Satellite Processor Research Articles

A 6.5Gb/s Shared Bus Using Electromagnetic Connectors for Downsizing and Lightening Satellite Processor System

A 6.5Gb/s Shared Bus Using Electromagnetic Connectors for Downsizing and Lightening Satellite Processor System

TASK ASSIGNMENT IN HOST-SATELLITE SYSTEMS

This paper deals with the problem of assigning task modules of a program over a multiple computer system such that the sum of execution and communication costs is minimized. If the number of processors is two, this problem can be solved efficiently using the network flow approach pioneered by Stone.13 However, the general n-processor problem (n>3) in a fully connected system is known to be NP-complete.14 A host-satellite system considered in this paper is composed of a powerful host processor p0 and N homogeneous satellite processors pk’s, 1≤k≤N, in which each satellite processor pk is connected to the host processor p0 through a communication link. When any two satellite processors are to communicate with each other, the host processor p0 must participate in the communication. Therefore, the interprocessor communication cost per unit of information transferred between any two satellite processors is twice as much as that between a satellite processor and the host processor p0. In this paper, we propose an algorithm which finds an optimal assignment on a host-satellite system in polynomial time. A task assignment problem for a host-satellite system is first transformed into a network flow problem, and then solved by applying the well known network flow algorithm in time no worse than O(NM3), where N and M are the number of satellites and the number of modules, respectively.

Test results from a Mobile Profiler System

AbstractA Mobile Profiler System is being developed to provide operational users with atmospheric soundings in near to real time. The reduction of refresh time from the 2 to 12 hours of traditional rawinsonde systems to as short as 3 to 5 minutes should considerably reduce errors caused by time staleness. The mobile profiler combines a small satellite receiver and processor with ground‐based remote‐sensing systems and a portable meteorological ground station. Ground‐based systems include a 924 MHz radar wind profiler, a radio acoustic sounding system for virtual temperature, and a multi‐channel microwave radiometer for virtual temperature and total water vapour and liquid water content. Satellite soundings contain temperature, dew point and the derived variables of wind speed and direction. This paper describes the mobile profiler, provides a very brief outline of the combined sounding technique and presents some results from field tests. Comparisons with rawinsonde soundings nearly coincident in space and time provide an indication of the accuracy of the system. For the merged soundings, average standard deviations and means for virtual temperature were about 1.5 to 2.0 K and ±0.5 K, respectively. Preliminary results for wind speed suggested values consistent with those reported in the literature, but were inconclusive for wind direction.

An integrated computer system for STEM data acquisition and processing

Several laboratories have reported digital data acquisition and control systems for electron microscopes. The considerations involved in implementation of such a system have been reviewed. All of these systems have used a relatively small minicomputer, either as a stand-alone, or as a satellite processor linked to a larger computer, so as not to burden the large host with the mundane task of operating a microscope. In recent years however, hardware costs have decreased sufficiently that many laboratories have their own superminicomputer (e.g., one of the Digital VAX series), or share one within a small group of users.

X-ray Diffraction Measurements via a UNIX+ Based System

We have automated a Seeman-Bohlin Guinier x-ray diffractometer by interfacing it to a minimally configured PDP 11/23 computer. The programs that run on the microcomputer to control the operation of the diffractometer are stored on a mainframe host running the UNIX+ operating system. A software interface allows a particular data acquisition program to be downloaded from the UNIX host and executed on the satellite processor. This same interface allows the collected data to be periodically off-loaded to the host for processing and storage.

UNIX with satellite processors

AbstractThe steps necessary to extend the UNIXUNIX is a trademark of Bell Laboratories. time sharing system to a network which includes a central processor and a set of satellite processors is described. Software interfaces permit a program in the satellite processor to behave as if it were running in the central processor. Tasks are executed in parallel in several processors resulting in improved reliability and response time. The economics of such systems becomes more feasible with the reduction of the cost of CPUs and memories and the increasing demand for dedicated local computers.

A real-time satellite system based on UNIX

One solution to the difficulty of running real-time applications under UNIX is to develop the application programs on an available UNIX system and execute them on a dedicated satellite processor. This combines the advantages of a powerful timesharing operating system with the real-time capabilities of a single-process system. PARASITE, a real-time satellite system, provides tools for developing the application program on the host and executing it on a satellite. A host utility serves to invoke the standard UNIX C compiler and link its output with the PARASITE library. The PARASITE library consists of routines that mimic the standard library and routines that read and write the real-time peripherals. PARASITE currently supports digital inputs and outputs, asynchronous serial-line interfaces, program-mable real-time clocks, and analog-to-digital and digital-to-analog converters. Another PARA-SITE utility downloads the object code of the user program and PARASITE support code into the satellite, where it runs independently. Once the application routine is executing on the satellite, it controls the satellite processor at all times and is continuously available for servicing hardware-generated interrupts. When a real-time peripheral interrupt routine is invoked by a hardware interrupt, it sends a software signal to the user program, in addition to processing the interrupt. This allows the user program to perform additional tasks that are specific to the application. All data to be permanently stored must be transferred to the host. Since the satellite has no direct access to the resources of the host, a process running on the host receives the data and manages files. PARASITE provides packet driver routines on both the host and the satellite, which together handle the data transmission protocol.

UNIX Time-Sharing System: A Minicomputer Satellite Processor System

A software support system for a network of minicomputers and microcomputers is described. A powerful time-sharing system on a central computer controls the loading, running, debugging, and dumping of programs in the satellite processors. The fundamental concept involved in supporting these satellite processors is the extension of the central processor operating system to each satellite processor. Software interfaces permit a program in the satellite processor to behave as if it were running in the central processor. Thus, the satellite processor has access to the central processor's I/O devices and file system, yet has no resident operating system. The implementation of this system was considerably simplified by the fact that all processors, central and satellite, belong to the same family of computers (DEC PDP-11 series). We describe some examples of how the SPS is used in various projects at Bell Laboratories.

Man-machine communication in computer-aided tolerance analysis of electronic circuits

In this paper the communication characteristics of a software system, designed to perform the on-line statistical analysis of electronic circuits on a multiprogrammed computer connected with a satellite graphics system, are described. A data structure which provides a systematic and flexible way of storing and manipulating all network information items is presented. The problem of connecting the central computer to the satellite processor is studied and a partition of data structure between the two computers is proposed.

Lunar Aimp Photographic Data Processing System

A data processing system which transforms photographic scans of the moon into rectified lunar pictures has been developed during the LUNAR AIMP satellite program of the National Aeronautics and Space Administration's Goddard Space Flight Center. Three coplanar narrowbeam optical sensors mounted on the spinning satellite provide the photographic input to the system. The satellite's processor determines what lunar image data to transmit, delta-modulating and interleaving these data with necessary navigational parameters. The ground processor reconstitutes the delta-modulated image data into lunar pictures, arranged so as to give the appearance of being the projection of the lunar surface onto one of 24 projection planes. This conversion is performed by first locating each lunar element corresponding to an item of image data. Next the projection plane is selected, either as input or by the program. The lunar elements are then mathematically projected onto the plane. This projection is formatted onto magnetic tape, from which the output picture is generated. In the paper, particular attention is paid to the information flow in the overall spacecraft/ ground-processor system. Some reisults of simulations of portions of the systems by personnel of NASA, Goddard Space Flight Center, and the Image Processing Department of the Federal Systems Division of International Business Machines Corporation (IBM), and of the processing of moon surface imagery on IBM's Electro-Optical Simulation Facility (EOSF) are provided.