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Modeling & Simulation

 

Emergent’s capabilities include the development of dynamic simulations on various computing platforms, including the development of high fidelity sensor and actuator models. Currently Emergent engineers are developing and implementing Rendezvous, Proximity Operations (RPO) guidance algorithms and machine vision algorithms for the Restore-L mission using NASA GSFC’s Freespace modeling and simulation software. Restore-L is a technology demonstration mission to perform on-orbit autonomous rendezvous, proximity operations and capture of a non-cooperative government-spacecraft (Landsat-7), followed by tele-robotic servicing and refueling, and finally relocation of the spacecraft to its operational orbit. We are validating the GN&C algorithms and flight software through a Hardware-in-the-Loop (HIL) implementation that incorporates both a simulation of relative spacecraft dynamics and industrial robots for flight system qualification testing. We do so in collaboration with the Robotics Team by using the integrated test facilities within NASA GSFC’s Robotic Operations Center. 

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Rendering of the Restore-L servicing spacecraft in proximity to Landsat-7 in the grapple stand-off position. This rendering follows a true dynamic simulation used to design the GN&C software and run analysis (inset: Visible Light Camera, Wide Field of View 2 image of Landsat 7’s Marmon ring).

 

A precursor mission to Restore-L, Raven is an integrated payload launched as a testbed for various machine vision and navigation algorithms. The Raven project was launched to the International Space Station (ISS) as a component of Space Test Program-H5 and is installed on ISS Express Logistics Carrier 1. Raven features a visible light camera, an infrared camera and a 3D flash LiDAR sensor on a pan-tilt gimbal able to independently track ISS Visiting Vehicles, including Dragon, Cygnus, HTV, Progress and Soyuz and will be used for testing and validating on-board algorithms for real-time relative navigation between non-cooperative spacecraft, including 6 degree-of-freedom pose measurements. Emergent engineers developed the pointing control system and worked on various aspects of Kalman Filter implementation, as well as machine vision and software interfaces for flight sensors and actuators. We also developed high-fidelity simulations in Freespace that incorporated actuation of the ISS and its Visiting Vehicles. Raven flight software components were then tested in the same Freespace environment before flight hardware testing. 

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The Raven Multi-Spectral Proximity Operations Sensor Suite, prior to environmental testing at NASA GSFC.

As a part of Lockheed Martin’s Orion Manned Spaceflight Program team, Emergent has developed and maintained Navigation and Fault Detection Isolation and Recovery (FDIR) flight software.  This includes design, implementation, documentation, and testing.  Units worked on include error processing and FDIR for inertial measurement unit, barometric altimeter, and GPS data; user parameter calculation; navigation state estimation and propagation; ephemeris construction for antenna pointing; and ground alignment. To support this effort, we developed and improved software models to support the Osiris and Antares simulation frameworks, such as the pad twist and sway model and updates to the inertial measurement unit model. Emergent also played a direct role in hardware-in-the-loop (HIL) testing.

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This figure illustrates the development of Orion GN&C Flight Software.  The initial development is done in a Matlab/Simulink/Stateflow environment (Ramses).  This code is then converted into C++ units using Matlab's auto-code capability. This C++ code is then integrated with the rest of FSW and tested against simulations with optional hardware-in-the-loop capability.  Once fully tested, the FSW will run on Orion during flight.