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At least 703 records · Page 39

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NASA NTRS1973

Potentialities of lunar laser ranging for measuring tectonic motions.

The lunar laser-ranging system at McDonald Observatory, Texas, is currently attaining accuracies of plus or minus 15 cm, and plus or minus 3 cm appears feasible. Numerical error analyses containing 97 parameters (35 of them for error sources) indicate that the plus or minus 3 cm system would measure station motions to plus or minus 1 cm/year accuracy within a year for east-west motions and within about 3 years for north-south. Furthermore, the correlations of station motions with other parameters are low, so that it is unlikely that the estimate is too optimistic because of modeling inadequacies of the error analysis.

Kaula, W. M.↗

NASA NTRS1973

Lunar Roving Vehicle Navigation System Performance Review

The design and operation of the lunar roving vehicle (LRV) navigation system are briefly described. The basis for the premission LRV navigation error analysis is explained and an example included. The real time mission support operations philosophy is presented. The LRV navigation system operation and accuracy during the lunar missions are evaluated.

Smith, Earnest C.↗

NASA NTRS1972

Mariner Jupiter/Saturn infrared instrument study

The Mariner Jupiter/Saturn infrared instrumentation conceptual design study was conducted to determine the physical and operational characteristics of the instruments needed to satisfy the experiment science requirements. The design of the instruments is based on using as many proven concepts as possible. Many design features are taken from current developments such as the Mariner, Pioneer 10, Viking Orbiter radiometers, and Nimbus D spectrometer. Calibration techniques and error analysis for the instrument system are discussed.

Source record↗

NASA NTRS1974

THREED: A computer program for three dimensional transformation of coordinates

Program THREED was developed for the purpose of a research study on the treatment of control data in lunar phototriangulation. THREED is the code name of a computer program for performing absolute orientation by the method of three-dimensional projective transformation. It has the capability of performing complete error analysis on the computed transformation parameters as well as the transformed coordinates.

Wong, K. W.↗

NASA NTRS1972

Wind speeds in lower atmosphere of Venus: Status report on possible measurement via differential VLBI tracking of entry probes

The potential of very-long-baseline interferometry (VLBI) is examined for use in the determination of wind speeds in Venus' lower atmosphere via the differential tracking of entry probes. A simplified mathematical model is presented in detail. An incomplete error analysis based on this model permits an educated guess to be made: an uncertainty in wind speed determination of no more than about 100/t m/sec, where t l is the corresponding time resolution in seconds, is an achievable goal, without the use of transponders on the miniprobes. If transponders are available on all probes, there should be little difficulty in estimating wind speeds with useful precision.

Shapiro, I. I.↗

NASA NTRS1974

Uncertainties in predicting solar panel power output

The problem of calculating solar panel power output at launch and during a space mission is considered. The major sources of uncertainty and error in predicting the post launch electrical performance of the panel are considered. A general discussion of error analysis is given. Examples of uncertainty calculations are included. A general method of calculating the effect on the panel of various degrading environments is presented, with references supplied for specific methods. A technique for sizing a solar panel for a required mission power profile is developed.

Anspaugh, B.↗

NASA NTRS1974

Ozone measurement systems improvements studies

Results are summarized of an initial study of techniques for measuring atmospheric ozone, carried out as the first phase of a program to improve ozone measurement techniques. The study concentrated on two measurement systems, the electro chemical cell (ECC) ozonesonde and the Dobson ozone spectrophotometer, and consisted of two tasks. The first task consisted of error modeling and system error analysis of the two measurement systems. Under the second task a Monte-Carlo model of the Dobson ozone measurement technique was developed and programmed for computer operation.

Thomas, R. W.↗

NASA NTRS1974

C-band station coordinate determination for the GEOS-C altimeter calibration area

Dynamical orbital techniques were employed to estimate the center-of-mass station coordinates of six C-band radars located in the designated primary GEOS-C radar altimeter calibration area. This work was performed in support of the planned GEOS-C mission (December, 1974 launch). The sites included Bermuda, Grand Turk, Antigua, Wallops Island (Virginia), and Merritt Island (Florida). Two sites were estimated independently at Wallops Island yielding better than 40 cm relative height recovery, with better than 10 cm and 1 m (relative) recovery for phi and gamma respectively. Error analysis and comparisons with other investigators indicate that better than 2 m relative recovery was achieved at all sites. The data used were exclusively that from the estimated sites and included 18 orbital arcs which were less than two orbital revolutions in length, having successive tracks over the area. The techniques employed here, given their independence of global tracking support, can be effectively employed to improve various geodetic datums by providing very long and accurate baselines. The C-band data taken on GEOS-C should be employed to improve such geodetic datums as the European-1950 using similar techniques.

Krabill, W. B.↗

NASA NTRS1974

A study of unmanned mission opportunities to comets and asteroids

Several unmanned multiple-target mission opportunities to comets and asteroids were studied. The targets investigated include Grigg-Skjellerup, Giacobini-Zinner, Tuttle-Giacobini-Kresak, Borrelly, Halley, Schaumasse, Geographos, Eros, Icarus, and Toro, and the trajectories consist of purely ballistic flight, except that powered swingbys and deep space burns are employed when necessary. Optimum solar electric rendezvous trajectories to the comets Giacobini-Zinner/85, Borrelly/87, and Temple (2)/83 and /88 employing the 8.67 kw Sert III spacecraft modified for interplanetary flight were also investigated. The problem of optimizing electric propulsion heliocentric trajectories, including the effects of geocentric launch asymptote declination on launch vehicle performance capability, was formulated, and a solution developed using variational calculus techniques. Improvements were made to the HILTOP trajectory optimization computer program. An error analysis of high-thrust maneuvers involving spin-stabilized spacecraft was developed and applied to a synchronous meteorological satellite mission.

Mann, F. I.↗

NASA NTRS1975

Sequential Least-Squares Using Orthogonal Transformations

Square root information estimation, starting from its beginnings in least-squares parameter estimation, is considered. Special attention is devoted to discussions of sensitivity and perturbation matrices, computed solutions and their formal statistics, consider-parameters and consider-covariances, and the effects of a priori statistics. The constant-parameter model is extended to include time-varying parameters and process noise, and the error analysis capabilities are generalized. Efficient and elegant smoothing results are obtained as easy consequences of the filter formulation. The value of the techniques is demonstrated by the navigation results that were obtained for the Mariner Venus-Mercury (Mariner 10) multiple-planetary space probe and for the Viking Mars space mission.

Bierman, G. J.↗

NASA NTRS1974

Digital simulation by partitioning and uncoupling the system model

The present work reviews state variable simulation and then proposes a technique for simulation of nonlinear time varying systems by partitioning the system state variable model and uncoupling the resulting subsystem models so that the linear time-invariant ones can be simulated by state variable solution. Computational requirements and computer time are shown to be reduced. The method does, however, introduce an integration error due to the treatment of the intercoupling terms between the subsystems as inputs which are assumed constant over a computation interval. A fictitious sampler is thereby introduced, which is then derived in the form of a state variable error model. The application of this method in a simulation error analysis for a Saturn V attitude control system model and the simulation of a detailed nonlinear, single-axis model of the LST fine pointing control system is described.

Henson, T. F.↗

NASA NTRS1975

Thermal study of the unilluminated surface of the waning moon

A program of lunar infrared radiometry which uses large-area scanning is described. Procedures for atmospheric-attenuation correction and data reduction to temperature by relative radiometry are outlined. The scan data of the waning moon taken during ten evenings in the 10- to 12-micron window are presented as isothermal contour maps of the lunar disk. More than 160 areas of anomalous thermal emission have been found in the lunar dark-side data. These are tabulated and are also shown on an accompanying map. An error analysis, derived from accuracy estimates of the independent parameters, is included.

Raine, W. L.↗

NASA NTRS1975

Measurement of the inertial properties of the Helios F-1 spacecraft

A gravity pendulum method of measuring lateral moments of inertia of large structures with an error of less than 1% is outlined. The method is based on the fact that in a physical pendulum with a knife-edge support the distance from the axis of rotation to the system center of gravity determines the minimal period of oscillation and is equal to the system centroidal radius of gyration. The method is applied to results of a test procedure in which the Helios F-1 spacecraft was placed in a roll fixture with crossed flexure pivots as elastic constraints and system oscillation measurements were made with each of a set of added moment-of-inertia increments. Equations of motion are derived with allowance for the effect of the finite pivot radius and an error analysis is carried out to find the criterion for maximum accuracy in determining the square of the centroidal radius of gyration. The test procedure allows all measurements to be made with the specimen in upright position.

Gayman, W. H.↗

NASA NTRS1975

Frequency stability requirements for two way range rate tracking

Accuracy limitations to two way range rate Doppler tracking due to master (reference) oscillator frequency instabilities are discussed. Theory is developed to treat both the effects of random and nonrandom oscillator instabilities. The nonrandom instabilities treated are drift, environmental effects, and coherent phase modulation. The effects of random instabilities on range rate accuracy are shown to be describable in terms of sigma y (2, T, tau). For the typical noise processes encountered in precision oscillators, range rate error is related to the more familiar sigma y (tau) and script L (f). Three examples are discussed to show how to determine range rate error from given sigma y (tau) or script L (f) curves, and approximations are developed to simplify the treatment of complex systems. An error analysis of range determined from rate data is also given.

Reinhardt, V.↗

NASA NTRS1976

Relativistic astrophysics

The design, experimental testing, and calibration (error analysis) of a high resolution Cerenkov-scintillation detector is presented. The detector is capable of detecting iron isotopes and heavy ions of cosmic rays, and of performing direct measurements of individual neighboring isotopes at charge resolution 26. It utilizes Lexan (trademark) sheets, and has been used in flight packages of balloons and on the Skylab. The detector will be able to provide more information on violet astrophysical processes, such as thermonuclear reactions on neutron stars. Ground support and display equipment which are to be used in conjunction with the detector are also discussed.

Price, P. B.↗

NASA NTRS1975

Vehicle systems and payload requirements evaluation

Techniques developed for identifying launch vehicle system requirements for NASA automated space missions are discussed. Emphasis is placed on development of computer programs and investigation of astrionics for OSS missions and Scout. The Earth Orbit Mission Program - 1 which performs linear error analysis of launch vehicle dispersions for both vehicle and navigation system factors is described along with the Interactive Graphic Orbit Selection program which allows the user to select orbits which satisfy mission requirements and to evaluate the necessary injection accuracy.

Rea, F. G.↗

NASA NTRS1976

A general geometric theory of attitude determination from directional sensing

A general geometric theory of spacecraft attitude determination from external reference direction sensors was presented. Outputs of different sensors are reduced to two kinds of basic directional measurements. Errors in these measurement equations are studied in detail. The partial derivatives of measurements with respect to the spacecraft orbit, the spacecraft attitude, and the error parameters form the basis for all orbit and attitude determination schemes and error analysis programs and are presented in a series of tables. The question of attitude observability is studied with the introduction of a graphical construction which provides a great deal of physical insight. The result is applied to the attitude observability of the IMP-8 spacecraft.

Fang, B. T.↗

NASA NTRS1975

Mariner-Venus-Mercury optical navigation demonstration - Results and implications for future missions

Optical navigation uses spacecraft television pictures of a target body against a known star background in a process which relates the spacecraft trajectory to the target body. This technology was used in the Mariner-Venus-Mercury mission, with the optical data processed in near-real-time, simulating a mission critical environment. Optical data error sources were identified, and a star location error analysis was carried out. Several methods for selecting limb crossing coordinates were used, and a limb smear compensation was introduced. Omission of planetary aberration corrections was the source of large optical residuals.

Acton, C. H., Jr.↗