Aerospace and Electronic Systems Magazine August 2016 - 15

Bhilawe et al. Table 1. Minor Cycles Definition Minor Cycle 1 Minor Cycle 2 Minor Cycle 3 Minor Cycle 4 Timing management Timing management Timing management Timing management Command execution logic Command execution logic Command execution logic Command execution logic Read and decode telecommands Macro execution check 1553 memory refresh OBT event decoding and sorting Thermal management Self test EBC condition sampling OBT event maturity check TC history transfer to BDH Snap logic EBC maturity check Page display refresh OBT offset calculation AOCE event detection AOCE telemetry acquisition Macro maturity check Remote program 1 AOCE event queue execution TM calibration voltage check Remote program 4 Memory refresh EBC condition sampling Remote program 3 Memory refresh Global memory refresh EBC maturity check Memory refresh Global memory refresh -- Remote program 2 Global memory refresh -- -- Memory refresh -- -- -- Global memory refresh -- -- lemetry frame. Therefore, the EBC sampling logic must check all conditions within a telemetry frame time. The timing management module maintains time for functionalities like TT, OBT, EBCs, etc. It periodically checks for TM health and initiates TM auto-changeover if necessary. The command execution logic decides the priority of command execution. It also handles execution of commands from various functionalities. MT c P SOFTWARE FUNCTIONS The MTcP software design is mainly focused on autonomy requirements and flexibility to meet mission requirements during various phases of MOM. Features like TM and MTcP auto-changeover makes it more robust. The software features minimize the ground control intervention in case of any failure as the mission involves significant delays in getting onboard telemetry, as well as visibility constraints. Features of MTcP software design are explained below. The features are divided as a) EBCs, b) TT Commands, c) FDIR, and d) other features. EVENT BASED COMMANDING Telemetry Event Based Commanding While operating the spacecraft, a general requirement is that when a particular parameter of a subsystem crosses some limit, or if a particular status is set or reset, some specific operation shall be carried out. To meet this requirement, the software monitors onboard AUGUST 2016 telemetry data of the subsystem/sensors and issues commands corresponding to that event. The software includes a set of arithmetic and logical checks (e.g., lesser, greater, all bits high, all bits low, etc.) for the telemetry data. Both event condition and commands are programmable from the ground. The sampling rate of the data is also programmable. A simplified block diagram for telemetry event based commanding logic is shown in Figure 7. The consistency of telemetry data is monitored and validated to avoid spurious event triggering. Multiple event conditions can also be combined for a particular action. The EBC feature is a general purpose feature and can be effectively used for normal operations as well as contingency management onboard. For example, an event can be programmed to switch off the payloads when the battery voltage falls below a particular value. EBCs are also used for battery management in spacecraft. In case of attitude loss, EBCs are used to detect Radio Frequency bit lock and sun presence by rotating the spacecraft. The same events can be programmed with different conditions and different actions during various phases of the mission. All of the events are provided with individual enable/disable control. The EBC logic is designed to work at all the telemetry data rates. AOCE Events Autonomy Functions The AOCE autonomy logic resides in MTcP software. AOCE sends events to MTcP and MTcP takes the action by executing commands corresponding to that event. The AOCE autonomy IEEE A&E SYSTEMS MAGAZINE 15

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