Session
Session 1: C&DH
Abstract
The NASA Operational Simulator for Small Satellites (NOS3) is a suite of software tools that significantly aids the SmallSat community with software development, integration and test (I&T), mission operations/training, verification and validation (V&V), and software systems check-out. NOS3 has been utilized extensively for NASA’s Simulation-to-Flight 1 (STF-1) cubesat mission with respect to V&V of its semiautonomous science operations. NOS3 provides a software development environment, a multi-target build system, operational interface/ground software, dynamics and environment simulations, and software-based hardware models. STF-1,a 3U cubesat due to launch in late 2017, is composed of five dissimilar science experiments: 1) A IV-V Nitride radiation durability experiment, 2) A global navigation system receiver for orbit determination, 3) Cluster of inertial measurement units for data aggregation, 4) A magnetosphere physics experiment including a Langmuir probe and particle counters, and 5) A visible light camera. Each of these experiments has its own set of software requirements, such as data acquisition times/rates, and operational specifications/modes. In addition to its science experiment software requirements, the STF-1 cubesat also has normal-operational software requirements, such as power monitoring, sensor data acquisition, experiment data storage, and uplink/downlink communications. These complex software requirements provide a significant V&V challenge due to limited hardware test bed accessibility; all science experiment hardware is custom without spares, and flight hardware testing time is not adequate for complete flight software V&V. Due to the short-duration seven-minute ground contact windows, the STF-1 cubesat must perform its operations without ground contact. STF-1 requires semiautonomous on-orbit operations to manage its five complex science experiments. STF-1, which is utilizing Goddard Space Flight Center’s (GSFC) open-source Core Flight System (cFS), contains a Manager (MGR) application that implements a state machine for starting, stopping, and monitoring the science experiments without ground intervention. MGR is also responsible for watchdog timers, power monitoring, and handling error states. NOS3 usage on STF-1 has allowed the team to execute months of MGR and additional flight software V&V tests without monopolizing flight hardware testing time. The NOS3 hardware models’ fidelity is such that flight software executes unaware that physical hardware is not present. This allows the flight software binaries to be compiled for both the simulation environment and the flight computer without changing the source code. Multiple engineers are able to simultaneously test the flight software, perform long-duration-multiple-orbit test scenarios, and verify recorded telemetry by utilizing the NOS3 virtual machine on laptops. NOS3 is expected to be open-source available to the entire SmallSat community by Summer 2017 to significantly assist projects with their flight software development. As NOS3 matures, additional hardware models will be added that are common to the small satellite community. Also planned in the near future is more hardware-in-the-loop functionality that allows a flight computer with I2C to connect to NOS3 simulators, thus providing representative data for additional flight software testing capabilities.
Utilization of the NASA Operational Simulator for Small Satellites (NOS3) for V&V of STF-1’s Semiautonomous On-Orbit Operations
The NASA Operational Simulator for Small Satellites (NOS3) is a suite of software tools that significantly aids the SmallSat community with software development, integration and test (I&T), mission operations/training, verification and validation (V&V), and software systems check-out. NOS3 has been utilized extensively for NASA’s Simulation-to-Flight 1 (STF-1) cubesat mission with respect to V&V of its semiautonomous science operations. NOS3 provides a software development environment, a multi-target build system, operational interface/ground software, dynamics and environment simulations, and software-based hardware models. STF-1,a 3U cubesat due to launch in late 2017, is composed of five dissimilar science experiments: 1) A IV-V Nitride radiation durability experiment, 2) A global navigation system receiver for orbit determination, 3) Cluster of inertial measurement units for data aggregation, 4) A magnetosphere physics experiment including a Langmuir probe and particle counters, and 5) A visible light camera. Each of these experiments has its own set of software requirements, such as data acquisition times/rates, and operational specifications/modes. In addition to its science experiment software requirements, the STF-1 cubesat also has normal-operational software requirements, such as power monitoring, sensor data acquisition, experiment data storage, and uplink/downlink communications. These complex software requirements provide a significant V&V challenge due to limited hardware test bed accessibility; all science experiment hardware is custom without spares, and flight hardware testing time is not adequate for complete flight software V&V. Due to the short-duration seven-minute ground contact windows, the STF-1 cubesat must perform its operations without ground contact. STF-1 requires semiautonomous on-orbit operations to manage its five complex science experiments. STF-1, which is utilizing Goddard Space Flight Center’s (GSFC) open-source Core Flight System (cFS), contains a Manager (MGR) application that implements a state machine for starting, stopping, and monitoring the science experiments without ground intervention. MGR is also responsible for watchdog timers, power monitoring, and handling error states. NOS3 usage on STF-1 has allowed the team to execute months of MGR and additional flight software V&V tests without monopolizing flight hardware testing time. The NOS3 hardware models’ fidelity is such that flight software executes unaware that physical hardware is not present. This allows the flight software binaries to be compiled for both the simulation environment and the flight computer without changing the source code. Multiple engineers are able to simultaneously test the flight software, perform long-duration-multiple-orbit test scenarios, and verify recorded telemetry by utilizing the NOS3 virtual machine on laptops. NOS3 is expected to be open-source available to the entire SmallSat community by Summer 2017 to significantly assist projects with their flight software development. As NOS3 matures, additional hardware models will be added that are common to the small satellite community. Also planned in the near future is more hardware-in-the-loop functionality that allows a flight computer with I2C to connect to NOS3 simulators, thus providing representative data for additional flight software testing capabilities.
