Eyes in the Sky
There are now thousands of artificial satellites orbiting our planet. What do they do? How did they get there? How do we find out where they are? How do they keep going? Scientist Vicki Smith leads us on a journey into laser ranging, satellite hunting and space weather.
Inspired by: Victoria Smith of the SGF
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Twinkle twinkle little star, how we wonder what you are.
Galileo showing the Doge of Venice,
Leonardo Donato his telescope.
Four of the moons of Jupiter
discovered by Galileo.
A copy of Sir Isaac Newton's second
When you look up at the stars in the night sky, you are doing something that has happened for tens of thousands of years by countless people including the ancient Greeks, Mayans and Medieval astronomers like the Italian, Galileo Galilei (1564-1642). Using a telescope that he made, Galileo discovered the four largest moons of Jupiter and by plotting their movements showed for the first time that the Earth orbited the Sun. Galileo's telescope was a refracting telescope.
Later astronomers, such as Sir Isaac Newton (1642-1727) tended to use reflecting telescopes.
“I can see the Earth. It is so beautiful.” the first words from space, Yuri Gagarin, 1961.
Now we have the technological capability to leave this planet, place telescopes in orbit around the globe and send probes to the furthest reaches of our solar system. From the first artificial satellite launched in 1957 'Sputnik 1 ' which broadcast radio signals for 22 days and began the 'space race' to the International space station begun in 1993 which has a permanent crew of 6 astronauts, to the hundreds of telecommunications, Earth observation and other artificial satellites orbiting our planet. The human race has never before been able to study its own planet in such incredible detail from such a vantage point.
A scale model of Sputnik 1.
The first artificial satellite (Sputnik –
Russian for Satellite) was put into
space in 1957. It was a 23 inch metal
ball which contained batteries and
two radio transmitters and antennae
and people on Earth were amazed to
hear it on the radio as it flew over
head. Sputnik 1 remained in orbit for
three months before crashing back to
Hear Sputniks 1957 broadcast below.
Today, space craft are observing the smallest changes in our planets climate, the ocean's temperature and level and the thickness of the ice at the poles, the deforestation of the Amazon, natural disaster monitoring, we can even map the cities we live in, all from space. Even the telephone calls you make or the TV you watch has almost certainly made the journey to outer space and back. We take all this for granted, but only a few decades ago, all this was no more than science fiction.
We will take a very brief look at Refracting [pirates favourite] Cassegrain [SGF favourite] Radio and Space telescopes.
There are lots of different kinds of telescopes. Some we can look through [optical] and some which can 'see' out side the optical spectrum to detect far away objects and other wildly interesting stuff. The Space Geodesy Facility (SGF) uses a telescope to see light reflected from mirrors in space. They fire a pulsed laser beam at retro reflectors mounted onto satellites. By measuring the time it takes for the beam to return, it is possible to measure where the base station is relative to the satellite and detect changes in the Earth’s rotation as well as movements of the ground (due to the pull of the Moon)
Different Types of Telescope
In a refracting telescope there are two lenses, inside the tube the light beams cross, but before they can spread out again the eyepiece lens bends the light beams again and sends them to the eye. Because the light beams cross, the image ends up upside-down.
Radio telescopes can produce images of objects in space that would have been missed by an optical telescope. Radio telescopes helped discover pulsars and quasars. Many radio telescopes use a bowl-shaped reflector called a dish to collect radio waves. The reflector focuses the waves onto a receiver that amplifies and detects radio signals. This information can be analysed by computers to create a picture of the source of the radio waves or to analyze the chemicals found in the source.
There are many space based telescopes but the most widely known is probably Hubble. The HST Hubble Space Telescope is part of the NASA Great Observatories Program, four space telescopes all looking at different wavelengths of radiation. The Compton Gamma Ray Observatory, the Chandra X-ray Observatory, the Spitzer Space telescope, and of course Hubble. Space telescopes have a huge advantage as they are above the atmosphere and get a clear view all the time.
RESEARCH. Karl Jansky, Grote Reber, Lyman Spitzer, Edwin Hubble.
The Spy Glass of Facts
Contrary to popular opinion, Galileo did not invent the telescope. In 1609 the great Italian scientist turned his telescope toward the stars and saw the craters of the moon, sunspots, the four large moons of Jupiter, and the rings of Saturn. He saw the rings as "horns" since his telescope could not resolve the gap between the rings. His telescope provided limited magnification--only 30 power--and a narrow field of view; Galileo could see no more than a quarter of the moon's face at a time without moving his telescope. He was the first to publish his findings and risk the censure of the church and his colleagues. Following is a chronological history of the invention and development of the telescope.
- c. 3500 B.C. Phoenicians cooking on sand discover glass.
- 424 B.C. Aristophanes uses a glass sphere filled with water to start fires. Lenses would not be used to study the stars for 2000 years.
- 14th century--convex lenses to correct farsightedness are developed.
- 15th century--concave lenses to correct nearsightedness are developed.
- 1608--In the Netherlands, Hans Lippershey discovers that holding two lenses up some distance apart bring objects closer.
- 1609--Thomas Harriot (1560 – 1621) English astronomer, is the first person to make a drawing of the Moon through a telescope, on July 26, 1609, over four months before Galileo.
- 1609--Galileo, after simply hearing that the device was invented, builds several telescopes of his own and turns them toward the heavens. He dared to publish his findings and was nearly burned at the stake for it.
- 1611--The term "telescope" is coined by Prince Frederick Sesi at a reception where Galileo is demonstrating his instruments.
- 1611--Johannes Kepler switches from a concave eyepiece to a convex eyepiece. This not only allows a wider field of view, but it also allowed for the projection of images (such as the sun) onto a flat white screen.
- Johannes Kepler studies the human eye and notices that the eye's lens is Spherical [ball like]. He suggests the use of Spherical lenses in the telescope.
- 1637--Philosopher Rene Descartes demonstrated that spherical lenses cannot produce pinpoints of light.
- 1673--Johannus Hevelius realized that the longer the telescope was, the closer together the different coloured points of light would be at the focal point, yielding a sharper image. He constructs a telescope 140 feet long which probably gave very sharp images..
- 1675--Christian Huygens suggests getting rid of the supporting tube and mounting the objective lens on the top of a long pole.
- 1668--Robert Hooke demonstrates how to shorten the tube by using three or four perfectly flat mirrors to reflect the image back and forth in a shorter tube. A 60-foot long telescope can be reduced to 12 feet long.
- 1636--Marin Mersenne hit upon the idea of using two paraboloidal [dome shaped] mirrors instead of lenses, but he never builds this telescope, having been persuaded by Descartes [the doubter] that it could never work.
- 1663--James Gregory designed a telescope using a concave primary mirror (slightly hyperboloid) concave ellipsoidal secondary mirror. The first mirror gathers the light and reflects it onto the secondary. The secondary mirror focuses the light back through a hole in the primary mirror.
- 1672--Cassegrain proposed a similar design using a convex secondary mirror that allowed the tube to be shortened even more. More importantly, it cancelled aberrations from the primary mirror and would have resulted in much sharper images, had opticians been able to produce quality mirrors.
- 1668--Newton produces the first successful reflecting telescope, using a two-inch diameter concave spherical mirror, a flat, angled secondary mirror, and a convex eyepiece lens.
- 1729--Chester Moor Hall develops an achromatic lens. Two pieces of glass with different indices of refraction can be combined to produce a lens that tends to focus most colours at a very close (though not exact) point.
- 1730--The Scottish Instrument maker James Short invents the first parabolic and elliptic, distortion less mirror ideal for reflecting telescopes.
- C.1757--Dolland improves upon the achromatic objective lens by placing a concave flint glass lens between two convex crown glass lenses. This triplet uses the natural differences between the refractive indices of the two types of glass to cancel out chromatic aberration even more.
- 1789--Sir William Herschel constructs a forty foot long telescope with a four-foot diameter mirror. Reflector telescopes have become popular again because they can be built with enormous mirrors, capable of gathering hundreds or even thousands of times more light than a refractor.
You might not think so, but we are moving all the time. Not only are we revolving on our polar axis at 1675 km/h and orbiting the sun at 100,000 km/h, our planet is pushed and pulled by incredible gravitational forces, and like the tides in the sea, the actual ground you are standing on can move up and down!
Satellites are usually placed to two main types of orbit: Geostationary and Polar:
Geostationary means the satellite is always in the same position relative to the rotating Earth. The satellite is put at a height (about 36,000 km) so that the time it takes to orbit is the same as the Earth (just under 24 hours). Satellites that monitor the weather are usually put in this time of orbit and can watch storms or hurricanes. Communication satellites that transmit telephone calls and television pictures are normally in a geostationary orbit.
Polar-orbiting satellites circle the Earth and travel over both the North Pole and South Pole . These type of satellite usually pass the Equator and each latitude at the same time each day; this is useful for collecting data at regular times and for comparisons over time, such as the amount of snow coverage in the Arctic. Also, these satellites can in effect 'scan' the whole surface of the Earth within a day.
There are a number of satellites dedicated to monitoring disasters, such as floods or droughts and helping efforts to get relief such as food supplies to the right areas. QUAKESAT is an earthquake detection system that is currently being tested. CRYOSAT – an amazing science satellite, launched by the European Space Agency and put in a polar orbit as one of its main roles is to observe the thickness of the polar ice caps using LIDAR (Light Detection And Ranging).
This text will be replacedThe Sun is behind the centre circle
you can see the flare as is expands away.
The Sun sometimes produces solar flares. These tremendous explosions in the atmosphere of the star directly affect the Earth's upper atmosphere. The Sun shoots out billions of tonnes of particles in events known as coronal mass ejections. If one of these heads towards the Earth it can trigger a disturbance of the Earths magnetic field called a geomagnetic storm.
These storms can cause power cuts and knock out communications satellites. NERC\'s British Geological Survey is helping monitor solar activity, and is advising power companies on how to limit disruption.
Left: A large sunspot region (AR1429) unleashed an X5-class flare, the second largest of the current solar cycle, late on 6 March 2012. The bright flash of the flare (along with several smaller flashes) was associated with a large coronal mass ejection (CME). This animation was acquired by the ESA/NASA SOHO orbiting solar observatory.
What is the cause of aurora? Video courtesy of NASA
It's not rocket science! Oh, hang on.....yes it is.
Until some one comes up with another way of doing things, if you want to put a satellite into space, your going to need a rocket. The European Space Agency's latest launch vehicle is the Vega, which stands about 30 meters tall and Weighs 137 tonnes. The first Vega lifted off in February 2012 at10:00 GMT from Europe's Spaceport in Kourou, French Guiana.
Cryosat-2 is designed to take precise
measurements of the thickness of ice
in the Arctic and Antarctica, helping
scientists better understand how
melting polar ice could affect ocean
circulation patterns,sea-level rise and
the global climate.
Up above the world so high, like a diamond in the sky.
If you want to be able to look down on planet Earth, you will need to get pretty high up. To do this you will need a rocket capable of leaving the Earths atmosphere and delivering your satellite and its delicate instrumentation to its orbital location.
At its most basic, a satellite is a platform for it's own equipment and solar panels (solar arrays) to generate power which is then stored for later use. A means of sending and receiving communications.
For instance an Earth Observation Satellite EOS, might have a powerful camera, such as NigeriaSat-2, which monitors disasters and can even see if individual bridges have been destroyed. Telecommunications satellite that you might get your favourite TV programs or your phone calls from, have antennas to receive and transmit signals, usually as microwaves and a lot of very clever electronics which amplify and direct the signals. Other uses of satellites are weather monitoring and for looking out to space, such as the Hubble Space Telescope.
Even when built and tested, things can go horribly wrong as occasionally the satellite can be destroyed if the rocket launching it explodes. If all goes well, and the satellite leave the protection of our atmosphere when in space, the satellite and its delicate electronics need to survive the extreme heat and radiation from the Sun.
How do you power a satellite
The solar panels used to power satellites
are like the ones you see on some houses.
Batteries can be used but just like the one in your phone they will eventually run out. One charging solution used are solar panels, that are able to turn solar energy into electricity. Lots of photovoltaic cells [PV] are connected together into arrays which can be placed on panels. The technology of PV cells is improving quickly; the cells contain semiconductor material. When light hits the cell, some photons are absorbed and transferred to the semiconductor; electrons are knocked loose and flow creating an electrical current.
Printing Your Own PV.
An innovative Oxford company, Oxford Photovoltaics has developed new solar cell technology that is made from cheap, abundant, nontoxic and non-corrosive materials and can be scaled to any volume. The device is a form of thin film solar technology, quite a new development in solar energy generation.
Harnessing the Sun’s energy, the solar cells are printed onto glass or other surfaces, are available in a range of colours and could be ideal for new buildings where solar cells are incorporated into glazing panels and walls.
source:Cath Harris, Oxford Science Blog
How big does a satellite have to be?
Satellites can cost up to hundreds of millions of pounds and take years to manufacture and launch, but things are changing and a new breed of satellite is on the horizon, the Sprite. Sprites are only about 25mm square, but have solar cells, a radio transceiver, and a micro controller (tiny computer) with memory and sensors - many of the capabilities a bigger spacecraft would have, just scaled down. The first version can't do much more than transmit its name and a few bits of data, like a miniature Sputnik - but future versions could include any type of sensor that will fit, from thermometers to cameras. The Sprites would be launched in a 10cm x 10cm Cubesat [microsatellite] and released in to open space to form what is known as a 'swarm'
Use this handy tool
Cryosat 2, a space laboratory, use LIDAR to
find the thickness of the Polar Ice Caps
300,000,000 metres per second, and that's the fastest speed there is.
The speed of light, its fast, very fast, nothing faster. The important thing is it is a CONSTANT speed which means you can use it to measure against. For instance if you can tell how long it takes light to get from one place to another you will find out the distance very accurately. Using this calculation scientists are able to locate satellites in space or measure the thickness of ice and monitor cloud cover via satellite with LIDAR.
LIDAR (Light Detection And Ranging) measures the time for the light to travel to the object and back. Since we know the speed of light and it is constant (300,000,000 metres per second) and so if we have the time then we can work out the distance of the object.
So, what is this light stuff? its all around you but you can't see it all with out the help of science. Over 2000 years ago the ancient Greek Lucretius (55BCE) thought that light was made of atoms shooting around, there were all sorts of theories about rays and beams coming out of our eyes. Newton said particles, Huygens said waves, Fizeau tried to see how fast it went, Maxwell proposed electromagnetic waves in 1864. It turns out that they were all right [except Fizeau who's equipment let him down other wise he would have got it.] Light is electromagnetic radiation and is made of both waves and particles [photons].This is referred to as wave-particle duality.
The Electromagnetic spectrum
The electromagnetic spectrum is the full range of electromagnetic radiation, which is a type of energy, that ranges from gamma rays through to radio waves. The visible spectrum is the part of this that our eyes can detect and enables us to see. You could argue that the ability to see this small slice of radiation is the basis for our entire civilisation.
Research: Lucretius, Christian Huygens, Sir Isaac Newton, Thomas Young, A. J. Fresnel, James Clerk Maxwell, Albert Einstein.
SGF Track Icelandic Ash Cloud
When Icelandic volcano Eyjafjallajökull erupted, the ash was thought to be dangerous to jet engines and the UK and European skies were closed to aircraft, perhaps you were trying to go on holiday and didn't? Airlines went bust, no one could go anywhere and everyone got very upset. Scientists at the Space Geodesy Facility used their laser in LIDAR-mode to test the transparency of the atmosphere. Looking at the refections from dust in the air showed that there was volcanic ash 1 to 2 km up. These observations, were used by the Met Office to decide whether to let air traffic back in the skies, and make all the travellers happy again.
The Speediest Speed is The Speed of light.
- Sunlight takes about 8 minutes, 19 seconds to reach the Earth
- Kilometres per second 300,000
- Kilometres per hour
- 1,080 million Miles per second
- 186,000 Miles per hour
- Distance Time:
- 134 ms From Moon to Earth
- 1.3 s From Sun to Earth (1 AU)
- 8.3 min From nearest star to Sun
- 4.24 years From the nearest galaxy (the Canis Major Dwarf Galaxy) to Earth 25,000 years
- Across the Milky Way 100,000 years
- From the Andromeda Galaxy to Earth 2.5 million years
- From the Andromeda Galaxy to Earth 2.5 million years
LASER Light Amplification by Stimulated Emission of Radiation.
Lasers are devices that amplify light and produce single colour light beams, ranging from infrared to ultraviolet. they can be very powerful and blind you in an instant! Not the wimpy little red laser pointers, but even they should never be shone in the eye as it may cause a temporary blind spot. Laser light can not exist in nature, a laser uses light from a single colour spectrum [monochromatic]. Some uses of lasers include: CD and DVD players, speed cameras, hair removal, eye surgery, joining and cutting materials, laser guided missiles and bar code readers in shops.
The SGF Laser
Main Laser: Nd:YAG (neodymium-doped yttrium aluminium garnet; Nd:Y3Al5O12)
secondary laser: Nd:VAN (neodymium-vanadate laser 1064 nm)
On the right is a photo of the frequency doubler crystals and an output window. The large crystal next to the pen lid is the crystal for a Nd:YAG laser, in the box is the tiny cube which is the frequency doubler for the kHz laser (Nd:VAN) and the output window from the frequency doubler assembly. The frequency doubler converts the fundamental wavelength of the laser (1064nm) to the second harmonic (532nm) so you see the nice shiny green beam.
Second harmonic generation was first demonstrated in 1961.
Earth observation: revolutionising how we view our planet.
Here, we take a closer look at the benefits of observation from space as provided by Europe’s leading space company, Astrium. With over 18,000 employees worldwide, mainly in France, Germany, the United Kingdom, Spain and the Netherlands Astrium is the third largest space technology company in the world. They have developed over thirty EOS and worked with countries across Europe, South Korea and Thailand, amongst others. As Astrium sees it; satellites provide a snap shot of vast areas of the Earth’s surface. Indeed, a single image from a meteorological satellite can show nearly half the planet! Further, by taking multiple pictures of the same place at different time points we can monitor natural or man-made phenomena as they evolve.
Galapagos is an archipelago consisting of volcanoes which are the result of so called
hot spot which “pierces” the Earth’s crust and builds up fiery mountains.
If you are able, and it is safe to do so, wrap up warm and take a trip out into the night. Try to get as far away from city lights as you can and take a look up. What do you see? The moon will probably be there, may be even another planet, however, the majority of sky will be taken up by stars. If you look carefully though you may be surprised to see that some of these “stars” appear to move across the sky rather quickly. What may surprise you even more is that these moving “stars” are actually looking back at you! There are currently between two to three thousand “Earth Observation Satellites” (EOS) orbiting us. From weather satellites to environmental satellites; from mapping the Earth to spying on it, their unique global perspective offers a new and unmatched method of better understanding, managing and protecting the Earth’s precious environment and resources.
The European remote sensing satellite (ERS) was the
European Space Agency's first Earth-observing satellite.
Above is a full size model of the ERS-2.
Thanks to such data provided by satellites, we are more aware than ever before of the impact of human activity on the Earth. Space-based observation systems continually enhance our knowledge of the Earth’s eco-system, highlighting factors that cause global warming, the greenhouse effect and the depletion of the ozone layer. Equally they are indispensable for keeping a close watch on geographical changes, such as the melting of ice-sheets, coastal erosion and desertification. They can even help during disasters such as earthquakes, volcanic eruptions and forest fires, which are often visible from space. Although satellites do not allow us to prevent such catastrophes they provide us with a tool for rapid response. Specifically, in the case of the 26 December 2004 Indian Ocean tsunami satellite mapping was vital to enable quick evaluation of the areas most affected allowing swift deployment of emergency aid. The history of man-made satellites is extremely short. However, in this short time we have begun to understand the physical processes that govern the Earth, its behaviour, its fragilities, and our responsibilities in terms of how we use its resources. Earth observation from space has truly revolutionised our place in the universe.
Compared to Earth, Mars has an incredibly hostile environment. Mars is an inhospitable, cold, and dry place. Its surface is covered with craters and giant volcanoes and made worse by gigantic planet-wide dust storms. The thin atmosphere on Mars contains virtually no oxygen, and gives no protection from incoming ultraviolet solar radiation. The planet experiences extreme temperatures from day to night, and the average surface temperature is a frosty -63°C. At these temperatures, water cannot exist in its liquid form, and all life as we know it, needs liquid water.
Roaming on the red planet.
On August 6th 2012 a laboratory on wheels the size of a Mini Cooper landed on Mars. Since then the rover, known as Curiosity, has taken photos, measured rock minerals and tweeted its way around Mars , increasing our understanding of the red planet immeasurably. However, getting even a robot to Mars has not been a simple task. Extreme temperatures as low as -60oC, as well as treacherous terrain have meant that, of the seven rovers that have landed on Mars, only the most recent three robots: Spirit (2004-2011); Opportunity (2004-present) and Curiosity (2012-present), have been successes.
With each success we gain more knowledge of how to build better rovers and our current hopes lie with the Astrium designed and European Space Agency funded Bridget and its children Bradley and Bruno, which will land on Mars in 2013. This is the first European funded rover since the ill fated Beagle 2 failed to contact Earth once it had landed.
Why are we sending rovers to Mars?
Not only is Bridget faster than the current rovers it is more intelligent as it can automatically choose the best path to new sites of interest. This is particularly useful as commands from Earth can take up to 20 minutes to get to Mars! This intelligence is made possible through the use of two cameras, which allow the rover to have depth perception in a similar way to human eyes .
But why are we sending rovers to Mars? What are they looking for? NASA has four big goals that it is trying to accomplish:
Determine whether Life ever arose on Mars;
Characterize the Climate of Mars;
Characterize the Geology of Mars;
Prepare for Human Exploration.
In order to achieve these goals the rover looks for the factor that they all have in common; water. Although liquid water is not present the rover looks for signs of water having been there in the past through rocks, minerals and geological landforms.
Why not send Manned missions to Mars?
But why can we not simply send a human and forget about all of the engineering problems that Astrium have faced? Humans can certainly survive the extreme cold, which is actually warmer than Antarctica’s coldest temperatures. Even hazards such as cosmic radiation, dust storms and the effects of weightlessness on muscle mass and cardiovascular fitness are not insurmountable. However, the problem of keeping a human healthy: on their way to; whilst on and returning from Mars is much tougher than designing an robot to do the work for us, which is why experts suggest that it will be at least 2030 before we see manned trips to Mars.
Until humans do finally set foot upon Mars’ rocky and barren surface we will be relying on rovers like Curiosity, Bridget, Bradley and Bruno to be our eyes and hands on other planets. But more importantly we will be relying on new young minds that drive the innovations and inventions of the future.