Engineering topics

Mclaughlin, W. I.

Publications and source records attributed to Mclaughlin, W. I..

At least 19 records

NASA NTRS1992

Galileo's progress

Data obtained to date by the Galileo spacecraft launched in October 1989 are discussed. It is noted that in April 1991 the spacecraft's high-gain antenna failed to deploy from its furled position. Since then, communications including return of images of the Gaspra asteroid have been performed through the low-gain antenna. It is considered to be possible to accomplish the majority of orbiter scientific objectives without the high-gain antenna including the return of high resolution images.

Mclaughlin, W. I.↗

NASA NTRS1992

Planetary mission operations

A high-level overview is presented of the process through which the uplink segment of NASA's prospective planetary missions will be instituted; the overview is supplemented by suggestions as to how costs can be reduced. Uplink costs constitute two-thirds of the total cost of operations. Attention is given to 'sequence loading', which is a time-lagged set of commands and supporting information that is prepared on the ground and uplinked to the spacecraft's onboard computer. The sequence is the primary guide used by the spacecraft to accomplish its mission; sequences are supplemented by real-time commands that are executed upon reception from the ground.

Mclaughlin, W. I.↗

NASA NTRS1991

Venus geology

The Magellan mission to Venus is reviewed. The scientific investigations conducted by 243-day cycles encompass mapping with a constant incidence angle for the radar, observing surface changes from one cycle to the next, and targeting young-looking volcanos. The topography of Venus is defined by the upper boundary of the crust and upwelling from lower domains. Tectonic features such as rift zones, linear mountain belts, ridge belts, and tesserae are described. The zones of tesserae are unique to the planet. Volcanism accounts for about 80 percent of the observed surface, the remainder being volcanic deposits which have been reworked by tectonism or impacts. Magellan data reveal about 900 impact craters with flow-like ejecta resulting from the fall of meteoroids. It is concluded that the age of the Venusian surface varies between 0 and 800 million years. Tectonic and volcanic activities dominate the formation of the Venus topography; such processes as weathering and erosion are relatively unimportant on Venus.

Mclaughlin, W. I.↗

NASA NTRS1990

Magellan orbits Venus

Various events surrounding Magellan's orbit of Venus are recounted. Significant events include the successful firing of a solid rocket motor while the spacecraft was behind Venus to transfer it from a solar-centered trajectory to an orbit around the planet. The spacecraft orbits Venus every 3.26 hours at a maximum altitude of 8500 km and minimum altitude of 291 km in an elliptical orbit. The successful August 16 test of the synthetic-aperture radar system is discussed, noting that it produced two strips, each about 20 km x 16,000 km, revealing details as small as 120 m. Two anomalies causing a delay in the start of mapping operations and subsequent breaks in the communication link with earth for 14.5 hours and 17.7 hours are discussed. Protective measures directed from the spacecraft's ROM during breach of contact are listed, and possible causes of the anomalies are suggested, such as solar activity or hardware or software elements, although the actual cause is not yet known.

Mclaughlin, W. I.↗

NASA NTRS1986

A SETI experiment

In order to increase the probability of contact in the search for extraterrestrial intelligence (SETI), it has been proposed to search more intensively in certain regions of the electromagnetic spectrum ('the water hole'). The present paper describes a similar narrowing of the search in the time domain. Application of this strategy results in the SETI experiments searching for signals from the Tau Ceti system late in 1986 and early in 1987, and from the Epsilon Eridani system in mid 1988.

Mclaughlin, W. I.↗

NASA NTRS1986

Display of celestial surveys conducted from orbit

Two methods are described for graphically displaying and numerically analyzing surveys of the celestial sphere as conducted by astronomical satellites. The methods are applicable to the design phase of a mission, for planning during operations, and for post-mission display of results. Both methods have been tested in use, including application to the Infrared Astronomical Satellite (IRAS).

Mclaughlin, W. I.↗

NASA NTRS1986

Voyager at Uranus

The engineering changes that had to be made in the Voyager 2 spacecraft in order to enable it to fly beyond the originally planned encounters with Jupiter and Saturn and the underlying engineering strategy leading to the encounter with Uranus are discussed. Fixes of the azimuth actuator failure, receiver failure, and memory failure, and capability upgrades of Image Data Compression, aperture augmentation protective coding, smear reduction, Image Motion Compensation, power management, and contingency planning are summarized. The use of the Computer Command Subsystem in the extension of the voyage is described. The ways in which the strategic priorities, including spacecraft preservation, protection of the near-encounter load, development of new ground and spacecraft capabilities, and repair or circumvention of existing spacecraft faults, were accomplished are reviewed, and the accomplishment of additional tasks is also discussed.

Mclaughlin, W. I.↗

NASA NTRS1985

Voyager at the seventh planet

The success of the Voyager 1 flyby of Titan permitted configuring the Voyager 2 trajectory for flybys of Uranus and Neptune. Satellite instruments will gather data on the Uranian atmosphere, rings, satellites and magnetosphere (if there is one). The observational sequences were coded for transmission to Voyager 2 in November 1985. Earlier commands have stabilized the spacecraft to avoid image smearing during the approach and have reduced the time of firing of the thrusters for course changes. Imaging data compression will economize on the degraded communications link to Voyager 2 and lower the demands on the slowly failing radiothermoelectric power supply. The encounter will take place in February 1986 and, should failure of the command link occur, be accompanied by carrying out of a preprogrammed set of observational and operational sequences lasting through a 1989 Neptune flyby.

Mclaughlin, W. I.↗

NASA NTRS1985

Voyager flight engineering - Preparing for Uranus

Two Voyager spacecraft are currently engaged in exploration of the outer solar system with Voyager 2 scheduled to conduct the first close-up investigation of the planet Uranus during the period November 4, 1985 through March 3, 1986. Flight engineering for the Voyager project has the objectives of delivering a functioning spacecraft containing observing sequences to the right places at the right times. Due to the changing environment as the mission has progressed outward from Jupiter to Saturn to Uranus (and on to Neptune), this engineering task has included the development of significant new capabilities. The paper utilizes the case-study method to examine some new spacecraft capabilities in three subsystems: data, attitude and articulation control, and power. The implementation of a new navigational data-type, delta DOR, is also reviewed. An overview is given of the Voyager sequencing process for the cruise and encounter phases with a case study focusing on late updating of part of the near encounter sequence. The prospective mission to Neptune is previewed.

Mclaughlin, W. I.↗

NASA NTRS1985

Kantian epistemology as an alternative to heroic astronomy

Theoretical and observational methods in astronomy have advanced to a point where certain of their outcomes are difficult to comprehend with the traditional categories of human knowledge. The philosophical discipline of epistemology, the theory of knowledge, is used here to address four current problems in observational astronomy, exobiology, cosmology, and quantum mechanics. The problems are united by an epistemological content which, when unrecognized, has resulted in some heroic solutions of an ad hoc nature. Kant's critical philosophy is employed because his work is consistent with basic attitudes in present-day physics and biology.

Mclaughlin, W. I.↗

NASA NTRS1984

Through the tail of a comet

The instrumentation, trajectory, and missions of the ISEE-3 spacecraft being sent to observe Comet Giacobini-Zimmer (GZ) are described. Originally parked at a libration point to observe the solar wind, ISEE-3 was directed to perform a complex series of flybys of the earth and the moon to move to a trajectory that will intersect the GZ tail in 1985. Renamed ICE, the spacecraft will record magnetic field and charged particle data on the interaction of the cometary tail with the solar wind.

Mclaughlin, W. I.↗

NASA NTRS1984

Starprobe - To confront the sun

Starprobe is an advanced-technology mission that is being planned for the purpose of making a very close approach to the sun; perhaps as near as four solar radii. The scientific experiments will accurately measure the solar quadrupole moment, conduct relativity experiments, measure the fields and particles environment, and image solar features at high resolution. An effective heat shield is required, and the communications system must be capable of returning data while the spacecraft is immersed in the noisy solar environment. The spacecraft's earth-inherited angular momentum will be removed for the drop into the sun by means of a close flyby of Jupiter.

Mclaughlin, W. I.↗

NASA NTRS1984

Final mission design for IRAS

The Infrared Astronomical Satellite (IRAS) was operated on orbit from 26 January to 22 November 1983 (GMT). Its primary purpose, successfully accomplished, was to conduct an all-sky survey in the infrared from 8 to 120 microns. The mission design for this project featured orbit selection; numerous exercises in the geometry of the sphere; computer simulation of mission, sky, and telescope; and an active interface with the IRAS Science Team. In addition to mission design, the subject of mission planning after launch is addressed. The paper makes extensive use of reference to other works on the topic and seeks to derive some general conclusions on the subject based upon the IRAS experience.

Mclaughlin, W. I.↗

NASA NTRS1983

Pathways of evolution for man and machine

A simplified model of the future is introduced in order to examine the relations between man, machine, and extraterrestrial intelligence. The observed lack of extraterrestrials on earth is used as a boundary condition for the model. Two exobiological conclusions are obtained: (1) advanced extraterrestrials exist but are difficult to observe or to distinguish from natural phenomena, (2) lower level, man-like extraterrestrials, which are potentially observable, are rare in the Universe because they are rapidly replaced in the evolutinary sequence by the intelligent machines which they create. The decline of man is inferred and may take place as soon as 100 years from now or as long as 100,000 years from the present time. Thus, we are a short-lived species, having a life expectancy of only a million years. A note is appended on the rationale and methods of the search for extraterrestrial intelligence in light of the above calculations. The Tau Ceti and Epsilon Eridani systems present favourable opportunities for a radio-search experiment in 1987 and 1988, respectively.

Mclaughlin, W. I.↗

NASA NTRS1983

Human evolution in the age of the intelligent machine

A systems analysis of the future evolution of man can be conducted by analyzing the biological material of the galaxy into three subsystems: man, intelligent machines, and intelligent extraterrestrial organisms. A binomial interpretation is applied to this system wherein each of the subsystems is assigned a designation of success or failure. For man the two alternatives are, respectively, 'decline' or 'flourish', for machine they are 'become intelligent' or 'stay dumb', while for extraterrestrial intelligence the dichotomy is that of 'existence' or 'nonexistence'. The choices for each of three subsystems yield a total of eight possible states for the system. The relative lack of integration between brain components makes man a weak evolutionary contestant compared to machines. It is judged that machines should become dominant on earth within 100 years, probably by means of continuing development of existing man-machine systems. Advanced forms of extraterrestrial intelligence may exist but are too difficult to observe. The prospects for communication with extraterrestrial intelligence are reviewed.

Mclaughlin, W. I.↗

NASA NTRS1981

The natural history of Halley's comet

The 1986 apparition of Halley's comet will be the subject of numerous space probes, planned to determine the chemical nature and physical structure of comet nuclei, atmospheres, and ionospheres, as well as comet tails. The problems of cometary origin remain inconclusive, with theories ranging from a purely interstellar origin to their being ejecta from the Galilean satellites of Jupiter. Comets can be grouped into one of two classes, depending on their periodicity, and statistical mechanics of the entire Jovian family of comets can be examined under the equilibrium hypothesis. Comet anatomy estimations have been determined, and there is speculation that comet chemistry may have been a factor in the origin of life on earth. Halley's comet was first noted using Newton's dynamical methods, and Brady (1972) attempted to use the comet as a gravitational probe in search of a trans-Plutonian planet. Halley's orbit is calculated by combination of ancient observations and modern scientific methods.

Mclaughlin, W. I.↗

NASA NTRS1980

Prediscovery evidence of planetary rings

The discoveries of the Uranian and Jovian ring systems were surprising events to most of the scientific community. However, as far back as 1787 reports of observations of rings about a planet other than Saturn were made; Herschel, the discoverer of Uranus, thought he had detected rings about that planet on several occasions. Although Herschel's observations were almost certainly due to defects in the optical system of his telescope, several valid observations and predictions have been made in the last two hundred years. This paper focuses on such prediscovery evidence for the Uranian and Jovian rings and for the newly designated F ring of Saturn. Some new work of the author on the structure of the Saturnian rings is included which is relevant to the F ring. The prospects for rings about Neptune and Pluto and a ring close to the Sun are also reviewed. The relevance of the prediscovery evidence to aspects of scientific methodology is discussed.

Mclaughlin, W. I.↗

NASA NTRS1980

Use of the transect method in satellite survey missions with application to the infrared astronomical satellite /IRAS/

The coverage of the celestial sphere or the surface of the earth with a narrow-field instrument onboard a satellite can be described by a set of swaths on the sphere. A transect is a curve on this sphere constructed to sample the coverage. At each point on the transect the number of times that the field-of-view of the instrument has passed over the point is recorded. This information is conveniently displayed as an integer-valued histogram over the length of the transect. The effectiveness of the transect method for a particular observing plan and the best placement of the transects depends upon the structure of the set of observations. Survey missions are usually characterized by a somewhat parallel alignment of the instrument swaths. Using autocorrelation and cross-correlation functions among the histograms the structure of a survey has been analyzed into two components, and each is illustrated by a simple mathematical model. The complex, all-sky survey to be performed by the Infrared Astronomical Satellite (IRAS) is synthesized in some detail utilizing the objectives and constraints of that mission. It is seen that this survey possesses the components predicted by the simple models and this information is useful in characterizing the properties of the IRAS survey and the placement of the transects as a function of celestial latitude and certain structural properties of the coverage.

Mclaughlin, W. I.↗