Aerospace and Electronic Systems Magazine August 2016 - 18

Design of Telecommand Software for the Mars Orbiter Mission remote system failure, the heart beat signal is exchanged between the local and remote system. The heart beat signal tells about the health of that system to the other system. If there is a problem in the heart beat signal of the local system in a time window, then the remote system automatically takes over. In local system failure, the local hardware detects it and initiates the changeover. OTHER FEATURES Configurable Command Blocks CCB is a block of commands. These commands don't have any delay/time associated with them. The uplinked commands are validated and stored onboard. The CCB is specified by a block number. The CCB is a set of commands which perform a definite operation when executed. The CCB can be reused again and again. For example, CCBs are used for storing load shedding commands and also configuration commands, which can be triggered whenever required. Real-Time Commands Real-time commands have the highest priority among all the commands. These commands are executed immediately after validating the uplinked command. For example, liquid engine burn commands are given in real time if the spacecraft is visible during the earth bound phase. Command/Data Transfer on 1553 Bus Figure 9. OBT logic block diagram. from the ground station so that their configuration and database remains synchronized if there is an uplink from the ground station. The changes done by the enabled/main processor in configuration onboard are transferred to a disabled/redundant processor so that their configuration remains the same after onboard actions. The functionalities running in a redundant processor monitor the same functionalities running in main processor and update their configuration by looking at what is happening in main processor. This helps the functionalities running in a redundant processor to resume operation from the same point where main processor failed. For example, the OBT module running in main MTcP executes the commands when the OBT matures, but the OBT module running in redundant processor deletes the OBT events whose time has matured instead of executing the commands. Therefore, both main and redundant OBT modules remain in synch. After MTcP auto-changeover happens, the OBT module running in redundant MTcP starts executing the commands and the OBT operation is as expected until the ground station intervenes. The functional diagram of TC autonomy is shown in Figure 10. Two kinds of failure detection are local and remote. For detecting 18 The TC system has a RT on the AOCE 1553B bus. All the 1553B commands/data are sent on this bus. The 1553B commands/data can be sent to AOCE BC and other RTs on the bus. The software supports real time, TT, OBT, and CCB commands through the 1553B bus. The software also transfers telemetry parameters to AOCE over the 1553B bus. All telemetry data are programmable. The MTcP software sends an executed telecommand history to a baseband data handling package on the 1553B bus. Therefore, the telecommand history is available in playback data. The executed telecommand history is very useful for post-operation analysis. The main MTcP software also transfers data to redundant MTcP software in order to keep redundant MTcP software configuration the same as the main MTcP software. This configuration synchronizes redundant MTcP to take over when MTcP auto-changeover happens. Remote Programming The remote programming feature enables the MTcP software to accommodate new requirements. If any new software modules are required to meet the new requirements, then new software modules can be uplinked through ground commands. The remote program is provided with an enable/disable feature. Linking Features The real strength of the MTcP software is the ability to combine various MTcP features to perform an operation. It provides flexibility to IEEE A&E SYSTEMS MAGAZINE AUGUST 2016

Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine August 2016