Global satellite communications technology and systems – An overview

Transmission planning for military and commercial satellite communications systems has traditionally followed separate (but parallel) paths and led to the development of distinct sets of tools which can handle either only military satellite systems or only commercial satellite systems. With the need to operate DoD communications networks on both military and commercial satellites a unified transmission planning model is required which can model both types of satellite systems in a common framework. This paper proposes a unified approach to transmission planning for military and commercial satellite systems, and discusses both the common requirements for such a transmission planning model, and those requirements specific to the structure and operation of military satellites such as the use of saturated transponders, null-forming multi-beam antennas, special waveform modulation techniques, jamming threats, etc., which need to be treated differently from their commercial counterparts. Software models are proposed for some of the key requirements, and issues related to their implementation are discussed. The paper also describes the capabilities of existing software which can be used for transmission planning on commercial satellites, and how it can be augmented to function in the military satellite communications environment.

The advent of satellite communications has revolutionized the world's ability to communicate. The first true communications satellite, which is the US Army's experimental Signal Communications by Orbiting Relay Equipment (SCORE), was developed by the Defense Department and launched on December 18, 1958 into an elliptical orbit ranging from about 100 to 900 mi. Throughout the 1960s, however, the main focus of commercial communications satellite activity was International Telecommunications Satellite (INTELSAT), which relied entirely on geosynchronous equatorial orbit (GEO), C‐band satellites. To a large extent, the geostationary technology that supports both domestic and international communications satellites has been built on the same National Aeronautics and Space Administration (NASA) and US military technological foundation. Commercial communications satellites split mainly between GEO and low earth orbiting (LEO). These were complemented by around 100 military and 100 civil government communications satellites, most of which were GEO.

Launch Vehicles as Support Subsystems for Communications Satellites

During the past decade requirements for commercial communications satellite system components have grown significantly. Initially these requirements were for 6 GHz uplink and 4 GHz downlink. More recently the requirements have been extended to 14 GHz uplink and 12 GHz downlink. These requirements, coupled with the changes in modulation techniques, are reflected in increasing demands on microwave tubes. The purpose of this paper is to provide an estimate of the present and anticipated technological needs for microwave tubes both in commercial satellites and earth stations. Performance in satellites invariably includes premiums for combined high efficiency, low distortion, long lived devices. Typical operating examples from current systems will be discussed illustrating FM and digital signal processing characteristics. Life data will also be reviewed, as well as some of the techniques being applied to select long lived tubes. Performance requirements in earth stations are in some respects similar to those of satellites in that again good life, linearity, and efficiency are premium qualities. However, earth station RF power requirements are typically several order of magnitudes higher than in satellites and the ability to minimize maintenance/application requirements modify the overall priorities. Typical sample applications will also be presented. Longer range considerations in terms of ultimate lifetime factors, as well as RF performance, are vital to the viability of future microwave tubes. For example can these now mature and highly sophisticated devices continue to be developed where essentially unattended operation (i.e. space as well as ground) is sought with virtually perfect performance for periods in excess of 7 or 10 years?

As charged by Congress and the Office of the Secretary of Defense, the Defense Information Systems Agency (DISA) created the Commercial Satellite Communications Initiatives (CSCI) program. The CSCI program's purpose is to assess the use of available and planned commercial communications satellites to fulfill, in a cost-effective manner, certain military communications that would be otherwise provided by Government satellite systems. This paper describes planned commercial satellite based personal communications systems (PCS) capable of providing voice, data and other services anywhere in the world to mobile users equipped with lightweight, handheld transceivers. The paper then provides an overview of issues associated with military use of satellite PCS services.

Over the past 20 years, commercial communications satellite systems have developed into effective and reliable global, regional, maritime, and domestic communications services. These systems provide telephone, telegraph, television, data, and facsimile transmission and reception. This paper reviews the history and status of today's commercial communications satellite systems and discusses the design and reliability considerations applicable to their key elements, satellites and ground stations.

[Abstract] Communication satellites are the work horse of space industry. The revenues of broadcast satellite services are the major contributor to the total space industry revenues. More than 80 % of the launches are performed to place communication satellites in orbit. A state of the art communications satellite is carrying transparent transponders to illuminate a large coverage area. The idea of replacing the transparent transponders by regenerative transponders is old and several years ago, was limited by the available technology. Advances in semiconductor technology have allowed implement and fly very advanced digital signal processing equipment on satellites. The first regenerative transponder developed in Europe was launched on the Italian satellite Italsat. About a decade ago, the first regenerative transponder, named Skyplex, was launched on a commercial European communication satellite Hot Bird 4. A whole family of Skyplex units were launched, including the first turbo decoder flown on a satellite. Another very advanced regenerative payload was developed and launched on another European communication satellite, Amazonas 1, which is providing coverage of Europe, North America and South America. This payload, named AmerHis, is receiving uplink signals according to the DVB-RCS standard and transmits DVB-S signals. The regenerative payload allows switching any uplink signal to any downlink signal. This paper will discuss the technical concepts of these regenerative payloads and will provide an outlook of a potential broadband communication satellite using regenerative transponders.

Global Positioning System (GPS) signals adopt spreading spectrum technology, which could effectively reduce the consumption of signal transmitting power. Nevertheless, the GPS signals may be blocked unexpectedly in complicated environments. In this case, the stronger signals transmitted from Low-Earth-Orbital (LEO) communication satellite systems could be considered to aid in GPS service provision. However, the dynamic of an LEO satellite is relatively high, which causes difficulties with its integration into the general GPS receiver design. Doppler positioning algorithms can benefit from this high dynamic characteristic. In this paper, considering Doppler shifts as measurements, a Doppler Positioning algorithm is introduced. Since no navigation message can be decoded from the signals, satellite orbit prediction using the two-line orbital element set (TLE) will be involved. One commercial LEO communication satellite system is selected as well as the configurable frontend Universal Software Radio Peripheral (USRP) for the LEO signal collection and processing. A static experiment in an open field is conducted in this research. The experimental results for the open field test indicate that the positioning performance might not gain improvement from the use of an LEO signal because of orbit prediction errors or the quality of its measurement is not as good as that of GPS; but the important thing is that the LEO signal can extend positioning service in situations where the number of GPS satellites in-view are less than four due to signal obstructions. This paper presents the results of the enhanced navigation service provided by GPS with the aid of the LEO satellite.

: Effective military communications capabilities are not only essential for command and control of military forces but can also be used to achieve information dominance in the battlespace. The U.S. has historically applied its technological advantage to win at command and control warfare. As budget cuts slow the pace of research, development, and acquisition of military communications systems, civilian commercial systems are surpassing their military counterparts in many capabilities. It is important that our senior commanders are cognizant of new commercial communications technology and its applicability in a myriad of military situations. This paper describes recent advances in the commercial communications arena which have obvious command and control warfare applications. Fiber optic transmission systems, long known for their ability to transport huge volumes of information, have recently been improved to overcome a number of earlier shortfalls. A description of these refinements, along with a number of resulting new military applications is presented. Commercial communications satellites are discussed in the final part of the paper. A number of new multibillion dollar constellations are about to enter service just as military funding for such satellites dries up. Both technologies play key roles in achieving battlespace dominance in the information age.

Space for society: How Eurisy’s activities and research support publicawareness raising on satellite applications in meeting societal needs

The era of satellite communications, now going on fifty years in length, has in many ways only just begun. Perhaps one day we will see broadband commercial satellite systems operating to support telecommunications services for the Moon and Mars. But the excitement of the early years will be hard to beat.

In today's environment, building a reliable and cost-effective spacecraft is perhaps emphasized more than ever before. Sponsors are looking for the same high-quality products but at lower costs and with shorter schedules. Whether it is a spacecraft for the Department of Defense (DoD), a research observatory for the National Aeronautics and Space Administration (NASA), or a commercial communications satellite, total cost is a significant factor. One of the areas where costs can escalate is in the integration and test (I&T) phase of the spacecraft life cycle. The I&T phase begins when the first component or subsystem is ready for integration into the spacecraft structure. As I&T progresses with additional subsystems (and associated test staff for those subsystems), scheduling tests becomes more complex because certain tests depend on other tests or tasks being completed. Because the large test team is on standby, any delays in testing can result in a substantial impact on cost. A way to help mitigate cost overruns is to incorporate automated testing. This paper is a follow-on discussion of a previous paper entitled "Reliability and Efficiency of Electrical Ground Support Equipment through Automation, Modularization, and Standardization" [1]. An enhancement proposed in this previous paper to automate the electrical ground support equipment (EGSE) acceptance testing has now been implemented, and the successes, as well as lessons learned, from this implementation are being presented here. As in the previous paper, the umbilical ground support equipment is the focus of the discussion. The design and implementation to automate the acceptance testing is described. Test durations of the automated and manual test cases are compared. To see the impact on cost of acceptance testing EGSE during the I&T campaign, the results are then extrapolated to include the typical set of EGSE used at The Johns Hopkins University Applied Physics Laboratory (APL).

In today's environment, building a reliable and cost effective spacecraft is perhaps emphasized more than ever before. Sponsors are looking for the same high quality products but at lower costs and with shorter schedules. Whether it is a spacecraft for the Department of Defense (DoD), a research observatory for the National Aeronautics and Space Administration (NASA), or a commercial communications satellite, total cost is a significant factor.

This paper addresses the challenge of carrier frequency estimation for commercial satellite handheld terminal signals in non-cooperative communication scenarios under low signal-to-noise ratio (SNR) conditions. Due to the limited antenna gain of handheld terminals and strong environmental noise, traditional methods struggle to accurately extract frequency features at low SNR. To overcome this, we propose a blind carrier frequency estimation method that combines stochastic resonance with cyclic spectrum analysis. The stochastic resonance module enhances weak signal characteristics, while the cyclic spectrum analysis extracts the discrete spectral lines corresponding to the carrier frequency. An estimation formula based on the spectral peak position is derived. By evaluating the resonance effect using singular value decomposition, the proposed method significantly improves estimation accuracy under complex modulation and low-SNR conditions. Experimental results show that, compared to conventional cyclic spectrum analysis alone, this method more effectively separates and accurately estimates carrier frequencies in noisy environments. It demonstrates greater robustness and general applicability to various modulated signals commonly used in commercial satellite communications.

Launchlog '84: NASA Embarks on Its Busiest Year