Space and Ground Facilities Ltd.
Space and Ground Facilities Ltd.
The Soviet/Russian Spectr X-ray Gamma (SXG) project’s scientific objective is: astronomical observations beyond the atmosphere of the Earth, in particular until now less observed X-ray and Gamma range. On the spacecraft there will be some scientific experiments, functioning in various energy ranges, as the contribution of numerous research centers in different countries, such as Russia, USA, Great Britain, France, Denmark, Germany, Italy, Finland, Israel.
The activity of our engineers covers the design and manufacture of the central data acquisition on-board computer (BIUS) and of its electrical ground support equipment. The correct operation of the BIUS is of decisive importance because almost all of the scientific experiments will be controlled by the BIUS and also the collected science data will be passed over to the Earth through it.
In order to avoid a malfunction due to any kind of erroneous operation of the external experiments, the BIUS has a modular construction in one hand; on the other hand, the external units and the modules of the BIUS are connected together on reserved, galvanically isolated, serial buses. The BIUS is composed of different, self-functioning modules having their own power supplies and the possibility of switching on/off independently of each other. The other advantage of modularity is that by implementing a standard protocol for data exchange, it makes possible to work out various flexible reservation methods. The need for a continuous operation, the extreme environmental circumstances (most dangerous of them is radiation) and the expected lifetime need to triplicate every module of the BIUS in cold reservation. The activation of reserved modules may be initiated from the Earth while the radio uplink is functioning. Since every single module is connected to the same link, switching over from one module to another does not need any extra hardware. The processor modules are connected to an internal serial bus in order to be able to test each other. Systematic exchange of critical parameters and regular test procedures running in the background ensure that the change of an active processor does not cause any loss of data and the functioning seems to be continuous, as seen by the external experiment.Every single module can be connected to an external computer on the serial bus without dismounting of BIUS. During ground tests, it makes the localisation of errors easier. The BIUS consists of the following modules: processor modules, Earth and onboard time code receivers, scientific telemetry interfaces (1 Mbps), service telemetry interfaces (16 kbps), plus power supply and analogue telemetry units.
The processor module uses an 80C86-type processor; its memory is 16 bits wide and protected with Hamming code. The memory is built up with PROM, EEPROM and RAM components. The clock generators of processor modules have component-level redundancy. The memory has error checking and correcting circuits. The computer, due to the built-in component and module level redundancy, should be able to keep the system in a working condition in case of gradual degradation.
The real-time multitasking operating system performs both system functions (kernel) and the control of scientific experiments (tasks). The kernel of the operating system is written in assembly language in order to increase speed while C programming language is used for developing the tasks. To support the software development for the computer without a man/machine interface, we have invented a solution including both hardware and software elements, by which, connected to the so-called technological connector of the computer, we can control the running of a program, stop it, and check or change parameters. The backup software is burnt into the PROM memory, which has a limited functionality and sequential activity.
The activity of our engineers covers the design and manufacture of the central data acquisition on-board computer (BIUS) and of its electrical ground support equipment. The correct operation of the BIUS is of decisive importance because almost all of the scientific experiments will be controlled by the BIUS and also the collected science data will be passed over to the Earth through it.
In order to avoid a malfunction due to any kind of erroneous operation of the external experiments, the BIUS has a modular construction in one hand; on the other hand, the external units and the modules of the BIUS are connected together on reserved, galvanically isolated, serial buses. The BIUS is composed of different, self-functioning modules having their own power supplies and the possibility of switching on/off independently of each other. The other advantage of modularity is that by implementing a standard protocol for data exchange, it makes possible to work out various flexible reservation methods. The need for a continuous operation, the extreme environmental circumstances (most dangerous of them is radiation) and the expected lifetime need to triplicate every module of the BIUS in cold reservation. The activation of reserved modules may be initiated from the Earth while the radio uplink is functioning. Since every single module is connected to the same link, switching over from one module to another does not need any extra hardware. The processor modules are connected to an internal serial bus in order to be able to test each other. Systematic exchange of critical parameters and regular test procedures running in the background ensure that the change of an active processor does not cause any loss of data and the functioning seems to be continuous, as seen by the external experiment.Every single module can be connected to an external computer on the serial bus without dismounting of BIUS. During ground tests, it makes the localisation of errors easier. The BIUS consists of the following modules: processor modules, Earth and onboard time code receivers, scientific telemetry interfaces (1 Mbps), service telemetry interfaces (16 kbps), plus power supply and analogue telemetry units.
The processor module uses an 80C86-type processor; its memory is 16 bits wide and protected with Hamming code. The memory is built up with PROM, EEPROM and RAM components. The clock generators of processor modules have component-level redundancy. The memory has error checking and correcting circuits. The computer, due to the built-in component and module level redundancy, should be able to keep the system in a working condition in case of gradual degradation.
The real-time multitasking operating system performs both system functions (kernel) and the control of scientific experiments (tasks). The kernel of the operating system is written in assembly language in order to increase speed while C programming language is used for developing the tasks. To support the software development for the computer without a man/machine interface, we have invented a solution including both hardware and software elements, by which, connected to the so-called technological connector of the computer, we can control the running of a program, stop it, and check or change parameters. The backup software is burnt into the PROM memory, which has a limited functionality and sequential activity.
Central Data Acquisition and Control System of Spectr X-ray
Gamma Satelite (SXG)
Gamma Satelite (SXG)
Telescpes of SXG
satelite
satelite
Test of the SXG's
central computer
central computer
A redundant unit of
the BIUS fligh model
the BIUS fligh model
