scholarly journals Methods of Correction for the “Wet” Atmosphere in Estimating Baseline Lengths from VLBI

1988 ◽  
Vol 129 ◽  
pp. 543-544
Author(s):  
G. Elgered ◽  
J. L. Davis ◽  
T. A. Herring ◽  
I. I. Shapiro
Keyword(s):  
Water Vapor ◽  
Propagation Delay ◽  
Propagation Path ◽  
Baseline Length ◽  
Space Observatory ◽  
Owens Valley ◽  
Use Of Data ◽  
Onsala Space Observatory ◽  
Vlbi Data ◽  
Water Vapor Radiometer

The error in VLBI estimates of baseline length caused by unmodelled variations in the propagation path through the atmosphere is greater for longer baselines. We present and discuss series of estimates of baseline lengths obtained using different methods to correct for the propagation delay caused by atmospheric water vapor. The main methods are use of data from a water-vapor radiometer (WVR) and Kalman-filtering of the VLBI data themselves to estimate the propagation delay. Since the longest timespan of WVR data associated with geodetic VLBI experiments was obtained at the Onsala Space Observatory in Sweden, we present results for the following three baselines: (1) Onsala–Wettzell, FRG (920 km), (2) Onsala–Haystack/Westford, MA (5600 km), and (3) Onsala–Owens Valley (7914 km).

scholarly journals Water Vapor Radiometry at the Onsala Space Observatory from 1980 to 1987

1988 ◽  
Vol 129 ◽  
pp. 547-548 ◽  
Author(s):  
J. M. Johansson ◽  
G. Elgered ◽  
B. O. Rönnäng
Keyword(s):  
Water Vapor ◽  
Atmospheric Water Vapor ◽  
Atmospheric Water ◽  
Space Observatory ◽  
Brightness Temperatures ◽  
Onsala Space Observatory ◽  
Water Vapor Radiometer ◽  
Sky Brightness

Variations in atmospheric water vapor are difficult to correct for in geodetic, astrometric, and mm-wave astronomy VLBI. The use of a water vapor radiometer (WVR) has given promising results. The algorithm which relates the sky brightness temperatures observed by the WVR to the delay caused by atmopheric water vapor is discussed. Examples of WVR measurements made at the Onsala Space Observatory from 1980 to 1987 are presented.

scholarly journals Earth Rotation Information Derived from Merit and Polaris VLBI Observations

1981 ◽  
Vol 63 ◽  
pp. 97-122 ◽  
Author(s):  
D. S. Robertson ◽  
W. E. Carter
Keyword(s):  
Earth Rotation ◽  
The United States ◽  
Geodetic Survey ◽  
West Germany ◽  
National Geodetic Survey ◽  
Space Observatory ◽  
Paper Briefly ◽  
Owens Valley ◽  
Radio Observatory ◽  
Onsala Space Observatory

AbstractIn September and October 1980, the National Geodetic Survey, jointly with the National Aeronautics and Space Administration and several other agencies and institutions, conducted a series of astronomical radio interferometry (VLBI) observing sessions to support the IAU/IUGG MERIT short campaign. A total of 14 days of observations, organized into two 7-day sessions, was collected by three observatories in the United States (Harvard Radio Astronomy Station (HRAS), Haystack Observatory, and Owens Valley Radio Observatory) and the Onsala Space Observatory in Sweden. Chilbolton Observatory, England, and Effelsberg Observatory, West Germany, also participated on some days. Immediately following the MERIT campaign, NGS initiated a series of 24-hour observing sessions, spaced at approximately 2-week intervals, as a pilot program to project POLARIS. All of these sessions included two observatories, HRAS and Haystack, and Onsala participated in about half of the sessions. The MERIT and POLARIS observations were made with the third generation MARK III VLBI system using procedures and schedules designed to yield high quality geodetic information, including Earth rotation values. This paper briefly traces the planning, observing, and data processing activities, and presents the Earth rotation information thus far derived from the data.

scholarly journals Sensing atmospheric structure: Tropospheric tomographic results of the small-scale GPS campaign at the Onsala Space Observatory

2000 ◽  
Vol 52 (11) ◽  
pp. 941-945 ◽  
Author(s):  
A. Flores ◽  
L. P. Gradinarsky ◽  
P. Elósegui ◽  
G. Elgered ◽  
J. L. Davis ◽  
...  
Keyword(s):  
Small Scale ◽  
Space Observatory ◽  
Atmospheric Structure ◽  
Onsala Space Observatory

scholarly journals Observing UT1-UTC with VGOS

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Rüdiger Haas ◽  
Eskil Varenius ◽  
Saho Matsumoto ◽  
Matthias Schartner
Keyword(s):  
Standard Deviation ◽  
Reference Frame ◽  
Earth Rotation ◽  
Space Observatory ◽  
International Earth Rotation ◽  
Onsala Space Observatory ◽  
X Band ◽  
First Results

AbstractWe present first results for the determination of UT1-UTC using the VLBI Global Observing System (VGOS). During December 2019 through February 2020, a series of 1 h long observing sessions were performed using the VGOS stations at Ishioka in Japan and the Onsala twin telescopes in Sweden. These VGOS-B sessions were observed simultaneously to standard legacy S/X-band Intensive sessions. The VGOS-B data were correlated, post-correlation processed, and analysed at the Onsala Space Observatory. The derived UT1-UTC results were compared to corresponding results from standard legacy S/X-band Intensive sessions (INT1/INT2), as well as to the final values of the International Earth Rotation and Reference Frame Service (IERS), provided in IERS Bulletin B. The VGOS-B series achieves 3–4 times lower formal uncertainties for the UT1-UTC results than standard legacy S/X-band INT series. The RMS agreement w.r.t. to IERS Bulletin B is slightly better for the VGOS-B results than for the simultaneously observed legacy S/X-band INT1 results, and the VGOS-B results have a small bias only with the smallest remaining standard deviation.

The Seoul Water Vapor Radiometer for the Middle Atmosphere: Calibration, Retrieval, and Validation

2011 ◽  
Vol 49 (3) ◽  
pp. 1052-1062 ◽  
Author(s):  
Evelyn De Wachter ◽  
Alexander Haefele ◽  
Niklaus Kampfer ◽  
Soohyun Ka ◽  
Jung Eun Lee ◽  
...  
Keyword(s):  
Water Vapor ◽  
Middle Atmosphere ◽  
Water Vapor Radiometer

scholarly journals Blockchain Network Propagation Mechanism Based on P4P Architecture

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Junjie Huang ◽  
Liang Tan ◽  
Sun Mao ◽  
Keping Yu
Keyword(s):  
Propagation Speed ◽  
Propagation Delay ◽  
Propagation Path ◽  
Propagation Mechanism ◽  
Internet Service ◽  
Network Provider ◽  
Network Propagation ◽  
System Overhead ◽  
Message Propagation

Blockchain is a mainstream technology in which many untrustworthy nodes work together to maintain a distributed ledger with advantages such as decentralization, traceability, and tamper-proof. The network layer communication mechanism in its architecture is the core of the networking method, message propagation, and data verification among blockchain nodes, which is the basis to ensure blockchain’s performance and key features. When blocks are propagated in peer-to-peer (P2P) networks with gossip protocol, the high propagation delay of the protocol itself reduces the propagation speed of the blocks, which is prone to the chain forking phenomenon and causes double payment attacks. To accelerate the propagation speed and reduce the fork probability, this paper proposes a blockchain network propagation mechanism based on proactive network provider participation for P2P (P4P) architecture. This mechanism first obtains the information of network topology and link status in a region based on the internet service provider (ISP), then it calculates the shortest path and link overhead of peer nodes using P4P technology, prioritizes the nodes with good local bandwidth conditions for transmission, realizes the optimization of node connections, improves the quality of service (QoS) and quality of experience (QoE) of blockchain networks, and enables blockchain nodes to exchange blocks and transactions through the secure propagation path. Simulation experiments show that the proposed propagation mechanism outperforms the original propagation mechanism of the blockchain network in terms of system overhead, rate of data success transmission, routing hops, and propagation delay.

scholarly journals Development of a high-stability water vapor radiometer

Radio Science ◽  
1998 ◽  
Vol 33 (2) ◽  
pp. 449-462 ◽  
Author(s):  
Alan B. Tanner
Keyword(s):  
Water Vapor ◽  
High Stability ◽  
Water Vapor Radiometer
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