Current Trends of Satellite Communications and
Their Application in the U.S. Military
Gregory McCaleb
Student # 4215642
ISSC341
Professor Alan Bowen

Abstract
This project paper will explore the current trends in Satellite Communications (SATCOM). There will be a focus on the application of SATCOM in the U.S. Military. The U.S. Military implements SATCOM in many ways and this paper will outline some of the current uses and capabilities of the technology. This paper will explore publications on the topic of Satellite Communications and list the differences in commercial versus military uses.

Current Trends of Satellite Communications and
Their Application in the U.S. Military Satellite Communications is a broad sense is sending data from one point to another point by means of a satellite in orbit. A satellite, by definition, is an object that orbits the Earth. There are natural satellites and there are artificial satellites. An example of a natural satellite would be the Moon. Coincidentally, the Moon was the first satellite used for data transmission when the United States Navy successfully conducted Operation Moon Bounce in the 1950s. Since this success, we have created artificial satellites that we can place in strategic locations and use satellite communications to its full power. The first artificial satellite ever produced and launched was Sputnik 1. Sputnik 1 was launched by the Soviet Union in 1957. The satellite orbited the earth for 92 days, completing 1440 orbits. The satellite was outfitted with radio signal broadcasters that were able to be picked up by receivers across the world, including amateur radio operators and U.S. Government stations. It was this event that really launched the Space Race. The U.S. realized that the Soviet Union was actually capable of launching satellites into orbit. A harmless satellite like Sputnik 1 may not pose a threat, but they realized the need to get involved soon before the Soviet Union advanced beyond our capabilities. Satellites could be used for surveillance, which was a major concern during the Cold War. Today, satellites are much more advanced. Satellites are outfitted with something called payloads. A payload is basically whatever equipment is installed on to the satellite, and determines is usage and capabilities. Two of the most common payloads are communications payloads and surveillance, or imaging payloads. Communications payloads have evolved from very simple low data rate transponders, to highly capable payloads that can rival even some terrestrial circuits. The basics of networking, or connecting two or more devices together, is quite simple. You have two devices and some sort of medium in which to connect them. This could be a cable for example. Very simple if the two devices are close in proximity to each other. What about if the devices are not located anywhere near each other? You could, in theory, run a longer cable in order to connect the two devices, but at a certain point, this becomes impossible. What if they are across the country, or even across the world? In order to achieve this, the capability of radio was introduced.
Radio transmissions involve taking your “data” and turning it in to a radio frequency signal that can be broadcasted wirelessly and received at another location by means of an antenna. This worked great for extending your range wirelessly. There are limitations to radio signals. You deal with obstructions such as trees, buildings, mountains, even the curvature of the earth comes in to play after a certain distance. The idea of satellites is that instead of going directly point to point between two antennas, you use the satellite as a relay. You shoot straight up into space, unobstructed, where the satellite can receive and rebroadcast your signal in same straight line back down to another location. There are no obstacles to deal with in the sky. Your only limitation sometimes is atmospheric conditions that can degrade your signal.
Technology
Data transmissions over satellite communications are quite complex when looking at it from a high level. However, as you break down the components of the system, the signal flow can be understood in an easier manner. Here we will examine the basic components that are included in the transport side of satellite communications. This will not examine the differences in payloads and capabilities just yet. There are a multitude of uses for satellite communications so we will assume that anything beyond the satellite terminal is ambiguous and will just be assumed and referred to as “data”. Additionally, we will examine some of the different types of orbits that satellites can be put into.
Signal flow The transmission of data begins by whatever end device you want to send the data from generating a digital signal, basically a string of 1s and 0s. Think of you PC generating the data and sending it to another PC. The basic 1s and 0s are formatted in certain ways, called protocols, that allow the transmission of the data between the devices, think TCP/IP. Now let’s examine how the data would travel across a SATCOM circuit. Data is received by the satellite terminal, sometimes referred to as the Earth Terminal to differentiate between the land and space segments, by means of a terrestrial cable, usually a coaxial cable. This is the first link between the end device and the SATCOM terminal. Since this is the first link, it is often referred to as the “intermediary”. The intermediary sends the data to the first stop of a SATCOM terminal, the multiplexer. A multiplexer is a piece of equipment that receives signals from multiple end devices and combines them into one signal for further processing in the SATCOM terminal. See, SATCOM terminals must operate off of essentially one input and one output, because of the nature of the transmission system, so the multiplexer is what allows you to do that. After the multiplexer, the data is sent to a modem. The word modem is a combination of the two words modulator/demodulator. There are many different types of modems and modulation techniques, some of which we will discuss later. For now, just know that the basic theory behind a modem is to convert signals from analog to digital, and vice versa. The modem takes your digital data and modulates it onto an analog frequency, called a carrier. This analog carrier is necessary for transmission over radio frequencies as there is no way to send 1s and 0s through the air. Think of the analog signal as taking those 1s and 0s and making it into a suitable radio frequency in which you can send out an antenna. After the modem, the data is sent further into the earth terminal, to the Upconverters. The Upconverters take the relatively low frequency and convert it into a much higher frequency suitable for transmission through space. The reason this is necessary is the output of the modem is a lower radio frequency which is susceptible to degradation over distance and atmospheric conditions. Higher frequencies use a shorter wavelength that is more robust and can travel to the satellite in space. Typically the bands used for space transmissions are C-Band, X-Band, Ku-Band, and Ka-Band. These are simply frequency ranges. Modems also put out relatively low power. You need a way to boost you power to carry the signal into space. For this we use what is called an amplifier. An amplifier is a quite common piece of equipment that takes a low power signal, and boosts the power to a desirable level. In the past, the Upconverters and amplifiers were separate pieces of equipment. You will still see them separate in older systems and legacy equipment. In modern technology though, the Upconverter and the amplifier are combined in to a single piece of equipment called a BUC or Block Upconverter. Now that your data has been converted to space transmission bands and the power raised to desirable levels, it is time to send it to the antenna. When most people think of an antenna, the picture a metal stick or rod. That is called an omnidirectional antenna and is not used for space transmissions. For satellite communications you must use a directional antenna. This commonly looks like a large hollowed out half circle with a point in the middle. The reason you must use a directional antenna is because the satellites you are trying to communicate with can be tens of thousands of miles away. Even the slightest deviation in antenna direction can send your signal miles off course and you will miss your target. The large circle shape also helps to collect the receive signal from the satellite over a broader surface area and collect it into a usable signal. The antenna now has transmitted your data to the satellite where it is received and rebroadcasted down in reverse order to another earth terminal. In almost an identical fashion the signal is collected by the antenna and forwarded for processing. At this point the signal has traveled many thousands of miles and is relatively low power. It is sent to another amplifier and then on to a Downconverter. The next stop is the modem, more specifically the demodulator side, where the signal is demodulated and forwarded to the intermediary. The intermediary carries the signal back to the end device, where the user receives the data.
Orbits
There are three major types of orbits. They are Low Earth Orbit (LEO), Medium Earth Orbit (MEO), and High Earth Orbit (HEO). The different types of orbits dictate where the satellite is positioned in Earth’s orbit and affects the speed and usage of the satellite. The LEO satellites typically range about 120 miles from the Earth’s surface. This means they will orbit the Earth very fast. LEO satellites can typically orbit the Earth once every 90 minutes. LEO satellites can typically carry imaging payloads, since their close proximity to the Earth is beneficial for capturing high quality images. The Global Positioning System also lies in the LEO category. High Earth Orbit satellites are much further in space. Typically a HEO satellite is going to be further than 20,000 miles in orbit. The most common HEO is known as geostationary orbit. A geostationary orbit is an orbit that has been precisely calculated to an exact distance that will orbit the Earth at the same speed that the Earth naturally rotates. This causes the Earth terminal to be aimed at what is perceived as a fixed point in space. This is highly beneficial for communications satellites. The further distance of HEO orbits also allows the satellites to have a larger coverage footprint on the Earth’s surface. LEO, MEO, and HEO satellites typically revolve around the center of the Earth for maximum effectiveness. They orbit right along the equator which gives a good coverage footprint. Geostationary orbits can typically cover about one third of the Earth at any given time. Due to the curvature of the Earth, not all points will be reachable at any given time. A common place that will not receive satellite coverage are the poles of the Earth. The poles of the Earth are too far from the equator to effectively use satellites in that orbit. For this, there are different types of orbits. There are incline orbits and highly elliptical orbits, which allow satellites to orbit the Earth’s vertical axis, providing coverage to the poles.
Future trends Satellite communications will continue to grow in the future. One of the major reasons SATCOM is not as prevalent as terrestrial circuits is simply the cost involved. It costs a lot of money to build and launch a satellite. It also costs money to maintain the satellite and manage the payload. All this translates to higher costs to the end user. Bottom line up front, satellite communications are more expensive than terrestrial circuits. Another limiting factor of satellite communications was the low data rate that early systems were capable of processing. With advanced modulation techniques, we can increase our bandwidth throughput on satellite links. Higher bandwidth throughput capabilities mean we can send more and more data through these links. A growing trend in the military, as well as the civilian sector, is the use of drones. These drones are capable of capturing live streaming video and sending the link to satellites that can redistribute the signal to users on the ground. Streaming video is a known data hog and as technology improves we can send it more efficiently.
Example companies You would be hard pressed to find a modern day company that doesn’t employ some form of satellite communications in their networking architecture. That means there is a huge demand for these services and many companies are involved in the SATCOM market. There are different ways in which companies are involved in satellite communications. There are two major categories that come to mind when thinking of SATCOM, the Space segment and the Earth segment. The Space segment will feature companies that engineer, research, assemble, and launch the satellites. Some of these companies are Lockheed Martin, Thales, and Boeing. These companies focus on the actual satellite itself and can often contract out certain payloads to be built by other companies and integrated into their satellite. The Earth segment will feature companies that manufacture ground based equipment that communicates with the satellites in space. Such equipment could be antennas, satellite terminals, and networking equipment that associates with it. The Earth segment is far larger than the Space segment and includes almost countless companies. Some of the major players are Northrupp Grumman, Raytheon, and Harris. When dealing with companies in the SATCOM field, you run in to a large deal of contracting and subcontracting. No one vendor is usually responsible for all things related to your SATCOM needs. There are some companies that do not manufacture any equipment and simply lease it from others, and then sell the airtime to consumers. Although involved in manufacturing as well, MTN (Maritime Telecommunications Networks) is a good example of this. They will pay money to other, larger satellite manufacturers to put their own transponder payloads onto their satellites. Once the satellite is in orbit and operational, they make their money back by leasing the airtime to customers.
Regulatory issues and global implications Regulatory issues concerning SATCOM can vary greatly from typical companies. Most companies are regionally, or perhaps, nationally based. This means that they have to usually conform to only the laws and regulations that apply to their host nation. The difference with SATCOM is you are now launching your business into Space. No country technically owns Space. However, there still must be a great deal of coordination done by everyone involved to ensure that satellites to not interfere, or even collide with each other. There are also concerns about what types of satellites will be placed over certain regions, because of surveillance concerns.
Conclusion
Satellite communications is a field that has grown in technology and capability. As it continues to grow satellite communications will become faster, cheaper, more efficient, and more robust. Satellite communications give users the ability to network beyond the limitations of standard terrestrial circuits. There will be a growing demand for SATCOM services in the future. The need for international oversight will continue to exists to ensure that as capabilities increase, we maintain the safety and security of all nation’s peoples.

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