Integrated satellite comprehensive electronic system

Abstract

The invention discloses an integrated satellite comprehensive electronic system, which consists of a spaceborne computer, a satellite power module, a satellite measurement and control module, a global navigation satellite module, an input / output routing module and an Ethernet switching module, and adopts a three-bus architecture: an internal controller local area network bus realizes information interaction of each functional module; the external controller local area network bus completes external conventional telemetering and remote control, and the Ethernet interface is responsible for high-speed data flow interaction; and the input and output routing module depends on an A3PE3000L type field programmable gate array to realize protocol analysis and function expansion of the controller local area network bus. The problems that an existing integrated comprehensive electronic system function module is poor in expandability, non-uniform in interface and difficult to adapt to rapid design and assembly of a satellite are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of satellite electronic systems, and in particular to an integrated satellite comprehensive electronic system. BACKGROUND

[0002] The traditional comprehensive electronic system is one of the core platform systems of a spacecraft, and together with the attitude and orbit control system, the thermal control system, the energy system, and the structure and mechanism system, it constitutes the five key platform systems of a spacecraft, and undertakes core tasks such as satellite data processing, command transmission, and function coordination. In the design and application of a 200kg-level satellite platform, from the actual needs of cost control, research and development cycle shortening, project progress guarantee, and the like, integrated integration of the comprehensive electronic system has become the mainstream trend of the industry - an integrated comprehensive electronic system integrates, through technology integration, core functions such as energy management, satellite management, attitude control, and TT&C interaction, greatly optimizing the volume, weight, and power consumption of the traditional decentralized system.

[0003] However, the current integrated comprehensive electronic system still has significant technical limitations: its integration method only stays at the structural type level of the above-mentioned function modules within the comprehensive electronic system, i.e., it only realizes the regularization and simple combination of the physical form of hardware, and does not design for the subsequent expansion needs of each function module. This limitation makes it difficult for the system to quickly complete module replacement, interface compatibility, and function expansion when facing satellite task iteration, function upgrade, or adaptation to different types of satellites, and thus cannot meet the development needs of future satellite systems in terms of rapid design, efficient assembly, convenient integration, and flexible testing, restricting the batch development and task response efficiency of satellite platforms. SUMMARY

[0004] The present application proposes an integrated satellite comprehensive electronic system, which internally interconnects satellite management, attitude control, energy, and TT&C within the comprehensive electronic system in the form of a standardized internal bus, and externally realizes conventional telemetry and telecontrol and high-speed data transmission functions using a double bus, thereby laying a foundation for batch design and testing of future satellite electronic systems.

[0005] The present application provides an integrated satellite comprehensive electronic system, comprising: a plurality of on-board computers connected to each other through an Ethernet exchange module and configured to process and control satellite information; a satellite power module configured to manage and control power distribution of the entire satellite; a satellite TT&C module configured to perform two-way data interaction between the satellite and the ground; a global navigation satellite module configured to perform satellite multi-system navigation and positioning; an input / output routing module configured to provide telemetry and telecontrol data interfaces for satellite management and attitude control; an Ethernet switching module configured to provide a data exchange channel between the on-board computer and the integrated electronic system or between the on-board computer and an external system; an internal bus connecting the on-board computer, a satellite power module, a satellite TT&C module, a global navigation satellite module and an input / output routing module, and configured to exchange information between the modules in the system; an external bus connecting the satellite integrated electronic system and an external system, and configured to be a data transmission channel outside the system; and a high-speed bus connecting the on-board computer and the Ethernet switching module to the external system, and configured to transmit high-speed data flow.

[0006] In an embodiment of the present application, the internal bus and the external bus are both configured as CAN buses, which transmit data in series at a rate of 1 Mbps; and the high-speed bus is configured to transmit high-speed data at a rate higher than that of the CAN bus.

[0007] In an embodiment of the present application, the satellite power module is configured to perform one or more of the following operations: control the charging and discharging process of the battery pack to ensure stable energy supply under different working conditions of the satellite; be responsible for the output of the satellite thermal control and power distribution management to maintain a stable operating environment for the equipment; and collect internal voltage and current data to monitor the operating state of the energy system in real time.

[0008] In an embodiment of the present application, the input / output routing module comprises: an asynchronous RS422 interface configured to realize bidirectional serial transmission of data related to satellite management and attitude control; an analog signal acquisition interface configured to acquire analog signals output by external equipment and convert them into digital signals for transmission to the internal system; a magnetic torque controller interface configured to send control signals to the magnetic torque controller to adjust the attitude of the satellite; an OC drive interface configured to drive external switching equipment or realize signal isolation transmission; and an SADA motor drive interface configured to control the rotation angle and speed of the solar wing to ensure that the solar cell array is always aligned with the sun.

[0009] In an embodiment of the present application, the input / output routing module is configured with a FLASH-type FPGA to realize CAN bus protocol analysis and external function expansion.

[0010] In an embodiment of the present application, the FPGA is an A3PE3000L type.

[0011] In an embodiment of the present application, the satellite TT&C module is configured to perform the following operations: When uplinking, receiving remote control instructions and injection data sent by the ground, and transmitting the data to the on-board computer after de-spreading and de-modulation; and When downlinking, receiving telemetry information of each module of the satellite, processing the information according to a preset protocol, spreading and modulating the digital signal to a specified frequency band, and transmitting the signal to the ground.

[0012] The present application also provides a method for operating the integrated satellite comprehensive electronic system, comprising the following steps: Performing satellite information processing and control by the on-board computer; Performing power distribution management and control of the whole satellite by the satellite power module; Performing satellite and ground bidirectional data interaction by the satellite TT&C module; Performing satellite multi-system navigation and positioning by the global navigation satellite module; Providing telemetry and remote control data interfaces for star management and attitude control by the input / output routing module; Providing data exchange channels for the on-board computers or the on-board computer and the comprehensive electronic system outside by the Ethernet switching module; The on-board computer, the satellite power module, the satellite TT&C module, the global navigation satellite module and the input / output routing module perform information interaction between the modules inside the system through an internal bus; The satellite comprehensive electronic system and the external system perform external data transmission through an external bus; and The on-board computer and the Ethernet switching module are connected to the external system through a high-speed bus to transmit high-speed data flow.

[0013] The present application has the following beneficial effects: (1) The “three-bus” layered transmission architecture is adopted, the conventional telemetry data and control instructions are transmitted through the CAN bus, and the high-bandwidth high-speed data flow (such as high-resolution imaging data and multi-spectral remote sensing data) is transmitted through the high-speed Ethernet, avoiding transmission delay or congestion caused by different types of data occupying the bandwidth.

[0014] (2) The internal CAN bus supports 110 node extensions, fully meeting the needs of adding new functions of the 200kg satellite platform and larger-scale satellites; on the other hand, the input / output routing (IOR) module relies on the FLASH type FPGA (model A3PE3000L) to realize flexible customization, which can adapt to diversified interface requirements such as dynamic adjustment of interface logic, asynchronous RS422, magnetic torque controller, SADA motor drive, and the system architecture is not limited to the 200kg satellite platform, but can adapt to the design of comprehensive electronic systems of satellites of different tonnage, greatly improving the application range of the system.

[0015] (3) The five core modules of the satellite computer (OBC), satellite power module (EPS), satellite telemetry and control module (TT&C), global navigation satellite module (GNSS), and input / output routing module (IOR) are interconnected through the internal CAN bus to unify the internal data interaction interface; at the same time, the "external CAN bus" is used as the standardized interaction carrier between the system and external systems such as satellite attitude and orbit control and thermal control, which completely solves the problems of chaotic internal and external interfaces and poor compatibility of traditional integrated electronic systems and reduces the data interaction barriers between modules and systems. Attached Figure Description

[0016] Figure 1 A block diagram of an integrated electronic system according to an embodiment of the present invention is shown; Figure 2 A functional block diagram of the integrated electronic system in one embodiment of the present invention is shown; and Figure 3 A functional block diagram of an input / output routing module according to an embodiment of the present invention is shown. Detailed Implementation

[0017] In the following description, the invention is described with reference to various embodiments. However, those skilled in the art will recognize that the embodiments may be practiced without one or more specific details or with other alternatives and / or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail so as not to obscure the inventive points of the invention. Similarly, for illustrative purposes, specific quantities, materials, and configurations are set forth to provide a comprehensive understanding of embodiments of the invention. However, the invention is not limited to these specific details.

[0018] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0019] In this specification, references to "an embodiment" or "this embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. The phrase "in one embodiment" appearing throughout this specification does not necessarily refer to the same embodiment in all instances.

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0021] Figure 1 A block diagram of an integrated electronic system according to an embodiment of the present invention is shown.

[0022] Figure 2 A functional block diagram of the integrated electronic system in one embodiment of the present invention is shown.

[0023] As Figure 1 And Figure 2 As shown in the embodiment of the present application, the integrated comprehensive electronic system comprises: The on-board computer (OBC-A, OBC-B) 100 comprises OBC-A 110 and OBC-B 120, which are connected through an Ethernet exchange module; the OBC-A and OBC-B are connected with the internal bus 710 (CAN1, CAN2), the external bus 720 (CANA, CANB) and the high-speed bus 730. The on-board computer 100 is the core unit of satellite information processing and control, and provides a hardware operation platform for application software such as satellite management and attitude control; it can be extended according to the working mode of the comprehensive electronic system; it supports high-speed Ethernet interface extension, meets the needs of high-speed data interaction within the system, coordinates the work of other modules, and is the core node of system function scheduling.

[0024] The satellite power module (EPS) 200 is connected with other modules through the internal bus (CAN1, CAN2), and has the following functions: During the satellite life cycle, it undertakes the key responsibility of energy management, manages the output power of the solar cell array to ensure effective energy collection; It controls the charging and discharging process of the battery pack to ensure stable energy supply under different working conditions of the satellite; It is responsible for the output of the whole satellite thermal control and power distribution management, and maintains the stable operation environment of the equipment; It collects important voltage and current data inside itself, monitors the running state of the energy system in real time, and provides a reliable energy foundation for other modules.

[0025] The satellite TT&C module (TT&C) 300 is connected with other modules through the internal bus (CAN1, CAN2). The satellite TT&C module 300 is the key module for bidirectional data interaction between the satellite and the ground. When uplinking, it receives the remote control commands and injection data sent by the ground, transmits them to the on-board computer 100 after de-spreading and demodulation; when downlinking, it receives the telemetry information of each module of the satellite, processes it according to the preset protocol, spreads and modulates the digital signal to the specified frequency band, and transmits it to the ground through the TT&C antenna, realizing the monitoring and control of the ground to the satellite.

[0026] The global navigation satellite module (GNSS) 400 is connected with other modules through the internal bus (CAN1, CAN2). The global navigation satellite module 400 focuses on satellite navigation and positioning services, provides satellite position, velocity and time information in the WGS-84 coordinate system, provides accurate space-time data for the on-board computer to carry out attitude control and orbit calculation, and ensures the stable operation of the satellite according to the predetermined orbit.

[0027] Input-output routing module (IOR-1, IOR-2) 500 is connected with other modules through internal bus (CAN1, CAN2). Input-output routing module 500 as a system interface expansion core module provides necessary telemetry and remote control data interface for star management and attitude control, including: Asynchronous RS422 interface, which is a key interface for input-output routing module 500 to interact with external devices through serial data. The core function is to realize the bidirectional serial transmission of data related to star management and attitude control. For example, it is connected with satellite attitude sensors (such as gyroscopes and accelerometers) to receive telemetry data such as satellite attitude angle and angular velocity collected by the sensors, and at the same time sends parameter configuration instructions (such as sampling frequency adjustment instructions) to the sensors. It can also be connected with external control devices to transmit attitude control auxiliary instructions issued by the on-board computer to ensure the stability and anti-interference ability of serial data during long-distance transmission.

[0028] Analog quantity acquisition interface, the main function is to acquire analog signals output by external devices and convert them into digital signals for transmission to the system. Specific application scenarios include acquiring voltage signals and current signals of satellite power module 200 (EPS) branch circuit, and acquiring analog temperature signals output by temperature sensors of thermal control system; the acquired analog quantities are processed internally (such as filtering and analog-to-digital conversion) and transmitted to the on-board computer 100 through the internal CAN bus to provide raw data support for the on-board computer 100 to analyze satellite energy state and thermal control state, and to ensure the real-time monitoring needs of star management on key satellite parameters.

[0029] Magnetic torque controller interface, which is specially used to connect satellite magnetic torque controller (attitude control actuator). The core function is to send accurate control signals to the magnetic torque controller to realize satellite attitude adjustment. The on-board computer generates magnetic torque controller control instructions according to the attitude control algorithm, which are transmitted to input-output routing module 500 through internal bus 710, and then input-output routing module 500 converts the instructions into drive signals (such as pulse signals) recognizable by the magnetic torque controller through the interface to control the magnetic torque controller to generate a magnetic field of specific size and direction, thereby adjusting the satellite attitude angle, offsetting the influence of interference torque in space environment on satellite attitude, and ensuring the stability of satellite attitude.

[0030] OC drive interface (collector open circuit drive interface), the main function is to drive external switching devices or realize signal isolation transmission, with high level driving ability and anti-interference characteristics. Typical applications include driving the relays outside the satellite (such as load device power supply relays), controlling the on-off of the relays through high and low level signals, realizing the power supply control of the load device; It can also be used to transmit switch state signals (such as external device fault alarm signals), and the collector open circuit output mode can improve the anti-interference ability of signal transmission, ensure that the switch state information is accurately fed back to the on-board computer, and support the state monitoring and fault diagnosis of external devices by the satellite management.

[0031] SADA motor drive interface (solar array drive mechanism motor drive interface), which is specially used to connect the motor of the satellite solar array drive mechanism (SADA), the core function is to control the rotation angle and speed of the solar array, to ensure that the solar cell array is always aligned with the sun, and to maximize the energy collection efficiency. The on-board computer generates SADA motor control instructions (such as rotation direction, rotation speed, target angle) according to the sun position information, which are transmitted to the input-output routing module 500 through the internal CAN bus, and then the input-output routing module 500 converts the instructions into motor drive signals (such as PWM signals) through the interface to drive the SADA motor to rotate the solar array; At the same time, the interface also collects the position feedback signal (such as encoder signal) of the SADA motor and returns it to the on-board computer, forming a closed loop control to ensure accurate positioning of the solar array and stable power supply of the satellite power module 200 (EPS).

[0032] Ethernet switching module 600 provides a high-speed data exchange channel for on-board computers, on-board computers and components with high-speed data exchange needs (such as satellite load devices), such as high-definition image data collected by the load and a large amount of calculation data between on-board computers, to supplement the shortcomings of CAN bus in high-speed data exchange scenarios and ensure fast and stable transmission of high-bandwidth data.

[0033] Internal bus 710 connects on-board computer 100, satellite power module 200, satellite TT&C module 300, global navigation satellite module 400, and input-output routing module 500, serving as a basic data transmission channel within the system to realize basic information exchange between the above-mentioned five core modules, transmit regular telemetry data and control instructions, and support collaborative work between modules. The above-mentioned functional units realize information exchange relying on the internal bus CAN interface, mainly based on the following considerations: (1) CAN bus uses serial data transmission, which can run at a rate of 1 Mbps on a 40m twisted pair, and supports multi-master controller mode; (2) The number of nodes on the CAN bus can reach 110, which fully meets the future expansion needs of the integrated electronics of the 200kg satellite platform; (3) The CAN bus transmits information through two signal lines CANH and CANL at the physical layer. When the above functional modules interact based on the CAN interface, the backplane interconnection is simple, reliable and easy to expand.

[0034] The external bus 720 serves as the system's external data transmission channel, enabling routine data interaction between the integrated electronic system and other external satellite systems. It transmits satellite status information (such as overall system operating parameters) and external control commands (such as scheduling commands from external systems to the integrated electronic system). As a standardized interaction carrier for the system, it ensures stable interoperability between the integrated electronic system and other satellite platform systems.

[0035] The high-speed bus 730 provides a high-speed data transmission channel for high-speed data exchange between onboard computers and between onboard computers and components outside the integrated electronics system (such as satellite payload equipment). It is specifically designed to transmit high-speed data streams (such as high-resolution imaging data, multispectral and hyperspectral remote sensing data, etc.), supplementing the shortcomings of the CAN bus in high-speed data scenarios, avoiding bandwidth contention between conventional data and high-speed data, and ensuring the rapid transmission of high-bandwidth data.

[0036] Figure 3 A functional block diagram of an input / output routing module according to an embodiment of the present invention is shown.

[0037] When constructing a comprehensive electronic internal bus architecture, OBC, GNSS, TT&C, and EPS typically have their specific functions implemented by the processor and peripheral circuits. The implementation of the CAN bus interface is relatively conventional. However, for the input / output routing module 500, the CAN bus interface needs to be implemented using an FPGA, such as... Figure 3 As shown, in one embodiment of the present invention, the core of the input / output routing module is based on a FLASH-type FPGA to realize CAN bus protocol parsing and external function expansion. The FPGA used is an A3PE3000L, which features fast power-on loading, non-volatility, and high-energy neutron immunity in the configuration area. Based on this architecture, it is easy to customize the functions and develop the software of the input / output routing module, thereby realizing the functional expansion of integrated electronics. The core process is as follows: The FPGA receives differential signals from the internal CAN bus (CAN1, CAN2) through a hardware interface. First, it performs signal filtering and level conversion at the physical layer to convert the external differential signals into digital signals that the FPGA can recognize, thus eliminating the impact of noise interference on data transmission. The hardware logic of CAN bus protocol analysis is fixed in the FPGA, which can analyze the CAN bus data frame structure (including frame start, arbitration field, control field, data field, CRC field, ACK field and frame end) in real time, extract the effective information (such as telemetry data identifier, control instruction code and data length) in the data frame, and check the data integrity (ensure that the data has no transmission error through CRC check). The effective data after analysis is distributed to the corresponding processing unit in the input and output routing module according to the preset logic by the FPGA, or is transmitted to the on-board computer through the internal link; at the same time, the FPGA receives the control instructions (such as interface configuration instructions and data acquisition instructions) issued by the on-board computer, encapsulates them into the frame structure conforming to the CAN bus protocol, and sends them to other modules through the CAN bus, so as to realize the bidirectional data interaction between the input and output routing module and the system.

[0038] The control logic of different types of interfaces can be fixed in the FPGA according to the requirements, without relying on external dedicated chips, so as to directly realize the functions of asynchronous RS422 interface, analog quantity acquisition interface, magnetic torque controller interface, OC drive interface and SADA motor drive interface. For the asynchronous RS422 interface, the FPGA realizes the logic of data string and parallel conversion, baud rate adaptation and parity check, so as to ensure the stable interaction of serial data with external devices (such as attitude sensors). For the analog quantity acquisition interface, the FPGA controls the sampling frequency and data precision of the analog-to-digital conversion (ADC) module, converts the external analog signals (such as voltage and current signals) into digital signals, and then transmits them to the OBC through the CAN bus. For the magnetic torque controller interface, OC drive interface and SADA motor drive interface, the FPGA generates accurate control signals (such as PWM signals and switching signals) to directly drive external actuators, and at the same time, collects the state feedback signals of the actuators to form a closed loop control.

[0039] Since the FLASH type FPGA supports online configuration, the interface logic in the FPGA (such as modifying the baud rate of the RS422 interface, adjusting the sampling period of the analog quantity acquisition, and adding the drive interface of a specific device) can be dynamically adjusted through the configuration instructions issued by the on-board computer, without the need to physically modify the hardware of the input and output routing module, so as to adapt to the differentiated requirements of different satellite tasks for external interfaces, realize the extension capability of "unchanged hardware and customizable function", and meet the requirements of rapid design and assembly of the system.

[0040] In an embodiment of the present application, a method for running the integrated satellite comprehensive electronic system is also provided, which includes the following steps: The satellite information is processed and controlled by the on-board computer. The satellite power module performs power distribution management and control of the whole satellite; The satellite TT&C module performs satellite and ground bidirectional data interaction; The global navigation satellite module performs satellite multi-system navigation and positioning; The input / output routing module provides telemetry and remote control data interface for star management and attitude control; The Ethernet switching module provides data exchange channel for onboard computers or between onboard computers and integrated electronics outside; The onboard computer, satellite power module, satellite TT&C module, global navigation satellite module and input / output routing module exchange information among the modules through internal bus; The satellite integrated electronic system and external system exchange data through external bus; and The onboard computer and Ethernet switching module are connected to external system through high-speed bus to transmit high-speed data stream.

[0041] Although the above describes the embodiments of the present application, it should be understood that they are presented only as examples, not as limitations. It is obvious to those skilled in the relevant art that various combinations, modifications and changes can be made without departing from the spirit and scope of the present application. Therefore, the breadth and scope of the present application disclosed herein should not be limited by the above disclosed exemplary embodiments, but should only be defined according to the appended claims and their equivalent replacements.

Claims

1. An integrated satellite electronic system, characterized in that, include: Multiple onboard computers are interconnected via Ethernet switching modules and configured to perform satellite information processing and control. The satellite power module is configured to perform power distribution management and control for the entire satellite; The satellite telemetry and control module is configured to perform two-way data interaction between the satellite and the ground. The Global Navigation Satellite Module is configured to perform multi-system satellite navigation and positioning. The input / output routing module is configured to provide telemetry and remote control data interfaces for satellite management and attitude control; Ethernet switching module, configured to provide a data exchange channel between onboard computers or between an onboard computer and an external integrated electronics system; The internal bus connects the onboard computer, satellite power module, satellite telemetry and control module, global navigation satellite module, and input / output routing module. It is configured to facilitate information exchange between the various modules within the system. The external bus connects the satellite integrated electronic system with external systems and is configured as the system's external data transmission channel. as well as A high-speed bus connects the onboard computer to the Ethernet switching module and external systems; it is configured to transmit high-speed data streams.

2. The system according to claim 1, characterized in that, Both the internal and external buses are configured as CAN buses with a transmission rate of 1 Mbps, using serial data transmission; and The high-speed bus is configured to perform high-speed data transmission at a rate higher than that of the CAN bus.

3. The system according to claim 1, characterized in that, The satellite power module is configured to perform one or more of the following operations: Controlling the charging and discharging process of the battery pack ensures a stable energy supply for the satellite under different operating conditions; Responsible for the overall satellite thermal control output and power distribution management, maintaining a stable operating environment for the equipment; and It collects its own internal voltage and current data to monitor the operating status of the energy system in real time.

4. The system according to claim 1, characterized in that, The input / output routing module includes: An asynchronous RS422 interface is configured to enable bidirectional serial transmission of data related to space management and attitude control. The analog signal acquisition interface is configured to acquire analog signals output by external devices, convert them into digital signals, and then transmit them to the system. A magnetic torquer control interface is configured to send control signals to the magnetic torquer to achieve satellite attitude adjustment; An OC driver interface is configured to drive external switching devices or to achieve signal isolation transmission; and The SADA motor drive interface is configured to control the rotation angle and speed of the solar array, ensuring that the solar cell array is always aligned with the sun.

5. The system according to claim 2, characterized in that, The input / output routing module is configured with a FLASH-type FPGA to realize CAN bus protocol parsing and external function expansion.

6. The system according to claim 5, characterized in that, The FPGA is an A3PE3000L model.

7. The system according to claim 1, characterized in that, The satellite telemetry and control module is configured to perform the following operations: During uplink remote control, it receives remote control commands and injected data sent from the ground, and transmits them to the onboard computer after despreading and demodulation; and During downlink telemetry, the system receives telemetry information from various satellite modules, frames and processes it according to a preset protocol, spreads and modulates the digital signal to the specified frequency band, and transmits it to the ground.

8. A method for operating an integrated satellite electronic system according to any one of claims 1 to 7, comprising the following steps: Satellite information processing and control are performed by the onboard computer; The satellite's power distribution module manages and controls the power distribution of the entire satellite. Two-way data exchange between the satellite and the ground is carried out by the satellite telemetry and control module; The global navigation satellite module performs satellite multi-system navigation and positioning. The input / output routing module provides a telemetry and remote control data interface for satellite management and attitude control. The Ethernet switching module provides a data exchange channel between onboard computers or between onboard computers and the integrated electronics external system. The onboard computer, satellite power module, satellite telemetry and control module, global navigation satellite module, and input / output routing module communicate with each other within the system via an internal bus. The satellite integrated electronic system transmits external data with external systems via an external bus. as well as The onboard computer and Ethernet switching module are connected to external systems via a high-speed bus to transmit high-speed data streams.

Images