The PISCES Project
Don J. Pearson
JSC/DM Flight Design & Dynamics Division
May 2002
don.j.pearson@jsc.nasa.gov
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PISCES
Platform
Independent
Software
Components for the
Exploration of
Space

Orbtial Mission Design and Analysis Components
– orbital propagation, basic trajectory components (library) for orbital
trajectories around Earth, the Moon, and Mars.
– Graphical input, visualized outputs
– Focus on Agency-wide (Program independent) Rendezvous
capability
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Technology Objectives

PISCES originated as an RTOP with 3 technology objectives:
– Re-establish civil service expertise in human missions beyond LEO
(Agency and Center emphasis) with a focus on Rendezvous
– Evaluate potential of a Java-based object-oriented mission
planning system
» web-based, distributed planning environment
» platform independence
» national interest in the use of Java for Science and Engineering
– Develop tools via partnerships with universities rather than
traditional aerospace contract
» economic decision / objective of project
» HEDS strategic initiative
“bring space exploration experience into the classroom...
new initiatives to inspire students to study science, math...”
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PISCES Components

Developed precision orbital propagation software
(100% completely re-engineered)
– Reusable utilities:
» Vector/Matrix math, iterators
» Time (JulianDate)
– Astronomical Body models
» physical models, lunar/planetary coordinate systems
» extremely high fidelity gravity models (e.g.: 75x75 Moon, 50x50 Mars), atmosphere
models, solar radiation models
– Spacecraft models
» transitioning from point mass vehicles with impulsive burns to vehicles with thrusters,
attitude profiles, etc
» precision integration models to move spacecraft through environment
– Rendezvous:
» Launch window: when/how to get off the planet
» Rendezvous Maneuver Targeting: how to chase down the satellite
– Graphical:
» 3D visualization: “immersive environment”
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PISCES Applications

Rendezvous design and real-time operations
– Target spacecraft onorbit (initial vector or ephemeris if maneuverable)
– Launch Window / Launch Targeting
» computes lift-off time, launch window, ascent cutoff state
» launch time and targeting depends on rendezvous strategy (phase wraps,etc)
– Orbit Maneuver Application (OMA)
» generic maneuver planning
» maneuvers scheduled based on time, DT, apsis conditions, orbital lighting, ground passes,
etc.
» mix of




phasing, height adjustments (targeted to various downrange,altitude conditions)
planar maneuvers
circularization, coelliptic maneuvers
Lambert maneuvers
– Relative motion plots

Validated on current Shuttle missions via streaming telemetry
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Rendezvous Planning
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Rendezvous Solutions
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Interactive 3D Visualization
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Interactive 3D visualization
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Planetary Rendezvous Capability
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Leap in State-of-Art Rendezvous Planning

Maneuver Planning Functionality Improvements :
– J2K, Metric
» M50, English units
– Modular, plug-N-play propagation schemes (detailed gravity, atmosphere
models, solar radiation modeling, N-body gravity, attitude profiles, variable
mass)
»
»
»
»
hardwired to analytic propagation techniques limited to 4x2 gravity
limited to Jacchia-Lineberry atmosphere, sampled ~6 times per orbit
no solar radiation or N-body effects
constant CD, area, mass (only adjusted for maneuver delta-v)
– Additional maneuver scheduling capabilities eliminating manual iterations
» relative apsis, ground passes
– Java
» Fortran, 6 character variables, large common blocks for data transfer
» 30 years of patching, Limited to LEO
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Unique Architecture Features

PISCES is (and our current operational mission planning software packages aren’t) :
– platform independent
» portability concerns are minimized
» reduced maintenance costs
– distributed
» client applications support multiple users
» reallocation of client/server responsibilities easy
– web-based
» programs architected to be run via the Internet


software maintained at JSC and used by clients across Agency
note: architected, but not currently in use via the Internet
– multi-threaded
» can run multiple processes simultaneously

eg: running multiple Kalman filters, targeting scenarios
– enticing to today’s emerging software professionals
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Summary

PISCES strategically positioned to become a “tool of choice” for
Agency-wide rendezvous mission design and analysis
– Architected for portability, expandability, maintainability
– Functional for LEO, HEO, planetary rendezvous
– Expandable component library
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