Engineering topics

Bergam, M. J.

Publications and source records attributed to Bergam, M. J..

4 records

NASA NTRS1987

Planning Orbiter Flights

Shuttle Mission Design and Operations Software (SMDOS) assists in design and operation of missions involving spacecraft in low orbits around Earth by providing orbital and graphics information. SMDOS performs following five functions: display two world and two polar maps or any user-defined window 5 degrees high in latitude by 5 degrees wide in longitude in one of eight standard projections; designate Earth sites by points or polygon shapes; plot spacecraft ground track with 1-min demarcation lines; display, by means of different colors, availability of Tracking and Data Relay Satellite to Shuttle; and calculate available times and orbits to view particular site, and corresponding look angles. SMDOS written in Laboratory Micro-systems FORTH (1979 standard)

Harris, H. M.↗

NASA NTRS1982

Comparison of starting values for iterative solutions to a universal Kepler's equation

General starting values for the iterative numerical solution of a universal Kepler's equation for position in a conic orbit at a specified time are investigated. Three starting values based on recent refinements of previously obtained bounds on the solution are derived and tested numerically. Of these, a simple starting value based on a cubic approximation to Kepler's equation provides the most rapid convergence using both first and second order Newton algorithms. The performance of the starting values are compared with similar studies which used the restricted case of elliptical orbits with the initial epoch at periapse.

Bergam, M. J.↗

NASA NTRS1982

Navigation system design for a Halley sample return mission

A ballistic sample return mission to Comet Halley was recently considered by the United States. This paper describes the navigation system and the navigation strategy which would have been employed in such a mission, assuming a launch in August of 1985, an arrival at the comet in March of 1986, and a return to earth in August of 1989. Estimates of spacecraft comet- and earth-relative orbit determination accuracies are presented as functions of time. Target-relative delivery accuracies for the spacecraft and associated trajectory correction maneuver requirements are presented also.

Wood, L. J.↗

NASA NTRS1981

Estimation of solar gravitational harmonics with Starprobe radiometric tracking data

The potential gravitational science return of a proposed spacecraft mission, called Starprobe, is investigated. The current mission plan is to place a spacecraft in a highly eccentric, highly inclined solar orbit with a perihelion distance of four solar radii. A covariance analysis based on Kalman filtering theory is performed to predict the accuracies with which gravitational parameters associated with the nonsphericity of the sun and relativistic effects can be estimated with radiometric tracking data. The accuracies are computed as functions of the quality and quantity of the radiometric data, the orbital parameters, the magnitude and character of the nongravitational accelerations acting on the spacecraft, and the errors in the tracking station locations and the ephemeris of the earth relative to the sun.

Mease, K. D.↗