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At least 19 records

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.

Application of DSN spacecraft tracking technology to experimental gravitation

Spacecraft tracking technology of the Deep Space Net (DSN) has been used in the past to measure the general-relativistic increase in round-trip group delay between earth and a spacecraft. As the DSN technology continues to improve, other gravitational experiments will become possible. Two possibilities are discussed in this paper. The first concerns the application of solar-system dynamics to the testing of general relativity. The second involves the detection of VLF gravitational radiation (0.1 to 0.0001 Hz) by means of Doppler tracking of spacecraft.

Anderson, J. D.

Surface refractivity measurements at NASA spacecraft tracking sites

High-accuracy spacecraft tracking requires tropospheric modeling which is generally scaled by either estimated or measured values of surface refractivity. This report summarizes the results of a worldwide surface-refractivity test conducted in 1968 in support of the Apollo program. The results are directly applicable to all NASA radio-tracking systems.

Schmid, P. E.

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.

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.

Precise spacecraft tracking using VLBI digital tone extraction for the purpose of gravitational wave detection

The prospect for the detection of a cosmic background of gravitational wave radiation is discussed. Experiments utilizing precise Doppler tracking of interplanetary spacecraft for the purpose of detecting this background are reviewed. Results of a recent experiment are presented which used facilities of NASA's Deep Space Tracking Network and Owens Valley Radio Observatory to track the Voyager spacecraft in an ultra precise manner using two independent hydrogen masers as frequency standards. The present limiting sensitivity of these experiments are believed to be tropospheric and plasma variations affecting the X band microwave signals at periods of between 1,000 - 10,000 seconds duration.

Anderson, A. J.

Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data

This software provides an automated capability to measure and qualify the frequency stability performance of the Deep Space Network (DSN) ground system, using daily spacecraft tracking data. The results help to verify if the DSN performance is meeting its specification, therefore ensuring commitments to flight missions; in particular, the radio science investigations. The rich set of data also helps the DSN Operations and Maintenance team to identify the trends and patterns, allowing them to identify the antennas of lower performance and implement corrective action in a timely manner. Unlike the traditional approach where the performance can only be obtained from special calibration sessions that are both time-consuming and require manual setup, the new method taps into the daily spacecraft tracking data. This new approach significantly increases the amount of data available for analysis, roughly by two orders of magnitude, making it possible to conduct trend analysis with good confidence. The software is built with automation in mind for end-to-end processing. From the inputs gathering to computation analysis and later data visualization of the results, all steps are done automatically, making the data production at near zero cost. This allows the limited engineering resource to focus on high-level assessment and to follow up with the exceptions/deviations. To make it possible to process the continual stream of daily incoming data without much effort, and to understand the results quickly, the processing needs to be automated and the data summarized at a high level. Special attention needs to be given to data gathering, input validation, handling anomalous conditions, computation, and presenting the results in a visual form that makes it easy to spot items of exception/ deviation so that further analysis can be directed and corrective actions followed.

Pham, Timothy T.

Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data

This software provides an automated capability to measure and qualify the frequency stability performance of the Deep Space Network (DSN) ground system, using daily spacecraft tracking data. The results help to verify if the DSN performance is meeting its specification, therefore ensuring commitments to flight missions; in particular, the radio science investigations. The rich set of data also helps the DSN Operations and Maintenance team to identify the trends and patterns, allowing them to identify the antennas of lower performance and implement corrective action in a timely manner. Unlike the traditional approach where the performance can only be obtained from special calibration sessions that are both time-consuming and require manual setup, the new method taps into the daily spacecraft tracking data. This new approach significantly increases the amount of data available for analysis, roughly by two orders of magnitude, making it possible to conduct trend analysis with good confidence. The software is built with automation in mind for end-to-end processing. From the inputs gathering to computation analysis and later data visualization of the results, all steps are done automatically, making the data production at near zero cost. This allows the limited engineering resource to focus on high-level assessment and to follow up with the exceptions/deviations. To make it possible to process the continual stream of daily incoming data without much effort, and to understand the results quickly, the processing needs to be automated and the data summarized at a high level. Special attention needs to be given to data gathering, input validation, handling anomalous conditions, computation, and presenting the results in a visual form that makes it easy to spot items of exception/deviation so that further analysis can be directed and corrective actions followed.

Pham, Timothy T.

Simulation gravity modeling to spacecraft-tracking data - Analysis and application

It is proposed that line-of-sight gravity measurements derived from spacecraft-tracking data can be used for quantitative subsurface density modeling by suitable orbit simulation procedures. Such an approach avoids complex dynamic reductions and is analogous to the modeling of conventional surface gravity data. This procedure utilizes the vector calculations of a given gravity model in a simplified trajectory integration program that simulates the line-of-sight gravity. Solutions from an orbit simulation inversion and a dynamic inversion on Doppler observables compare well (within 1% in mass and size), and the error sources in the simulation approximation are shown to be quite small. An application of this technique is made to lunar crater gravity anomalies by simulating the complete Bouguer correction to several large young lunar craters. It is shown that the craters all have negative Bouguer anomalies.

Phillips, R. J.

Characterizing DSN System Frequency Stability with Spacecraft Tracking Data

This paper describes a recent effort in characterizing frequency stability performance of the ground system in the NASA Deep Space Network (DSN). Unlike the traditional approach where performance is obtained from special calibration sessions that are both time consuming and require manual setup, the new method taps into the daily spacecraft tracking data. This method significantly increases the amount of data available for analysis, roughly by two orders of magnitude; making it possible to conduct trend analysis with reasonable confidence. Since the system is monitored daily, any significant variation in performance can be detected timely. This helps the DSN maintain its performance commitment to customers.

performance analysis

Radiometric Spacecraft Tracking for Deep Space Navigation

Interplanetary spacecraft navigation relies on three types of terrestrial tracking observables.1) Ranging measures the distance between the observing site and the probe. 2) The line-of-sight velocity of the probe is inferred from Doppler-shift by measuring the frequency shift of the received signal with respect to the unshifted frequency. 3) Differential angular coordinates of the probe with respect to natural radio sources are nominally obtained via a differential delay technique of (Delta) DOR (Delta Differential One-way Ranging). The accuracy of spacecraft coordinate determination depends on the measurement uncertainties associated with each of these three techniques. We evaluate the corresponding sources of error and present a detailed error budget.

ranging

Differential spacecraft tracking by interferometry

This study estimates measurement system errors for two space vehicles on the surface of Mars, and for two Mars orbiting spacecraft, which are being tracked by differential interferometry. In these examples, signals from all spacecraft lie within the same beamwidth of an earth-based radio antenna. The measurements of all spacecraft signals are made simultaneously; errors that scale with angular source separation or with temporal separation between measurement epochs are practically removed. It is shown that errors due to system thermal noise and to systematic effects within ground receiver electronics dominate, except for geometries when signals pass close to the sun, when solar plasma becomes the dominant error source. The instantaneous relative position of two orbiters may be measured to within ten meters, leading to 50-meter three-dimensional orbital accuracy.

Border, James S.

Response of Doppler spacecraft tracking to gravitational radiation

A calculation is made of the effect of gravity waves on the observed Doppler shift of a sinusoidal electromagnetic signal transmitted to, and transponded from, a distant spacecraft. We find that the effect of plane gravity waves on such observations is not intuitively immediate and in fact can have surprisingly different spectral signatures for different spacecraft directions and distances. We suggest the possibility of detecting such plane waves by simultaneous coherent Doppler tracking of several spacecraft.

Estabrook, F. B.