Some solar system (and beyond) science

As ESA’s living planet symposium continues, news comes in of a number of missions that point inwards rather than outwards, using data gathered from the planets and Earth itself to improve our own understanding of this world.

First off, we have MetOp-B. This is a weather satellite, presently stuck in the middle of the Large Space Simulator in ESTEC. This vacuum chamber simulates the pressures and temperatures the satellite is likely to routinely face. It is large enough to house a double decker bus stood upright and previously held the Alpha Magnetic Spectrometer, which is due to fly to the International Space Station on the final scheduled mission. Its next inhabitant will be part of the BepiColumbo mission to Mercury.

Forty-nine years ago today, another satellite that gave aid to people on Earth was launched. Transit-4A was a navigational satellite that beamed out signals on two radio wavebands. The Doppler shifts from these monitored over a fifteen minute pass could then be used to estimate position on Earth. The system was replaced by Navstar’s gps and the satellites fell out of navigational use in 1996, but then transferred over to the Naval Ionospheric Monitoring Systems, which used the refraction of the signal by the ionosphere to monitor the ionised layers of the upper atmosphere. Transit 4A was also a testbed for the first nuclear power source sent into space.

Another anniversary, this one looking a bit further back to the tune of one hundred and forty two years ago, is the birth of George Ellery Hale. He was a solar astronomer who invented the spectroheliograph. This was essentially a prism or spectrograph that split up all the visible light from the Sun, selected one or two colours of interest and ignored all the rest. Because this meant most of the light from the Sun had been ignored, the image was then faint enough to view or to photograph, allowing the sort of details to be seen that modern solar telescopes view regularly with filters and the like.

Another interesting thing scientists look at when studying our planet is the gravity field. A recent satellite called GOCE, still up there, still watching and recording, has been mapping the gravitational pull of the Earth. Deviations can be caused by changes in composition (sea water pulls differently from land, which pulls differently from magma inside a volcano) or density (temperature and currents in the sea). This feeds through to the atmosphere, which is bound to the Earth by gravity. As such, researchers like to have a map of what is known as the Geoid – the apparent shape of the Earth as measured by its gravity field. The GOCE team has taken a parabolic curve that matches a smooth Earth and produced a contour map of deviations in depth that the Geoid has from this simpler shape. The one presented today is only made from the initial GOCE data. GOCE itself was quite a technological marvel when first put together. In order for the gyroscopes to smoothly measure the gravity of the Earth, moving parts that would cause the satellite to jerk one way or another were banned. The engine was an ionic system that put out smooth bursts to counteract the slowdown caused by friction with the thin atmosphere. This system worked so well, GOCE operated at very low altitudes for satellites – averaging 254.9km, the lowest for any long period Earth Observation satellite.

In order to have a good idea of how planets in general operate, we need data from as large a sample of them as possible. Fortunately, one extrasolar planet has been confirmed as being the first one ever photographed after further study of its orbital features ruled out it being a line of sight pseudo-planet. The planet is eight times the mass of Jupiter and was first introduced to the public back in 2008. With more than four hundred planets of this ilk confirmed and a similar number from the Kepler mission alone waiting for confirmation, a conference to chart the diversity of the worlds we’ve found has been scheduled at Exeter (ExoTerra?) on the 7th-10th September this year. ExoClimes 2010: Exploring the Diversity of Planetary Atmospheres will look at topics such as atmospheric models, atmospheric-interior coupling, comparative planetology within this solar system, extending those models to the known characteristics of some exoplanets and then habitability and climate change.

And it goes both ways as techniques used to study minerals on Earth are being fixed onto Mars rovers to explore Earth-analogue minerals on Mars, to determine when and how widespread Earth like conditions could once have been on the Red Planet.

If this has raised any questions, or left plenty unanswered, then a NASA specialist, Dr Jonathan Cirtain, will be available to answer questions on the solar system at 8-9pm BST on Thursday the 1st of July on this webpage.


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