Space shuttle landing navigation using precision distance measuring equipment
Evaluation of precision distance measuring equipment for space shuttle landing navigation
Widnall, W. S.↗
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A note on correlation distance of the equatorial ionosphere
Equatorial ionosphere correlation distance regarding VHF telemetry disturbances and satellite tracking, determining antenna ground spacing
Golden, T.↗
Orientation-dependent effects in Oort's theory of comet origin. I - Evolution of the orbital orientations and perihelion distances of long-period comets
Long period comets orbital orientations and perihelion distances, discussing Oort evolutionary theory modification
Joss, P. C.↗
Minimum distance properties of convolutional code words of arbitrary length
Convolutional code words minimum distance- arbitrary length relationship for path memory performance measurement
Huth, G. K.↗
Strengthened lower bound on definite decoding minimum distance for periodic convolutional codes
Binary periodic convolutional codes with lower bound everywhere stronger than Wagner on definite decoding minimum distance
Costello, D. J., Jr.↗
Possible upper limit to the distance of BL Lacertae
BL Lac extragalactic source of radio, IR and visual radiation, estimating upper limit to distance based on spectrum model
Gillett, F. C.↗
The estimated distance to Cygnus X-1 based on its low-energy X-ray spectrum
Cygnus X-1 distance estimate based on low energy X ray spectrum obtained by sounding rocket
Gorenstein, P.↗
Multiple crossings of the earth's bow shock at large geocentric distances
Earth bow shock multiple crossings identification by magnetic field experiment onboard Pioneer 8 at geocentric distances
Bavassano, B.↗
Subsonic and transonic pressure distributions around a bluff afterbody in the wake of a 120 deg cone for various separation distances
A wind-tunnel investigation was conducted at free-stream Mach numbers from 0.20 to 1.00 and Reynolds numbers, based on maximum afterbody diameter, from 2.25 million to 6.90 million on solid models of an attached inflatable decelerator (AID) concept. Tests were conducted to obtain static and ram surface pressure distributions about the basic shapes and at various separation distances between the 120 deg conical forebody and the inflated afterbody shape. The resulting data were used to study the feasibility of extracting a payload from a conical forebody by means of an AID.
Sawyer, J. W.↗
Long distance tracking of birds
The application of radio telemetry techniques to the long distance tracking of birds is discussed. The types of equipment developed and methods for attachment to a bird are described. The operating range of the radio transmitter receiver system is examined, and methods for acquiring and analyzing the data are explained.
Cochran, W. W.↗
The relation of QRS amplitude to the frontal QRS axis and the heart-electrode distance.
The relation between QRS amplitude, QRS axis deviation and heart position was studied in 360 subjects, using the 12-lead EKG. The height of the V sub 6 R wave was used as the measure of QRS amplitude. The distance from the left lateral border of the heart was used to indicate heart position. The frontal and horizontal QRS axes were determined by noting the isoelectric limb and precordial leads, measured according to Schmitt's values.
Dougherty, J. D.↗
Analysis of four optical distance measuring instrument configurations using electrooptical polarization modulators.
Four possible optical configurations for optical distance-measuring instruments using electrooptical polarization modulators are discussed. Criteria are developed for a meaningful comparison of the four systems. A summary of the compared characteristics of the systems is given in tabular form, and the comparative merits of each system are reviewed.
Hernandez, E. N.↗
Plasma sheet at lunar distance - Structure and solar-wind dependence.
Analysis of Explorer 35 observation of low-energy (0.1 to 3 keV) electrons in the distant geomagnetic tail at 60 earth radii, and comparison with the solar-wind conditions monitored simultaneously by Explorer 33. The plasma sheet extends to the lunar distance with almost the same characteristics as those observed in the near tail region; the thickness is several earth radii, and the flux, density, and energy are of the order of 10 to the 9th per sq cm per sec, 1 per cu cm, and 0.6 keV, respectively. The latitudinal boundaries of the plasma sheet are essentially parallel to magnetic-field lines. Indication is seen of the thinning of the plasma sheet during polar substorms. The average energy of electrons is correlated with the solar-wind velocity in agreement with the view that plasma-sheet electrons originate from the magnetosheath. The flux is correlated with the solar-wind dynamic pressure, reflecting the dynamic balance between the solar wind and the geomagnetic tail.
Nishida, A.↗
Space Shuttle landing navigation using precision distance measuring equipment.
Precision distance measuring equipment (DME) aiding onboard inertial navigation can be used to meet the stringent landing navigation requirements of the Space Shuttle. The required accuracy is achieved by using a ten-state-variable Kalman filter to process the measured range and delta-range data from the DME. The DME transponders are required to meet the accuracy requirements: two are deployed under the final approach path and one is deployed to the side. Failure considerations require deployment of additional redundant transponders. Initialization of the landing navigation after hypersonic entry is accomplished using the transponders at the airport.
Widnall, W. S.↗
A comparison of open and closed loop applications of the minimum distance guidance technique
A comparison is made of open and closed loop applications of a second order guidance algorithm, using the minimum distance strategy. A nonlinear reoptimization procedure is used as the ideal guidance history. The system model used for the comparison is a low-thrust vehicle performing a minimum time, three-dimensional, heliocentric Earth-Mars transfer. For the example problem considered, closed loop guidance proves to be much more accurate on satisfaction of the final state than the open loop procedure. On the other hand, closed loop guidance proves to be much more vulnerable to perturbation by highly nonlinear regions in the trajectory. Finally, the results indicate that for this problem the best loop closure interval is at each integration step, about one day, or more often, if possible.
Lattimore, J. P., Jr.↗
A novel laser ranging system for measurement of ground-to-satellite distances
A technique was developed for improving the precision of laser ranging measurements of ground-to-satellite distances. The method employs a mode-locked laser transmitter and utilizes an image converter tube equipped with deflection plates in measuring the time of flight of the laser pulse to a distant retroreflector and back. Samples of the outgoing and returning light pulses are focussed on the photocathode of the image converter tube, whose deflection plates are driven by a high-voltage 120 MHz sine wave derived from a very stable oscillator. From the relative positions of the images produced at the output phosphor by the two light pulses, it is possible to make a precise determination of the fractional amount by which the time of flight exceeds some large integral multiple of the period of the deflection sinusoid.
Golden, K. E.↗
Observation of plasma flow in the neutral sheet at lunar distance during two magnetic bays.
Simultaneous observations of a southward directed magnetic field and a plasma flowing away from the earth across the neutral sheet at lunar distance during two weak magnetic bays. These observations are shown to be in good agreement with predictions based on magnetic merging models for the generation of magnetic substorms.
Burke, W. J.↗
Curve fits of predicted inviscid stagnation-point radiative heating rates, cooling factors, and shock standoff distances for hyperbolic earth entry
Curve-fit formulas are presented for the stagnation-point radiative heating rate, cooling factor, and shock standoff distance for inviscid flow over blunt bodies at conditions corresponding to high-speed earth entry. The data which were curve fitted were calculated by using a technique which utilizes a one-strip integral method and a detailed nongray radiation model to generate a radiatively coupled flow-field solution for air in chemical and local thermodynamic equilibrium. The range of free-stream parameters considered were altitudes from about 55 to 70 km and velocities from about 11 to 16 km.sec. Spherical bodies with nose radii from 30 to 450 cm and elliptical bodies with major-to-minor axis ratios of 2, 4, and 6 were treated. Powerlaw formulas are proposed and a least-squares logarithmic fit is used to evaluate the constants. It is shown that the data can be described in this manner with an average deviation of about 3 percent (or less) and a maximum deviation of about 10 percent (or less). The curve-fit formulas provide an effective and economic means for making preliminary design studies for situations involving high-speed earth entry.
Suttles, J. T.↗