Transfer Through Satellite Communication Systems

¶ … Transfer through Satellite Communication Systems

Satellite Subsystems

Development of Satellite Subsystems

Low-cost Satellite Systems

Requirements for Developing Low-Cost Satellite Subsystems

Examples of Low-cost Satellite Subsystems

Implementation of Low-cost Satellite Subsystems

Constraints of Effective Implementation

Guidelines for Effective Implementation of Low-cost Satellite Subsystems

Implementing a Low-cost Satellite Subsystem:

There is an increasing need for the obtaining information from sources that are distributed in a wide area. Moreover, there is a growing need for the development and control of devices that disperse such information in a large area. Satellites have largely emerged as the necessary devices for the transmission and control of information within a huge area. This is largely because they facilitate communication to and from remote terminal units without the use of infrastructures needed for group-based communications systems in a wide service area. Therefore, a satellite communication system is regarded as an optimized for a specific kind of message transmission. However, the development and implementation of low-cost satellite communication systems is vital in enhancing communication. This is particularly because of the need to lessen the complexity of every satellite while maintaining the ability of the systems to provide communication services that are optimized to an expected kind of information transfer.

Information Transfer through Satellite Communication Systems:

Communication via a satellite system requires the transmission of a signal from a ground station at an adequate satellite to signal ration (SNR). On the other hand, the transmitted signal by the satellite must be obtained at the anticipated ground station at an adequate SNR. The signal-to-noise ratio can be enhanced through increasing the received power of density of the signal or lessening the power density of the received noise. In order to customize the obtained power density, the directional antennas should be utilized to narrow the transfer beam width. This results in the increase of the section of transmitted power being obtained by the receiving through lessening the distribution of the transmitted power.

The implementation of a low-cost design satellite subsystem requires minimal number of the satellite systems used. In order to lessen the number of these satellites over a large geographic area, every utilized satellite must have an antenna in an area that covers a huge amount of the service area of the satellite. This is to enable the satellite systems to have a considerably low-gain wide-beamwidth antenna. In contrast, the ground station utilizes a high-gain narrow-beamwidth antenna to offer a high signal-to-noise ratio for communications.

Satellite Subsystems:

The contemporary satellite has become an extremely and more complex equipment consisting of over half-a-dozen main subsystems with thousand of parts. Since satellites entirely function in space, they are normally subjected to extremely hostile environments. There are several satellite subsystems that are used to enhance communication including & #8230;

Propulsion:

The propulsion subsystem is considered as the only partly component that facilitates or enables the satellite to function in an orbit. The other components used to get the satellite into orbit include electrical or chemical motors. These motors get the system into the appropriate orbit when deflected out of the suitable trajectory by the magnetic fields, atmospheric drag, or solar winds. In addition to changing the angle of the trajectory, the motors provokes the satellite back to the accurate altitude and either slow down or speed up the satellite.

Communications:

This subsystem deals with all the functions associated with transferring and receiving communications. It mainly consists of transmitters, receivers, and transponders and its size varies depending on the size of the satellite. it's important to note that the communications component is mainly used to provide a means of transmitting voice, data, and video in the orbit. In most cases, these subsystems are developed and designed to offer the greatest traffic capacity possible in order for the satellite to function effectively.

Power:

The effective functioning of satellite communication requires power subsystems that are commonly made up of the combination between solar panels and batteries to provide constant supply of electrical power. While solar panels are used when the satellite is in direct sunlight, the batteries are used when it's not in direct sunlight for the satellite to continue functioning ("Satellite Subsystems," par, 3). Solar cells act as the most common source of power to satellite systems though their efficiency tends to decline due to surface etching and aging.

Superstructure:

Since the satellite needs to survive the violent forces caused by the rocket ride into space in order to function effectively, the superstructure subsystem is an important component that supports it in space. This component provides support by lessening the vibration and shock that the internal components may experience during the launch.

Attitude:

As the satellite communication must face the earth every time, the attitude component acts as the control system to enable the satellite to be pointed appropriately. The attitude control systems are normally very small or tiny motors as compared to the propulsion subsystem. Together with the orbital control, the attitude control system is important to ensure that the narrow beam antennas are positioned correctly to the earth.

Thermal:

The main function of this subsystem is to regulate the temperature of the satellite's subsystems to ensure that differences in temperature don't end the useful period of the satellite. In most cases, the component regulates the temperature by dissipating the heat away from earth into space to prevent any interference with the operation of the satellite.

Telemetry and Command:

The telemetry and command subsystems enable the satellite to provide feedback to its operations center regarding its present state and its location in orbit. These components are usually simple beacon systems that are used to track the satellite in orbit at the ground station. Some of the other information provided to the ground system by these components includes the state of the operating system and programs, its operating temperature, and other internal functions.

The successful launch and operation of a communication satellite system is usually dependent on the safety and efficiency of the command structure. The command system is mainly used for controlling the communications system, making changes in attitude and orbit correction, and expanding the solar sails. Moreover, the command subsystem protects against errors in received commands developed in the command structure. The system also checks the validity and sent back through the telemetry component where it's re-checked in the computer (Dawoud, p.133). When the command instruction is accurately received, the instruction for execution is transmitted to the satellite. The entire process lessens chances of any malfunctioning since its takes minimal time that usually range from 5 to 10 seconds.

Tracking System:

The tracking subsystem is a vital component in the development of a satellite because it's used for the determination of the present orbit and the spacecraft's position. In order to achieve its functions, the component utilizes the acceleration and velocity sensors. The determination of the rate of change of the range through the tracking system involves the use of the control earth station to examine the Doppler shift of the telemetry carrier.

A typical telemetry, tracking, and command system is demonstrated in the following diagram & #8230;

Development of Satellite Subsystems:

The conceptual development and design of a satellite subsystem or system tends to be a major engineering problem and very challenging task due to its complexity. The development process of these systems can be regarded as a series of design activities that travel from inputs to outputs. Generally, this process can be categorized into two major sections i.e. The design of the important components of the satellite and the system engineering module. The design of the components involves the development of subsystems that have been previously discussed. On the contrary, the system engineering module includes several activities like mission and payload definition, selection of the launcher, space environment, ground and atmosphere, and the design of the preliminary and subsystems.

The definition and evaluation of the design process is conducted based on the mass, power, budgets, data rate, propellant, thermal, and data link. The other subsystems models to be considered in the design process are power, structure, data handling, communication, propulsion, and Attitude Dynamic and Control System (ADCS). There is an activity being considered to be performed in the future in development of satellite communication system known as the Multi-Disciplinary Optimization technique. As a major aspect in subsystems design, the activity will be an automatic technique for managing all subsystems and parameters and examining all the programming aspects. There are several challenges or problems that have characterized the development of satellite subsystems including & #8230;

More Development Time:

This is one of the major problems associated with this process because the design is usually complex and very challenging. For a long period of time, satellite development efforts have extended for a long period of time that is usually several years from its inception to formation. Actually, it's reported that the process extends past the time frame of an engineering college student. The major reasons attributed to the prolonged development time of these systems are their complexities and demands.

Leveraged Launched Opportunities:

The prolonged development time is coupled by the challenges of leveraged launch opportunities of these systems through the standardized launch deployment system. After the completion of the design and development of satellites, the systems are normally subjected to waiting periods that span for several years before the identification of an appropriate launch opportunity.

Design and Implementation Cost:

The third major problem in the development and implementation of satellite communication is the software development costs. This includes money spent on all bus systems, ground support equipment, systems engineering, communication payloads, program management, and integration and test. In most cases, the development and implementation costs are difficult to estimate since there are recurring and non-recurring cost drivers in the process. The non-recurring cost drivers include heritage, number of prototypes and engineering models, and technology readiness while the recurring cost-drivers are complexity, project scope, and quantity of production.

The production quantity refers to the number of flight units developed, combined, and tested on similar contract to the development initiatives. While the development and production initiatives tend to overlap, there are production contracts with high production capabilities and minimal non-recurring costs. However, the development and implementation costs tend to be high when there is a higher production quantity. Therefore, the development costs of a satellite communication system are strongly linked to its production quantity.

Regardless of the impact of production quantity on the design costs, the development and implementation of satellite communication systems is usually costly. Notably, these costs are influenced by cost drivers that are classified into three categories i.e. primary, secondary, and tertiary categories. The primary cost drivers are the unit weight that accounts for a huge portion of the budget whereas the secondary drivers are the quantity on contract and the tertiary drivers are the complexity characteristics of satellite system. it's reported that complexity drivers tend to perform poorly over time as yesterday's complex system may be the low-cost alternative of today's system (Burgess & Menton, p. 25).

Low-Cost Satellite Systems:

With the growing need for effective communication within a wide geographic area, satellite communication systems have emerged as the means to handle this growing need and promote effective communication. Nonetheless, the development and implementation of these systems has been largely affected by several challenges, especially the costs associated with them. As a result, low-cost satellite subsystems have been developed as an alternative to this problem in order to enhance satellite communication.

The main reason attributed to the development of low-cost satellite system is because they provide an economical and useful means for enhancing satellite communications. Low-cost satellite systems use the Control Area Network (CAN) protocol to offer a communication link across several subsystems. Despite of its effective performance as tested on previous satellite mission, the Control Area Network has a restricted data rate and consists of a harness overhead. In most cases, the reduction of harness results in the lessening of spacecraft construction complexities and reduction of total mass. The lessening of mass can also take place through the elimination of electronic interference boards on subsystem electronics.

While the data rate of the Control Area Network is restricted to approximately 32 kbps, there are other types of these systems with a higher baud rate estimated at 38.4 kbps with a fraction of the mass. The achievement of efficient communication across satellites through low-cost systems requires the formation of a communication web.

Requirements for Developing Low-Cost Satellite Systems:

There are some necessary requirements and consideration for the development of low-cost satellite systems that enhance communication. In addition to the necessary components and design procedures, low-cost satellite systems have specific requirements that enable them to be suitable for space applications. These necessary requirements include & #8230;

Less Mass and Power Consumption:

There is a great need for less mass and power consumption in the design of the low-cost satellite systems. The minimum mass usually contributes to a total mass reduction of the spacecraft that lessens the overall cost of the mission. Lessening or minimizing the power consumption is important in order to reduce additional need for solar cells, batteries, battery-charge regulators, and other power subsystems.

Minimum Complexity:

As previously mentioned, the complexity of the system forms a significant portion of a satellite communication subsystem. The development and implementation of low-cost satellites require the reduction of complexity in order to substantially decrease the overall cost of the mission. Increased spacecraft costs and assembly time are realized when extended tests are conducted to check the accurate connectivity and functioning of different subsystems. Moreover, lessening the overall costs of developing a satellite system can be achieved through the use of mass-produced miniature commercial motes that act as alternatives to the expensive custom space hardware.

Radiation Tolerance:

This is particularly an important requirement for the development of long-distance deep space missions. In these kinds of satellite subsystems, it's necessary to test the radiation hardening of the electronic components (Lappas et. al., p.176).

Maximum Performance:

The need for maximum performance of satellite systems has resulted in the design and development of miniature commercial off-the-shelf motes with enhanced data rates that the present Control Area Networks.

Maximum Reliability and Lifetime:

This is achieved through the use of a huge number of micro-sensors to result in a self-healing strong network. This kind of procedure enhances maximum reliability and lifetime unlike increasing the reliability of the network through enhanced redundancy.

Examples of Low-cost Satellite Subsystems:

There are various types of low-cost satellite subsystems that have been developed and used across different kinds of missions. Some of the major examples of these systems include & #8230;

Cubesat Subsystem:

The Cubesat subsystem is the most common type of low-cost satellite subsystems that has been developed in order to prove the practicability of a new series of standardized pico-satellites. These systems have also been developed to lessen the development time and minimize cost while providing enhanced access to space. The designers of these subsystems have the opportunity to form, develop, and test the functioning of their satellite communication system in space within an average time frame of the time of a college student. This is largely because the Cubesat low-cost satellite subsystems incorporate the use of simple standardized satellite geometry (Noe, p.5).

The Cubesat subsystem has emerged as the most common type of low-cost satellite subsystem because of its huge success to an extent that it has been launched in several countries such as Denmark, Canada, the United States, and Netherlands in the recent past. The success of this project or satellite system is attributed to its simple volume specifications and small mass. Actually, the specifications of these subsystems have established strict requirements on their mass and volume. To ensure that the project promotes effective communication, functions correctly, and fits properly, the established requirements on volume and mass are usually non-negotiable. In most cases, Cubesat satellite subsystems are not permitted to have over 1 kg of mass that include their electronics, structure, payload, and power.

Polysat System:

The main concept in the development of these systems is to design or develop a generic opportunity for experimenting particular subsystems or components in space. In order to maintain reduced development time and low costs, Polysat satellites adheres to mass and size constraints. The main challenge handles by these types of satellites systems is offer a similar degree of qualification functionality and testing as a larger satellite system. The challenge is coupled by the need for the systems to achieve these goals within the size, power, and cost constraints that are similar to those of the Cubesat systems.

As an important aspect of these systems, communication with the earth-based communication station is through the use of a wide range of radio frequencies. This range of radio frequencies is determined by the requirements of data rate, the costs of earth station equipment, and licensing limitations. Notably, the systems use frequencies that are within the available amateur radio bands in order to handle licensing aspects and equipment cost.

KUTEsat Subsystem:

KUTEsat subsystem is a low-cost satellite developed and evolving into the Kansas Universities Technology Evaluation Satellite. The system conducts preprogrammed measurements and experiments independently through a secondary communication system to the ground station while maintaining communication with the primary control module. The system has been developed with individual components that are locally controlled by microprocessors that communicate with the central control microprocessor in the control system. It provides modularized intelligence on the subsystem level that permits overall system sophistication while facilitating timely response to any system changes being developed (Marz, p. 24).

Implementation of Low-cost Satellite Subsystems:

Low-cost satellite subsystems have emerged as the most suitable alternative to larger systems to enhance satellite communications. The implementation of these systems is usually an important aspect that requires careful consideration to ensure that they function effectively and achieve their communication goals. In most cases, the implementation process of the systems have focused on several areas like communications subsystems, mission operations, data archival and dissemination, and control and data handling subsystem. Consequently, there is need for coordinated efforts in three main areas i.e. infrastructure development, data archival and dissemination, and subsystems design and mission operations activities.

Infrastructure development focuses on establishing a platform for design, support instruction, and performance evaluation functions to provide support to the missions operations. On the other hand, data archival and dissemination is geared towards setting up mechanisms that promote distribution of scientific data and related products to the internal and external components. The subsystems design and mission operations activities are efforts towards the development of the system and conducting the operations of the satellite system.

However, there are several important points to consider when implementing the low-cost satellite subsystems through the three major fronts. These considerations include & #8230;

Infrastructure Development:

Infrastructure development in the process of implementing low-cost satellite subsystems requires the setting up of a laboratory in order to support all the related design activities. The laboratory helps in promoting increased focus and emphasis on systems engineering and mission operations that in turn enhance all the support design and instruction activities. The facility also helps in housing all the equipments that are necessary for the development of these subsystems to enhance satellite communications (Starks et. al., p.2).

Laboratory acts as an important facility to the process as it's a vital feature for systems engineering and mission operations that support performance evaluation of the communication systems. As a performance evaluation facility, the laboratory enables the complete simulation of inter-satellite channels, satellite uplink, and satellite downlink with the ability to insert hardware components to interface with a computer. The computer simulation tool is a crucial part of the laboratory because of the huge number of parameters needed in the design and the intrinsic non-linearity of the satellite.

During the implementation process, conducting an evaluation is also critical to enhance satellite communication. This evaluation will incorporate several components like the required coding and modulation scheme, link budget analysis, and countermeasures to interference in network satellites among other areas. As a result, the evaluation promotes the evaluation of the advantages and disadvantages of the alternative and different components that can be used to promote the efficiency of the satellite subsystem.

Subsystems Design and Mission Operations Activities:

There is a great need to develop a subsystems design and mission operations activities facility that promotes an effective implementation of a satellite subsystem experience. The facility provides a platform for involvement in the processing and archival of scientific data received from the anticipated system. The design of the system's communications components includes the data handling and control subsystem. The effective implementation of a low-cost satellite subsystem requires the use of necessary sequence that incorporate design activities. The sequence basically entails evaluating an area, developing a design, and providing a presentation.

Data Archival and Dissemination:

This aspect of implementing a low-cost satellite subsystem involves the establishment of decision support systems. In addition to helping operators, the decision support system provides techniques for artificial intelligence to promote mission operations. Data archival and dissemination requires knowledge in database management and communications to handle information gathered from the scientific components. it's important to establish necessary measures that ensure that all the parties involved in the implementation communicate with each other efficiently. This is coupled by the need to set up creative ways to transmit scientific data or information and data products to the inner and outer constituencies.

Constraints of Effective Implementation:

The design and implementation of low-cost satellite subsystems is usually characterized by several constraints like restricted communication window, limited funds and power budget, and harsh space environment. A satellite's communication window can be described as the amount of time required for a ground command station to transmit and obtain signals from the satellite system. The length of the communication window is usually determined by the orbital parameters i.e. The acquisition of signal and loss of signal. Implementing the low-cost subsystems experiences constraints associated with limited communication window because of the low-altitude attributes of the orbit, short duration, multiple pass, and low-cost requirement of the mission.

On the contrary, the harsh space environment challenges emanate from the fact that this environment tends to interfere with the internal functioning of the satellite system. Moreover, the constraints are fueled by interactions between charged alpha particles with the satellites electronics resulting in malfunction because of the lack of atmosphere in low-earth orbits. This contributes to the need to develop communications subsystem that function in the extreme conditions and test its behavior before launch. This helps in preventing conditions of single event upsets and single event latch ups that interfere with the anticipated state of electronics.

Some of the low-cost satellite subsystems function under limited budget since most of their funding comes from space technology grants, sponsorships of payload electronics, and corporate donations. In most cases, the amount of funding is totally dependent on the payload complexities and generosity of sponsors. Due to the limited access of funds required to develop these low-cost satellite subsystems, there is need to design them in consideration of the minimized costs. The final constraint is the limited power budget as the basic source of power for these satellites is on-board batteries and charged solar panels. Given that the batteries should support total functionality of the system, power consumption should be strictly budgeted within the satellite components and subsystems. Generally, necessary efforts should be made to lessen power consumption of the subsystem during the design and implementation process.

Guidelines for Effective Implementation of Low-cost Satellite Subsystems:

Despite of the constraints in design and implementation of the low-cost satellite subsystems, they have emerged as the most suitable alternative to the larger systems. Therefore, there is need to adopt necessary and effective implementation procedures to ensure that the systems work efficiently to enhance satellite communication. In order to accomplish this, there are several recommendations that could act as guidelines to the implementation process including & #8230;

Implementing Simple Beacons: