Satellite Communication Today and Tomorrow

SATELLITE COMMUNICATION Today and Tomorrow JANUARY 19, 2015 MATT DAVIS Center for Information and Communication Sciences - Ball State University  1 Introduction The communications industry changed forever in October of 1957 when Sputnik a Russian satellite, the first satellite, was launched into Earth’s orbit (2004, Pelton). Since that time governments around the globe have continued to launch satellites to assist them with communication, observation, and research. Yet, without their ability to communicate satellites would be virtually useless, nothing more than hunks of metal circling the Earth at thousands of miles per hour in a perpetual freefall. To exchange information with objects not on the Earth’s surface requires free-space or wireless communication, such as the radio which is a technology we have been using and improving for decades. This has been adequate for the first fifty years of satellite communication, but with an ever growing population of satellites that are sending consistently richer data streams a new form of wireless communication is required. Which brings us to our question; what is the next step for space communication? The current space communication network To better understand where our space-based communication network must go next, we must know what it is now. The biggest player in space communication is NASA with their Space Communication and Navigations (SCaN) network; unlike Earth networks, space networks must inherently include navigations as everything in the solar system is in motion. SCaN is comprised of three networks the Near Earth Network (NEN), the Space Network (SN), and the Deep Space Network (DSN); utilizing the S, X, Ku, and Ka bands of the radio frequency spectrum which operates in ranges from 2 – 40 Giga Hertz (2014, nasa.gov).  2 An advantage of using a radio frequency (RF) system is that antennas direct the electromagnetic energy in a cone, so being able to receive the incoming stream of data is a simple as putting a device within the cone. The issue here is twofold, first the frequency used is “spent” for all devices in that cone meaning any other communication to those devices must use a different frequency, and second since any device in the local area can receive the incoming RF signal security can be difficult to manage (2000, Mott). RF is not without its vices though, too high of a frequency and the signal will not penetrate the atmosphere or too low and it will reflect off airborne aerosols. This leaves a few ranges of electromagnetic spectrum such as those used by NASA’s SCaN network that will reach from the Earth’s surface to objects in space; limiting the bandwidth capable of carrying data. With the available RF spectrum that is able to slip through the atmosphere and reach objects in near Earth orbit, i.e. between Earth and the Moon, capacity has become an issue of discussion in many sitcom circles. Sure, technological improvements have allowed us to squeeze out more bandwidth and increase our efficiency of transmission, yet we are approaching network saturation with each new uplink. Another issue with using the RF spectrum as the primary data carrier is communication with objects via the DSN. A one way trip for data from Earth to Mars is on average six to seven minutes, and it takes about 20 hours to send 250 Megabits of data (2014, mars.jpl.nasa.gov). As we conduct more deep space missions we will require more bandwidth and the further away those missions are conducted the more delayed and weak those RF signals will be. This is why there is a need to develop and deploy a new space network capable of faster, stronger, and more efficient transmission.  3 Optical communication satellites On Earth fiber optic cabling comprises the backbone of the Internet and is in the process of being connected directly to homes by the tens of thousands (2014, Davis, Koza, Mitchell, Parker, Shanabarger). This is due to the bandwidth and throughput that optical communication networks are capable of handling, 100’s of Gigabits to 10’s of Terabits (2002, Goff). Regretfully, running a cable from a NASA research center to a satellite in geostationary orbit (GEO) is nigh impossible. Still, wireless optical communication has many advantages over older radio frequency technology. Wireless optical communication arrays are smaller in both size and weight than those that produce RF meaning that they cost less to ship into orbit via a rocket. Additionally, laser-based communication uses less power per bit making them more energy efficient, a very important factor when satellites maintain their energy reserves using solar panels (2000, Mott). Because optical satellites are only required to send a narrow beam of light to and from the Earth’s surface it makes it very difficult to for unwanted interceptions to take place, a great boon for security. A single laser communication satellite on its own will not improve the existing space network. Rather, a contingent of these satellites spread between MEO (mid-Earth orbit) and GEO would make up the proverbial backbone of the space network (2004, Pelton). Once a primary fleet of optical communication and navigation satellites are deployed other organization could “install” their own optical satellites to further extend this high bandwidth network. Additionally, a new  4 generation of ground-based receivers and transmitters would need to be installed to relay data to and from the satellites. This is the next step for satellite-based communication. The future of space communication The future of space-based communication and navigation is already unfolding. From October of 2013 to April of 2014 NASA conducted the Lunar Laser Communications Demonstration (LLCD), sending 20 Megabits of data per second and receiving 622 Megabit per second from LADEE, a satellite orbiting the Moon (2014, nasa.gov). NASA’s next step is the Laser Communication Relay Demonstration (LCRD) which will send data from one ground station, to an optical satellite, and down to another ground station at data rates in the Gigabits. By 2022 NASA plans to have the majority of its SCaN network working in the optical realm. On the private sector front Planetary Resources Inc., an asteroid hunting and mining company, plans on sending up its own optical communication network (2014, planetaryresources.com). Planetary Resources, like many other blooming private space exploration companies, believe that they cannot rely on a space network operated by a national government. Another player in the aerospace industry, Space Exploration Company or more commonly known as SpaceX, is looking to establish the first colonies on Mars, but before they put the first human foot on red soil a high- speed as well as reliable communication network to Earth must be in place (2015, engadget.com). So what happens to the RF spectrum when it is no longer being used by entities such as NASA or SpaceX for their communication and navigations networks? Perhaps the answer lies in small firms  5 such as Outernet, whose goal is to provide a free Internet service to the entire globe (2015, outernet.is).  6 References Davis, M., Koza, C., Mitchell, A., Parker, Z., & Shanabarger, R. F. W. (2014). Internet Infrastructure: The past, present, and future of Internet infrastructure technologies and their potential business applications, 1–44. Engadget.com. (2015). Elon Musk spills details on SpaceX’s $10 billion space internet venture. Retrieved January 20, 2015, from http://www.engadget.com/2015/01/17/elon-musk-spacex- internet/ Goff, D. (2002). Fiber Optic Reference Guide: A Practical Guide to Communication Technology (3rd ed.). Woburn, MA: Elsevier Science. Mai, T. (2013). Optical Communications Demonstrations. Retrieved from http://www.nasa.gov/directorates/heo/scan/engineering/technology/txt_opticalcomm_start.h tml#.VL3F6UfF8z4 Mars.jpl.nasa.gov. (2014). Data Rates/Returns. Retrieved January 20, 2015, from http://mars.jpl.nasa.gov/msl/mission/communicationwithearth/data/ Mott, W., & Sheldon, R. (2000). Laser Satellite Communication: The Third Generation. Westport, CT: Quorum Books. Pelton, J., Oslund, R., & Marshall, P. (2004). Communications Satellites: Global Change Agents. Mahwah, NJ: Lawerance Erlbaum Associates Inc. Planetaryresources.com. (2014). Technology | Planetary Resources. Retrieved January 20, 2015, from http://www.planetaryresources.com/technology/#space-communications Sadiku, M. (2002). Optical and Wireless Communications: Next Generation Networks. Boca Rotan, FL: CRC Press. Tzinis, I. (2013, June 18). Technology and Engineering. Retrieved from http://www.nasa.gov/directorates/heo/scan/engineering/overview/index.html#.VL2KrkfF8z 5