Engineering topics

Farless, D. L.

Publications and source records attributed to Farless, D. L..

8 records

NASA NTRS1986

The application of periodic orbits to TOPEX mission design

This report develops analytic techniques for the application of periodic earth orbits to the design of the Ocean Topography Experiment (TOPEX) mission. The TOPEX orbit design space is described in terms of altitude and inclination. Periodic orbits that lie within that space are determined. Specific inclinations are determined that place a ground track grid node over a point on the earth at which a radar altimeter verification site is located. The number of orbit revolutions between the two ground tracks that cross at this grid node are also calculated. Then, periodic orbits that place a ground track directly over two different verification sites are calculated and displayed in the TOPEX orbit design space. The results are used to decide on a specific orbit altitude and inclination set that satisfies TOPEX requirements.

Farless, D. L.↗

NASA NTRS1986

TOPEX/POSEIDON - Mapping the ocean surface

Global efforts are under way to model the earth as a complete planet so that weather patterns may be predicted on time scales of months and years. A major limitation in developing models of global weather is the inability to model the circulation of the oceans including the geostrophic surface currents. NASA will soon be initiating a satellite program to correct this deficiency by directly measuring these currents using the science of radar altimetry. Measurement of the ocean topography with broad, frequent coverage of all ocean basins for a long period of time will allow the derivation of the spatial and temporal behavior of surface ocean currents. The TOPEX/POSEIDON mission is a cooperative effort between NASA and the French Centre National d'Etudes Spatiales. This paper describes the goals of this research mission, the data type to be acquired, the satellite and sensors to be used to acquire the data, and the methods by which the data are to be processed and utilized.

Yamarone, C. A.↗

NASA NTRS1983

Galileo atmospheric entry probe mission description

The mission goals, control parameters, and instrumentation for the Galileo entry probe are described. The goal for the probe is to penetrate the Jovian atmosphere to 10 bars, begin data gathering and transmission at about 0.1 bar, and make as many in-situ cloud measurements as possible. The probe will pass through a 16,000 K shock layer, which has led to a ratio of 5 kg of heat shield to every kg of instrumentation on the probe. An entry angle between -7.0 to -10.2 deg will be used, and possible targets with respect to declinations associated with a 1986 launch are discussed. The preentry mission phase, entry/descent sequence, and the baseline mission relay link performance are outlined. Data may be available down to 20 bars, and the probe performance will aid in design goals for subsequent Saturn and Uranus probes.

Vojvodich, N. S.↗

NASA NTRS1979

Viking navigation

A comprehensive description of the navigation of the Viking spacecraft throughout their flight from Earth launch to Mars landing is given. The flight path design, actual inflight control, and postflight reconstruction are discussed in detail. The preflight analyses upon which the operational strategies and performance predictions were based are discussed. The inflight results are then discussed and compared with the preflight predictions and, finally, the results of any postflight analyses are presented.

Oneil, W. J.↗

NASA NTRS1979

Trajectory description

The launch, interplanetary, encounter, and Mars orbit phases of the Viking 1 and 2 spacecraft trajectories are described. Time history plots of several parameters relative to the trajectories are presented along with tables of the geocentric, heliocentric, aerocentric, and injection orbital elements appropriate to each of the spacecraft trajectories.

Farless, D. L.↗

NASA NTRS1979

Maneuver analysis

The maneuver design for Viking was accomplished in two phases. First, there was the preflight design and strategy development that was dictated by mission objectives and requirements. Orbit determination and maneuver execution accuracy statistics were used, together with propellant budget considerations, to determine specific maneuver requirements and strategies. The second phase of the maneuver design occurred in flight. The maneuver analyses that were performed in flight, the software that was employed, and the actual inflight results for the entire orbital phase of the nominal Viking Mission are described with emphasis on prelanding objectives and geometry considerations. The actual adaptive design and implementation of the maneuvers as the mission progressed are considered. This design process included the minimization of both propellant usage and the effects of maneuver execution errors, while complying with several mechanization constraints.

Mitchell, R. T.↗

NASA NTRS1978

Orbit trim maneuver design and implementation for the 1975 Mars Viking Mission

The Viking Mission included the insertion of two unmanned spacecraft into orbit about Mars and the deployment of a soft-lander from each. A description is presented of the adaptive design and implementation of the spacecraft propulsive maneuvers as these flights progressed, taking into account also the inflight results for the orbital phase of the primary Viking mission. The design process included the selection of target parameters and the minimization of both propellant usage and the effects of execution errors, while complying with mission and operational constraints. All maneuvers performed to trim the spacecraft orbits are considered. Attention is given to navigation requirements, geometry definitions and terminology, maneuver mechanization and constraints, and maneuver capability.

Hintz, G. R.↗

NASA NTRS1974

Maneuver strategies for the extended Pioneer 11 Jupiter/Saturn mission

The Jupiter-bound Pioneer 11 spacecraft was launched in April 1973, eight months before the Jupiter encounter of the front-running spacecraft, Pioneer 10. Near-Earth maneuvers placed Pioneer 11 on an interim flight path designed to retain a later retargeting capability to repeat the Pioneer 10 flyby geometry or encounter a wide variety of alternate Jupiter aimpoints, including one resulting in an extended five-year trajectory to Saturn. Pioneer 11 was retargeted to this aimpoint in April 1974, subsequent to the successful Pioneer 10 encounter in December 1973. This paper presents the retargeting and trimming maneuver strategies necessary to assure a productive Pioneer 11 Jupiter encounter in early December 1974, followed by a Saturn encounter in late 1979.

Frauenholz, R. B.↗