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All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Feasibility study of low angle planetary entry

The feasibility of a Jovian entry by a probe originally designed for Saturn and Uranus entries is examined. An entry probe is described which is capable of release near an outer planet's sphere of influence and descent to a predetermined target entry point in the planet's atmosphere. The probe is designed so as to survive the trapped particle radiation belts and an entry heating pulse. Data is gathered and relayed to an overflying spacecraft bus during descent. Probe variations for two similar missions are described. In the first flyby of Jupiter by a Pioneer spacecraft launched during the 1979 opportunity is examined parametrically. In the second mission an orbiter based on Pioneer and launched in 1980 is defined in specific terms. The differences rest in the science payloads and directly affected wiring and electronics packages.

Defrees, R. E.↗
NASA NTRS1974

Program manual for HILTOP, a heliocentric interplanetary low thrust trajectory optimization program. Part 1: User's guide

A performance-analysis computer program, that was developed explicitly to generate optimum electric propulsion trajectory data for missions of interest in the exploration of the solar system is presented. The program was primarily designed to evaluate the performance capabilities of electric propulsion systems, and in the simulation of a wide variety of interplanetary missions. A numerical integration of the two-body, three-dimensional equations of motion and the Euler-Lagrange equations was used in the program. Transversality conditions which permit the rapid generation of converged maximum-payload trajectory data, and the optimization of numerous other performance indices for which no transversality conditions exist are included. The ability to simulate constrained optimum solutions, including trajectories having specified propulsion time and constant thrust cone angle, is also in the program. The program was designed to handle multiple-target missions with various types of encounters, such as rendezvous, stopover, orbital capture, and flyby. Performance requirements for a variety of launch vehicles can be determined.

Mann, F. I.↗
NASA NTRS1975

Pioneer 11's encounter with Jupiter and mission to Saturn

Plans for Pioneer 11's approach to Saturn are described. A flyby somewhat parallel to the ring plane is being proposed as an interim target, with a future option held for a possible high risk (or suicide) plunge through the nearly transparent space between Saturn and its rings.

Dyer, J. W.↗
NASA NTRS1974

Interplanetary spacecraft design using solar electric propulsion

Emphasis of the electric propulsion technology program is now on the application of solar electric propulsion to scientific missions. Candidate planetary, cometary, and geosynchronous missions are being studied. The object of this paper is to describe a basic spacecraft design proposed as the means to accomplish (1) a comet Encke slow flyby, (2) a comet Encke rendezvous, and (3) an out-of-the-ecliptic mission. The discussion includes design differences foreseen for the various missions and indicates those areas where spacecraft design commonality is possible. Particular emphasis is placed on a solar electric propulsion module design which permits an attractive degree of design inheritance from mission to mission.

Duxbury, J. H.↗
NASA NTRS1974

The Mariner Jupiter/Saturn 1977 mission

A dual flyby mission to the planets and satellite systems of Jupiter and Saturn is being planned for Fall 1977 launch. Two Mariner spacecraft, fully attitude-stabilized and carrying about 90 kg of instruments to support some eleven experiments, will make interplanetary measurements for a minimum of about four years. They will spend several weeks investigating the planets and several of their satellites at close range, using TV cameras, ultraviolet and infrared spectrometers, and a variety of other scanning instruments, field and particle sensors, and radio devices. The mission and equipment designs are described in terms of the integrated plan for a thorough and coordinated scientific exploration of the two planetary systems.

Schurmeier, H. M.↗
NASA NTRS1974

Approach guidance for outer planet Pioneer missions

An overall parametric system analysis of the use of an optical approach guidance measurement system (using a V-slit electrooptical 'star-pipper') onboard a Pioneer-type spin-stabilized spacecraft for outer planet missions. Optical measurements of satellites of Saturn and Uranus against the star background are considered. Measurement geometry and spacecraft attitude are evaluated in depth with respect to two Pioneer missions: Saturn-Uranus and Jupiter-Uranus atmospheric entry probe missions with departure from Earth in November/December, 1980. A preliminary evaluation of long-term attitude stability measurements of Pioneer 10 is presented in the Appendix. The major conclusions are: (1) at Saturn flyby, viewing some medium period satellites can provide the best measurement results. (2) At Uranus approach, viewing the planet may give best measurements if early bus-probe separation is required. (3) Final measurement accuracy depends on the data format transmitted to Earth and the applied data interpretation techniques.-

Bejczy, A. K.↗
NASA NTRS1974

Planetary spacecraft in the U.S. program

In the U.S. program for the exploration of the solar system, the Pioneer spacecraft are used for initial studies of the planets and the planetary and interplanetary environment. The Mariners have been employed for planet-oriented flyby missions followed by more detailed planet investigations with orbiting missions. The Viking lander is designed for surface exploration of the planet Mars. The various planetary missions conducted so far or planned for the next few years are discussed in some detail, giving attention also to the design of the spacecraft employed.

Kraemer, R. S.↗
NASA NTRS1975

Imaging on ballistic missions to comet Encke

Imaging for navigation and science has been studied for a 1980 Encke flyby at 0.4 to 0.8 AU from the sun with spinning and three-axis spacecraft. Trajectory errors, maneuvers, encounter geometry, imaging performance, and data transmission were considered. Onboard comet sightings are needed for navigation. Recommended for a three-axis spacecraft are two vidicon cameras and a nucleus sensor for closed-loop pointing control. The cameras are essentially the Mariner 9 and Mariner 10 instruments; the nucleus sensor is an updated version of a sensor flown on Mariners 6 and 7. For a spinning spacecraft, a framing camera using a charge-coupled device and a spin-scan photometer are proposed. The framing camera would be a new design; it would not be despun, but the spin axis should point along the comet-centered velocity vector. The photometer is essentially that flown on Pioneer 10 and 11.-

Jaffe, L. D.↗
NASA NTRS1974

Future NASA plans for the exploration of the terrestrial and planetary atmospheres

A brief outline of NASA's space exploration plans for the 1970s is given. Research of the upper atmosphere and near-earth space will slack off in comparison with that which was done in the past, although now missions with very specific tasks will be launched, instead of those intended to get a general picture of these regions. Space Shuttle and Spacelab will open up the possibility of using the ionosphere as a huge plasma laboratory without walls. Exploration of other planets will continue with the Mars Lander and Viking Lander, the Pioneer-Venus program, and flybys of Jupiter and Saturn.

Bauer, S.↗
NASA NTRS1975

Statistical analysis of trim maneuvers in low thrust interplanetary navigation

An analytical technique for the statistical analysis of a low thrust trim maneuver in interplanetary navigation has been developed. The maneuver is treated rigorously as a nonlinear function of the trajectory errors to be removed, and the corresponding nongaussian statistics are developed. The method determines the statistical properties of the maneuver direction and duration, as well as the final state dispersion covariance. The analytical technique is applied to the terminal maneuver in a 1980 Encke slow flyby mission and is found to yield accurate statistical results with much less effort than Monte Carlo simulation. The method permits consideration of a shorter terminal maneuver than does linear analysis, with a consequent improvement in delivery accuracy.

Rinker, G. C.↗
NASA NTRS1975

Saturn's rings and Pioneer 11

Quantitative predictions of the diffuse reflection and transmission properties of Saturn's rings, relevant to the September 1979 Pioneer 11 flyby, are presented. Predictions are based on an elementary anisotropic scattering model. Interparticle separations are considered to be sufficiently large that mutual shadowing is negligible. Likely ranges in both the single scattering albedo and perpendicular optical thickness of the ring are considered. Situations of pronounced back-scattering and of isotropic scattering are treated individually. Spacecraft measurement of the radiation suffering diffuse scattering by the ring can provide a useful test of the basic ring model.

Price, M. J.↗
NASA NTRS1975

Acquisition and description of Mariner 10 television science data at Mercury

The Mariner 10 television science subsystem was an improved version of the Mariner 9 system, using 1500-mm-focal-length optics. An elaborate picture-taking sequence resulted in transmission of over 4000 frames back to earth during two flyby encounters with Mercury. These sequences utilized a real-time data rate of 117.6 kbit/s, resulting in coverage of about 75% of the lighted portion of Mercury's surface at a resolution of better than 2 km. The complete set of useful images, which amounted to about 3000 frames, was processed with three different types of digital image-processing enhancements.

Danielson, G. E., Jr.↗
NASA NTRS1975

The MVM imaging system and its spacecraft interactions

The present work describes the main considerations and steps taken in determining the functional design of the imaging system of the Mariner Venus/Mercury (MVM) spacecraft and gives examples of some of the interactions between the spacecraft and the imaging instrument during the design and testing phases. Stringent cost and scheduling constraints dictated the use of the previous Mariner 9 dual-camera TV system. The TV parameters laid the groundwork for the imaging definition. Based on the flyby distances from Venus and Mercury and the goal of surface resolution better than 500 meters per sample pair, calculation was performed on focal length, format size, planetary coverage, and data rates. Some problems encountered in initial mechanical operation and as a result of spacecraft drift during the mission are also discussed.

Vescelus, F. E.↗
NASA NTRS1975

Our present view of Mercury and Venus

The discipline of planetology received a quantum jump in new information on the planets Mercury and Venus from the Mariner 10 spacecraft. A detailed look at the ultraviolet markings in the upper atmosphere of Venus and their attendant motion has stimulated a considerable reevaluation of theories concerning the circulation, composition, and nature of this planet's upper atmosphere. The geologic history of Mercury as revealed by Mariner 10's television science data, from two close flybys, has challenged the prevalent theories of planetary evolution. The Mercury surface morphology and optical properties resemble those of the moon and seem to record a similar sequence of events despite their differences in density and proximity to both the sun and the asteroid belt.

Danielson, G. E., Jr.↗
NASA NTRS1975

Effects of turbulence on radio-occultation scale heights

It is shown that turbulent scattering can produce a spurious value for the radio-occultation-derived scale height of a planetary atmosphere. Application to the Jovian atmosphere indicates that recent measurements obtained during the flyby of Pioneers 10 and 11 can be substantially affected if suitable large-amplitude turbulence is present. Other implications of this possibility are briefly discussed.

Hubbard, W. B.↗
NASA NTRS1975

Mariner Jupiter/Saturn 1977 navigation strategy

This paper presents selected navigational aspects of the Mariner Jupiter/Saturn 1977 mission. Emphasis is given to the trajectory correction strategy. In addition to science return and propellant costs, specific considerations affecting the strategy include a large number of candidate trajectories, relatively close satellite flybys, use of trajectory correction maneuvers for trajectory shaping, and the requirement for an optical data type to achieve precision satellite encounters. Finally, important error sources and mission constraints are identified, and their impact on the strategy is discussed.

Mckinley, E. L.↗
NASA NTRS1975

Planetary exploration - Earth's new horizon /12th von Karman Lecture/

The article gives an account of the history of unmanned exploration of the planets of the solar system, including both earthbound exploration and exploration with spacecraft. Examples of images of the Martian surface are presented along with images obtained in Jupiter and Mercury flybys. Data are presented on the growth of US launch vehicle performance capability, navigation performance, and planetary data rate capability. Basic information regarding the nature of the scientific experiments aboard the Pioneer and Viking spacecraft is given. A case is put forward for the ongoing exploration of the planets as a worthwhile endeavor for man.

Schurmeier, H. M.↗
NASA NTRS1977

Geodetic control net

Computer program, originally developed for Mariner flyby missions, computes planetary control net from measurements of topographical features identified on television pictures. Program solves for areocentric coordinates of 115 surface points and orthogonal camera matrices of 57 far and near encounter pictures.

Davies, M. E.↗