Time Service of the U. S. Naval Observatory

1932 ◽  
Vol 51 (2) ◽  
pp. 538-540 ◽  
Author(s):  
J. Frederick Hellweg
Keyword(s):  
Time Service ◽  
Naval Observatory

scholarly journals Some Results from the Automatic PZT at Richmond, Florida

1972 ◽  
Vol 48 ◽  
pp. 136-138
Author(s):  
Don R. Monger
Keyword(s):  
Probable Error ◽  
Time Service ◽  
Automatic Operation ◽  
Naval Observatory ◽  
The U.S

Automatic operation of the PZT located at the U.S. Naval Observatory Time Service Substation, Richmond, Florida was initiated February 1, 1970. A comparison of one year's automatic operation with the previous year's operation has shown a significant increase in the number of time and latitude sights obtained.Based on an improved ventilating system within the PZT, the probable error of a single night's observation has been reduced.

The 65 cm PZT of the U. S. Naval Observatory

1975 ◽  
Vol 26 ◽  
pp. 309-313
Author(s):  
W. J. Klepczyński
Keyword(s):  
Field Of View ◽  
Proper Motions ◽  
Time Service ◽  
The Earth ◽  
Naval Observatory ◽  
Rotation Of The Earth ◽  
The U.S

AbstractThe Time Service Division of the U.S. Naval Observatory has undertaken a program to construct and install at Washington, D. C. (latitude +39°) a 65 cm photographic zenith tube (PZT) telescope to be used in studies pertaining to the rotation of the Earth. It is expected to improve the precision with which the rate of rotation of the variation of latitude can be determined by photographic techniques and, in addition, will make possible more frequent determinations of these qualities. Due to itp larger field of view, direct intercomparison with the results obtained with other instruments near latitude, +39° will be feasible. Also, it is expected to contribute to studies of the proper motions of stars near declination +39°.

Sub-nanosecond one-way real-time time service system based on UTC

GPS Solutions ◽  
2021 ◽  
Vol 25 (2) ◽  
Author(s):  
Meifang Wu ◽  
Baoqi Sun ◽  
Yuanxin Wang ◽  
Zhe Zhang ◽  
Hang Su ◽  
...  
Keyword(s):  
Real Time ◽  
Service System ◽  
Time Service

scholarly journals CPC2 Reduction with Hipparcos and Proper Motions in The Southern Hemisphere

1998 ◽  
Vol 11 (1) ◽  
pp. 551-551
Author(s):  
N. Zacharias ◽  
M.I. Zacharias ◽  
C. de Vegt ◽  
C.A. Murray
Keyword(s):  
Southern Hemisphere ◽  
Systematic Errors ◽  
Reference Star ◽  
Proper Motions ◽  
Positional Accuracy ◽  
Star Catalog ◽  
Naval Observatory ◽  
Celestial Reference System ◽  
First Time ◽  
Better Than

The Second Cape Photographic Catalog (CPC2) contains 276,131 stars covering the entire Southern Hemisphere in a 4-fold overlap pattern. Its mean epoch is 1968, which makes it a key catalog for proper motions. A new reduction of the 5687 plates using on average 40 Hipparcos stars per plate has resulted in a vastly improved catalog with a positional accuracy of about 40 mas (median value) per coordinate, which comes very close to the measuring precision. In particular, for the first time systematic errors depending on magnitude and color can be solved unambiguously and have been removed from the catalog. In combination with the Tycho Catalogue (mean epoch 1991.25) and the upcoming U.S. Naval Observatory CCD Astrograph Catalog (UCAC) project proper motions better than 2 mas/yr can be obtained. This will lead to a vastly improved reference star catalog in the Southern Hemisphere for the final Astrographic Catalogue (AC) reductions, which will then provide propermotions for millions of stars when combined with new epoch data. These data then will allow an uncompromised reduction of the southern Schmidt surveys on the International Celestial Reference System (ICRS).

scholarly journals Variation of Low-Frequency Time-Code Signal Field Strength during the Annular Solar Eclipse on 21 June 2020: Observation and Analysis

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1216
Author(s):  
Xin Wang ◽  
Bo Li ◽  
Fan Zhao ◽  
Xinyu Luo ◽  
Luxi Huang ◽  
...  
Keyword(s):  
Field Strength ◽  
Solar Eclipse ◽  
Low Frequency ◽  
Signal Propagation ◽  
Normal Operation ◽  
Time Code ◽  
Long Distance ◽  
Time Service ◽  
Annular Solar Eclipse ◽  
Signal Field

Due to the occlusion of the moon, an annular solar eclipse will have an effect on the ionosphere above the earth. The change of the ionosphere, for the low-frequency time-code signal that relies on it as a reflection medium for long-distance propagation, the signal field strength, and other parameters will also produce corresponding changes, which will affect the normal operation of the low-frequency time-code time service system. This paper selects the solar eclipse that occurred in China on 21 June 2020, and uses the existing measurement equipment to carry out experimental research on the low-frequency time-code signal. We measured and analyzed the signal field strength from 20 June 2020 to 23 June 2020, and combined solar activity data, ionospheric data, and geomagnetic data, and attempted to explore the reasons and rules of the change of signal parameters. The results showed that the field strength of the low-frequency time-code signal changed dramatically within a short time period, the max growth value can reach up to 17 dBμV/m and the variation trend yielded ‘three mutations’. This change in signal field strength is probably due to the occurrence of a solar eclipse that has an effect on the ionosphere. When the signal propagation conditions change, the signal strength will also change accordingly.

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