Space Observation
Nicholas
Drake
Apart
from scientific analysis of asteroids and moon rock, our observations of the
universe are made in the study of light and the electromagnetic spectrum.
Light
from distant galaxies yields a wealth of information and our understanding of
the universe’s secrets is limited only by the equipment with which we remotely
sense with. Radiation which comes to us from the cosmos comes in many forms;
from shortest wavelength to longest, light contains: X-Rays, Gamma rays, Light
(visible), Infrared, Microwaves and Radiowaves (see fig.1). It is the study of
any component of this electromagnetic radiation that gives us the applications
of remote sensing in Astronomy and Cosmology. This passage is adapted from the
introduction to The Nature of Light in The Science of Astronomy.
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Figure 1: The electromagnetic
spectrum
The
field of Astronomy has experienced a recent history of scientific breakthroughs
with the applications of remote sensing. It is first documented that records
relating to the stars date back to Egyptian civilisations[1].
Although information was gathered about the stars, a scientific understanding
as to the actual mechanisms driving these planets was not yet known. The Great
Pyramids of Egypt are built into celestial alignment with the constellation of
Orion as it would have looked c.3000 years ago. Another important aspect of
early astronomy which still guides our lives today was the establishment of the
24 clock and lunar calendar. The number 24 is a very ‘nice’ mathematical
number, it’s is divisible by 2, 4, 6 and 12. Giving fractions of 1/12, 1/6, ¼
and 1/2 . These fractions are also the square reduction of the previous number.
Space
observation and a keen will to apply definitive cycles to celestial events led
historically to the construction of stone observation moments across Earth
dating between 2000 and 1500BC.
Our
understanding of the mechanisms present in the universe was not significantly
increased until the advent of the scientific/technology era of beyond AD1600.
The
understanding of optics and the principles of magnification, refraction,
contraction and radiation helped provide an important first footstep in the
evolutionary process of remote sensing in astronomy. The first milestone in
understanding the nature of light came in the 1600’s when Isaac Newton, an
English physicist discovered by chance that passing light through a prism
splits the wave into low and high wavelength energy, known as the visible spectrum
(see below fig.2)
Figure
2: Light separating in a prism
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Following
the identification of light not as a single wave, but as a combination of many
waves, the next milestone in astronomy came after laboratory experiments in the
mid-1800’s as to the speed of light. Roughly given as 300,000km/s. This gives
us the ability to track the distance to celestial objects, and with an
understanding of wavelengths and the nature of shortest wave light being in the
blue spectrum with longest light in the red spectrum we can understand how fast
and far objects are moving in the universe. This is with the understanding of
the Doppler effect to light as-well as sound waves.
As
we enter the 1900’s we have the addition of Albert Einstein, probably the
greatest mind to bless astronomy and science ever. His theories, models and
formulae still provide the fundamentals of scientific understanding today. He
conclusively proved amongst other things, speed of light, nature of light in a vacuum,
the theory of relativity, the effects of gravity on bodies, theoretical
wormhole and multi-dimensional spaces.
Aside
form the advances being made throughout the 1900’s by many European physicists,
there was also rapid development in the field of technology, man’s greatest
tool.
As
mentioned previously, the understanding of light; magnification, refraction etc
led to the development of the first optical telescopes. The first, constructed
by Galileo Gallia in 1642 was only 2-3inch in diameter and yet gave the view an
unparalled view into space.
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Concurrent
evolution of optical technology gave rise to the 40-inch Yerkes Observatory
telescope in the 1890’s[3].
This is the largest example of a refracting telescope, built with the
understanding of the nature of refracted light. Further advancements led to the
assemblage of multi-lens telescopes across the globe.
Another
significant milestone in astronomy was the development of the Radio telescope in
the 1930’s. Before this time, observed measurements were made using visible
light. This I believe is the most important of remote sensing aspects to
astronomy, as this was the first observation of remote objects made in the
non-visible spectrum but still in the electromagnetic spectrum.
Radio
waves are collected by the large dish and focused towards the centre where
information is digested by computers to provide a image of radio-waves received
from distant objects.
Radio
waves, having the longest wavelength in the electromagnetic spectrum are
capable of penetrating through atmospheres of planets indicating the geologic
composition of the planet below.
The
implications for humanity as a whole from an advancement of such magnitude are
enormous, if previously all observation were made in the visible spectrum and
now with the use of Radiometry and other wavelengths, we are beginning to uncover
a vast quantity of information relating to distant solar objects.
The
field of remote sensing, which began in the 1930’s with the first strapping of
a photographic camera onto a pigeon and taking an aerial photograph has also
seen much technological advancement in recent history. Much of the development
in remote sensing has come from the advancement made in military technology. Remote
sensing conducted by a satellite in geosynchronous orbit can provide the enemy
with a complete battlefield scenario map, assess the health of vegetation,
track population movements and settlements and military vehicles.
There
are currently many satellites tracking environmental changes on Earth that have
provided us with a far more detailed interpretation of the mechanics of how the
Earth works and the ‘fluid’ motions of global climate and ocean thermal systems.
These
instruments and sensors can and have been applied to the interpretation of
celestial objects. In August and September of 1977, two satellites, Voyager 1
and Voyager 2 were launched from Earth. These satellites’ first mission was to
send back images of the ‘outer’ solar system planets such as Jupiter, Saturn,
Neptune and Uranus. All the images sent back to earth from these craft
represented further milestones in the understanding of distant planets. Whereas
before using ground based observation, the size and shape of planets could be
identified, with sensors on the Voyager craft, atmospheric analysis could take
place which most certainly broadened our understanding of these planets in our
solar system. For example, the Red Spot on Jupiter was analysed and found to be
a super-massive cyclonic system driven by thousand mile and hour winds.
Currently,
nearly 40yrs later, these two spacecraft represent mankind’s furthest reaches
into the universe and they remain today travelling further into deep space.
I
must draw mention to the ‘golden discs of voyager’ which contain a library of
information relating to life on Earth. Burned onto an golden LP, are images of
Earth, greetings from the languages of the world and core mathematical
equations including the relative position of Earth in the solar system. An
image of the disc can be seen in figure 3.
Figure
3: The Golden Disc of Voyager
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These
Voyager spacecraft represent the first steps of distant Astronomical remote
sensing.
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Later
missions, included space probing missions. A ‘probe’ is a single or many
instruments designed to enter a planet and conduct experiments remotely. An
example of such a planetary mission may be the Mars Pathfinder mission of 1997.
On-board the entry capsule was the buggy named ‘Sojourner’ (figure 4). It had
the ability to analyse the chemical composition of the rocks on the Martian
surface and so present scientists back on Earth with unique information about
Mars.
This
is an example of extremely remote, remote sensing.
Planned
space probe missions include an exploration of the planet Europa, one of
Jupiter’s moons. It has been estimated using remotely sensed data that under a
thick ice-sheet may lie water and therefore may contain the pre-requests for
the development of bacterial evolution.
Figure 4: The Mars
Pathfinder capsule
Other
than spacecraft which travel past distant objects, another very important
advancement in the field of remote sensing and space observation was the
introduction of the world’s biggest and most powerful telescope, the Hubble
Telescope.
Hubble
lies in orbit above Earth, this means that it is free from the scattering
effect of the atmosphere, and interference from other forms of electromagnetic
energy including human induced urban zones.
Hubble
has for 10 years, proved the most amazing of telescopes available for use. “The
Hubble Space Telescope or HST could be operated from the infrared through the
violent range and far out in the ultraviolet”[4].
Using
this instrument, scientists have been able to calculate the speed at which the
universe is expanding, observe the creation and destruction of distant planets
and solar systems, track and locate black holes and has provided a wealth of
information about the solar system which we previously had no knowledge of.
The
implications of the HST are revolutionary. We have for thousands of years
looked to the stars without any real knowledge of what is out there. With the
introduction of the first earth-based telescopes, we saw a little ‘closer’
however at the dawn of the 21st century, we are equipped with a very
powerful telescope in outer-orbit that can see to the depths of the universe in
nearly all wavelengths. It is only our interpretation of this information which
derives the scientific importance of the data. The keys to the universe can be
found from analysis of the mechanisms driving distant galaxies, helping us to
understand our creation and broaden the understanding of potential for extra-terrestrial
life.
The
use of radio telescopes exists today and can be seen on many places on Earth. Radio
telescopes can be used together in a process known as ‘interferometry’[5]
which can increase the resolution of received radio signals dramatically. There
is a further stage of radio-telescope co-operation known as Very-Long Baseline
Interferometry (VBLI). This combines data-sets from telescope thousands of
miles apart. A current use of radio
telemetry in VLBI arrangement is the program SETI, which stands for Search for
Extra Terrestrial Intelligence, which is mapping every arc minute of the night
sky in search for a radio signal or indication of intelligent life.
In
conclusion, in less than one hundred years, mankind’s understanding (or at
least, potential understanding) of the universe has significantly increased.
From
ground-based observations using optical telescopes, through the development of
radio telescopes in-line with increased knowledge about light as a wave and
it’s integral components, into satellite developments of the cold-war era which
gave the world the first lunar footsteps and successive missions to distant
objects (see Voyager mission) and finally into the advanced stages of
technological advancement and sensory refinement and planetary exploration, we
have benefited from an evolutionary boom in the technology available in remote
sensing.
There
is no doubt that without the technological evolution of remote sensing
technology, as-well as the human mind’s ability to understand and interpret
such complex mathematical models, the human race would be far further down to
intelligence ladder than we are at currently. The images received from space
are difficult to truly digest because of the sheer distances involved between
objects and galaxies in space however, with correct interpretation and
scientific understanding, we can view with images from the HST, and discover all
(or many) of the mechanisms in the universe.
It
has been an evolutionary process of progression to the stage we are at in 2002
and the future of space observation and remote sensing is within our grasp. The
technological advancements possible in the future may be the dreams of science
fiction but may present themselves as scientific fact in the near future.
If
we have evolved the technology in 50 yrs to visit our nearest neighbour and
beyond, why not in another 50yrs might we be travelling close to the speed of
light.
And
our source of energy, the electromagnetic spectrum*.
*
It has been said that the Universe is as small inwards as it appears outwards.
Meaning that the sub-atomic (nuclear fission), quantum (quark) and neutrino world
may be of more use than initially envisaged.
2,200
words
Bibliography
The
Science of Astronomy – Harper & Row publishers 1974
Discovering
the Universe 4ed. William J. Kaufman III and Neil F. Comins – W.H.Freeman and
Company
The
State of the Universe – Edited by Geoffrey Bath,
Introduction
to Remote Sensing – 2ed. James B. Campbell – Taylor & Francis 1996
Observing
the Universe – Edited by Nigel Henbest – NewScientist publication
Satellite
Remote Sensing – An Introduction – Ray Harris
All
images obtained via www.google.com