MESSENGER

MESSENGER
	; Messenger preparing to start
NSSDC ID	2004-030A
Mission goal	Mercury
Client	NASA
Launcher	Delta II 7925H
construction
Takeoff mass	1093 kg
Course of the mission
Start date	August 3, 2004, 06:15 UTC
launch pad	CC , LC-17B
End date	April 30, 2015, 19:26 UTC

MESSENGER ( English Me rcury S urface, S pace En vironment, Ge ochemistry and R was concerned ; German as " Mercury surface, environmental, Geochemie- and ranging ") was a NASA - spacecraft of the Discovery program , which the planets nearest the sun Mercury explored. The abbreviation results in the English word for 'messenger' and thus also refers to the Roman god Mercurius , the messenger of the gods. The probe was launched on August 3, 2004. On its way to the inner part of the solar system, it emitted so much kinetic energy in several fly- by maneuvers of Earth, Venus and Mercury that on March 18, 2011, on the fourth fly-by of Mercury, it gave off a 15- minute braking maneuver swung into orbit around the planet. Messenger was the second spacecraft to visit Mercury after Mariner 10 and the first to orbit it as an orbiter . The mission ended on April 30, 2015 when the probe struck Mercury after running out of fuel.

The mission was led by the Applied Physics Laboratory (APL) at Johns Hopkins University , which also built the spacecraft. The instruments were supplied by both the APL and NASA's Goddard Space Flight Center , the University of Michigan, and the University of Colorado . The cost of the mission, including the spacecraft and its instruments, the launcher, as well as the implementation of the mission and data analysis by the end of the primary mission in March 2012, amounted to around 427 million US dollars .

Mission objectives

Graphic representation of messenger near Mercury

Mercury is one of the least explored planets in the solar system . This is mainly due to the very inhospitable conditions for space probes in the vicinity of the sun , such as the high temperature and intense radiation, as well as numerous technical difficulties that have to be taken into account when flying to Mercury. Even from earth orbit, the observation conditions are too unfavorable to be able to observe it with telescopes .

Mercury was only visited by a single spacecraft until the first flyby of Messengers, the American Mariner 10 , which passed the planet three times from 1974 to 1975. However, only 45 percent of its surface could be mapped. In addition, Mariner 10 examined Mercury in the infrared and UV light and took measurements of the magnetic field and the charged particles.

In contrast to the Mariner-10 probe, which only performed fly-bys at Mercury, Messenger was able to explore the planet much more precisely from an orbit with its numerous instruments.

The probe's primary mission in Mercury orbit was designed for exactly one year. Messenger was able to completely map the planet for the first time and dedicated itself specifically to the investigation of the geological history of Mercury and its composition. Furthermore, the probe should search for the origin of the magnetic field, determine the size and condition of the planet's core, examine the polar caps of the planet and explore the exosphere and the magnetosphere .

construction

Structure of messengers

Messenger consisted of a 1.27 m × 1.42 m × 1.85 m (= 3.3 m ³ ) large body and was protected from the sun by a semi-cylindrical, approximately 2.5 m high and 2 m wide protective shield. Only two solar panels on opposite sides of the body and a 3.6 m long magnetometer boom were attached outside of the protective shield. The total launch mass of the spacecraft was 1093 kg; The probe itself weighed 485.2 kg, the remaining 607.8 kg was accounted for by the fuel ( hydrazine and nitrogen tetroxide ) and compressed helium gas.

Instruments

Messenger carried seven scientific instruments, and the space probe's communication system was also used to determine Mercury's gravitational field ( radio science ). Five of the instruments were mounted in the lower part of the probe, one (EPPS) in the upper and on the side and the MAG on a 3.6 m long boom.

Mercury Dual Imaging System (MDIS)

MDIS consisted of a wide angle camera with a field of view of 10.5 ° and a narrow angle camera with a field of view of 1.5 °. The light entered the instrument through a 12 cm × 12 cm window, which only let through the visible and near-infrared light up to a wavelength of 1.1 µm. The main tasks of MDIS were: color images of Mercury during the flyby, high-resolution images of selected areas and stereo images for high-resolution topography . A global monochrome mosaic of Mercury with an average resolution of 250 m per pixel was to be created during the first six months of the mission. During the next six months, the recording of the mosaic should be repeated from a different angle in order to be able to generate stereo images. Wide-angle color photographs with all ten color filters should cover approximately 40% of the surface.

The wide-angle camera had a achromatic Cooke triplet - lens with a diameter of 30 mm and mm focal length 79th The camera was equipped with a 12-position filter wheel. Two of the filters were bandpass filters with a bandwidth of 100 nm, centered on 600 nm and 750 nm, respectively. Another ten filters were color filters, centered on 415 nm (40 nm bandwidth), 480 (30), 560 (10), 650 (10 ), 750 (10), 830 (10), 900 (10), 950 (20), 1000 (30) and 1020 (40). The incident light was picked up by a frame transfer CCD with 1024 × 1024 picture elements (pixels). Each pixel is 14 µm². Images in full pixel size could be acquired every four seconds, partial images (512 × 512 or smaller) every second. The resolution of the camera was 72 m at a distance of 200 km and 5.4 km at a distance of 15,000 km.

The narrow-angle camera used a Ritchey-Chretien telescope with a focal length of 550 mm. Only one filter was available to the camera. A CCD identical to that of the wide-angle camera was used to take the images. The resolution was 5.2 m at a distance of 200 km and 390 m at a distance of 15,000 km.

MDIS weighed 7.9 kg and required an average of 10 watts of power. A total of 12 Gb of data from MDIS were expected by the end of the primary mission . The instrument was developed by the Applied Physics Laboratory at Johns Hopkins University.

Gamma-Ray and Neutron Spectrometer (GRNS)

The composition of Mercury was researched with the GRNS, in particular the occurrence of such elements as oxygen (O) , silicon (Si) , sulfur (S) , iron (Fe) , hydrogen (H) , potassium (K) , thorium (Th ) and uranium (U) . The main aim of the GRNS was to study the geological history of the planet and to search for ice on its polar caps. The experiment consisted of two instruments: the Gamma-Ray Spectrometer and the Neutron Spectrometer.

The gamma-ray spectrometer measured gamma radiation , which is produced either by bombardment with galactic cosmic rays (O, S, Si, Fe, and H) or by natural radioactive decay (K, Th and U), down to a depth of about 10 cm. The gamma-ray spectrometer was a 31 cm high cylinder which contained the actively shielded scintillator . This was protected by a 9 cm × 9.5 cm, 1.25 cm thick shield made of bismuth germanate (BGO), behind which a photomultiplier was located. The shield allowed a 45 ° field of view. A germanium semiconductor crystal , which was cooled to a temperature of −183 ° C, served as the detector . The measurable energy range was 0.3 to 10 MeV , the integration length was 5 minutes in the periapsis and 30 minutes in the apoapsis .

The neutron spectrometer recorded low-energy neutrons , which are caused by bombardment with cosmic rays and subsequent collisions with hydrogen-rich material in the upper 40 cm of the planet's surface. The spectrometer consisted of two scoop-shaped GS20 glass scintillators (6.6% lithium ) with an area of 80 cm² each and a thickness of 6.5 cm, separated by two neutron-absorbing BC454 scintillators ( borated plastic) with a total area of 80 cm². The GS20 scintillators measured thermal, BC454 scintillators epithermal and fast neutrons.

GRNS weighed 13.1 kg and required an average of 4.5 watts (maximum 23.6 watts) of power. A total of 3.9 Gb of data from GRNS was expected by the end of the primary mission . The instrument was developed by the Applied Physics Laboratory at Johns Hopkins University.

Magnetometer (MAG)

The magnetometer measured the magnetic field of Mercury. Based on the data provided, a three-dimensional model of the planet's magnetosphere was created. To avoid interference from the on-board magnetic field, the instrument was mounted on a 3.6 m long boom, which pointed in the opposite direction to the sun. MAG measured the magnetic flux density in the range from −1024 to +1024 nT . For quantization of the measured values were 16 bits are available, therefore the achievable measurement resolution was 0.03 nT. The scanning rate of the detector was 40 Hz, measured values could be read out at adjustable time intervals of 25 ms to 1 s.

MAG weighed 4.4 kg together with the boom and required an average of 2 watts (maximum 4.2 watts) of power. A total of approx. 440 Mbytes of data from the magnetometer were expected by the end of the primary mission. The instrument was developed by NASA's Goddard Space Flight Center.

Mercury Laser Altimeter (MLA)

Using laser pulses , the travel time of which was measured from the probe to Mercury and back, MLA was able to gain topographical knowledge about Mercury. Measurements could be made as soon as the height of the orbit of the probe was less than 1000 km above the planet's surface. Since Messenger moved on a highly elliptical orbit, the lowest point of which was 60 ° north latitude , MLA could only cover the northern hemisphere of the planets .

MLA was based on the instruments MOLA (Mars Orbiter Laser Altimeter) of the space probe Mars Global Surveyor and GLAS (Geoscience Laser Altimeter System) of the ICESat satellite. The instrument used a Cr: Nd: YAG laser with a wavelength of 1064 nm. The laser operated at a frequency of 5 Hz and emitted light pulses with an energy of 20 mJ and a duration of 5 ns. The pulses reflected from the planet were picked up by a receiver consisting of four sapphire lenses. The transit time of a light pulse was measured with an accuracy of 3.3 ns, which resulted in a measurement resolution of 0.5 m.

MLA weighed 7.4 kg and required an average of 20 watts (maximum 38.6 watts) of power. A total of around 1.5 Gb of data from MLA were expected by the end of the primary mission. The instrument was developed by NASA's Goddard Space Flight Center.

Mercury Atmospheric and Surface Composition Spectrometer (MASCS)

This spectrometer investigated the composition of the atmosphere of Mercury. MASCS weighed 3.1 kg and required an average of 3 watts (maximum 8.2 watts) of power. The instrument was developed by the University of Colorado.

Energetic Particle and Plasma Spectrometer (EPPS)

EPPS measured the nature and distribution of charged particles such as electrons and various ions in Mercury's magnetic field. EPPS weighed 3.1 kg and required an average of 2 watts (maximum 7.8 watts) of power. The instrument was developed by the University of Michigan and the Applied Physics Laboratory at Johns Hopkins University.

X-Ray Spectrometer (XRS)

Gamma and X-rays from the Sun can cause elements on Mercury's surface to emit low-energy X-rays. XRS was able to track these down and thus allow conclusions to be drawn about the composition of Mercury. XRS detected the elements magnesium (Mg) , aluminum (Al) , sulfur (S) , calcium (Ca) , titanium (Ti) and iron (Fe) from the upper 1 mm thick surface layer.

XRS was a modified version of the XGRS instrument of the NEAR Shoemaker spacecraft . XRS contained three cylindrical proportional counters filled with gas , which were mounted behind a 25 µm thick beryllium window. XRS weighed 3.4 kg and required an average of 8 watts (maximum 11.4 watts) of power. A total of around 1.5 GB of data from XRS was expected by the end of the primary mission. The instrument was developed by the Applied Physics Laboratory at Johns Hopkins University.

Radio Science (RS)

As part of the RS, small deviations in the speed of the probe were measured by the on-board communication system using the Doppler effect . The mass distribution of Mercury can be inferred from these data. By radio occultation also the exact dimensions of the planet and the amplitude were his libration measured. RS is managed by NASA's Goddard Space Flight Center.

Mission history

Preparations and start

Messengers flight to Mercury

Launch of NASA - space probe Messenger aboard a Delta II rocket 7925H

First Merkur fly-by in January 2008

The project of a space probe to Mercury called Messenger was among the finalists of the Discovery program selection in 1997 , but could not prevail against other missions. In March 1998 Messenger was again included by NASA in the selection for a mission in the context of the Discovery program, in November 1998 Messenger was one of the five finalists with the best scientific yield of a total of 26 proposals. Finally, on July 7, 1999, Messenger was approved for funding under the Discovery program with Deep Impact . The cost of the space probe was then put at 286 million US dollars.

The 19-day start window initially planned in March 2004 and the second 12 -day start window in mid-May 2004 could not be kept for technical reasons. On July 30, 2004, another 15-day window opened. However, a launch on August 2nd was canceled due to dense cloud cover over the Cape Canaveral spaceport . On August 3, 2004 at 02:15:56 local time ( EDT ), the probe finally launched on a carrier rocket of the type Delta II 7925H . Due to the new start window, a different trajectory had to be chosen, which postponed the arrival originally planned for 2009 by two years.

Swing-by maneuvers

The space probe had flown around eight billion kilometers through the solar system when it was the first to enter orbit around Mercury in March 2011. For the sake of fuel savings more had to swing-by maneuver of Earth , Venus and Mercury are performed. The probe lost part of its orbital energy due to an asymmetrical approach to the planets and was thus slowed down.

The only swing-by on earth took place on August 2nd, 2005. On October 24, 2006 and June 5, 2007, Venus was swing-by. On these occasions, some on-board instruments were also activated to take measurements on the two planets.

The first of three swing-by maneuvers on Mercury took place on January 14, 2008, the second on October 6, 2008 and the last on September 29, 2009. Overall, the three maneuvers consumed about 33% of the energy. During these maneuvers, Messenger flew at an altitude of around 200 km above the planet's surface, carried out measurements and mapped regions that could not be recorded by Mariner 10 during the flyby . Only during the third swing-by could no observation data be obtained during the closest distance to Mercury, as the probe unexpectedly switched to safe mode four minutes earlier for several hours.

Circumnavigations and end of the mission

On March 18, 2011, the probe swiveled into an orbit around Mercury with a braking maneuver (change in speed 862.4 m / s). The probe circled Mercury at altitudes between 200 and 15,000 km. Because of the slow rotation of the planet, Messenger's orbit had a special shape in order to be able to observe Mercury in sunlight and not to expose the probe to the heat of the sun reflected from the surface for too long.

The first mission began as planned on April 4, 2011. The space probe flew around the planet once every 12 hours for a period of one year on earth (corresponds to 2 days of Mercury). On October 5, 2011, the scientists published their results from the first 6 months of the mission at the European Planetary Science Congress in Nantes . The data showed unexpectedly high levels of magnesium and calcium on Mercury's night side. In addition, the magnetic field of the planet is not in the center, but is shifted far to the north.

On March 17, 2012, the expansion of the mission started in order to also be able to observe the maximum of the sunspot cycle . In November 2012, NASA reported that the spacecraft at the North Pole found both frozen water and organic materials in craters on Mercury's surface that are never exposed to sunlight. In February 2013 NASA published a current and most detailed 3D map of Mercury's surface to date. It consists of thousands of pictures that Messenger took during the mission.

On March 17, 2013, Messenger also ended this extended mission and extended it again to March 2015. The probe was to be deliberately crashed on this date. In November 2013, Messenger succeeded in photographing both the Encke's comet (2P / Encke) and the comet ISON (C / 2012 S1).

On January 21, 2015, a maneuver was successfully carried out in order to increase the orbit in order to extend the mission and to be able to make further recordings. The next maneuver should follow in March 2015. On April 24, 2015, the spacecraft's orbit was corrected one last time. The fuel was now exhausted. On April 30th, Messenger hit the remote side of Mercury at around 7:26 p.m. UTC (9:26 p.m. CEST ) at a speed of about 3.91 kilometers per second (14,081 km / h), leaving a crater behind whose diameter is estimated to be around 16 meters.

Tabular overview

The following table gives an overview of the course of the flight and the most important way stations.

Flight history
date	event	Remarks
August 3, 2004	begin
August 24, 2004	TCM * 1	215 seconds engine burn time with Δ v (change in speed) of about 18 m / s
September 24, 2004	TCM 2	62 seconds engine burn time with Δ v ≈ 4.59 m / s
November 18, 2004	TCM 3	48 seconds engine burn time with Δ v ≈ 3.24 m / s
June 23, 2005	TCM 5	174 seconds engine burn time with Δ v ≈ 1.1 m / s, previously planned TCM 4 was not necessary
July 21, 2005	TCM 6	23 seconds engine burn time with Δ v ≈ 0.15 m / s
August 2, 2005	Swing-by on earth	First swing-by on earth at an altitude of 2347 km
December 12, 2005	TCM 9 / DSM ** 1	Engine burn time of 524 seconds with Δ v ≈ 315.63 m / s, previously planned TCM 7 and TCM 8 were not required
February 22, 2006	TCM 10	A little over 2 minutes engine burn time with Δ v ≈ 1.4 m / s
September 12, 2006	TCM 11	a little under 4 minutes engine burn time with Δ v ≈ 1.68 m / s
October 5, 2006	TCM 12	58 seconds engine burn time with Δ v ≈ 0.498 m / s
October 24, 2006	Swing-by on Venus	First swing-by on Venus at an altitude of 2990 km (second swing-by in total)
December 2, 2006	TCM 13	3607 seconds engine burn time with Δ v ≈ 25.6 m / s
April 25, 2007	TCM 15	140 seconds engine burn time with Δ v ≈ 0.568 m / s. A delta v of 0.767 m / s was planned, but it was not achieved due to position control disturbances. The smaller change in speed increases the distance during the Venus flyby on June 6, 2007 by about 200 km
May 25, 2007	TCM 16	36 seconds engine burn time with Δ v ≈ 0.212 m / s. Errors that occurred during TCM-15 could be corrected
June 5, 2007	Swing-by on Venus	Second swing-by on Venus. At 23:08 UTC, the smallest distance to the planet's surface was reached at approx. 337 km
January 14, 2008	Swing-by on Mercury	First swing-by on Merkur at an altitude of approx. 200 km
October 6, 2008	Swing-by on Mercury	Second swing-by on Merkur at an altitude of approx. 200 km
September 29, 2009 21:55 UTC	Swing-by on Mercury	Third swing-by on Merkur at an altitude of approx. 228 km
March 18, 2011	Arrival at Mercury	Swing into an elliptical orbit around Mercury
June 15, 2011	Path correction	First orbit correction for a circular orbit and a reduction of the smallest distance from Mercury from a good 500 to about 200 km
March 17, 2012	End of the primary mission	End of the one-year primary mission, start of the first extended mission phase
17th March 2013	End of the extended mission	End of the first extended mission phase. Planning of further mission phases.
April 30, 2015	Completion of the mission / crash	Final end of the mission as predicted due to lack of fuel and the resulting impact of the probe into the surface of Mercury

* TCM = Trajectory Correction Maneuver (path correction maneuver)
** DSM = Deep Space Maneuver (path change maneuver)

Web links

Commons : MESSENGER - collection of images, videos and audio files

Individual evidence

↑ ^a ^b ^c NASA Completes MESSENGER Mission with Expected Impact on Mercury's Surface. NASA, April 30, 2015, accessed April 30, 2015 .

↑ ^a ^b ^c ^d ^e ^f ^g ^h MESSENGER Launch Press Kit. (PDF; 33 pages; 2.3 MB) (No longer available online.) NASA, August 2004, archived from the original on October 1, 2012 ; accessed on May 5, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.

↑ NSSDC Master Catalog Display: Mercury Dual Imaging System (MDIS)

↑ NSSDC Master Catalog Display: Gamma-Ray and Neutron Spectrometer (GRNS)

↑ NSSDC Master Catalog Display: Magnetometer (MAG)

↑ NSSDC Master Catalog Display: Mercury Laser Altimeter (MLA)

↑ NSSDC Master Catalog Display: Mercury Atmospheric and Surface Composition Spectrometer (MASCS)

↑ NSSDC Master Catalog Display: Energetic Particle and Plasma Spectrometer (EPPS)

↑ NSSDC Master Catalog Display: X-ray Spectrometer (XRS)

↑ NSSDC Master Catalog Display: Radio Science (RS)

↑ NASA: Five Discovery Mission Proposals Selected for Feasibility Studies ( Memento of the original from November 7, 2004 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , November 12, 1998 @1@ 2

↑ NASA: NASA Selects Missions to Mercury and a Comet's Interior as Next Discovery Flights ( Memento of the original from November 19, 2004 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , August 7, 1999 @1@ 2

↑ MESSENGER flyby successful - but without data. Raumfahrer.net, October 1, 2009, accessed October 5, 2009 .

↑ MESSENGER Kicks Off Yearlong Campaign of Mercury Science. (No longer available online.) Johns Hopkins University Applied Physics Laboratory, April 4, 2011, archived from the original on April 12, 2013 ; accessed on December 18, 2013 .

↑ MESSENGER Team Presents New Mercury Findings at Planetary Conference. (No longer available online.) Johns Hopkins University Applied Physics Laboratory, Oct 5, 2011, archived from the original on May 13, 2013 ; accessed on December 18, 2013 .

↑ Mercury's water ice at north pole finally proven. BBC, November 30, 2012, accessed December 18, 2013 .

^ Mercury shows off its colorful side. BBC, February 16, 2013, accessed December 18, 2013 .

↑ MESSENGER Detects Comets ISON and Encke, Prepares for Closer Encounters

↑ Maneuver Successfully Delays MESSENGER's Impact, Extends Orbital Operations ( Memento from February 27, 2015 in the Internet Archive )

↑ APL: Mercury-bound MESSENGER Launches from Cape Canaveral ( Memento of the original from January 11, 2012 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , August 3, 2004 @1@ 2

↑ APL: Trajectory Correction Maneuvers: August 24, 2004 ( Memento of August 19, 2008 in the Internet Archive )

↑ APL: MESSENGER Status Report ( Memento from August 19, 2008 in the Internet Archive )

↑ APL: Trajectory Correction Maneuvers: November 18, 2004 ( Memento of December 1, 2008 in the Internet Archive )

↑ APL: Trajectory Correction Maneuvers: June 23, 2005 ( Memento from December 1, 2008 in the Internet Archive )

↑ APL: Trajectory Correction Maneuvers: July 21, 2005 ( Memento from December 1, 2008 in the Internet Archive )

↑ APL: MESSENGER Completes Successful Earth Swingby ( Memento from August 19, 2008 in the Internet Archive ), August 2, 2005

↑ APL: Trajectory Correction Maneuvers: December 12, 2005 ( Memento of August 19, 2008 in the Internet Archive )

↑ APL: Trajectory Correction Maneuvers: February 22, 2006 ( Memento from August 19, 2008 in the Internet Archive )

↑ APL: MESSENGER Tweaks Its Route to Mercury ( Memento from May 3, 2015 in the Internet Archive ), September 15, 2006

↑ APL: Trajectory Correction Maneuvers October 5, 2006 ( Memento from July 10, 2012 in the web archive archive.today )

↑ APL: MESSENGER Completes Venus Flyby ( Memento from May 13, 2013 in the Internet Archive ), October 24, 2006

↑ APL: MESSENGER Lines Up For Its Second Venus Flyby ( Memento from May 3, 2015 in the Internet Archive ), December 2, 2006

↑ APL: MESSENGER LINES UP FOR SECOND PASS AT VENUS ( Memento from August 19, 2008 in the Internet Archive ), May 2, 2007

↑ APL: MESSENGER Zeros In On Venus ( Memento from August 19, 2008 in the Internet Archive ), May 25, 2007

↑ APL: MESSENGER Completes Second Flyby of Venus, Makes Its Way toward First Flyby of Mercury in 33 Years ( Memento from December 1, 2008 in the Internet Archive ), June 6, 2007

↑ MESSENGER fills the "white spots" in the Merkur Atlas: first results after a successful flyby. DLR, January 30, 2008, accessed June 14, 2013 .

↑ MESSENGER Flyby of Mercury. (No longer available online.) Johns Hopkins University Applied Physics Laboratory, September 29, 2009, archived from the original on April 27, 2015 ; accessed on September 30, 2009 .

↑ MESSENGER Adjusts Its Orbit around Mercury. (No longer available online.) Johns Hopkins University Applied Physics Laboratory, June 15, 2011, archived from the original on April 12, 2013 ; accessed on July 15, 2011 .

↑ MESSENGER Completes Primary Mission at Mercury, Settles in for Another Year. (No longer available online.) Johns Hopkins University Applied Physics Laboratory, March 19, 2012, archived from the original on May 13, 2013 ; accessed on March 21, 2012 (English).

[impact-1] NASA Completes MESSENGER Mission with Expected Impact on Mercury's Surface. NASA, April 30, 2015, accessed April 30, 2015 .

[launch_press_kit-2] ↑ ^a ^b ^c ^d ^e ^f ^g ^h MESSENGER Launch Press Kit. (PDF; 33 pages; 2.3 MB) (No longer available online.) NASA, August 2004, archived from the original on October 1, 2012 ; accessed on May 5, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2

[3] NSSDC Master Catalog Display: Mercury Dual Imaging System (MDIS)

[4] NSSDC Master Catalog Display: Gamma-Ray and Neutron Spectrometer (GRNS)

[5] NSSDC Master Catalog Display: Magnetometer (MAG)

[6] NSSDC Master Catalog Display: Mercury Laser Altimeter (MLA)

[7] NSSDC Master Catalog Display: Mercury Atmospheric and Surface Composition Spectrometer (MASCS)

[8] NSSDC Master Catalog Display: Energetic Particle and Plasma Spectrometer (EPPS)

[9] NSSDC Master Catalog Display: X-ray Spectrometer (XRS)

[10] NSSDC Master Catalog Display: Radio Science (RS)