Engineering Papers⌕ Search

Engineering topics

Chao, C. C.

Publications and source records attributed to Chao, C. C..

16 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Transmission of sound across a vortex layer enclosing a cylindrical column of jet

An approximate solution to the problem of transmission of sound across a cylindrical vortex was obtained. Results are considerably different from the plane vortex sheet case because of the added role played by the curvature of the jet. In comparison with the plane case, the specularly transmitted waves are more complex and require some numerical integration. Resonance waves are identically predicted for M 2, but there is also a wave field whose modified effect appears to extend the region of resonance just as the instability waves cover a region in space and time. The instability waves are predicted to exist for all Mach numbers but vanish for wavelengths that are large compared to the jet radius. The region of propagation is similarly wavelength dependent.

Luh, R.↗
NASA NTRS1980

Transmitted sound field due to an impulsive line acoustic source bounded by a plate followed by a vortex sheet

The propagation of sound due to a line acoustic source in the moving stream across a semiinfinite vortex sheet which trails from a rigid plate is examined in a linear theory for the subsonic case. A solution for the transmitted sound field is obtained with the aid of multiple integral transforms and the Wiener-Hopf technique for both the steady state (time harmonic) and initial value (impulsive source) situations. The contour of inverse transform and hence the decomposition of the functions are determined through causality and radiation conditions. The solution obtained satisfies causality and the full Kutta conditions. The transmitted sound field is composed of two waves in both the stady state and initial value problems. One is the wave scattered from the edge of the plate which is associated with the bow wave and the instability wave. These waves exist in the downstream sectors. The other is the wave transmitted through the vortex sheet which is also associated with the instability wave. Regional divisions of the transmitted sound field are identified.

Miura, T.↗
NASA NTRS1978

A demonstration of differenced dual-station one-way doppler conducted with Pioneer 11

Simultaneous one way Doppler demonstrations performed on Pioneer 11 are described. The data noise of the differenced one way doppler as computed from the pseudo residuals is around 0.002 Hz, which is nearly an order of magnitude smaller than the one way Doppler noise and about the same as differenced two way/three way Doppler noise. The demonstration results and the applicability of differenced one way radio metric data to spacecraft navigation are discussed.

Chao, C. C.↗
NASA NTRS1978

A demonstration of dual spacecraft tracking conducted with the Viking spacecraft during the approach phase

The potential improvements in navigation capability of dual spacecraft tracking were demonstrated using Viking approach data. Under unfavorable conditions of large plasma noise, low spacecraft declination and large earth-spacecraft distance, the dual spacecraft tracking technique improved the Viking B approach accuracy based on short-arc radio metric data, by a factor of 7, to less than 200 km at Mars orbit insertion minus 3 days. From the results of an analytical expansion and the Viking demonstration with a large intentional error in Mars ephemeris, that dual spacecraft data types are shown to be insensitive to ephemeris error. Results also reveal the potential reduction of tracking time requirements during planet approach.

Chao, C. C.↗
NASA NTRS1978

Mission applications of the dual spacecraft tracking technique

The potential application of the dual spacecraft tracking technique to the Voyager mission is discussed. The concept and technology status is reviewed and results pertaining to the JSX-Uranus option Saturn encounter, where potential navigation benefits are greatest, are presented. Results for a Jupiter encounter demonstration also are given and, finally, software modifications and tracking requirements are examined.

Chao, C. C.↗
NASA NTRS1977

A demonstration of dual spacecraft tracking conducted with the Viking spacecraft during the approach phase

In the case of interplanetary space missions involving two spacecraft, such as Viking, significant navigation advantages may sometimes be achieved (at least for the trailing vehicle) by determining the orbit of one relative to the other, or otherwise combining the data from the two spacecraft. Dual spacecraft navigation concepts have been investigated by Chao et al. (1976). New analytical models for the dual spacecraft data types are presented and results are reported from a more recent demonstration conducted during the approach phase of the Viking mission. The demonstration was based on data taken two weeks before Mars orbit insertion of the second Viking spacecraft. The demonstration was designed to show that the approaching probe could be tied accurately to the planet through the orbiter. Attention is given to the geometry of the Viking B approach trajectory, the accuracy of the delivered estimates for midcourse maneuvers, and an algorithm of data processing.

Chao, C. C.↗
NASA NTRS1977

Improvements in navigation resulting from the use of dual spacecraft radiometric data

When two interplanetary spacecraft lie along similar geocentric lines-of-sight, navigational advantages may be achieved by navigating one spacecraft with respect to the other. Opportunities to employ this technique will become more common as more multiprobe missions are launched. The two Viking spacecraft and the two Mariner Jupiter/Saturn '77 spacecraft will be within two and three degrees of each other, respectively, for a large portion of their missions. Results of simulated analysis as well as the processing of real tracking data from the two Viking spacecraft reveal the following advantages of the dual spacecraft navigation technique: (1) cancellation of platform parameter and transmission media modeling errors in short arc solutions, (2) accurate encounter guidance for the trailing spacecraft, (3) reduction of total tracking requirements, and (4) rapid determination of the orbit following a maneuver on either spacecraft.

Chao, C. C.↗
NASA NTRS1976

Improvements in navigation resulting from the use of dual spacecraft radiometric data

If two spacecraft lying along similar geocentric lines-of-sight are simultaneously tracked by two nearby ground stations (dual spacecraft two-station tracking), navigational capabilities may be substantially improved. A thorough accuracy analysis study of dual spacecraft tracking using simulated tracking data based on the trajectories of Viking and Mariner Jupiter-Saturn '77(MJS '77) missions has been carried out. Results of the study reveal the following advantages: (1) cancellation of platform parameter and transmission media modelling errors in short arc solutions, (2) accurate encounter guidance for the trailing spacecraft, (3) reduction of total tracking time requirements, and (4) rapid determination of the orbit following a maneuver on either spacecraft. It is shown that dual spacecraft data types can improve navigational capabilities by a factor of 5 to 10, under the conditions of small angular separation (not exceeding 3 degrees) of the two spacecraft and well determined trajectory of the reference spacecraft. The research to carry out and the data to obtain before the new technique can be used in interplanetary navigation are pointed out.

Chao, C. C.↗
NASA NTRS1976

Computer assisted expansion of 1/Delta series with Newton iteration

The Newton iteration method has been widely applied to the solution of various equations such as Kepler's equation. In this study it is used in planetary and satellite theory as a general procedure for Fourier series inversion. The method is used for the construction of the 1/Delta series either in literal form or in numerical form with small eccentricities and inclinations substituted in advance. This usually results in very compact series. With the Newton iteration procedure and a computerized series manipulation technique, the Fourier series of 1/Delta of the mutual perturbations among most natural satellites can be easily constructed.

Chao, C. C.↗
NASA NTRS1974

Conditioning of MVM '73 radio-tracking data

An extensive effort was undertaken to edit Mariner 10 radiometric tracking data. Interactive computer graphics were used for the first time by an interplanetary mission to detect blunder points and spurious signatures in the data. Interactive graphics improved the former process time by a factor of 10 to 20, while increasing reliability. S/X dual Doppler data was used for the first time to calibrate charged particles in the tracking medium. Application of the charged particle calibrations decreased the orbit determination error for a short data arc following the 16 March 1974 maneuver by about 80%. A new model was developed to calibrate the earth's troposphere with seasonal adjustments. The new model has a 2% accuracy and is 5 times better than the old model.

Koch, R. E.↗
NASA NTRS1974

Demonstration of new data types for use in interplanetary navigation

Mariner 10 was the first mission which contained many elements of the advanced navigation system which will be used in the late 1970's and 1980's. Preliminary navigation demonstrated were conducted using S/X charged particle calibrations, simultaneous Doppler data, nearly simultaneous range data, and bright object/star imaging data. The results of these demonstrations are very encouraging and a navigation system based upon these data types should be an order of magnitude better than the current system.

Ondrasik, V. J.↗
NASA NTRS1974

Frequency standards requirements of the NASA deep space network to support outer planet missions

Navigation of Mariner spacecraft to Jupiter and beyond will require greater accuracy of positional determination than heretofore obtained if the full experimental capabilities of this type of spacecraft are to be utilized. Advanced navigational techniques which will be available by 1977 include Very Long Baseline Interferometry (VLBI), three-way Doppler tracking (sometimes called quasi-VLBI), and two-way Doppler tracking. It is shown that VLBI and quasi-VLBI methods depend on the same basic concept, and that they impose nearly the same requirements on the stability of frequency standards at the tracking stations. It is also shown how a realistic modelling of spacecraft navigational errors prevents overspecifying the requirements to frequency stability.

Fliegel, H. F.↗
NASA NTRS1973

Interplanetary orbit determination

The logistical aspects of orbit determination (OD) in the interplanetary phase of the Mariner Mars 1971 mission are described and the working arrangements for the OD personnel, both within the Navigation Team and with outside groups are given. Various types of data used in the OD process are presented along with sources of the data. Functional descriptions of the individual elements of the OD software and brief sketches of their modes of operation are provided.

Zielenbach, J. W.↗