The JPL/DSN J2000 Radio Reference Frame

Development of a radio reference frame of very high accuracy has become necessary in order to obtain the required accuracy in spacecraft navigation for current and future planetary missions. The antennas of the NASA Deep Space Network are being utilized on a regular basis to obtain the positions of over 100 compact extragalactic radio sources distributed over the sky down to a declination of −45 degrees with uncertainties of less than 0.005 arcseconds.

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Radio Reference Frame Stability from VLBI Data

Symposium - International Astronomical Union ◽

10.1017/s0074180900134898 ◽

1988 ◽

Vol 129 ◽

pp. 331-332

Author(s):

O. J. Sovers ◽

R. N. Treuhaft

Keyword(s):

Reference Frame ◽

Independent Sets ◽

Radio Sources ◽

Deep Space ◽

Deep Space Network ◽

Space Network ◽

Rates Of Change ◽

Upper Limits ◽

Vlbi Data ◽

Almost All

Intercontinental radio interferometric measurements between NASA's Deep Space Network stations yield a catalog of positions of 106 extragalactic radio sources, uniformly distributed between −45° and +85° declination. Almost all of the source positions have formal uncertainties between 0.5 and 3 milliarcseconds. Estimates of three independent sets of 32 source coordinates at average epochs 1980.0, 1983.2, and 1984.5 assess the level of stability of the reference frame over a five-year period. Comparisons of the three sets of source coordinates show a number of cases of > 2σ differences, particularly betwen the 1984–85 and 1981–83 periods. No sources, however, show 2σ shifts among both pairs of epochs. Upper limits of the order of 1 mas/yr can be placed on the time rates of change of the 32 source coordinates.

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Accurate Positions of 120 Radio Sources with Declinations Above −45°

Symposium - International Astronomical Union ◽

10.1017/s0074180900078499 ◽

1984 ◽

Vol 110 ◽

pp. 363-364

Author(s):

A. E. Niell ◽

J. L. Fanselow ◽

O. J. Sovers ◽

J. B. Thomas ◽

K. M. Liewer ◽

...

Keyword(s):

Reference Frame ◽

Radio Sources ◽

Deep Space ◽

Entry Angle ◽

Positional Accuracy ◽

Deep Space Network ◽

Space Network ◽

Vlbi Observations

Development of a catalogue of approximately 100 radio sources having positional accuracy of ~0.005 arcseconds is one goal of the DSN radio reference frame program. This objective is set by the navigation requirements of the Galileo Project for reconstruction of the probe entry angle into the atmosphere of Jupiter. These radio positions are determined by VLBI observations using the antennas of the NASA Deep Space Network on two intercontinental baselines – California-Spain and California-Australia. Since 1978, measurements have been made simultaneously at 2.3 and 8.4 Ghz. Sixteen to twenty-four hours of data on each of the two baselines are usually obtained within a few days of each other, and since mid-1982 these pairs of observations have been made at approximately six week intervals.

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An Extragalactic Reference Frame From DSN VLBI Measurements–1989

Symposium - International Astronomical Union ◽

10.1017/s0074180900086915 ◽

1990 ◽

Vol 141 ◽

pp. 261-270 ◽

Cited By ~ 4

Author(s):

O. J. Sovers

Keyword(s):

Reference Frame ◽

Systematic Errors ◽

Radio Sources ◽

Dual Frequency ◽

Source Position ◽

Deep Space Network ◽

Space Network ◽

Data Analyses ◽

Accuracy Level ◽

The Impact

Assessment of the impact of recent improvements in Deep Space Network (DSN) instrumentation, as well as of joint data analyses, provide a prognosis for the accuracy level to be expected in future realizations of an inertial radio reference frame. Intercontinental dual-frequency radio interferometric measurements during 68 sessions (including two recent sessions employing Mark III instrumentation) from 1978 to 1989 using NASA's DSN stations in California, Spain, and Australia give 8900 pairs of delay and delay rate observations. Analysis yields a catalog of positions of 200 extragalactic radio sources north of —45° declination. The resulting source position formal uncertainty distributions peak below 1 milliarcsecond, with three fourths being smaller than 2 mas. Comparison with independent measurements shows some evidence for systematic errors at the milliarcsecond level.

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An Assessment of the Accuracy of the Deep Space Network Extragalactic Reference Frame

Symposium - International Astronomical Union ◽

10.1017/s0074180900173152 ◽

1993 ◽

Vol 156 ◽

pp. 173-178

Author(s):

C. S. Jacobs ◽

O. J. Sovers

Keyword(s):

Water Vapor ◽

Reference Frame ◽

Signal To Noise Ratio ◽

Systematic Errors ◽

Noise Signal ◽

Deep Space ◽

Deep Space Network ◽

Space Network ◽

Stochastic Errors ◽

Realistic Assessment

The Deep Space Network (DSN) Radio Reference Frame consists of a catalog of angular positions for 281 extragalactic radio sources based on VLBI measurements made during the period from 1978 to 1992. A realistic assessment of the accuracy of these source position estimates must consider both modeled stochastic errors and systematic model deficiencies. Modeled stochastic errors include thermal noise (signal-to-noise ratio) and fluctuations in tropospheric refractivity due to the changing distribution of water vapor. These modeled errors result in a median formal position uncertainty of ≈0.3 milliarcseconds (mas). In particular, we examine the effect of changing the model for inter-observation correlations of water vapor fluctuations on estimated parameters. Next, a comparison of our radio source positions with independently determined positions is presented as evidence of systematic errors at ≤ 0.5 mas. We discuss several aspects of VLBI model accuracy focussing on tidal effects, antenna thermal expansion, pressure loading, source structure, precession and nutation. Prospects for reducing these errors are also discussed. We conclude by combining these estimates of modeled stochastic errors and systematic errors into an overall assessment of < 1.0 mas for the current accuracy of the DSN extragalactic radio frame.

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An Assessment of the Accuracy of the Deep Space Network Extragalactic Reference Frame

Developments in Astrometry and Their Impact on Astrophysics and Geodynamics ◽

10.1007/978-94-011-1711-1_31 ◽

1993 ◽

pp. 173-178 ◽

Cited By ~ 2

Author(s):

C. S. Jacobs ◽

O. J. Sovers

Keyword(s):

Reference Frame ◽

Deep Space ◽

Deep Space Network ◽

Space Network

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A microwave performance calibration system for NASA's Deep Space Network antennas. Part 1: assessment of antenna gain and pointing, and calibration of radio sources

Tenth International Conference on Antennas and Propagation (ICAP) ◽

10.1049/cp:19970226 ◽

1997 ◽

Cited By ~ 1

Author(s):

P.H. Richter

Keyword(s):

Radio Sources ◽

Antenna Gain ◽

Calibration System ◽

Deep Space ◽

Deep Space Network ◽

Space Network

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Long Coherence Intercontinental Interferometry

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000013151 ◽

1972 ◽

Vol 2 (2) ◽

pp. 114-115 ◽

Cited By ~ 1

Author(s):

J. S. Gubbay

Keyword(s):

Fine Structure ◽

Flux Density ◽

Total Flux ◽

Radio Sources ◽

Deep Space ◽

Deep Space Network ◽

Space Network ◽

Order Of Magnitude

Compact radio sources have been observed over several years at 2.3 GHz by interferometers of the NASA-JPL Deep Space Network with trans- or inter-continental baselines to study the secular behaviour of fine structure appearing in these sources. A comparison of the variation in flux density of components of diameter < 0.001 arcsec with the corresponding variation in total flux density of the source at the same frequency indicated that variations could be wholly ascribed to components of this order of magnitude.

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