On board computer satellite pdf

What is on board computer. Satellite computer definition. On board computer satellite pdf. Define satellite in computer. How many satellites does oneweb have.

The On Board Computer (OBC) is essentially the brain of a satellite, controlling various critical functions such as navigation and communication. However, choosing the right OBC for a specific mission can be complex due to varying technical specifications, hardware components, and software implementations across different manufacturers. When
evaluating potential OBCs, engineers often consider factors like processing speed, memory capacity, power consumption, and thermal management. Additionally, they must ensure that the chosen OBC meets specific satellite-related requirements, such as radiation hardness, redundancy, and fault tolerance. The market offers a range of OBC
configurations, from basic processors to more complex systems integrating multiple functions, such as power management, communication protocols, and data formatting. Some OBCs are designed with modularity in mind, allowing users to pick and choose specific functionalities based on their mission needs. In recent years, the trend has shifted
towards more integrated and compact designs, leveraging advances in semiconductor technology to reduce volume, mass, and power consumption. This evolution is expected to continue as newer, denser, and lower-power integrated circuits become available on the market. Some OBCs now utilize System-on-Chip (SoC) technology, combining
processing, memory, and interface capabilities within a single chip. These SoC-based OBCs offer improved performance, reduced power consumption, and increased reliability due to their inherently modular architecture. Engineers should also consider factors such as software compatibility, debugging tools, and the availability of documentation and
support from the manufacturer when selecting an OBC for a satellite mission. By carefully weighing these technical requirements and market trends, they can choose the most suitable OBC for their specific needs, ensuring successful mission execution and optimal performance. When choosing an On-Board Computer (OBC) for a satellite, its avionic
sub-system plays a crucial role in running the on-board software that controls many aspects of the satellite's operation. This guide highlights 11 key criteria to consider when selecting an OBC. One critical factor is determining the orbit in which the satellite will operate. There are three primary orbits: LEO (Low Earth Orbit), MEO (Medium Earth
Orbit), and GEO (Geosynchronous Equatorial Orbit). Each orbit has unique characteristics that affect signal delay, coverage area, radiation exposure, and service lifetime. For instance, telecommunications satellites typically operate in geostationary orbit to ensure high-speed data transmission over a wide area, whereas Earth Observation or
Automatic Identification System satellites usually run in LEO orbit for their short-term, high-resolution operations. The OBC itself also has an operating lifetime that depends on its electronic components and the radiation level of the space environment. To ensure longer mission durations, using radiation-hardened components is essential, especially
for long-duration missions. Additionally, power consumption is critical, as solar cells generate limited power. Choosing an OBC with efficient power consumption while maintaining effective operation is vital during satellite operations that involve imaging, compressing, and transmitting processes. FPGAs in OBCs are critical components that impact
power consumption calculations. Different FPGA technologies exhibit varying power characteristics, with flash and anti-fuse FPGAs being live-at-power-up technologies that don't produce large inrush currents at startup. Additionally, non-volatile Flash FPGAs eliminate the need for high configuration current during each power cycle. While other OBC
components can be considered to some extent, the processor's power consumption is a major focus. The OBC's size and weight must also align with the satellite's dimensions and mass requirements. For example, nanosatellites typically have a maximum weight of 10 kg, while microsatellites have no standard size requirement but require lightweight
designs. Understanding resources like power, memory, weight, and time is crucial for space missions. Satellites need to transfer data within narrow windows (3-10 minutes) during which the ground station awaits transmission. Fast processing and computing power are essential for completing tasks on schedule. The main criteria for determining
required computing power include the satellite's primary task, side tasks, and data transfer requirements. Hardware should support fast processors that utilize clock signals generated by the hardware to avoid excessive power consumption. OBCs must also provide sufficient communication ports and protocols to interact with various sub-systems,
such as UART, RS485, CAN, SPI, I2C, and GPIO. Employing CAN bus communications network in satellites enables lower power consumption and reduced wiring and connectors required compared to conventional MIL-STD-1553 and RS-485 interfaces. This approach allows for multiple nodes to be connected to a single bus, significantly reducing
system and cable costs. In addition to communication protocols, the weight and miniaturization of physical connectors are crucial factors. The OBC should be as small and light as possible to fit into mass and size limits, utilizing lightweight composites, rugged plastics, and electromagnetic interference shielding for component design elements. To
guarantee system reliability, fault-tolerant design approaches can be adopted. Low-cost COTS components allow satellite developers to exploit radiation hardening techniques through hardware redundancy, making the components suitable for space use. Although this doesn't promise 100% reliability, it can improve overall system reliability to a great
extent. A watchdog may serve as the last line of defense against radiation, repairing software malfunctions with a soft restart. The STM MICROSATPRO is designed to be tolerant to Single Event Effects (SEE) in logic and data storage with enhanced error detection and correction. This protection is provided through the use of a Fault Tolerant
processor core, Triple Modular Redundancy in FPGA, Error Detection and Correction in memory units, watchdog on software, and Latch-up Current Limiter in power units. Satellites also require memory for mission tasks, and dynamic memory size mostly depends on the software to be loaded. Effective dynamic memory is essential for complex
satellites, while data collected in each orbit determines static memory requirements. For example, if a satellite's main task is recording high-resolution video footage, it should store the footage in static memory as dynamic memory could be erased in case of a power interruption or restart. This way, task results can be preserved even after system
resets. To ensure reliable data transfer and minimize risks, satellite software can be stored in multiple static memories. This includes a primary memory that holds the main software code and a secondary memory with a backup copy of the same code. In case of malfunction or bug, the system can switch to the secondary memory, minimizing
downtime and potential losses. Aerospace applications require careful management of dynamic memory allocation to prevent overflows and malfunctions. Before selecting an onboard computer (OBC), it's crucial to conduct rigorous testing in various environmental conditions, including thermal vacuum, vibration, shock, radiation, and electromagnetic
interference/magnetic field (EMI/EMC). These tests simulate the satellite's exposure to space conditions and ensure that no operational problems arise. The customer can choose an OBC based on their budget and requirements, considering factors like processor architecture, software optimization, and memory usage. The OBC should be designed to
withstand extreme temperatures, vibrations, shocks, and radiation levels. Tests are conducted in accordance with relevant standards, such as ECSS-E-10-03A for thermal vacuum, vibration, and shock tests, and ECSS-Q-HB-60-02A for radiation testing. Additionally, EMI/EMC testing is performed to verify the OBC's electromagnetic interactions before
launch. By considering these factors and conducting thorough testing, satellite mission computers can be ensured to function reliably in space environments, minimizing risks and ensuring successful missions. Power leads: 30 Hz to 150 kHz; Conducted Susceptibility (CS114); Bulk Cable Injection (CS115); Impulse Excitation (CS116); Damped
Sinusoidal Transients (RE102), 10 kHz to 100 MHz. Radiated Emissions (RS103): Electric Field, 2 MHz to 40 GHz. To ensure reliability and avoid redesign costs for satellites and onboard computers (OBCs), a legacy is typically requested from customers. This includes sensors divided into three categories: mission-critical, system health, and
navigation and positioning. Mission-critical sensors vary depending on the mission objective, while system health sensors monitor critical indicators like voltage, current, and temperature. Navigation and positioning sensors are used for orbit rotation or movement. Choosing the right OBC is crucial, considering 11 criteria such as price, location, lead
times, and more. This selection process can shorten development and testing cycles, leading to a better satellite. Find out more about STM's portfolio of OBCs on satsearch or contact the company for further questions. The Avionics Reference Architecture Figure 1 presents the reference architecture for Avionics, defined by the SAVOIR Advisory
Group, applicable to ESA Science and Earth Observation missions, Telecom missions, and Commercial earth observation missions. The On-Board Computer (SMU or CDMU) serves as the central core of Spacecraft Avionics, hosting the Execution Platform SW and Application SW, with Volatile and Non-volatile Memories, On Board Timer, Interface
controllers, and Reconfiguration modules as key components. A Remote Terminal Unit (RIU), commonly found on medium-large size spacecraft, offloads data acquisition and actuators control tasks from the On-Board Computer. The Telemetry/Telecommand system comprises two categories: high priority commands (HPC) executed by the Command
Pulse Distribution Unit (CPDU), and normal commands relayed to the OBC CPU for processing or transmission on the system bus. Internal command and control busses, such as MIL-STD-1553B and CAN Bus, facilitate communication between systems, with the latter being standardized for space applications. The SpaceWire technology is widely used
to control AOCS sensors and combine command and control functions with high-speed data transfer. The space community demands improved communication protocols that harmonize physical interfaces, low-level data link protocols, and proprietary solutions above the basic link layer. In contrast to commercial markets on ground, which use
multilayer protocol stacks for simple integration and multi-vendor compatibility, space avionics have traditionally utilized proprietary solutions, increasing development and integration costs. The DMS-R system, developed by ESA and its industrial team led by Daimler-Benz Aerospace (DASA), provides a fault-tolerant computer architecture with hot
redundancy and voting mechanism to ensure the availability of critical mission systems.