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11. Recent Progress in the VLBI2010 Development

Author

Behrend, D, Böhm, J, Charlot, P, Clark, T, Corey, B, Gipson, J, Haas, R, Koyama, Y, MacMillan, D, Malkin, Z, Niell, A, Nilsson, T, Petrachenko, B, Rogers, A, Tuccari, G, Wresnik, J, and Sideris, Michael G, editor

Published
2009
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12. Demonstration of a Broadband Very Long Baseline Interferometer System: A New Instrument for High-Precision Space Geodesy

Author

Haystack Observatory, Niell, A., Barrett, J., Burns, A., Cappallo, R., Corey, B., Derome, M., Eckert, C., Elosegui, P., McWhirter, R., Poirier, M., Rajagopalan, G., Rogers, A., Ruszczyk, C., SooHoo, J., Titus, M., Whitney, A., Behrend, D., Bolotin, S., Gipson, J., Gordon, D., Himwich, E., Petrachenko, B., Haystack Observatory, Niell, A., Barrett, J., Burns, A., Cappallo, R., Corey, B., Derome, M., Eckert, C., Elosegui, P., McWhirter, R., Poirier, M., Rajagopalan, G., Rogers, A., Ruszczyk, C., SooHoo, J., Titus, M., Whitney, A., Behrend, D., Bolotin, S., Gipson, J., Gordon, D., Himwich, E., and Petrachenko, B.

Published
2022

13. Comparison of Realizations of the Terrestrial Reference Frame

Author

Ma, C, Macmillan, D, Bolotin, S, Le Bail, K, Gordon, D, and Gipson, J

Subjects
Geosciences (General)
Abstract

IGN and DGFI both generated realizations of the terrestrial reference frame under the auspices of the IERS from combination of the same space geodetic data. We compared the IGN and DGFI TRFs with a GSFC CALC/SOLVE TRF. WRMS position and velocity differences for the 40 most frequently observed sites were 2-3 mm and 0.3-0.4 mm/year. There was a scale difference of 0.39/0.09 ppb between the IGN/DGFI realizations and the GSFC solution. When we fixed positions and velocities to either the IGN or DGFI values in CALC/SOLVE solutions, the resulting EOP estimates were not significantly different from the estimates from a standard TRF solution.

Published
2015

14. Modernizing and expanding the NASA Space Geodesy Network to meet future geodetic requirements

Author

Haystack Observatory, Merkowitz, S. M, Bolotin, S., Elosegui, P., Esper, J., Gipson, J., Hilliard, L., Himwich, E., Hoffman, E. D, Lakins, D. D, Lamb, R. C, Lemoine, F. G, Long, J. L, McGarry, J. F, Haystack Observatory, Merkowitz, S. M, Bolotin, S., Elosegui, P., Esper, J., Gipson, J., Hilliard, L., Himwich, E., Hoffman, E. D, Lakins, D. D, Lamb, R. C, Lemoine, F. G, Long, J. L, and McGarry, J. F

Abstract

NASA maintains and operates a global network of Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), and Global Navigation Satellite System ground stations as part of the NASA Space Geodesy Program. The NASA Space Geodesy Network (NSGN) provides the geodetic products that support Earth observations and the related science requirements as outlined by the US National Research Council (NRC in Precise geodetic infrastructure: national requirements for a shared resource, National Academies Press, Washington, 2010. http://nap.edu/12954, Thriving on our changing planet: a decadal strategy for Earth observation from space, National Academies Press, Washington, 2018. http://nap.edu/24938). The Global Geodetic Observing System (GGOS) and the NRC have set an ambitious goal of improving the Terrestrial Reference Frame to have an accuracy of 1 mm and stability of 0.1 mm per year, an order of magnitude beyond current capabilities. NASA and its partners within GGOS are addressing this challenge by planning and implementing modern geodetic stations colocated at existing and new sites around the world. In 2013, NASA demonstrated the performance of its next-generation systems at the prototype next-generation core site at NASA’s Goddard Geophysical and Astronomical Observatory in Greenbelt, Maryland. Implementation of a new broadband VLBI station in Hawaii was completed in 2016. NASA is currently implementing new VLBI and SLR stations in Texas and is planning the replacement of its other aging domestic and international legacy stations. In this article, we describe critical gaps in the current global network and discuss how the new NSGN will expand the global geodetic coverage and ultimately improve the geodetic products. We also describe the characteristics of a modern NSGN site and the capabilities of the next-generation NASA SLR and VLBI systems. Finally, we outline the plans for efficiently operating the NSGN by centralizing and automating the operatio

Published
2021

17. Theory and Realization of Global Terrestrial Reference Systems

Author

Ma, C, Bolotin, S, Gipson, J, Gordon, D, Le Bail, K, and MacMillan, D

Subjects
Earth Resources And Remote Sensing
Abstract

Comparison of realizations of the terrestrial reference frame. IGN and DGFI both generated realizations of the terrestrial reference frame under the auspices of the IERS from combination of the same space geodetic data. We examined both results for VLBI sites using the full geodetic VLBI data set with respect to site positions and velocities and time series of station positions, baselines and Earth orientation parameters. One of the difficulties encountered was matching episodic breaks and periods of non-linear motion of the two realizations with the VLBI models. Our analysis and conclusions will be discussed.

Published
2010

18. Galactocentric acceleration in VLBI analysis

Author

MacMillan, D., Fey, A., Gipson, J., Gordon, D., Jacobs, C., Krásná, H., Malkin, Z., Titov, O., Wang, Gang, Xu, M., Lambert, Sébastien, Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2019

19. El Nino, La Nina and VLBI Measured LOD

Author

Clark, Thomas A, Gipson, J. M, and Ma, C

Subjects
Geophysics
Abstract

VLBI is one of the most important techniques for measuring Earth orientation parameters (EOP), and is unique in its ability to make high accuracy measurements of UT1, and its time derivative, which is related to changes in the length of day, conventionally called LOD. These measurements of EOP give constraints on geophysical models of the solid-Earth, atmosphere and oceans. Changes in EOP are due either to external torques from gravitational forces, or to the exchange of angular momentum between the Earth, atmosphere and oceans. The effect of the external torques is strictly harmonic and nature, and is therefore easy to remove. We analyze an LOD time series derived from VLBI measurements with the goal of comparing this to predictions from AAM, and various ENSO indices. Previous work by ourselves and other investigators demonstrated a high degree of coherence between atmospheric angular momentum (AAM) and EOP. We continue to see this. As the angular momentum of the atmosphere increases, the rate of rotation of the Earth decreases, and vice versa. The signature of the ENSO is particularly strong. At the peak of the 1982-83 El Nino increased LOD by almost 1 ms. This was subsequently followed by a reduction in LOD of 0.75 ms. At its peak, in February of 1998, the 1997-98 El Nino increased LOD by 0.8 msec. As predicted at the 1998 Spring AGU, this has been followed by an abrupt decrease in LOD which is currently -0.4 ms. At this time (August, 1998) the current ENSO continues to develop in new and unexpected ways. We plan to update our analysis with all data available prior to the Fall AGU.

Published
1998

20. Global Positions and Velocities from One Year of GPS Data

Author

Heflin, M. B, Blewitt, G, Jefferson, D, Vigue, Y, Webb, F, Zumberge, J, Argus, D, Gipson, J, Ma, C, and Clark, T

Subjects
Geophysics
Abstract

A generalized no-fiducial approach has been developed to obtain global positions and velocities without fixing any individual position or velocity components. The method used can be applied to any global geodetic technique and proceeds in three general steps. First, daily solutions derived with weak constraints are combined to yield one global set of positions and velocities. Second, 14 minimal constraints are applied to remove uncertainties due to the loosely defined reference frame. Third, transformation from one reference frame to another is accomplished with a 14 parameter transformation. One year of daily FLINN solutions, each made with data from about 40 sites, have been combined to yield our best fit global model...

Published
1993

21. Modernizing and expanding the NASA Space Geodesy Network to meet future geodetic requirements

Author

Merkowitz, S. M., primary, Bolotin, S., additional, Elosegui, P., additional, Esper, J., additional, Gipson, J., additional, Hilliard, L., additional, Himwich, E., additional, Hoffman, E. D., additional, Lakins, D. D., additional, Lamb, R. C., additional, Lemoine, F. G., additional, Long, J. L., additional, McGarry, J. F., additional, MacMillan, D. S., additional, Michael, B. P., additional, Noll, C., additional, Pavlis, E. C., additional, Pearlman, M. R., additional, Ruszczyk, C., additional, Shappirio, M. D., additional, and Stowers, D. A., additional

Published
2018
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22. Demonstration of a Broadband Very Long Baseline Interferometer System: A New Instrument for High-Precision Space Geodesy

Author

Niell, A., primary, Barrett, J., additional, Burns, A., additional, Cappallo, R., additional, Corey, B., additional, Derome, M., additional, Eckert, C., additional, Elosegui, P., additional, McWhirter, R., additional, Poirier, M., additional, Rajagopalan, G., additional, Rogers, A., additional, Ruszczyk, C., additional, SooHoo, J., additional, Titus, M., additional, Whitney, A., additional, Behrend, D., additional, Bolotin, S., additional, Gipson, J., additional, Gordon, D., additional, Himwich, E., additional, and Petrachenko, B., additional

Published
2018
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25. VizieR Online Data Catalog: VLBI ICRF2 (Fey+, 2015)

Author

Fey, A. L., Gordon, D., Jacobs, C. S., Ma, C., Gaume, R. A., Arias, E. F., Bianco, G., Boboltz, D. A., Bockmann, S., Bolotin, S., Charlot, P., Collioud, A., Engelhardt, G., Gipson, J., Gontier, A.-M., Heinkelmann, R., Kurdubov, S., Lambert, S., Lytvyn, S., Macmillan, D. S., Malkin, Z., Nothnagel, A., Ojha, R., Skurikhina, E., Sokolova, J., Souchay, J., Sovers, O. J., Tesmer, V., Titov, O., Wang, G., Zharov, V., and Pomies, Marie-Paule

Subjects
[SDU.ASTR.IM] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

We present the second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years of Very Long Baseline Interferometry observations. The earliest observations used are from 1979 August and the latest are from 2009 March. ICRF2 consists of accurate positions of 295 new "defining" sources and positions of 3119 additional compact radio sources to densify the frame. ICRF2 has more than 5 times as many sources as ICRF1 (Ma et al. 1997, cat. I/251), is roughly 5-6 times more accurate, and is nearly twice as stable in the orientation of its axes.(3 data files).

Published
2016

28. IVS OBSERVATION OF ICRF2-GAIA TRANSFER SOURCES

Author

Haystack Observatory, Corey, Brian E., Titus, Michael A., Le Bail, K., Gipson, J. M., Gordon, D., MacMillan, D. S., Behrend, D., Thomas, C. C., Bolotin, S., Himwich, W. E., Baver, K. D., Bourda, G., Charlot, P., Collioud, A., Haystack Observatory, Corey, Brian E., Titus, Michael A., Le Bail, K., Gipson, J. M., Gordon, D., MacMillan, D. S., Behrend, D., Thomas, C. C., Bolotin, S., Himwich, W. E., Baver, K. D., Bourda, G., Charlot, P., and Collioud, A.

Abstract

The second realization of the International Celestial Reference Frame (ICRF2), which is the current fundamental celestial reference frame adopted by the International Astronomical Union, is based on Very Long Baseline Interferometry (VLBI) data at radio frequencies in X band and S band. The European Space Agency's Gaia mission, launched on 2013 December 19, started routine scientific operations in 2014 July. By scanning the whole sky, it is expected to observe ~500,000 Quasi Stellar Objects in the optical domain an average of 70 times each during the five years of the mission. This means that, in the future, two extragalactic celestial reference frames, at two different frequency domains, will coexist. It will thus be important to align them very accurately. In 2012, the Laboratoire d'Astrophysique de Bordeaux (LAB) selected 195 sources from ICRF2 that will be observed by Gaia and should be suitable for aligning the radio and optical frames: they are called ICRF2-Gaia transfer sources. The LAB submitted a proposal to the International VLBI Service (IVS) to regularly observe these ICRF2-Gaia transfer sources at the same rate as Gaia observes them in the optical realm, e.g., roughly once a month. We describe our successful effort to implement such a program and report on the results. Most observations of the ICRF2-Gaia transfer sources now occur automatically as part of the IVS source monitoring program, while a subset of 37 sources requires special attention. Beginning in 2013, we scheduled 25 VLBI sessions devoted in whole or in part to measuring these 37 sources. Of the 195 sources, all but one have been successfully observed in the 12 months prior to 2015 September 01. Of the sources, 87 met their observing target of 12 successful sessions per year. The position uncertainties of all of the ICRF2-Gaia transfer sources have improved since the start of this observing program. For a subset of 24 sources whose positions were very poorly known, the uncertainty has decre

Published
2016

30. IVS OBSERVATION OF ICRF2-GAIATRANSFER SOURCES

Author

Le Bail, K., primary, Gipson, J. M., additional, Gordon, D., additional, MacMillan, D. S., additional, Behrend, D., additional, Thomas, C. C., additional, Bolotin, S., additional, Himwich, W. E., additional, Baver, K. D., additional, Corey, B. E., additional, Titus, M., additional, Bourda, G., additional, Charlot, P., additional, and Collioud, A., additional

Published
2016
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32. Assessing the Importance of Gender Roles in Couples’ Home-Based Sexual Health Services in Malawi

Author

Gipson, J. D., Muntifering, C. J., Chauwa, F. K., Taulo, F., Tsui, A. O., and Michelle Hindin

Subjects
Adult, Male, Health Knowledge, Attitudes, Practice, Health Services Needs and Demand, Malawi, Focus Groups, Home Care Services, Article, Interviews as Topic, Sex Factors, Sexual Partners, Family Planning Services, Humans, Female, Gender roles and gender issues, HIV/Aids, contraception, community-based programs and interventions, Malawi, Africa
Abstract

To more effectively address individuals’ and couples’ sexual and reproductive health needs, innovative service delivery strategies are being explored. These strategies are logistically and ethically complicated, considering prevailing gender inequalities in many contexts. We conducted an exploratory study to assess the acceptability of couples’ home-based sexual health services in Malawi. We collected qualitative data from six focus group discussions and 10 husband-wife indepth interviews to gain a more thorough understanding of how gender norms influence acceptability of couples’ sexual health services. Findings reveal that women are expected to defer to their husbands and may avoid conflict through covert contraceptive use and non-disclosure of HIV status. Many men felt that accessing sexual health services is stigmatizing, causing some to avoid services or to rely on informal information sources. Gender norms and attitudes toward existing services differentially impact men and women in this setting, influencing the perceived benefits of couples’ sexual health services (Afr J Reprod Health 2010; 14[4]: 63-73).

Published
2010

33. THE SECOND REALIZATION OF THE INTERNATIONAL CELESTIAL REFERENCE FRAME BY VERY LONG BASELINE INTERFEROMETRY

Author

Fey, A. L., primary, Gordon, D., additional, Jacobs, C. S., additional, Ma, C., additional, Gaume, R. A., additional, Arias, E. F., additional, Bianco, G., additional, Boboltz, D. A., additional, Böckmann, S., additional, Bolotin, S., additional, Charlot, P., additional, Collioud, A., additional, Engelhardt, G., additional, Gipson, J., additional, Gontier, A.-M., additional, Heinkelmann, R., additional, Kurdubov, S., additional, Lambert, S., additional, Lytvyn, S., additional, MacMillan, D. S., additional, Malkin, Z., additional, Nothnagel, A., additional, Ojha, R., additional, Skurikhina, E., additional, Sokolova, J., additional, Souchay, J., additional, Sovers, O. J., additional, Tesmer, V., additional, Titov, O., additional, Wang, G., additional, and Zharov, V., additional

Published
2015
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34. Recent Progress in the VLBI2010 Development

Author

Behrend, J., Boehm, J., Charlot, P., Clark, T., Corey, B., Gipson, J., Haas, R., Koyama, Y., MacMillan, D., Malkin, Z., Niell, A., Nilsson, T., Petrachenko, B., Rogers, A., Tuccari, G., Wresnik, J., Max-Planck-Institut für Radioastronomie (MPIFR), NVI, Inc., NASA Goddard Space Flight Center (GSFC), institut de geodesie et geophysique de Vienne (INSTITUT DE GEODESIE ET GEOPHYSIQUE), Institut de geodesie et geophysique, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire aquitain des sciences de l'univers (OASU), MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Kashima Space Technology Center, National Institute of Information and Communications Technology [Tokyo, Japan] (NICT), Pulkovo Observatory, Geodetic Survey Division, Istituto di Radioastronomia di Noto, and Istituto Nazionale di Astrofisica (INAF)

Subjects
[PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], next generation VLBI2010, IVS, geodetic VLBI, Monte Carlo simulations
Abstract

chapter in book series "International Association of Geodesy Symposia" book "Observing our Changing Earth" ISBN 978-3-540-85425-8; International audience; From October 2003 to September 2005, the International VLBI Service for Geodesy and Astrometry (IVS) examined current and future requirements for geodetic VLBI, including all components from antennas to analysis. IVS Working Group 3 ‘VLBI 2010', which was tasked with this effort, concluded with recommendations for a new generation of VLBI systems. These recommendations were based on the goals of achieving 1 mm measurement accuracy on global baselines, performing continuous measurements for time series of station positions and Earth orientation parameters, and reaching a turnaround time from measurement to initial geodetic results of less than 24 hours. To realize these recommendations and goals, along with the need for low cost of construction and operation, requires a complete examination of all aspects of geodetic VLBI including equipment, processes, and observational strategies. Hence, in October 2005, the IVS VLBI2010 Committee (V2C) commenced work on defining the VLBI2010 system specifications. In this paper we give a summary of the recent progress of the VLBI2010 project.

Published
2008

35. Recent Progress in the VLBI2010 Development

Author

Behrend, D, primary, Böhm, J, additional, Charlot, P, additional, Clark, T, additional, Corey, B, additional, Gipson, J, additional, Haas, R, additional, Koyama, Y, additional, MacMillan, D, additional, Malkin, Z, additional, Niell, A, additional, Nilsson, T, additional, Petrachenko, B, additional, Rogers, A, additional, Tuccari, G, additional, and Wresnik, J, additional

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49. Influence of Night Temperature on Growth and Development of Cotton (Gossypium hirsutum L.). I. Fruiting and Boll Development1

Author

Gipson, J. R. and Joham, H. E.

Abstract

Different night temperature regimes were maintained throughout the boll development period on cotton growing in the field during the 1963, 1964, and 1965 seasons. Both fruiting and boll development were found to be closely associated with night temperature. Decreased night temperature resulted in the formation of more flowers and, in some cases, increased fruit set. Relative fruitfulness increased as night temperature decreased between the interval of 21 and 8.8 C and 21 and 14.4 C with ‘Paymaster’ and ‘Acala’ varieties respectively. Temperatures above 19.4 and below 13.3 C reduced fruiting index. Rate of boll development was inversely related to temperature, with a decrease of either day or night temperature resulting in slower boll dvelopment, thus, increasing boll periods. However, in this work night temperature was the dominant environmental factor associated with boll periods. In general, the Paymaster variety appeared to be better adapted to low night temperatures than the Acala variety.

Published
1968
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