Search NASA⌕ Search

Engineering topics

Estefan, Jeff A.

Publications and source records attributed to Estefan, Jeff A..

4 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

A Multifaceted Approach to Modernizing NASA's Advanced Multi-Mission Operations System (AMMOS) System Architecture

The Advanced Multi-Mission Operations Systems (AMMOS) is NASA's premier space mission operations product line offering for use in deep-space robotic and astrophysics missions. The general approach to AMMOS modernization over the course of its 29-year history exemplifies a continual, evolutionary approach with periods of sponsor investment peaks and valleys in between. Today, the Multimission Ground Systems and Services (MGSS) office-the program office that manages the AMMOS for NASA-actively pursues modernization initiatives and continues to evolve the AMMOS by incorporating enhanced capabilities and newer technologies into its end-user tool and service offerings. Despite the myriad of modernization investments that have been made over the evolutionary course of the AMMOS, pain points remain. These pain points, based on interviews with numerous flight project mission operations personnel, can be classified principally into two major categories: 1) information-related issues, and 2) process-related issues. By information-related issues, we mean pain points associated with the management and flow of MOS data across the various system interfaces. By process-related issues, we mean pain points associated with the MOS activities performed by mission operators (i.e., humans) and supporting software infrastructure used in support of those activities. In this paper, three foundational concepts-Timeline, Closed Loop Control, and Separation of Concerns-collectively form the basis for expressing a set of core architectural tenets that provides a multifaceted approach to AMMOS system architecture modernization intended to address the information- and process-related issues. Each of these architectural tenets will be further explored in this paper. Ultimately, we envision the application of these core tenets resulting in a unified vision of a future-state architecture for the AMMOS-one that is intended to result in a highly adaptable, highly efficient, and highly cost-effective set of multimission MOS products and services.

Estefan, Jeff A.↗
NASA NTRS1992

Precise orbit determination of high-earth elliptical orbiters using differenced Doppler and ranging measurements

Recent advances in Deep Space Network station calibration methods have led to renewed interest in the use of differenced Doppler and range data types for interplanetary navigation. Described here is an orbit determination error analysis of the performance of these differenced data types when used with conventional two-way Doppler for precise navigation of High-Earth Orbiters. Three highly elliptical earth orbits are investigated, with apogee heights on the order of 20,000 km, 70,000 km, and 156,000 km. Results indicate that the most significant navigational accuracy improvements, relative to the performance obtained from two way Doppler alone, are achieved for the lowest altitude orbit by using differenced Doppler measurements with two way Doppler (assuming that spacecraft onboard downlink antennas have no ground footprint limitation in the near-apogee regime). In the case of the two higher altitude orbit accuracy improvements over Doppler-only performance, although less dramatic, are also achieved when differenced range measurements are combined with two-way Doppler.

Estefan, Jeff A.↗
NASA NTRS1992

Precise orbit determination of high-earth elliptical orbiters using differenced Doppler and ranging measurements

Recent advances in NASA's Deep Space Network station calibration methods have led to renewed interest in the use of differenced radiometric data types for interplanetary navigation, particularly differenced Doppler and range. An orbit determination error analysis which compares the performance of these differenced data types when used in concert with conventional two-way Doppler for precise navigation of high-earth orbiters is described. Three highly elliptical orbits are investigated, with apogee heights on the order of 20,000 km, 70,000 km, and 156,000 km. The analysis assumes that each orbiter's downlink antenna has no ground footprint limitation in the near apogee regime. Results indicate that the most significant navigational accuracy improvements are seen for the lowest-altitude orbit by using differenced Doppler measurements in conjunction with two-way Doppler. The results for the two higher-altitude orbits, although less dramatic, suggest that accuracy improvements can also be achieved when differenced range measurements are combined with two-way Doppler.

Estefan, Jeff A.↗