Sonda Messenger na órbita de Mercúrio

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Sonda Messenger já está na órbita de Mercúrio


A sonda americana Messenger tornou-se esta madrugada o primeiro engenho espacial a instalar-se na órbita de Mercúrio, o planeta mais próximo do sol, anunciou a NASA.

A sonda começou a sua rotação em torno de Mercúrio às 02h00 e irá continuar em redor do planeta mais quente do sistema solar durante um ano, indicou a agência espacial norte-americana.

O engenho espacial começou a sua viagem há quase sete anos, tendo já passado em diversas ocasiões nas proximidades de Vénus e de Mercúrio, sem nunca se ter instalado nas suas órbitas.

Os instrumentos a bordo do Messenger serão activados e verificados no dia 23 de Março e no dia 4 de Abril irá começar a fase científica da missão.

O aparelho transporta diversos instrumentos científicos, nomeadamente um sistema de recolha de imagens, um espectrómetro de análise da atmosfera e do sol e um espectrómetro de observação do plasma e das partículas energéticas.

A sonda completará a rotação de Mercúrio em 12 horas a uma altitude mínima de 200 quilómetros, precisou a NASA. Tudo isto acontecerá a 46 milhões de quilómetros do sol e a 155 milhões de quilómetros.

A sonda já percorreu cerca de oito mil milhões de quilómetros no espaço desde o seu lançamento, em Agosto de 2004.

http://www.publico.pt/Ciências/sonda-messenger-ja-esta-na-orbita-de-mercurio_1485470



A longa e complicada viagem para chegar à órbita de Mercúrio, que incluiu 3 passagens próximas do mesmo planeta, bem como uma a Vénus e à própria Terra.

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Traveling to Mercury requires an extremely large velocity change (see delta-v) because the relative closeness of Mercury's orbit places the planet deeper in the Sun's gravity well. As MESSENGER travels to Mercury, it is constantly being accelerated as it falls toward the Sun. For planets such as Venus and Mars, a technique known as aerobraking is used to slow a spacecraft to orbital speed. However, the tenuous atmosphere of Mercury is far too thin for this maneuver to work for MESSENGER. Instead MESSENGER made extensively use of gravity assist maneuvers to gradually slow the spacecraft. This process greatly reduced the amount of propellant necessary to slow the spacecraft, but at the cost of prolonging the trip by many years and to a total distance of 5.9 billion miles. To further minimize the amount of necessary propellant, the spacecraft was planned to enter a highly elliptical orbit around Mercury during an orbital insertion maneuver that was to be much shorter in duration than other interplanetary missions.

http://en.wikipedia.org/wiki/MESSENGER#Launch_and_trajectory




A missão:


The first few days after orbit insertion will be focused on ensuring that the spacecraft systems are all working well in the harsh thermal environment of orbit; this interval is known as the orbital commissioning phase. On March 24, 2011, the instruments will be turned on and checked out, and on April 4, 2011, the science phase of the mission will begin and the first orbital science data from Mercury will be returned.

Why Mercury?

Question 1: Why is Mercury so dense?

Mercury's density implies that a metal-rich core occupies at least 60% of the planet's mass, a figure twice as great as for Earth! MESSENGER will acquire compositional and mineralogical information to distinguish among the current theories for why Mercury is so dense.

Question 2: What is the geologic history of Mercury?

Before the MESSENGER mission, only 45% of the surface of Mercury had been photographed by a spacecraft! Using its full suite of instruments, MESSENGER will investigate the geologic history of Mercury in great detail, including the portions of the planet never seen by Mariner 10.

Question 3: What is the nature of Mercury's magnetic field?


Mercury has a global internal magnetic field, as does Earth, but Mars and Venus do not. By characterizing Mercury's magnetic field, MESSENGER will help answer the question of why the inner planets differ in their magnetic histories.

Question 4: What is the structure of Mercury's core?


Through a combination of measurements of Mercury's gravity field and observations by the laser altimeter, MESSENGER will determine the size of Mercury's core and verify that Mercury's outer core is molten.

Question 5: What are the unusual materials at Mercury's poles?

At Mercury's poles, some crater interiors have permanently shadowed areas that contain highly reflective material at radar wavelengths. Could this material be ice, even though Mercury is the closest planet to the Sun? MESSENGER will find out.

Question 6: What volatiles are important at Mercury?


MESSENGER will measure the composition of Mercury's thin exosphere, providing insights into the processes that are responsible for its existence.


messengersatellite.jpg

http://messenger.jhuapl.edu/spacecraft/index.html

overviewlg.jpg

http://messenger.jhuapl.edu/instruments/index.html