scholarly journals Method for the Absolute Calibration of Direct-Current Current Transducers

2019 ◽  
Vol 68 (6) ◽  
pp. 1961-1966 ◽  
Author(s):  
Jianting Zhao ◽  
Yunfeng Lu ◽  
Changwei Zhai ◽  
Qing He ◽  
Xiaoding Huang ◽  
...  
Keyword(s):  
Direct Current ◽  
Absolute Calibration ◽  
The Absolute

scholarly journals Absolute Calibration or Validation of the Altimeters on the Sentinel-3A and the Jason-3 over Lake Issykkul (Kyrgyzstan)

2018 ◽  
Vol 10 (11) ◽  
pp. 1679 ◽  
Author(s):  
Jean-François Crétaux ◽  
Muriel Bergé-Nguyen ◽  
Stephane Calmant ◽  
Nurzat Jamangulova ◽  
Rysbek Satylkanov ◽  
...  
Keyword(s):  
Satellite System ◽  
Reference Points ◽  
Absolute Calibration ◽  
In Situ Data ◽  
Absolute Bias ◽  
Weather Stations ◽  
Field Campaigns ◽  
The Absolute ◽  
Gps System ◽  
Water Height

Calibration/Validation (C/V) studies using sites in the oceans have a long history and protocols are well established. Over lakes, C/V allows addressing problems such as the performance of the various retracking algorithms and evaluating the accuracy of the geophysical corrections for continental waters. This is achievable when measurements of specific and numerous field campaigns and a ground permanent network of level gauges and weather stations are processed. C/V consists of installation of permanent sites (weather stations, limnigraphs, and GPS reference points) and the organization of regular field campaigns. The lake Issykkul serves as permanent site of C/V, for a multi-mission purpose. The objective of this paper is to calculate the altimeter biases of Jason-3 and Sentinel-3A, both belonging to an operational satellite system which is used for the long-term monitoring of lake level variations. We have also determined the accuracy of the altimeters of these two satellites, through a comparison analysis with in situ data. In 2016 and 2017, three campaigns have been organized over this lake in order to estimate the absolute bias of the nadir altimeter onboard the Jason-3 and Sentinel-3A. The fieldwork consisted of measuring water height using a GPS system, carried on a boat, along the track of the altimeter satellite across the lake. It was performed at the time of the pass of the altimeter. Absolute altimeter biases were calculated by averaging the water height differences along the pass of the satellite (GPS from the boat system versus altimetry). Jason-3 operates in a Low Resolution Mode (LRM), while the Sentinel-3A operates in Synthetic Aperture Radar (SAR) mode. In this study we found that the absolute biases measured for Jason-3 were −28 ± 40 mm with the Ocean retracker and 206 ± 30 mm with the Ice-1 retracker. The biases for Sentinel-3A were −14 ± 20 mm with the Samosa (Ocean like) retracker and 285 ± 20 mm with the OCOG (Ice-1-like) retracker. We have also evaluated the accuracy of these two altimeters over Lake Issykkul which reached to 3 cm, for both the instruments, using the Ocean retracker.

scholarly journals The Status of the Absolute Calibration of Stellar Fluxes Between 912 and 1200 Å

1985 ◽  
Vol 111 ◽  
pp. 479-483
Author(s):  
R. S. Polidan ◽  
J. B. Holberg
Keyword(s):  
Planetary Nebula ◽  
White Dwarfs ◽  
Main Sequence ◽  
Absolute Calibration ◽  
Energy Distributions ◽  
B Stars ◽  
The Status ◽  
The Absolute ◽  
Flux Calibration

Recent results have shed new light on the status of the calibration of absolute stellar fluxes between 912 and 1200 Å. Observations of hot white dwarfs, subdwarfs and planetary nebula nuclei with the Voyager ultraviolet spectrometers provide evidence that the current calibration agrees very well with extrapolations of IUE energy distributions shortwards of 1200 Å. Voyager observations of main sequence B-stars used as flux calibration sources have revealed that many are variable in brightness in the 912–1200 Å region. We conclude there is no current observational motivation for any revision of the 912 to 1200 Å calibration described by Holberg et al. (1982).

scholarly journals The Absolute Calibration of the HR Diagram: Fundamental Effective Temperatures and Bolometric Corrections

1978 ◽  
Vol 80 ◽  
pp. 65-76 ◽  
Author(s):  
D. S. Hayes
Keyword(s):  
Spectral Type ◽  
Absolute Calibration ◽  
Effective Temperatures ◽  
The Absolute ◽  
Hr Diagram

Scales of fundamental bolometric connections (B.C.) and effective temperatures (Teff) as a function of spectral type or color are necessary for the comparison of observations and theory in the HR diagram.

New developments for the absolute calibration of light intensities in the far ultraviolet

Physica ◽  
1969 ◽  
Vol 41 (1) ◽  
pp. 209-212 ◽  
Author(s):  
J.F.M. Aarts ◽  
F.J. De Heer ◽  
B.F.J. Luyken ◽  
F.W. Saris ◽  
L. Vriens ◽  
...  
Keyword(s):  
Absolute Calibration ◽  
New Developments ◽  
Light Intensities ◽  
The Absolute ◽  
Far Ultraviolet

scholarly journals Absolute Calibration of Stellar Temperatures

1973 ◽  
Vol 54 ◽  
pp. 153-155
Author(s):  
H. Kienle ◽  
D. Labs
Keyword(s):  
Spectral Energy Distribution ◽  
Black Body ◽  
Absolute Temperature ◽  
Spectral Energy ◽  
Absolute Calibration ◽  
Standard Star ◽  
The Absolute ◽  
Stellar Temperatures ◽  
Image Position ◽  
Radiation Laboratory

The scale of effective temperatures Teff is based on observed absolute radiation temperatures Tr, which are defined by Planck's radiation law where TAu designs the absolute temperature of the gold point. A relative scale of radiation temperatures can be derived from spectrophotometric comparisons with a standard star. The absolute calibration of the standard star (α Lyr or Sun) demands a careful comparison with a standard radiation source of well known spectral energy distribution (Black Body or Synchrotron). With ground-based observations atmospheric extinction is to be taken into account; with extraterrestrial observations detectors may be used which are absolutely calibrated in a radiation laboratory under space conditions.

Application of System Identification to the Absolute Calibration of Acoustic Emission Signals

1994 ◽  
Vol 116 (4) ◽  
pp. 562-566 ◽  
Author(s):  
Pei-Ling Liu ◽  
Tseng-Hwa Song ◽  
Tsung-Tsong Wu
Keyword(s):  
Acoustic Emission ◽  
System Identification ◽  
Source Function ◽  
Characteristic Curve ◽  
Absolute Calibration ◽  
Vertical Force ◽  
Glass Capillary ◽  
Plate Fracture ◽  
Identification Approach ◽  
The Absolute

This paper studies the absolute calibration of acoustic emission signals. The experiments were conducted on a thin plate. Fracture of a glass capillary was adopted to generate a vertical force with a unit-step source function, and an NBS conical transducer was used to record the surface response. It is found that the output of the conical transducer contains surplus wiggles and exhibits amplitude decay. The system identification method is introduced to determine the dynamic model of the system. Calibration using the system model successfully recovers the amplitude and greatly suppresses the surplus wiggles. The method is further improved by subtracting the characteristic curve of the wiggles from the experimental data before the system identification approach is carried out.

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