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Encke's method as modified by Potter to increase the accuracy of orbit computations of gravitationally interacting bodies is applied to the problem of relative motion of non-interacting space vehicles. This technique is then combined with a simple transformation of the independent variable to arrive at a system of equations from which the relative motion may be determined with increased precision.
The paper describes a precision insolation instrument - the Mark 3 Kendall Radiometer - developed for field survey work and for use as a calibration transfer standard. The instrument, which can be used to make accurate measurements of solar irradiance, has a windowless black cavity receptor mounted in a massive heat sink and has equal sensitivity to ultraviolet, infrared, and visible radiation. Attention is given to a calibration stability analysis over two years of operation.
The effects of the transmission media - the earth's troposphere and ionosphere, and the solar wind - on precise Doppler tracking are discussed. The charged particle effects can be largely removed by dual frequency observations; however there are limitations to these corrections (besides system noise and/or finite integration times) including the effects of magnetic fields, diffraction, and differential refraction, all of which must be carefully evaluated. The earth's troposphere can contribute an error of delta f/f approximately 10 to the minus 14th power.
The linear X-ray polarization of the Crab Nebula has been precisely measured at 2.6 keV and 5.2 keV with the OSO 8 graphite crystal polarimeters. The 1.4 ms time resolution of these instruments permitted the removal of any contribution to the polarization from the pulsar. The nebular polarization is 19.2% plus or minus 1.0% at a position angle of 156.4 plus or minus 1.4 deg at 2.6 keV. At 5.2 keV the corresponding results are 19.5% plus or minus 2.8% at 152.6 plus or minus 4.0 deg.
The Starlette satellite, launched in February 1975 was designed to minimize the effects of nongravitational forces and to obtain the highest possible accuracy for laser range measurements. Analyses of the first four months of laser tracking data from nine stations have confirmed the stability of the orbit and the precision to which the satellite's position can be established. Initial orbit computations using the GSFC GEM - 7 gravity model produced rms fits of about 8 to 10 meters for arc lengths of 5 days. After tailoring a gravity model specifically to Starlette, the rms fits for the 5 day arcs were reduced significantly to the 1 to 2 meter level. An rms fit of 4.3 meters was obtained for a 90 day arc. Five day arcs overlapped by 2.5 days showed rms satellite position differences generally less than 2 meters. Prediction errors at the end of two months were less than 30 milliseconds.
As part of its advanced development work, JPL is developing a Precision Pointing and Tracking System (PPTS) for science platform control on unmanned planetary spacecraft. The PPTS will extend science capabilities on future missions by providing highly accurate (10 arcsec) and stable (0.2 arcsec) pointing of the platform. Key features of the design include closed-loop tracking of target bodies using an optical sensor and decoupling of spacecraft dynamics via high-bandwidth, inertially stabilized control. This paper discusses the analyses and design. Computer simulations were used to establish the feasibility of the design approach and to verify that the performance requirements can be met. A breadboard demonstration of the entire system is expected in late 1980.
Today's emerging fighter aircraft are maneuvering as well at normal accelerations of 7 to 8 g's as their predecessors did at 4 to 5 g's. This improved maneuvering capability has significantly expanded their operating envelope and made the task of evaluating handling qualities more difficult. This paper describes a technique for assessing the precision controllability of highly maneuverable aircraft, a technique that was developed to evaluate the effects of buffet intensity on gunsight tracking capability and found to be a useful tool for the general assessment of fighter aircraft handling qualities. It has also demonstrated its usefulness for evaluating configuration and advanced flight control system refinements. This technique is believed to have application to future aircraft dynamics and pilot-vehicle interface studies.
Attitude determination algorithms for a multimission spacecraft are derived and their performance analyzed. The attitude determination system is composed of a strapdown Inertial Reference Unit (IRU), two fixed head star trackers, and an onboard computer. IRU data is processed to maintain real-time knowledge of spacecraft attitude relative to an inertial reference frame. Star tracker data is processed using Kalman filtering techniques to estimate and correct the attitude determination errors and the gyro drift compensation errors. The results of a star availability analysis for stellar, solar and earth pointing missions are presented. Linear covariance analysis techniques are used to evaluate nominal attitude determination performance, the effects of sensor measurement accuracy variations, the effects of errors in knowledge of sensor measurement accuracy, and the effects of star tracker misalignment errors. Results of a nonlinear simulation analysis of attitude determination performance are also presented. These analyses show that precision attitude determination for stellar, solar and earth pointing missions is achieved.
Device scribes fine lines to precise tolerances on flat or round surfaces. Scriber is used in conjunction with toolmaker's microscope and will scribe metal of nonmetallic surfaces. When not in use, scriber is easily retracted or swung out of way so microscope can be used for other purposes.
Large, precise space systems such as space lasers, space telescopes, and space power transmitters cannot be realized until certain fundamental meteorological problems are first solved. It must be shown: (1) how a spatially distributed system of elements can be tied together in terms of a master coordinate system, (2) how master coordinates for these distributed elements can be determined with great accuracy, and (3) how mechanical integration of the elements to desired master coordinates of such accuracy can be achieved. Solutions to these problems are discussed.
Technical proposals and recommendations for revising FORTRAN were studied and categorized. In the area of numerical precision, the proposals basically agree on a set of necessary parameters, although a wide range of nomenclature and specific function names are used. Environmental parameters identified include the following: (1) base of floating point representation, (2) largest positive real number, exponent and integer, (3) largest negative real number, exponent and integer, (4) number of significant digits, and (5) exponent bias.
The planning, observations and adjustment of high-precision gravity survey networks established on the islands of Maui and Oahu as part of the geodetic-geophysical program in support of lunar laser ranging at Haleakala, Maui, Hawaii are described. The gravity survey networks include 43 independently measured gravity differences along the gravity calibration line from Kahului Airport to the summit of Mt. Haleakala, together with some key points close to tidal gauges on Maui, and 40 gravity differences within metropolitan Honolulu. The results of the 1976-1978 survey are compared with surveys made in 1961 and in 1964-1965. All final gravity values are given in the system of the international gravity standardization net 1971 (IGSN 71); values are obtained by subtracting 14.57 mgal from the Potsdam value at the gravity base station at the Hickam Air Force Base, Honolulu.
Surface temperature gradients were measured with miniature thermocouples installed in a 58.5 cm (23-inch) square window. Test measurements at 25 locations were made under vacuum and with the window operating in radiant heat transfer mode. The analysis of thermocouple design and installation is presented along with a lead wire routing scheme to allow for both differential and absolute temperature measurements while using a minimum number of signal feedthru paths through the test chamber wall. Typical test data and operational precautions are presented along with the accuracy analysis for installation effects and measurement effects to support differential temperature measurement precision values of + or - 0.06 C RMS + or - 0.1 F RMS).
Diurnal and long period earth tides were measured to high accuracy and precision with the superconducting gravimeter. The results provide new evidence on the geophysical questions which have been attacked through earth tide measurements in the past. In addition, they raise new questions of potential interest. Slow fluctuations in gravity of order 10 micron gal over periods of 3 to 5 months were observed and are discussed.
An approach developed to improve the ground instrumentation time tagging accuracy and adapted to support the Minuteman ICBM program is desired. The Timing Insertion Unit (TIU) technique produces a telemetry data time tagging resolution of one tenth of a microsecond, with a relative intersite accuracy after corrections and velocity data (range, azimuth, elevation and range rate) also used in missile guidance system analysis can be correlated to within ten microseconds of the telemetry guidance data. This requires precise timing synchronization between the metric and telemetry instrumentation sites. The timing synchronization can be achieved by using the radar automatic phasing system time correlation methods. Other time correlation techniques such as Television (TV) Line-10 and the Geostationary Operational Environmental Satellites (GEOS) terrestial timing receivers are also considered.
A modular CAMAC based system is described which was developed to meet a variety of precise time and frequency measurement and distribution needs. The system was based on a generalization of the dual mixer concept. By using a 16 channel 100 ns event clock, the system can intercompare the phase of 16 frequency standards with subpicosecond resolution. The system has a noise floor of 26 fs and a long term stability on the order of 1 ps or better. The system also used a digitally controlled crystal oscillator in a control loop to provide an offsettable 5 MHz output with subpicosecond phase tracking capability. A detailed description of the system is given including theory of operation and performance. A method to improve the performance of the dual mixer technique is discussed when phase balancing of the two input ports cannot be accomplished.
Precise (to about 20 arcsec) positions are reported for the Large Magellanic Cloud X-ray sources LMC X-1, X-2, and X-3, determined with the HEAO 1 scanning modulation collimator. The error regions for LMC X-1 and X-3 contain, respectively, the B5 supergiant R148 and a possibly variable B III-IV star. Spectra taken of the latter confirm the spectral type and show that it is a member of the LMC. A search for a previously reported extended component of LMC X-1 yields upper limits which exclude it.
Automated cutter precisely chops filaments of glass, graphite, plastic, and other materials into fibers for use in composites and other applications. Cutter uses movable blade that is pushed and pulled across fixed blade. Because mass of movable blade is small and stroke is short, operation is fast, and wear and energy consumption are low. Blade cuts on both forward and return movements. Operator selects fiber length and chopping rate. After each cut, blast of air blows filament away so it can be collected.