IRISH TUNES MAKE IT TO SPACE
Astronaut Cady (Catherine) Coleman played a couple of Irish tunes to celebrate St. Patrick’s Day on her 90th day living at the International Space Station.
Coleman claims a quarter Irish heritage from both of her parents and loves to celebrate her Irishness whenever she has the chance. She borrowed a couple of instruments from a famous Irish band, “The Chieftains
Cady played Matt Malloy’s 100 year old flute and Paddy Maloney’s tin whistle. A nice surprise for the famous folk Irish band as they were told that she was going to take the wind instruments to a business trip but never mentioned the trip was to the ISS.
A MILESTONE FOR HUMANITY
Today humanity reached another milestone in the exploration of space. Spacecraft Messenger successfully entered into orbit around Mercury, the fifth planet in our solar system around which we achieve orbit.
This is the opportunity to learn about the creation of our solar system and study the effects of time and solar radiation at such a close distance to our star.
This is a historical St. Patrick’s Day you can tell your grandchildren about.
After 3 flybys close to Mercury, at 1:30 UTC on 18 March 2011, spacecraft Messenger entered into orbit after a successful burn of its engines to regulate its speed.
At an altitude of 281 km from the surface of the first planet of our system, the spacecraft performed perfectly, mostly in an autonomous way as there is an 8 minute delay in communications to and from Mission Operations Center at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md, USA.
The last moments of tension at Mission Operations dissipated when data sent by Messenger seemed to be almost exactly to that calculated by the engineering team lead by Eric Finnegan, Mission Systems Engineer.
According to Sean Solomon, Principal Investigator of the mission, “It took 15 years from PowerPoint to Orbit.” He recalls that the original idea of gaining orbit emerged in 1976, shortly after Mariner 10 reached Mercury for the first time.
The mission was quite an achievement, particularly for the navigations team responsible of the precise calculations of the 6 and a half year trajectory of the spacecraft, launched in 2004.
WHY MERCURY?
Mercury is the smallest, the densest, the hottest, the closest planet to the Sun, it has the oldest surface and is the planet that receives the most radiation from the Sun. Understanding this planet can tell us a lot about the history of planetary systems, their composition and about how planets work.
Together with Venus, Earth and Mars, they make the innermost rocky planets of our solar system, therefore we expect to find some similarities. There are a number of questions that this mission will attempt to answer:
- Why is Mercury twice as dense as Earth?
- What is its geologic history?
- What is in the 55% of its surface that we never had the chance to see?
- Why does it have an internal global magnetic field like earth, not found in Venus or Mars?
- What is the size of its inner core? And is it the outer core molten?
- What is the highly reflective material inside the permanently shadowed craters at its poles? What is the composition of its thin atmosphere?
THE SPACECRAFT AND THE MISSION
Data from mission Mariner, 30 years ago was invaluable as that was the first spacecraft to reach the vicinity of Mercury and Venus. The monumental task of sending an autonomous spacecraft took 15 years to plan and develop.
Messenger, an acronym meaning “Mercury Surface, Space Environment, Geochemistry and Ranging” is a spacecraft that cleverly uses the assistance of gravitational forces of the 3 planets on its 7.9 billion kilometre journey, to its destination.
Launched in the summer of 2004, it moved away from the Earth keeping its instruments side towards the sun, as they were designed to work at close to terrestrial room-temperature. As it moved towards the sun, it turned around to protect its sensitive side under the highly developed heat-shield. From then on a game of hiding from lethal solar radiation was to keep the spacecraft in working order.
This spacecraft is known as the “solar sailor” because it uses angulations of its own features as sails to use the energy of the sun to make slight changes to its trajectory as it travels at speeds of up to 225,300 km/h. Flying close to Venus and to Mercury itself, it used their gravitational pull to slow down enough to approach Mercury. The final burst of its engines slowed it down to a precisely calculated speed to enter into an elliptical orbit, which it will maintain for the next year.
One of the biggest challenges was to shelter the instruments from the extreme heat of the Sun at such a close distance. The shield had to allow the instruments to work at room temperature while it receives temperatures close to 450 degrees Celsius. The instruments were also protected from temperatures in the dark side of Mercury, which can be as low as 0.2 degrees Kelvin.
The shield is made of a ceramic cloth developed originally to protect jet aircraft from the heat of their engines. This was improved with layers of special plastics.
The rest of the spacecraft is mostly fuel. The instruments had to be crafted over a carbon fibre structure to keep it as light as possible.
In order to save fuel, Messenger uses solar energy generated by solar panels but the sun is so strong that they had to be modified to avoid high temperatures as they only work within freezing and boiling water temperatures. Their structure includes 3/2 mirrors and 1/3 solar cells to diverge light, instead of facing the sun they are tilted so that the exposure is feathered for protection.
Other instruments on board include:
- Mercury Dual Imaging System (MDIS): A set of 2 cameras, one with a long lens for the distant points of the elliptical orbit and a wider angle when the spacecraft is close to the planet.
- Gamma-Ray and Neutron Spectrometer (GRNS): Detects titanium and hydrogen, which will come useful in determining the possible presence of ice water.
- X-Ray Spectrometer (XRS): Determines the composition of the surface of Mercury. Magnetometer (MAG): Measures the magnetic field.
- Mercury Laser Altimeter (MLA): Infrared laser to map the surface of the planet.
- Mercury Atmospheric and Surface Composition Spectrometer (MASCS): Measures Ultraviolet and Infrared light to determine the composition of the atmosphere.
- Energetic Particle and Plasma Spectrometer (EPPS): Studies charged particles around the planet.
- Radio Science (RS): Measures the precise distance from Earth and takes care of communications. Signals travelling at the speed of light take 8 minutes to arrive to Earth.
FIRST IMAGES
The first images received gave a sense of reality to the project. They showed areas hardly seen before, including the area known as “the spider” formed of large concentric valleys and possible proof of volcanism with craters partially filled with flows of lava. More images will come later in the year. As Messenger orbits Mercury going around the planet twice a day.
WHAT NEXT
Initially, the next revolutions around Mercury will provide data to establish if the orbit is correct. Then the real mission starts, collecting and analysing data captured by all the instruments on board. Understanding of the planet is the final goal to help us explain how planets were born and what will happen next.
References
¤ Mariner 10 to Venus and Mercury (2011). NASA-JPL. [Online]. Available here. (Accessed: 18 March 2011).¤ Messenger (2011). NASA. [Online]. Available here. (Accessed: 17 March 2011).
¤ Tunis, W. (2010). The Musical Box: The Chieftains. [Online]. Available here. (Accessed: 18 March 2011).
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