Engineering topics
Publications and source records attributed to Srinivasan, J..
We will discuss a new data assimilation model of ionosphere, the Global Assimilative Ionosphere Model (GAIM), capable of integrating measurements from GPS and other sensors with a physics-based ionospheric model, to provide detailed global nowcasts of ionospheric structure, useful for science and applications.
In this article we describe the developments in the third and last year of this effort, and discuss the current status of the system and its potential future evolution.
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The StarLight Mission, an element of NASA's Origins Program, was designed for first-time demonstration of two technologies: formation flying optical interferometry between spacecraft and autonomous precise formation flying of an array of spacecraft to support optical interferometry. The design overview and results of the technology effort are presented in this paper.
They present an overview of long-life reconfigurable processor technologies and of a specific architecture for implementing a software reconfigurable (software-defined) network processor for space applications.
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The BlackJack family of GPS receivers has been developed at JPL to satisfy NASA's requirements for high-accuracy, dual-frequency, Y-codeless GPS receivers for NASA's Earth science missions. In this paper we will present the challenges that were overcome to meet this accuracy requirement. We will discuss the various reduced dynamic strategies, Space Shuttle dynamic models, and our tests for accuracy that included a military Y-code dual-frequency receiver (MAGR).
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A recent Mars Exploration Program Architecture Definition Study, conducted by NASA with strong international participation, recommands establishment of a low cost in-situ communications and navigation relay satellite network to provide enabling and enhancing support for the international exploration of Mars.
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In February 1998 Student Nitric Oxide Explorer (SNOE) was successfully launched and began scientific observations.
Three years ago, facing a growing list of stringent navigation science requirements for future low-cost Earth missions, NASA began a program to develop a new high performance spaceborne GPS receiver.
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We describe results from an experiment in which TDRS and GPS satellites were tracked simultaneously from a small (3 station) ground network in the western United States. We refer to this technique as 'GPS-like tracking' (GLT) since the user satellite - in this case TDRS - is essentially treated as a participant in the GPS constellation. In the experiment, the TDRS K(sub space-to-ground link (SGL) was tracked together with GPS L-band signals in enhanced geodetic-quality GPS receivers (TurboRogue). The enhanced receivers simultaneously measured and recorded both the TDRS SGL and the GPS carrier phases with sub-mm precision, enabling subsequent precise TDRS orbit determination with differential GPS techniques. A small number of calibrated ranging points from routine operations at the TDRS ground station (White Sands, NM) were used to supplement the GLT measurements in order to improve determination of the TDRS longitude. Various tests performed on TDRS ephemerides derived from data collected during this demonstration - including comparisons with the operational precise orbit generated by NASA Goddard Space Flight Center - provide evidence that the TDRS orbits have been determined to better than 25 m with the GLT technique.
An experimental system, called GPS-like tracking, was used to track TDRS and GPS satellites simultaneously from a small (3 station) ground network. Comparison with the operational precise orbit indicates that GLT determined the TDRS orbit to within 25 m.