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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
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NASA NTRS1974

Dynamic techniques for studies of secular variations in position from ranging to satellites

Satellite laser range measurements were applied to the study of latitude variation arising from polar motion, and the solid-earth and ocean tidal distortion of the earth's gravity field. Experiments involving two laser tracking stations were conducted. The relative location of one station with respect to the other was determined by performing simultaneous range measurements to a satellite from two stations several hundred kilometers apart. The application of this technique to the San Andreas Fault Experiment in California is discussed. Future capabilities of spacecraft equipped with laser retroreflectors include: (1) determination of the product of the earth's mass and gravitational constant; (2) measurement of crustal and tectonic motions; (3) determination of the elastic response of the solid-earth tidal forces; (4) measurement of the amplitudes and phase of certain components of the ocean tides; and (5) self-monitoring of the latitude and height variations of the tracking station.

Smith, D. E.↗
NASA NTRS1973

Orientation of the moon by numerical integration

The differential equations of rotational motion of the moon are solved by numerical integration methods. Euler's dynamical equations transformed to a convenient form are treated by techniques analogous to ordinary orbit determination procedures. The proposed method is fully consistent with the ephemeris of the moon and can utilize a variety of observational material for the solution of the selected parameters. Examples are given of comparison between the proposed method and Eckhardt's 1970 model of the physical librations of the moon. The merits of the new method are discussed in the light of conventional data sources like earth-based or satellite-based photography as well as newly available data types like laser ranging to retroreflectors on the moon.

Papo, H. B.↗
NASA NTRS1972

Second generation timing system for ranging experiment Apollo lunar laser

The status of the timing electronics for the lunar laser ranging station in Hawaii is discussed. The aim of the experiment is to measure, with high accuracy, the distance from a fixed point on earth to a retroreflector array which was placed on the lunar surface. The operating procedure for conducting the experiment is described. The components of the system are analyzed to show the effectiveness and accuracy of the facility.

Currie, D. G.↗
NASA NTRS1974

Laser geodynamic satellite thermal/optical/ vibrational analyses and testing. Volume 2: Technical report, book 1

The results of the LAGEOS thermal/optical/vibrational analysis and test program are reported. Through analyses and tests it is verified that the MSFC LAGEOS design provides a retroreflector thermal environment which maintains acceptable retroflector internal thermal gradients. The technical results of the study, organized by the major task areas are presented. The interrelationships of the major tasks are described and the major decisions are identified.

Source record↗
NASA NTRS1975

Satellite laser ranging work at the Goddard Space Flight Center

Laser ranging systems, their range and accuracy capabilities, and planned improvements for future systems are discussed, the systems include one fixed and two mobile lasers ranging systems. They have demonstrated better than 10 cm accuracy both on a carefully surveyed ground range and in regular satellite ranging operations. They are capable of ranging to all currently launched retroreflector equipped satellites with the exception of Timation III. A third mobile system is discussed which will be accurate to better than 5 cm and will be capable of ranging to distant satellites such as Timation III and LAGEOS.

Mcgunigal, T. E.↗
NASA NTRS1974

Progress in laser ranging to satellites - Achievements and plans

Theoretical and mathematical considerations involved in the design of retroreflectors for the GEOS-C and Timation III laser ranging satellites are described, laser ranging systems used by the Goddard Space Flight Center are reviewed, and planned systems changes are outlined. Equations are derived for the design of a cube corner array on a gravity gradient stabilized satellite in a circular orbit, and the required cube corner for GEOS-C is computed. Use of fixed threshold triggers and electronic and analytic pulse height compensation in present laser ranging systems is discussed. Proposed changes are outlined, including the incorporation of split gate triggers and trackers into the ranging systems and the use of analog and digital centroid measurement techniques. A theoretical consideration of the effects of velocity aberration on the reflected light beam is appended.

Plotkin, H. H.↗
NASA NTRS1974

Apollo scientific experiments data handbook

A brief description of each of the Apollo scientific experiments was described, together with its operational history, the data content and formats, and the availability of the data. The lunar surface experiments described are the passive seismic, active seismic, lunar surface magnetometer, solar wind spectrometer, suprathermal ion detector, heat flow, charged particle, cold cathode gage, lunar geology, laser ranging retroreflector, cosmic ray detector, lunar portable magnetometer, traverse gravimeter, soil mechanics, far UV camera (lunar surface), lunar ejecta and meteorites, surface electrical properties, lunar atmospheric composition, lunar surface gravimeter, lunar seismic profiling, neutron flux, and dust detector. The orbital experiments described are the gamma-ray spectrometer, X-ray fluorescence, alpha-particle spectrometer, S-band transponder, mass spectrometer, far UV spectrometer, bistatic radar, IR scanning radiometer, particle shadows, magnetometer, lunar sounder, and laser altimeter. A brief listing of the mapping products available and information on the sample program were also included.

Eichelman, W. F.↗
NASA NTRS1975

Spaceborne Earth Applications Ranging system (SPEAR)

A technique is discussed for the accurate (i.e. to within fractions of cm/yr) detection of earth surface motions utilizing the latest space technology. It is shown that over a six day period and assuming a 50% cloud cover (as experienced over the last few years of laser operation) utilizing spaceborne precision ranging systems, intersite distances on the order of 5 to 15 km can be determined in the vertical and horizontal components with errors in the 0.5 to 1.5 cm range. These errors are almost independent of ground survey errors up to 0.25 meters and orbit errors up to 200 meters. A spaceborne laser ranging system is assumed to range simultaneously to two or more ground emplaced retroreflectors. The fundamental advantage derived from simultaneous ranging is the elimination to first order of errors due to the system. This means elimination of bias errors in the ranging system, errors due to propagation effects, and errors associated with the spacecraft's motion in its orbit.

Vonbun, F. O.↗
NASA NTRS1976

Optical alignment device

A patent application was presented for an invention whose principal objective is the provision of an improved alignment device for observing the degree of coalignment of a pair of objects. The device includes a beamsplitter to be interposed between a pair of objects for observing the degree of coalignment. Light from one of the objects is reflected from the beamsplitter into a retroreflector which reflects the light back through the beamsplitter into an imaging system. Light from the other object is reflected from the beamsplitter into the same imaging system. The amount of displacement of the two images is inversely related to the degree of coalignment of the two objects. The optical alignment device is useful for aligning a mirror with an object, two objects or two mirrors.

Thomas, N. L.↗
NASA NTRS1976

Ultraviolet absorption experiment MA-059

The ultraviolet absorption experiment performed during the Apollo Soyuz mission involved sending a beam of atomic oxygen and atomic nitrogen resonance radiation, strong unabsorbable oxygen and nitrogen radiation, and visual radiation, all filling the same 3 deg-wide field of view from the Apollo to the Soyuz. The radiation struck a retroreflector array on the Soyuz and was returned to a spectrometer onboard the Apollo. The density of atomic oxygen and atomic nitrogen between the two spacecraft was measured by observing the amount of resonance radiation absorbed when the line joining Apollo and Soyuz was perpendicular to their velocity with respect to the ambient atmosphere. Information concerning oxygen densities was also obtained by observation of resonantly fluorescent light. The absorption experiments for atomic oxygen and atomic nitrogen were successfully performed at a range of 500 meters, and abundant resonance fluorescence data were obtained.

Donahue, T. M.↗
NASA NTRS1975

Satellite laser ranging work at the Goddard Space Flight Center

The pulsed-laser satellite ranging systems presently being operated by the Goddard Space Flight Center are described along with their range and accuracy capabilities. The major subsystems are outlined, operation of the fixed system and the two mobile systems is discussed, and the performance of all three systems is evaluated. It is noted that these systems have an accuracy of better than 10 cm on a carefully surveyed range as well as in regular satellite ranging operations and are capable of ranging to all currently launched retroreflector-equipped satellites with the exception of Timation III. Future improvements discussed include a third mobile system which will be able to range distant satellites, such as Timation III, with an accuracy of better than 5 cm and the use of a frequency-doubled Nd:YAG laser in place of the ruby lasers now being employed.

Mcgunigal, T. E.↗
NASA NTRS1976

Remote measurements of ambient air pollutants with a bistatic laser system

The ambient air pollutants ozone, nitric oxide, and ethylene have been monitored in the Pasadena area with a bistatic IR laser apparatus. These pollutants were measured with a differential absorption technique, using selected wavelengths in the 9.5-, 5.2-, and 10.5-micron regions, respectively. The transmitted laser radiation was detected using both direct and heterodyne detection techniques. In the direct detection case, cube corner retroreflectors provided the return, and the heterodyne detection responded to scattered radiation from various rough surfaces, ranging from 400 m to 1.9 km in distance from the apparatus. Significant departures from ambient background concentration levels were noticed in the region near a local freeway during periods of moderate and heavy traffic.

Menzies, R. T.↗
NASA NTRS1976

An estimate of the geodetic accuracy attainable with a transportable lunar laser station

A transportable lunar laser ranging station can be expected to measure the range to the lunar corner retroreflectors from a site on the earth's surface with an uncertainty of about 3 cm. The accuracy with which that station can infer its geocentric position is influenced by many factors including the uncertainties in the pole position and rotation rate of the earth and the data loss due to weather. The results of a simplified modeling study intended to include these factors are presented in cartographic form. The modeling indicates that, assuming the successful operation of three or more widely separated fixed laser stations, the transportable station will be able to determine its relative geocentric position in all three coordinates with an accuracy comparable to the original range uncertainty.

Silverberg, E. C.↗
NASA NTRS1977

High-accuracy range measurements to the moon

The lunar ranging station at the University of Texas McDonald Observatory has made more than 1800 range measurements to the four lunar retroreflectors during the first six years of its operation. Each range consists of a normal point constructed of from 5 to 20 single photoelectron returns. Normal point accuracies to about four parts in 10 to the tenth plus or minus 10 cm have become routine. The availability of excellent commercial timing equipment means that the error for such a measurement is primarily dependent on the width of the transmitted laser pulse. Second generation systems using mode-locked subnanosecond lasers can probably achieve routine normal point accuracies approaching one part in 10 to the tenth plus or minus 2 cm. High speed pockel cells may permit such accuracies to be realized with conventional Q-switched lasers.

Silverberg, E. C.↗
NASA NTRS1977

Spaceborne earth applications ranging system /SPEAR/

A technique is discussed for the accurate (i.e., to within fractions of centimeters per year) detection of earth surface motions utilizing the latest space technology. It is shown that, over a six-day period and assuming a 50% cloud cover (i.e., as experienced over the past few years of laser operation), by using spaceborne precision ranging systems, intersite distances on the order of 5 to 15 km (dependent mostly on the beam width of the laser) can be determined in the vertical and horizontal components, with errors in the 0.5- to 1.5-cm range. These errors are almost independent of ground survey errors up to 0.25 m and orbit errors up to 200 m. A spaceborne laser ranging system is assumed to range to two or more ground-emplaced retroreflectors. This can be done either in a simultaneous or nonsimultaneous mode. Hardware is under development for the latter technique.

Vonbun, F. O.↗
NASA NTRS1977

Correction of laser tracking data for the effects of horizontal refractivity gradients

Pulsed laser ranging systems are being used to measure accurately the distance from the earth to retroreflector equipped satellites. At the lower elevation angles horizontal refractivity gradients can introduce centimeter level errors into the range measurements. A correction formula which compensates for the gradient effects is developed and evaluated using typical meteorological data obtained from weather stations located near Washington, D.C.

Gardner, C. S.↗