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Ellis, J.

Publications and source records attributed to Ellis, J..

62 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

An analysis of network deployment for a dedicated navigation tracking system

Stringent navigation accuracy requirements for future deep space missions are expected to be met by conventional two way radio metric data supplemented with Very Long Baseline Interferometric (VLBI) data provided by a dedicated tracking network. The performance of several proposed VLBI network configurations have been evaluated by comparing navigation capability for the probe delivery and post flight probe trajectory phases of the Galileo mission. Candidate configurations include stations located at the current intercontinental DSN sites, a network with sites in Hawaii, Florida and Washington, Regional (300 km) and a Micro (30 km) baseline systems. Sensitivity to systematic error sources, network deployment, viewing period and sampling strategy are investigated. The dominant factor in performance is shown to be the baseline length.

Ellis, J.↗
NASA NTRS1979

Large scale state estimation algorithms for DSN tracking station location determination

Estimation of precise tracking station locations for deep space navigation is based on combining state estimates derived from a multitude of planetary encounter missions with planet direction information provided by the planetary ephemeris. Procedures for reducing the dimensionality of the station location estimation problem and for analytically correcting estimates for ephemeris updates have been developed. Using Householder transforms the large scale state estimation problem is decomposed into a sequence of dynamically uncoupled problems of lower dimension. The effect of an ephemeris update is shown to be adequately approximated by Brouwer-Clemence Set III perturbations for the earth-moon barycenter and the target planet for each mission.

Ellis, J.↗
NASA NTRS1979

LS47: A DSN station location set compatible with JPL development ephemeris DE108

An updated Deep Space Network station location set, LS47, is presented which is compatible with JPL Development Ephemeris DE108. Analytic procedures for linearly correcting station spin axis and longitude estimates for an ephemeris update based on Brouwer-Clemence Set III parameters are briefly discussed. The validity of this technique is demonstrated by a comparison of a linearly corrected solution with one explicitly determined by reprocessing the data. A mission data base, including Viking 1 and 2 encounter data, is first used to obtain an updated DE96 compatible station location solution, LS46, which in turn is adjusted to form the DE108 solution, LS47. Improved station Z-heights are estimated by using available very long baseline interferometry data. Spin axis differences between LS46 and LS47 are relatively insignificant; however, the ephemeris change introduces a -0.8 x 10 to the -5 power degree rotation in the DE96 longitude ephemeris.

Ellis, J.↗
NASA NTRS1974

Orbit determination for a Jupiter orbiter tour of the Galilean satellites

Current NASA planning envisions an ambitious Jupiter tour mission which will arrive at the planet in the year, 1984. The objectives of this mission are to broaden our knowledge of the outer solar system and in particular to extend our understanding of the physical processes at work in the Jupiter and Galilean satellite environment. To achieve these goals, precise spacecraft navigation is a fundamental requirement inasmuch as very near encounters with the satellites are necessary both for the planned scientific investigations and to reduce fuel requirements necessary for orbital insertion about the planet. This paper, deals with problems of producing precise spacecraft state estimates relative to the Galilean satellites, with the aid of both earth-based radio and on-board video data.

Russell, R. K.↗
NASA NTRS1974

Outer planet mission guidance and navigation for spinning spacecraft

The orbit determination accuracies, maneuver results, and navigation system specification for spinning Pioneer planetary probe missions are analyzed to aid in determining the feasibility of deploying probes into the atmospheres of the outer planets. Radio-only navigation suffices for a direct Saturn mission and the Jupiter flyby of a Jupiter/Uranus mission. Saturn ephemeris errors (1000 km) plus rigid entry constraints at Uranus result in very high velocity requirements (140 m/sec) on the final legs of the Saturn/Uranus and Jupiter/Uranus missions if only Earth-based tracking is employed. The capabilities of a conceptual V-slit sensor are assessed to supplement radio tracking by star/satellite observations. By processing the optical measurements with a batch filter, entry conditions at Uranus can be controlled to acceptable mission-defined levels (+ or - 3 deg) and the Saturn-Uranus leg velocity requirements can be reduced by a factor of 6 (from 139 to 23 m/sec) if nominal specified accuracies of the sensor can be realized.

Paul, C. K.↗
NASA NTRS1973

Advanced Pioneer guidance and navigation requirements for outer planet missions

Three advanced Pioneer missions to the outer planets are analyzed to assess midcourse velocity and navigation requirements. Selecting the results of the Saturn/Uranus mission as representative values for the three missions, the Earth-Saturn midcourse mean plus 3-sigma velocity correction is 80 m/sec. Earth-based radio-only tracking results in a navigational error of 2000 km at Saturn which in turn requires a mean plus 3-sigma velocity correction of 140 m/sec on the Saturn-Uranus leg to nullify this error mapped to Uranus. In contrast to these figures, if a proposed optical V-slit sensor is incorporated into the spacecraft navigational system, a Saturn B-plane error of only 350 km results with a corresponding required mean plus 3-sigma post-Saturn velocity correction of 23.2 m/sec. An 8000 km miss at Uranus results from radio-only tracking at Saturn which can be considerably reduced to 1400 km by utilizing the optical sensor during the Saturn flyby.

Paul, C. K.↗