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Caption: The Hubble Space Telescope in low earth orbit]
Space: The Highest Ground
[Teaser:] STRATFOR presents a primer on the terrain of earth orbit, which is fast
becoming essential for global military operations.
Summary
Like the sea and air before it, space has become a critical enabling domain for global
military operations. And the terrain of earth orbit, like geography, is a fixed reality
central to understanding larger geopolitical issues. One important lesson is that gravity,
velocity and the limited ability to maneuver -- as well as orbital debris -- place very real
constraints on the freedom of action in orbit.
Analysis
Space has become a <link nid="114469">pivotal domain for enabling military
operations</link> around the world, particularly for the United States. It is how the
national command can communicate with its deployed forces on the other side of the
earth and it is how those forces can navigate and communicate with each other. Spacebased assets provide the intelligence, surveillance and reconnaissance that helps enable
the use of precision strike weapons. These and other assets in orbit have come to play a
central role in a variety of military operations around the globe.
Other nations and potential adversaries are keenly aware of the advantage the United
States has gained through its exploitation of space and are seeking ways to exploit these
advantages themselves -- and to deny the Pentagon their utility in a crisis.
The Basics
“Weightlessness gives us the illusion of freedom. In reality, space is a realm in which
gravity and the laws of motion rule with an iron hand.” -- The Future of War[Nate would
like us to link to Geo’s book somehow -- or at least to a marketing page or
something. Or should we list it FOR FURTHER READING or as a SPECIAL
TOPIC PAGE?]
Like fixed-wing aircraft, objects orbiting the earth are continually moving under the
influence of gravity -- indeed, they must in order to maintain their position. In the
atmosphere of earth, were a fixed-wing aircraft to come to a halt mid-flight, air stops
flowing over its wings and the lift created by the flow of air ceases to exist. Similarly, a
spacecraft’s motion is an inescapable component of its position above the surface of the
earth. Forward motion combines with the earth’s gravity so that, while a satellite is
constantly being pulled toward the earth’s surface, its velocity allows it to essentially fall
around the earth, following the path of a circle or an ellipse. We call this path an orbit.
The velocity that keeps satellites in orbit is first provided when they are launched and
inserted into orbit. Precise velocity is critical. Too slow and the orbit quickly decays,
allowing the satellite to slip slowly back to earth; too fast and the satellite breaks free of
the orbit. Over time, due to a number of influences like friction, orbits decay anyway.
The International Space Station (ISS), for example, must regularly be boosted into higher
orbit to counteract this decay. This requires considerable energy.
The fuel for this energy, like every other manmade object above the earth, must also be
launched into orbit. This is expensive, although the price for boosting payloads into orbit
is falling, and there are several private firms like SpaceX that are trying to make a
generational leap in reducing the high cost of a space launch. But weight considerations
will continue to be a matter of fundamental significance for spacecraft design in the
foreseeable future. And there are very strict limits to the amount of fuel a spacecraft can
carry to maintain its orbit and maneuver within it over time.
The problem is that spacecraft do not have a thick atmosphere to push against in order to
maneuver as aircraft do -- indeed, if they did, their velocity would be quickly slowed and
the orbit would decay. The only way for spacecraft to change direction or orientation is to
burn fuel. So any alteration to an orbit must be carefully calculated, and factors such as
gravity, velocity and available fuel must be constantly taken into account.
Debris
There is also the problem of orbital debris. This can be anything from the discarded upper
stages of a launch vehicle to a tool dropped by an astronaut working on the ISS. More
than 18,000 pieces of orbiting debris can be tracked from earth. All are traveling at
phenomenal speeds, and even a collision with an object as small as a screw can have
catastrophic consequences. Spacecraft are also constantly being peppered by a
microscopic assortment of cosmic debris, be it natural or man-made.
This debris problem is most pronounced where human activity has been the heaviest, in
the most densely populated bands of low earth orbit (LEO). And the problem is only
getting worse. It is thought that as few as several dozen highly energetic anti-satellite
events like the <link nid="32159">Chinese ASAT test</link> in January 2007 could
render whole swaths of LEO unusable for years or even decades.
The problem is widely recognized, though just what to do about it remains unclear. In the
meantime, debris-mitigation measures are increasingly standard practice for satellite
insertions, and every space-faring nation has a great incentive to avoid devastating wars
in space that could greatly multiply the amount of debris in LEO.
Basic Orbits
Essentially, LEO begins where the friction of the atmosphere is low enough that orbit can
be maintained -- from about 500 kilometers to 2,000 kilometers above the earth. This is
where the bulk of the earth’s satellites, including the Hubble Space Telescope and the ISS
-- as well as most orbital debris -- reside. Where atmosphere ends and space begins is a
little fuzzier. Satellites can be found orbiting as low as 200 kilometers above the earth’s
surface, well within the thermosphere -- the second highest layer of the earth’s
atmosphere -- where the friction of the atmosphere is not prohibitively intense.
[Graphic: <https://clearspace.stratfor.com/docs/DOC-3682>]
Less powerful launch vehicles can boost small payloads to LEO, making it the most
accessible -- and the most crowded. To maintain altitude at this level, orbital objects
move very fast in relation to the ground beneath them, often orbiting the earth many
times in a single day. Generally, to maintain constant coverage over a single point on
earth, a constellation of satellites alternately providing coverage is necessary. Being
closer to the earth in LEO can be beneficial for a number of reasons. Optical spy satellites
can achieve better resolution in their imagery, signals intelligence satellites can achieve
greater sensitivity and communications satellites can broadcast a stronger signal with
lower power requirements.
The next major mark is geostationary orbit (GSO), about 36,000 kilometers above the
equator. At this altitude, along the equatorial plane, satellites can be placed into orbit
where they can remain stationary in relation to a specific point on the surface of the earth.
Unlike LEO, GSO is limited to the equatorial plane, not the entire sphere of orbit over the
surface of the earth. GSO is home to, among other things, the U.S. Defense Support
Program (DSP) satellite constellation that provides a constant, global infrared launchdetection capability.
Though definitions can vary, medium earth orbit (MEO) is usually distinguished as the
space between LEO and GSO. Consisting of trillions of cubic kilometers of open space,
MEO is an enormous area much less densely packed than LEO. The dozens of satellites
that comprise the Global Positioning System (GPS) constellation are in MEO.
Orbits can also be defined by their inclination (the angle relative to the equatorial plane)
or their eccentricity (how closely the orbital path resembles a circle). A common example
of the former are highly inclined orbits generally classed as polar orbits because they go
over the poles. Both the <link nid="132076">Iridium satellite and the Russian satellite
that collided</link> in February 2009 were in polar orbits; they hit over Siberia as they
passed near the North Pole in LEO. (That this had not happened before is a testament to
the enormous -- although increasingly cramped
-- volume of empty space above the earth.)
[<CLICKABLE
<http://www.stratfor.com/mmf/132077>
<http://web.stratfor.com/images/Satellite-Collision-800.jpg>]
There are also more eccentric orbits known as highly elliptical orbits (HEO), which can
take many different shapes and inclinations. This kind of orbit has a much greater
difference between the apogee (its highest altitude point) and the perigee (its lowest
point) than a less eccentric (more circular) orbit. Velocity will also vary more in an HEO.
There can be specific considerations that make this kind of orbit desirable, especially
long loiter time over a certain point of geography without having to boost a large satellite
all the way out to GSO. HEO orbits are particularly beneficial for Russia, since even
satellites in GSO provide poor coverage of Russian territory, which lies at too great an
angle for optimal coverage from an equatorial orbit.
Lagrange Points and the Moon
Far beyond even GSO is the orbit of the moon, which varies from around 365,000
kilometers to more than 400,000 kilometers. The moon does not rotate relative to the
earth, so the view of the surface of the moon is always the same from earth
(notwithstanding the phases of the moon, which vary according to the alignment of the
earth, moon and sun).
Together, these two orbiting bodies -- the earth and moon -- create Lagrange (or
libration) points, as does the sun-earth system. Lagrange points are positions in space
where all gravitational forces are equal. The sun-earth system also creates these points.
(The graphic below shows the five Lagrange points of the sun-earth system. The points
would be in the same pattern for the earth-moon system, though on a smaller scale.) In
both cases there are five points in space where the gravitational effects of the two bodies
create areas of equilibrium. NASA research satellites already orbit the sun-earth system’s
L1 and L2 points, which exist in a sort of gravitational “saddle” and are dynamically
unstable, meaning that fuel must be expended for station keeping and course correction.
(L3 has this same dynamic instability, but over a longer period than L1 and L2; L4 and
L5, however, are considered stable.)
[<Lagrange graphic><https://clearspace.stratfor.com/docs/DOC-3682>]
The potential scientific, economic and military utility of the Lagrange points and the
moon are not yet well understood. Like the geography of the earth’s surface, however,
they are fixed realities and bear watching as the United States tries to find the funding
and political will to continue manned spaceflight and as China expands its manned
program (with India following in its footsteps) and more and more countries employ
satellites for strategic purposes.
But understanding geography is only the first step. Recognizing where the high ground is
does not mean having the ability to claim and defend it. As the theory and practice of
utilizing strategic assets in orbit evolve, the powers in space must learn how to deal with
their adversaries’ assets. This is not to say that space should be <link
nid="114469">“weaponized”</link>. It is STRATFOR’s belief that it already has been --
and that countries interested in global military operations on earth have nowhere to go but
up.
RELATED LINKS
http://www.stratfor.com/analysis/u_s_implications_satellite_intercept
http://www.stratfor.com/analysis/china_russia_u_s_unpromising_treaty
http://www.stratfor.com/analysis/space_and_u_s_military_operationally_responsive_spac
e
http://www.stratfor.com/analysis/space_and_u_s_military_strategic_tactical_exploitation
http://www.stratfor.com/analysis/u_s_satellites_and_fractionalized_space
SPECIAL TOPIC PAGES
http://www.stratfor.com/theme/ballistic_missile_defense
http://www.stratfor.com/theme/u_s_military_dominance
[Can we link here to The Future of War under ‘FOR FURTHER READING’ or as a
SPECIAL TOPIC PAGE?]