Professional Experience Summary
Aerospace Engineer – Orbit Analyst – Software Engineer
20+ years experience in orbital mechanics and astrodynamic analyses, design, simulation development and modeling with specialization in Orbit Determination (OD) and parameter estimation, and satellite constellation earth coverage design & analysis.
Supported the SGT/Raytheon Orbit software program contract for the proposed New Space Fence, designed to maintain the catalog of space objects that are significantly smaller and many times more numerous than the current system. The program segments process design state of the art phased array radar high accuracy measurements which are in turn form 1) the initial single pass OD estimates, 2) compute correlation measures for earlier ephemeris and covariance estimates, 3) update correlated orbital ephemeris states and covariance, and 4) generate propagated ephemeris and covariance predictions at the Fence crossing time epochs.
Supported the Naval Space Command DB15 OD Program (classified) software development & test, and configuration control for 13 years. The work included implementing software enhancements for 1) higher accuracy earth gravity and polar motion modeling, 2) extended duration satellite DV thrusting, 3) solar panel radiation pressure and panel dynamics 4) numerous other force modeling modifications, 5) implementation of modified Doppler measurement types, 6) robust and refined estimation techniques, and 7) responsible for the OD software installations and checkout at the mission ops ground support stations.
Software test & development in support of a concept & design phase of a program for a unique open-loop Pitch Control attitude control program (PCS), formulated by Dr. J. Vahlberg which proved as a key development that extended the Navy/Air Force DB15 multi-constellation satellite mission many years beyond the expected mission life plan. The PCS program was developed as a workaround after critical satellite sub-system failures threatened to terminate the multi-satellite classified mission.
Prior to working for SGT and Raytheon, Mr. Elsner worked for Lockheed Missiles & Space Co. (now, Lockheed-Martin) Space Systems Division Orbital Mechanics Dept. in Sunnyvale, CA. The work involved a variety of orbit analysis tasks and developing orbital software simulations employing general perturbation models. Primary focus included analysis and software simulation development for evaluating satellite & constellation earth coverage, satellite payload trade study performance assessments, and other studies for numerous proposed DOD and NASA satellite systems.
Developed orbital simulations for deriving cross-range maneuver requirements for a proposed eight-man re-entry atmospheric lifting body vehicle (Assured Crew Return Vehicle, or ACRV) to serve as a lifeboat for the (then planned) International Space Station, or ISS. In addition, simulations were developed for demo and conducting trade studies and Monte-Carlo analysis for evaluating de-orbit landing site selection options.
The above software development work and analysis were performed on a variety of computer platforms such as Alpha, SUN, and HP Workstations, as well as PC, VAX Mainframe, CRAY, and others. Operating systems included VMS, VAX, UNIX, and PC Windows. The programming was done primarily in FORTRAN 77 & 95, VMS/VAX command scripts, MS Windows batch scripts, and some C and UNIX.
Sgt Inc., Greenbelt, MD Aug 2007 – Aug 2012
Principal Systems Engineer
Provided software simulation development, modeling, and support for Raytheon/SGT proposed New Space Fence system. The modeling and simulation tasks were performed on PC Windows platforms with computational programming code performed in FORTRAN 95 and PC Windows scripts.
The Space Fence software development involved the programming, test, and analysis for automated functional blocks for orbit object sequenced OD processing, object correlations, and propagated orbit state and covariance. Scenarios for up to several hundred thousand orbit objects were simulated and the SGT program consistently correctly correlated objects much better than spec requirements. The Space Fence task required knowledge of special perturbation (SP) earth orbit models, orbit determination (OD), covariance analysis, astrodynamic, Maximum Likelihood correlation, inertial & rotating coordinate systems and transformations, and implementation of the SGT and NASA Goddard GEODYN Precision OD program. Software configuration control management was maintained for frequent program development enhancements and updates.
Raytheon Technical Services Co. Lanham, MD Oct 1994 – Aug 2007
Principal Systems Engineer
Software enhancement modifications, testing and development of the Naval Space Command DB15 satellite surveillance system orbit determination (OD) program. The primary responsibilities included the development & test, validation, software maintenance, and updates to the OD Estimation Program and the corresponding special perturbation (SP) orbit propagation program software executed at the global remote station sites.
Enhancements to the DB15 OD Program provided orbital accuracy improvement on the order of 2-3x over the original operational program for the multi-satellite missions. Enhancements included implementing a 40x40 WGS84 earth gravity model; automated updates for earth spin axis orientation, removal of Doppler station survey biases, variable weighted fit-span option which demonstrated significantly improved orbit accuracy spanning solar/atmospheric events. In addition, programming changes for the Y2K transition epoch.
Conducted a comprehensive error analysis studies to accurately model satellite thrusting force for long duration thrusts, as well as consecutive rev thrusting. This enabled mission planners more flexibility to command longer duration, larger V orbit adjust maneuvers with small ephemeris errors for remote station prediction accuracy.
Provided a satellite station-keeping simulation program and software tools for the mission planners to much more accurately and optimally plan satellite station-keeping thrusts. The program utilized a position-velocity phase-plane control concept which resulted in reducing the total number of thrusts, maintaining tighter station-keeping control, and also provided advance alerts for mission planners when relative position rates were high.
Created a simulation for optimizing satellite electrical power for reduced solar panel functionality when multiple solar panel step-motor failure events occurred on multiple satellites. The analysis led to implementing optimal fixed configurations for a range of angles (solar/orbit geometry) on multiple satellites. This operational implementation significantly restored the mission payload tasking level near the original spec for full panel function.
Supported design phase testing and development of the PCS (Pitch-Control-System) open-loop attitude control program (devised by Dr. J. Vahlberg) that was the key factor in extending the mission life for the DB15 mission for up to 8 years beyond its designed life. Also provided PCS daily operations monitoring, optimized momentum wheel controls generation and working in concet with mission ops crews that extended the overall mission life.
Lockheed Missiles & Space Co. (Lockheed-Martin) Sunnyvale,CA 1985 – 1994
Sr. Research Engineer
Supported orbit analysis tasks as part of the Space System Division (SSD) Orbital Mechanics Group on DOD and NASA proposed satellite programs, including SDI Boost Surveillance Tracking System (BSTS), MILSTAR, DMSP, ACRV (ISS), IRIDIUM, and numerous others.
Specialization in satellite constellation design and earth coverage simulation tools, ground station revisit time analysis, derived BSTS (classified) payload earth coverage requirements. One of four team members that designed and developed Lockheed’s Integrated Coverage Analysis Program (ICAP) which provided broad program applicability and flexibility.
Designed / implemented a simulation program for analysis and demo for deriving the ACRV manned re-entry spacecraft cross-range maneuver requirements and landing site options.
Computers: ALPHA, PC WINDOWS, VAX Mainframe, CRAY, SUN, HP
Languages/Applications: FORTRAN 77 & 95, VMS scripts, PC Windows scripts, C, WORD, EXCEL
M.S., Aeronautical & Astronautical Engineering, University of Illinois, Urbana-Champaign, IL 1985
B.A., Liberal Arts & Sciences Economics, University of Illinois, Urbana-Champaign, IL 1978
DOD T.S. and SCI/Poly debriefed in 2011 at end of mission. DOD SECRET debriefed Aug 2012.
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