High-accuracy time transfer via geostationary satellites: preliminary results

1988 ◽  
Vol 37 (3) ◽  
pp. 418-423 ◽  
Author(s):  
D.A. Howe
Keyword(s):  
High Accuracy ◽  
Time Transfer ◽  
Preliminary Results ◽  
Geostationary Satellites

scholarly journals Multimode Detections from Surveys

2000 ◽  
Vol 175 ◽  
pp. 192-204
Author(s):  
C. Aerts
Keyword(s):  
High Accuracy ◽  
The Other ◽  
Time Base ◽  
Be Stars ◽  
Preliminary Results ◽  
Other Hand ◽  
Multiple Frequencies

AbstractIn this study we present an overview of the search for multiple frequencies in variable Be stars from surveys. We review the recent ground-based photometric surveys and conclude from them that multiperiodicity is not detected. The photometric experiment on board Hipparcos, on the other hand, does allow us to derive multiple periods for a few Be stars. We present the results of our frequency searches in the Hipparcos data for 50 λ Eri stars.Further we review the recent spectroscopic campaigns dedicated to some stars. It seems that all of these campaigns point to multiperiodic phenomena, although for most of them the time base is insufficient to derive the periods with high accuracy. Moreover, the spectroscopic periods are often not the same as those found from the photometry. This clearly demonstrates the necessity of long-term simultaneous photometric and spectroscopic campaigns. We present the preliminary results of such a campaign for the λ Eri star HD 105382.We close with reflections on the cause of the variability observed in the λ Eri stars and on the best viewpoint for further research in this area.

scholarly journals The stellar occultations by the largest satellite of the dwarf planet Haumea, Hi'iaka

2021 ◽  
Author(s):  
Estela Fernández-Valenzuela ◽  
Jose Luis Ortiz ◽  
Bryan Holler ◽  
Monica Vara-Lubiano ◽  
Nicolas Morales ◽  
...  
Keyword(s):  
Light Curve ◽  
North Africa ◽  
High Accuracy ◽  
The Body ◽  
Light Curves ◽  
Effective Diameter ◽  
Preliminary Results ◽  
Stellar Occultations ◽  
The Times ◽  
Triaxial Shape

<p>Two stellar occultations by the largest satellite of the dwarf planet Haumea, Hi'iaka, were predicted to happen on April, 6th and 16th, 2021. Additional high accuracy astrometric analysis was carried out in order to refine the prediction for April 6th, using several telescopes in the 1.2-m to 2-m range, with the final shadow path crossing North Africa. We successfully detected the first event from TRAPPIST-North telescope at Oukaïmeden Observatory (Morocco). Although it was recorded from only one site, this first detection allowed us to improve the prediction for the second that crossed North America from East to West. We had a good success recording six positive detections and several negative detections that constrain the shape and size of the body. The light curves obtained from the different observatories provide the time at which the star disappears and reappears, which are translated into chords (the projected lines on the sky-plane as observed from each location). Additionally, we carried out a campaign to study Hi'iaka's rotational light-curve, studying the residuals of Haumea's rotational light-curve to a four-order Fourier fit. We obtained the rotational phases at the times of the occultations, which is critical for the analysis of the occultations, given that Hi’iaka is clearly non-spherical. Our preliminary results show that Hi'iaka indeed has a triaxial shape with a larger effective diameter than what has been published so far. The preliminary results and their implications will be discussed in this talk. </p>

Short-term analysis of internal and external CORS clocks

2020 ◽  
Vol 14 (3) ◽  
pp. 355-359 ◽  
Author(s):  
Kamil Maciuk
Keyword(s):  
High Accuracy ◽  
High Rate ◽  
Time Transfer ◽  
Short Term ◽  
International Gnss Service ◽  
External Stability ◽  
Gnss Measurements ◽  
Internal And External Stability ◽  
Term Analysis

AbstractThe International GNSS Service (IGS) provides high-accuracy clock products for both GNSS satellites and stations. On board of each GNSS satellite are located 3–4 atomic oscillators. In the case of CORS oscillators, the majority of them are equipped with internal oscillators and a part uses external, high-rate clocks. In the IGS network there are four types of external oscillators: quartz, rubidium, caesium and H-maser. These CORS are often reference stations for precise GNSS measurements or for time transfer. In this paper the author provides analyses of the internal and external stability of the reference stations oscillators via the usage of Allan variations. The results show a strong advantage of the external clocks over internal ones by about five orders of magnitude.

Time transfer via geostationary satellites

1986 ◽  
Vol 74 (1) ◽  
pp. 161-162 ◽  
Author(s):  
C.C. Costain
Keyword(s):  
Time Transfer ◽  
Geostationary Satellites

scholarly journals The Intumescent Paint Layers Thickness Influence on the Load-Bearing Capacity of the Steel Joints

2014 ◽  
Vol 969 ◽  
pp. 332-339 ◽  
Author(s):  
Ioan Száva ◽  
Károly Jármai ◽  
Sorin Vlase ◽  
Tibor Bodnár ◽  
Valentin Vasile Ungureanu ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Electric Furnace ◽  
Steel Structures ◽  
High Accuracy ◽  
Image Correlation ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Full Field ◽  
Preliminary Results ◽  
Steel Joints

In order to improve the steel structures protection against fire, the intumescent paint method can be applied along with other methods. The intumescent paints layers numbers have to be optimized though. An uniform layer of intumescent paint, foreseen to protect the whole structure, represents both a higher cost and an uneconomical solution. The authors started examination on this problem, by analyzing one of the most recommended steel joints from the earthquake-proof criteria. The conceived and realized original electric furnace allows both a high-accuracy tuning/adjustment of the temperature and a good-stability of its, by means of the original electronic command. In order to perform high-accuracy and full-field monitoring of the displacements, the authors used a modern optical non-contact system, the Video Image Correlation one. The obtained preliminary results are very promising and will be continued in the next period by this international team.

High accuracy continuous time transfer with GPS IPPP and T2L2

2018 ◽  
Author(s):  
Julia Leute ◽  
Gerard Petit ◽  
Pierre Exertier ◽  
Etienne Samain ◽  
Daniele Rovera ◽  
...  
Keyword(s):  
Continuous Time ◽  
High Accuracy ◽  
Time Transfer
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