The Jet Propulsion Laboratory (JPL) is developing a high-fidelity spacecraft simulator for Entry, Descent and Landing (EDL) on planetary and small-bodies. This simulator, DSENDS (Dynamics Simulator for Entry, Descent and Surface landing), is an EDL-specific extension of a JPL multi-mission simulation toolkit (Darts/Dshell) which is capable of modeling spacecraft dynamics, devices, and subsystems, and is in use by interplanetary and science-craft missions such as Cassini, Galileo, SIM, and Starlight. DSENDS is currently in use by the JPL Smart Lander project [1] to provide a high-fidelity testbed for the test of precision landing and hazard avoidance functions for future Mars missions. We first briefly describe the core tool capabilities in dynamics, instrument/actuator device models, and real-time simulation engineering. These allow the modeling of the flight-train elements during various phases of EDL and all of the spacecraft responses. We then address the various EDL-specific aspects of the simulator. These include the high-fidelity entry-body and parachute aerodynamic models and supporting atmospheric models. In addition the simulator provides real-time terrain and instrument simulations for terrain imaging lidars and radars. The simulator hosts guidance/navigation simulation modules for hypersonic steering and powered descent. Models for landing kinematics and dynamics are being incorporated to determine contact and impact forces. We also discuss the automated state-machine driven model switching used to handle spacecraft separations and re-configurations, as well as specific visualization tools developed to support EDL execution interpretation. The DSENDS system is capable of supporting the entire mission lifecycle use of simulators. This includes the facility to embed the simulator into a Matlab/Simulink environment where control analysts can use the same high-fidelity simulation used in real-time operations within a familiar analysis environment. DSENDS also provides stand-alone simulations to provide mission visualization and support for Monte-Carlo analysis. Using the real-time features of the underlying Darts/Dshell toolkit, DSENDS can be made to operate in a VxWorks/VxSim real-time testbed.

is a n i n-d e v e l o p m e n t s p a c e c r a f t s i m u l a t o r for E n t r y , D e s c e n t , a n d L a n d i n g , d ev e l o p e d i n i t i a l l y t h r o u g h D N P f u n d i n s s t J P L a n d c u r r e n t l y a l a t e d f o r use in t h e M a r s S m a r t L a n d e r m i s s i o n as a n s n a l y i s a n d v e r i f i c a t i o n t o o l. B a s e d on t h e J P L-d e v e l o p e d Dshell sim " l at o r. t h e n e e d t o c o n s o l i d a t e a n d e o m b i n e t o o l 8 from d i s p a r a t e s o u r c e s a n d w i t h v a r y i n g d e g r e e s o f c o m p l e t e n e s s h a s p r e s e n t e d u n i q u e c h a l l e n g e r. T h i s p a p e r d i s c u s s e s s o m e o f t h o a e c h a l l e n g e s a n d a n d t h e i r 1 1 0 I~t i o n s .

The Mars Science Laboratory developed the WorkStation TestSet (WSTS) to support flight software development. The WSTS is the non-real-time flight avionics simulator that is designed to be completely softwarebased and run on a workstation class Linux PC. This provides flight software developers with their own virtual avionics testbed and allows device-level and functional software testing when hardware testbeds are either not yet available or have limited availability. The WSTS has successfully off-loaded many flight software development activities from the project testbeds. At the writing of this paper, the WSTS has averaged an order of magnitude more usage than the project's hardware testbeds.