Engineering topics

Bryant, W. C., Jr.

Publications and source records attributed to Bryant, W. C., Jr..

4 records

NASA NTRS1977

A geostationary longitude acquisition planning algorithm

The paper is concerned with the phase of the geosynchronous mission termed station acquisition, which involves the maneuvering of a spacecraft to its geostationary longitude by means of the spacecraft propulsion system. An algorithm which assists in maneuver planning is described, and examples of its use are presented. The algorithm can be applied when sequences of more than three maneuvers are to be expected. While, in general, three maneuvers are sufficient to achieve the desired end conditions when orbital mechanics are the only consideration, operational considerations may add constraints resulting in an increased number of maneuvers required.

Petruzzo, C. J.↗

NASA NTRS1975

A study of orbit determination accuracies for future earth observatory missions

It is anticipated that global orbital accuracies of 10 meters will be required for future earth observatory missions. Results are presented of a study of the LANDSAT-1 orbit to determine position accuracies obtainable today so as to assess what future advancements are necessary to meet a 10-meter goal. Accuracies of 50 meters were determined to be achievable now from two-day tracking arcs. One-half-day arcs yield accuracies of about 30 meters. The dominant error source was found to be geopotential model uncertainty. All other systematic errors produced less than 10 meters total position error.

Bryant, W. C., Jr.↗

NASA NTRS1974

Lunar gravity analysis results from Explorer-49

An analysis of the lunar gravity field utilizing 234 days of Explorer-49 mean Keplerian elements is presented. A third-degree and third-order gravity model developed at the Goddard Space Flight Center (GSFC) for mission operations is compared with published models derived from Lunar Orbiter data. Improved predictions of e and Omega using the GSFC model are observed. The results suggest that use of Explorer-49 orbital data in a multisatellite solution would lead to improved global estimates of low-order spherical harmonic coefficients of the lunar gravitational potential.

Bryant, W. C., Jr.↗

NASA NTRS1973

Tracking and orbit determination of near earth orbiting satellites using earth synchronous relay satellites

A Tracking Data Relay Satellite System (TDRSS) made up of two earth synchronous data relay satellites is proposed for the late 1970s to aid in the tracking, or take the place of ground tracking, or near-earth orbiters. Theoretical error analysis studies were conducted to evaluate the TDRSS concept of tracking user satellites. All major factors affecting orbit determination accuracy were considered in the analysis, including tracking system and dynamic modeling errors.

Bryant, W. C., Jr.↗