On-board Processing Capabilities Research Articles

Advanced Attitude-and Orbit Control Concepts for 3-Axis-Stabilized Communication and Application Satellites

Abstract The rapidly increasing demands and the large variety of technical and economic requirements for future communication-and application satellites necessitate an advance of the efficiency in all areas of system development. In addition to technical performance improvements, optimal use of equipment, and ease of operability especially stringent economic boundary conditions are to be met. Such ambitious goals cannot be achieved on the basis of efforts made on the level of an individual subsystem and its equipment only but requires a well balanced overall system approach. Presently, based on a cooperation agreement between DASA/MBB and Aerospatiale companies, joint efforts are being undertaken towards an optimized approach of this kind, within the so-called “Spacebus Improvement Program” (SIP). The key issue of the approach adopted is an Integrated Control and Data System (ICDS), which combines the versatility and flexibility inherent to the Attitude-and Orbit Control Subsystem (AOCS) with the Data Management and Control (DMC) tasks, making best possible use of modem equipment technology and onboard processing capabilities.

Payload design for a switchboard in the sky

The architecture of an experimental payload with on-board processing capabilities is described. Since the system is proposed as an experimental one it operates with only four beams in the 20/30 GHz frequency band. Special emphasis is put on the design of the switch and its associated control. The switch operates in a synchronous circuit-switching manner and provides a throughput of 131 Mb/s. To derive the requirements for the on-board controller, a process model is established. This model shows that an implementation in a finite state machine will not give enough flexibility. Therefore a microprocessor system is proposed for the controller.

VSAT networking concepts and new applications development

The authors present some innovative very small aperture terminal (VSAT) technology that can be used to support new applications. The first of these applications explores the possibility of realizing a VSAT-based satellite wide area network (SWAN) to provide flexible interconnection between local area networks (LANs) and metropolitan area networks (MANs) as well as gateway access to centralized information databases and computing services. A second application deals with the potential provision of ISDN-compatible services via VSATs in conjunction with existing satellites as well as future advanced satellites (ADSATs) having onboard switching and processing capabilities. The use of VSATs to solve backhaul interconnection/internetworking problems associated with evolving mobile satellite (MSAT) communication networks is discussed. >

Autonomous Meridian Scanning Photometer For Auroral Observations

The system design of an automated meridian scanning photometer developed for the Canadian Auroral Network is described. The instrument operates unattended year round in an arctic environment. The instrument has considerable on-board processing capability for data analysis, communication functions, and fail-safe operation.

Combined Random/Reservation Access for Packet-Switched Transmission Over a Satellite with On-Board Processing--Part II: Multibeam Satellite

The idea of combining the desirable features of random access (at low utilization) and reservation access (at high utilization) motivated the proposal of a combined random/reservation multiple access (CRRMA) scheme for a global beam satellite described in [13] and a multispot beam satellite described and analyzed in this paper. A key element in the proposed CRRMA protocol is the assumption of an onboard processing capability to interrogate uplink headers, to buffer successful requests, and to create and broadcast channel assignments to enhance system performance. A scheduling algorithm is introduced to enable a proper division of packet transmissions via random access and reservation access. Numerical results indicate that the proposed CRRMA protocol indeed exhibits good delay-throughput performance over a wide range of utilization.

Encryption and Authentication in On-Board Processing Satellite Communication Systems

Encryption is an efficient method for information protection in communication links which are subject to wiretapping. In this paper we discuss the application of encryption to satellite communication systems in which the satellite has on-board processing capability. The on-board processor can be used in the key distribution process. Two examples of such processes are described. The first requires the storage in the satellite of one key for each user of the communication system. These are used together with a conventional encryption algorithm (DES, for example) to distribute communication keys to the users. The communication keys are then used to encrypt and decrypt information. The other key distribution process utilizes a trap-door one-way function, whose inverse is implemented in the satellite. The need for storage space in the satellite is smaller than that with the first method.

Shuttle Computer Complex

The Shuttle Computer Complex provides the on-board data processing capability for Space Shuttle Orbiter avionics. It performs the data processing necessary for guidance, navigation, and control; pay-load handling and management; and performance monitoring functions. It is made up of five interconnected but independent general purpose computers to satisfy the overall avionics requirements in fault tolerance, partitioning, and functional isolation. Each general purpose computer consists of a central processing unit and an input/output processor; with the former performing all computations associated with the application programs, and the latter controlling the transfer of information between the computer and other subsystems of the Space Shuttle. The functions, characteristics, mechanization, and operation of the Shuttle Computer Complex are described in this paper.