Cassini navigation during solar conjunctions via removal of solar plasma noise
The Cassini spacecraft and its ground segment are currently testing a novel radio frequency multilink technology to perform radio science experiments.
navigation↗
Engineering topics
Ekelund, J. E.
Publications and source records attributed to Ekelund, J. E..
A gravity field to support Magellan navigation and science at Venus
The development and validation of the revised JPL Venus Gravity Model are described with attention given to the incorporation of data regarding the longitudinal coverage. The motivation for the JPL Venus Gravity Model 1B (VGM1B) is related to the determination of orbit-support requirements for the Magellan mission. Existing gravity models for Venus are reviewed, and the present model is based on orbit-prediction data taken from Doppler tracking data from the Pioneer Venus Orbiter (PVO). Revised information arrays are developed incorporating more complete data describing the longitudinal conditions of the gravity field. Improvements are noted in the Doppler residual statistics taken from field-validation fits to the PVO and Magellan tracking data by using the VGM1B harmonic field. The VGM1B gravity field is also shown to reduce the trajectory errors from PVO and Magellan navigation.
Mcnamee, J. B.↗
A program for the accurate generation of ephemerides for Halley's Comet
This is a discussion of an orbit determination computer program designed at the Jet Propulsion Laboratory to support the International Halley Watch and the European Space Agency's Giotto flight project to comet Halley. The program processes observational data received from the Astrometric Network of the International Halley Watch for the purpose of generating very accurate, up-to-date cometary ephemerides for Halley. An accurate comet ephemeris is essential if the Giotto spacecraft is to be navigated closely enough to the comet to satisfy its encounter objectives. Features discussed include the modelling of the nongravitational properties of Halley and the associated variational equations. The software has been implemented on several computers including the Honeywell and Siemens computers at the European Space Operations Center in Darmstadt, West Germany.
Ekelund, J. E.↗
Trajectory Analysis and the Orbit Determination
Two programs aid in trajectory analysis. DPTRAJ, ODP and their supporting utility programs capable of handling massive amounts of data and performing numerical calculations required for solving navigation problems associated with planetary fly-by and lander missions. Used extensively in support of Voyager.
Alderson, D. J.↗
The JPL orbit determination software system
The Jet Propulsion Laboratory (JPL) orbit determination software system is described. Consisting of a set of computer programs, this system has been developed at JPL for the primary purpose of determining the flight path of deep-space mission spacecraft in NASA's planetary program. Secondary uses include science studies in celestial mechanics and extraterrestrial atmospherics. Attention is given to such features as the capability for processing 30 data types from up to 15 tracking stations, and for precise navigation to natural satellites of outer planets. In addition, the system contains models for such conditions as mascons, atmospheric drag, attitude control, and finite motor burns, to provide for extensive solve-on capabilities.
Ekelund, J. E.↗