaic of two images is a zone of lighter terrain extending a bit west of north from the crater itself, possibly providing information about the direction of impact. This unnamed crater is partially superposed on an older and smaller crater to the south.

Additional information and features from this encounter will be available online at http://messenger.jhuapl.edu/mer_flyby3.html. Be sure to check back frequently to see the latest released images and science results!



Highlights from Three Mercury Flybys

Tonight, three MESSENGER team members – Principal Investigator Sean Solomon, of the Carnegie Institution of Washington, Project Manager Peter Bedini, of APL, and Co-Investigator Louise Prockter, of APL – will talk about what we’ve learned about Mercury from MESSENGER’s encounters with the planet, and release new pictures from the spacecraft’s third flyby of Mercury. The event, to be held at the Kossiakoff Center on the campus of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., will begin at 5 p.m.


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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None of the links in the above post work, they all have a weird "mhtml" string before the actual url. Here's a bookmarklet that removes that from the links so they work:

Code:
javascript:(function(){var l = document.getElementsByTagName("a");var str = /mhtml:.*(http.*)/; for(var i = 0; i < l.length; i++) if(decodeURIComponent(l[i].href).match(str) != null) l[i].href = decodeURIComponent(l[i].href).match(str)[1];})();
Copy this to the address bar and press enter, and the links will work.

Edit: Here's one that works with links in the forum's post editor window (inline edit and post preview):

Code:
javascript:(function(){for(var j = 0; j < window.frames.length; j++) {try{var l = window.frames[j].document.getElementsByTagName("a");var str = /mhtml:.*(http.*)/; for(var i = 0; i < l.length; i++) if(decodeURIComponent(l[i].href).match(str) != null) l[i].href = decodeURIComponent(l[i].href).match(str)[1];}catch(e){}}})();
With this one, you can edit your post, run the bookmarklet, save the post, and the links will be fixed.
 
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Any word yet on what caused the "safing" just prior to closest approach and if there will be any adverse impact on the mission?
 

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None of the links in the above post work, they all have a weird "mhtml" string before the actual url. Here's a bookmarklet that removes that from the links so they work:

Code:
javascript:(function(){var l = document.getElementsByTagName("a");var str = /mhtml:.*(http.*)/; for(var i = 0; i < l.length; i++) if(decodeURIComponent(l[i].href).match(str) != null) l[i].href = decodeURIComponent(l[i].href).match(str)[1];})();
Copy this to the address bar and press enter, and the links will work.

Edit: Here's one that works with links in the forum's post editor window (inline edit and post preview):

Code:
javascript:(function(){for(var j = 0; j < window.frames.length; j++) {try{var l = window.frames[j].document.getElementsByTagName("a");var str = /mhtml:.*(http.*)/; for(var i = 0; i < l.length; i++) if(decodeURIComponent(l[i].href).match(str) != null) l[i].href = decodeURIComponent(l[i].href).match(str)[1];}catch(e){}}})();
With this one, you can edit your post, run the bookmarklet, save the post, and the links will be fixed.
Sorry about that, had this before:
http://www.orbiter-forum.com/showthread.php?t=1895&page=2
in #29.

Don't know why this happens occasionally. I can't check, as they always seem fine in this browser.

N.
 

Notebook

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If the links below don't work for you try the technique bt 2552 in #54 above.


MESSENGER Mission News
October 1, 2009
http://messenger.jhuapl.edu



NEW MESSENGER MERCURY IMAGES

A Bright Spot in the Latest Imaging
Humans have now had three views of the bright area shown near the top center of this image. The first view was as a mere tiny bright spot seen in telescopic images of Mercury obtained from Earth by astronomer Ronald Dantowitz. The second view was obtained by the MESSENGER Narrow Angle Camera during the spacecraft's second Mercury flyby on October 6, 2008. At that time, the bright feature was just on the planet's limb (edge) as seen from MESSENGER. Now MESSENGER has provided a new, even better view. The geometry of MESSENGER's third Mercury flyby allows us to see the feature and its surroundings in greater detail, including the smooth plains in the foreground and the rim of a newly discovered impact basin at lower left. Surprisingly, at the center of the bright halo is an irregular depression, which may have formed through volcanic processes. Color images from MESSENGER's Wide Angle Camera reveal that the irregular depression and bright halo have distinctive color. This area will be of particular interest for further observation during MESSENGER's orbital operations starting in 2011.

Evening Shadows
These imageswere taken on approach to Mercury during the spacecraft’s second (left) and third (right) flybys. The image from the second flyby was featured in an earlier release. The image on the right was taken about 75 minutes before MESSENGER’s closest approach. The two images cover very nearly the same terrain, but for the right image the Sun’s illumination is more nearly grazing (local time is almost sunset) and the viewing perspective of the spacecraft is more nearly vertical. The large impact crater bisected with a prominent scarp or cliff is the same feature in both images. Because of Mercury’s rotation between the two encounters, the position of the crater in the right image is nearly at the terminator (the division between the dayside and night side of the planet), and thus the shadows are longer. The near-grazing illumination emphasizes the topography of the crater floor, including the relief of the wrinkle ridges on either side of the large scarp. To the west of the crater, the shadows and viewing angle show that the terrain is far more rugged than it appeared from the second flyby.

Seeing Double?
This image shows a double-ring impact basin, with another large impact crater on its south-southwestern side. Smaller, more recent impacts formed comparatively fresh craters across the entire surface visible in this image. The floor within the inner or peak ring appears to be smoother than the floor between the peak ring and the outer rim, possibly the result of lava flows that partially flooded the basin some time after impact. Double-ring basins are formed when a large meteoroid strikes the surface of a rocky planet.

Crater Ejecta and Chains of Secondary Impacts
This newly observed flat-floored crater was viewed at an oblique angle as MESSENGER approached Mercury for its third flyby, about two hours from closest approach. This crater is younger than nearby craters of similar size, indicated by the distinctive halo of small secondary craters that radiate outward from the central structure. Many of these secondaries are aligned in chain-like formations and some show characteristic “herringbone” features pointing back to the crater of origin. Crater chains are just one of many ejecta types observed on Mercury. Other ejecta features include distinct continuous ejecta and crater rays, which are composed of both ejecta and secondaries. Another ejecta feature of note in this mosaic of two images is a zone of lighter terrain extending a bit west of north from the crater itself, possibly providing information about the direction of impact. This unnamed crater is partially superposed on an older and smaller crater to the south.

Additional information and features from this encounter will be available online at http://messenger.jhuapl.edu/mer_flyby3.html. Be sure to check back frequently to see the latest released images and science results!



Highlights from Three Mercury Flybys

Tonight, three MESSENGER team members – Principal Investigator Sean Solomon, of the Carnegie Institution of Washington, Project Manager Peter Bedini, of APL, and Co-Investigator Louise Prockter, of APL – will talk about what we’ve learned about Mercury from MESSENGER’s encounters with the planet, and release new pictures from the spacecraft’s third flyby of Mercury. The event, to be held at the Kossiakoff Center on the campus of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., will begin at 5 p.m.


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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Notebook

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Dwayne Brown
Headquarters, Washington Nov. 3, 2009
202-358-1726
[email protected]

Paulette Campbell
Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
240-228-6792
[email protected]

RELEASE: 09-257

MESSENGER SPACECRAFT REVEALS MORE HIDDEN TERRITORY ON MERCURY

WASHINGTON -- A NASA spacecraft's third and final flyby of the planet Mercury gives scientists, for the first time, an almost complete view of the planet's surface and provides new scientific findings about this relatively unknown planet.

The Mercury Surface, Space Environment, Geochemistry and Ranging spacecraft, known as MESSENGER, flew by Mercury on Sept. 29. The probe completed a critical gravity assist to remain on course to enter into orbit around Mercury in 2011. Despite shutting down temporarily because of a power system switchover during a solar eclipse, the spacecraft's cameras and instruments collected high-resolution and color images unveiling another 6 percent of the planet's surface never before seen at close range.

Approximately 98 percent of Mercury's surface now has been imaged by NASA spacecraft. After MESSENGER goes into orbit around Mercury, it will see the polar regions, which are the only unobserved areas of the planet.

"Although the area viewed for the first time by spacecraft was less than 350 miles across at the equator, the new images reminded us that Mercury continues to hold surprises," said Sean Solomon, principal investigator for the mission and director of the Department of Terrestrial Magnetism at the Carnegie Institution of Washington.

Many new features were revealed during the third flyby, including a region with a bright area surrounding an irregular depression, suspected to be volcanic in origin. Other images revealed a double-ring impact basin approximately 180 miles across. The basin is similar to a feature scientists call the Raditladi basin, which was viewed during the probe's first flyby of Mercury in January 2008.

"This double-ring basin, seen in detail for the first time, is remarkably well preserved," said Brett Denevi, a member of the probe's imaging team and a postdoctoral researcher at Arizona State University in Tempe. "One similarity to Raditladi is its age, which has been estimated to be approximately one billion years old. Such an age is quite young for an impact basin, because most basins are about four times older. The inner floor of this basin is even younger than the basin itself and differs in color from its surroundings. We may have found the youngest volcanic material on Mercury."

One of the spacecraft's instruments conducted its most extensive observations to date of Mercury's exosphere, or thin atmosphere, during this encounter. The flyby allowed for the first detailed scans over Mercury's north and south poles. The probe also has begun to reveal how Mercury's atmosphere varies with its distance from the sun.

"A striking illustration of what we call 'seasonal' effects in Mercury's exosphere is that the neutral sodium tail, so prominent in the first two flybys, is 10 to 20 times less intense in emission and significantly reduced in extent," says participating scientist Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory, or APL, in Laurel, Md. "This difference is related to expected variations in solar radiation pressure as Mercury moves in its orbit and demonstrates why Mercury's exosphere is one of the most dynamic in the solar system."

The observations also show that calcium and magnesium exhibit different seasonal changes than sodium. Studying the seasonal changes in all exospheric constituents during the mission orbital phase will provide key information on the relative importance of the processes that generate, sustain, and modify Mercury's atmosphere.

The third flyby also revealed new information on the abundances of iron and titanium in Mercury's surface materials. Earlier Earth and spacecraft-based observations showed that Mercury's surface has a very low concentration of iron in silicate minerals, a result that led to the view that the planet's crust is generally low in iron.

"Now we know Mercury's surface has an average iron and titanium abundance that is higher than most of us expected, similar to some lunar mare basalts," says David Lawrence, an APL participating mission scientist.

The spacecraft has completed nearly three-quarters of its 4.9-billion-mile journey to enter orbit around Mercury. The full trip will include more than 15 trips around the sun. In addition to flying by Mercury, the spacecraft flew past Earth in August 2005 and Venus in October 2006 and June 2007.

The spacecraft was designed and built by APL. The mission is managed and operated by APL for NASA's Science Mission Directorate in Washington.

For more information about the mission, visit:





-end-​
 

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MESSENGER Mission News
November 24, 2009
http://messenger.jhuapl.edu



Deep-Space Maneuver Positions MESSENGER for Mercury Orbit Insertion

The Mercury-bound MESSENGER spacecraft completed its fifth and final deep-space maneuver of the mission today, providing the expected velocity change needed to place the spacecraft on course to enter into orbit about Mercury in March 2011. A 3.3-minute firing of its bi-propellant engine provided nearly all of the probe’s 177 meter per second (396 mile per hour) increase in its speed relative to the Sun.

MESSENGER was 230.4 million kilometers (143.2 million miles) from Earth when today’s maneuver began at 4:45 p.m. EST. Mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of the maneuver about 12 minutes, 49 seconds later, when the first signals indicating spacecraft thruster activity reached NASA’s Deep Space Network tracking station outside Goldstone, Calif.


“The team was well-prepared for the maneuver,” said MESSENGER Mission Systems Engineer Eric Finnegan, of APL. “Initial data analysis indicates an extremely accurate maneuver execution. After sifting through all the post-burn data I expect we will find ourselves right on target.”


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 having completed 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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MESSENGER Mission News
December 15, 2009
http://messenger.jhuapl.edu

MESSENGER Team Releases First Global Map of Mercury

NASA’s MESSENGER mission team and cartographic experts from the U. S. Geological Survey have created a critical tool for planning the first orbital observations of the planet Mercury – a global mosaic of the planet that will help scientists pinpoint craters, faults, and other features for observation. The map was created from images taken during the MESSENGER spacecraft’s three flybys of the planet and those of Mariner 10 in the 1970s. A presentation on the new global mosaic is being given today at the Fall Meeting of the American Geophysical Union in San Francisco.

The MESSENGER spacecraft completed its third and final flyby of Mercury on September 29, concluding its reconnaissance of the innermost planet. The MESSENGER team has been busily preparing for the yearlong orbital phase of the mission, beginning in March 2011, and the near-global mosaic of Mercury from MESSENGER and Mariner 10 images is key to those plans.

“The production of this global mosaic represents a major milestone for everyone on the MESSENGER imaging team,” says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. “Beyond its extremely important use as a planning tool, this global map signifies that MESSENGER is no longer a flyby mission but instead will soon become an in-depth, non-stop global observatory of the Solar System’s innermost planet.”

“The process of making a mosaic may seem relatively straightforward—simple software can stitch together panoramas from multiple images. However, the challenging part has been to make cartographically accurate maps from a series of images with varying resolution (from about 100 to 900 meters per pixel) and lighting conditions (from noontime high Sun to dawn and dusk) taken from a spacecraft traveling at speeds greater than 2 kilometers per second (2,237 miles per hour),” says Arizona State University’s Mark Robinson, a member of the MESSENGER Science Team.

Small uncertainties in camera pointing and changes in image scale can introduce small errors between frames, he says. “And with lots of images, small errors add up and lead to large mismatches between features in the final mosaic. By picking control points—the same features in two or more images—the camera pointing can be adjusted until the image boundaries match.” This operation is known as a bundle-block adjustment and requires highly specialized software.

Cartographic experts at the USGS Astrogeology Science Center in Flagstaff, Ariz., picked the control points to solve the bundle-block adjustment to construct the final mosaic using the Integrated Software for Imagers and Spectrometers (ISIS). For the MESSENGER mosaic, 5,301 control points were selected, and each control point on average was found in more than three images (18,834 measurements) from a total of 917 images. Scientists at ASU and the Johns Hopkins University Applied Physics Laboratory (APL) were also instrumental in making the mosaic possible.

“This mosaic represents the best geodetic map of Mercury’s surface. We want to provide the most accurate map for planning imaging sequences once MESSENGER achieves orbit around Mercury”, says Kris Becker of the USGS. “As the systematic mapping of Mercury’s surface progresses, we will continually add new images to the control point network, thus refining the map”, he says. “It has already provided us with a start in the process of naming newly identified features on the surface.”

In the final bundle-block adjustment the average error was about two-tenths of a pixel or only about 100 meters—which is an excellent match from image-to-image. The biggest remaining issue is the absolute control of features on the surface. For instance, if the north pole is not precisely at the spin axis you could have a mosaic in which all the seams overlapped perfectly, but the whole mosaic could slide around like the skin of an orange that somehow became detached from the interior fruit.

Much work was done with the Mariner 10 images collected in 1974 and 1975 to make an absolute control network even though only 45% of the planet was seen at the time. The longitude system for Mercury is tied to a small crater named Hun Kal (the number twenty in an ancient Mayan language, because the crater is centered at 20°W). For now, MESSENGER data are tied to the earlier Mariner 10 control network.

Absolute positional errors in the new mosaic are about two kilometers, according to the MESSENGER team. Once the MESSENGER spacecraft orbits Mercury, much progress will be made refining the relative and absolute control of the MESSENGER (and Mariner 10) images, and the entire planet will be imaged at even higher resolution. The global mosaic is available for download on the USGS Map-a-Planet web site, http://www.mapaplanet.org.




Link to data table.
http://i89.photobucket.com/albums/k207/Notebook_04/MessengerTable.jpg
 
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