Details
| Original language | English |
|---|---|
| Title of host publication | International Symposium on Earth and Environmental Sciences for Future Generations - Proceedings of the IAG General Assembly |
| Editors | Laura Sanchez, Jeffrey T. Freymueller |
| Publisher | Springer Verlag |
| Pages | 69-75 |
| Number of pages | 7 |
| ISBN (electronic) | 9783319691701 |
| ISBN (print) | 9783319691695 |
| Publication status | Published - 2018 |
| Event | International Symposium on Earth and Environmental Sciences for Future Generations, 2015 - Prague, Czech Republic Duration: 22 Jun 2015 → 2 Jul 2015 |
Publication series
| Name | International Association of Geodesy Symposia |
|---|---|
| Volume | 147 |
| ISSN (Print) | 0939-9585 |
Abstract
The absolute measurement of g is currently realized through the laser interferometric measurement of a free falling retro-reflector. The Micro-g LaCoste FG5X is a free-fall gravimeter with a laser interferometer in Mach-Zehnder configuration which uses simultaneous time and distance measurements to calculate the absolute value of g. Because the instrument itself contains the necessary working standards for precise time and length measurements, it is considered independent of external references. The timing is kept with a 10 MHz rubidium oscillator with a stability of 5 ×10-10. The length unit is realized by the laser interferometer. The frequency calibrated and iodine stabilized helium-neon laser has a wavelength of 633 nm and an accuracy of 2.5 ×10-11. In 2012 the FG5-220 of the Institut für Erdmessung (IfE) was upgraded to the FG5X-220. The upgrade included a new dropping chamber with a longer free fall and new electronics including a new rubidium oscillator. The metrological traceability to measurement units of the Système International d’unités (SI unit) is ensured by two complementary and successive approaches: the comparison of frequencies with standards of higher order and the comparison of the measured g to a reference measured by absolute gravimeters defined as primary standards within the SI. A number of experiments to test the rubidium oscillator were performed. The oscillator showed a linear drift of 0.2 ×10-3 per month (= 0.3nms-2 per month) in the first 18 months of use. A jump in the frequency of 0.01 Hz (= 20nms-2 was revealed recently and the drift rate changed to -0.4 ×10-3/month. Since the upgrade of the absolute gravimeter the instrument participated in several international comparisons, which showed no significant measuring offset between the instrument prior and after the upgrade.
Keywords
- Absolute gravimetry, Frequency standard, Gravimeter comparison, SI units
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Computers in Earth Sciences
- Earth and Planetary Sciences(all)
- Geophysics
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International Symposium on Earth and Environmental Sciences for Future Generations - Proceedings of the IAG General Assembly. ed. / Laura Sanchez; Jeffrey T. Freymueller. Springer Verlag, 2018. p. 69-75 (International Association of Geodesy Symposia; Vol. 147).
Research output: Chapter in book/report/conference proceeding › Conference contribution › Research › peer review
}
TY - GEN
T1 - Traceability of the Hannover FG5X-220 to the SI units
AU - Schilling, Manuel
AU - Timmen, Ludger
N1 - Funding information: This work was in part funded by Research Foundation (DFG, MU 1141/16-1).
PY - 2018
Y1 - 2018
N2 - The absolute measurement of g is currently realized through the laser interferometric measurement of a free falling retro-reflector. The Micro-g LaCoste FG5X is a free-fall gravimeter with a laser interferometer in Mach-Zehnder configuration which uses simultaneous time and distance measurements to calculate the absolute value of g. Because the instrument itself contains the necessary working standards for precise time and length measurements, it is considered independent of external references. The timing is kept with a 10 MHz rubidium oscillator with a stability of 5 ×10-10. The length unit is realized by the laser interferometer. The frequency calibrated and iodine stabilized helium-neon laser has a wavelength of 633 nm and an accuracy of 2.5 ×10-11. In 2012 the FG5-220 of the Institut für Erdmessung (IfE) was upgraded to the FG5X-220. The upgrade included a new dropping chamber with a longer free fall and new electronics including a new rubidium oscillator. The metrological traceability to measurement units of the Système International d’unités (SI unit) is ensured by two complementary and successive approaches: the comparison of frequencies with standards of higher order and the comparison of the measured g to a reference measured by absolute gravimeters defined as primary standards within the SI. A number of experiments to test the rubidium oscillator were performed. The oscillator showed a linear drift of 0.2 ×10-3 per month (= 0.3nms-2 per month) in the first 18 months of use. A jump in the frequency of 0.01 Hz (= 20nms-2 was revealed recently and the drift rate changed to -0.4 ×10-3/month. Since the upgrade of the absolute gravimeter the instrument participated in several international comparisons, which showed no significant measuring offset between the instrument prior and after the upgrade.
AB - The absolute measurement of g is currently realized through the laser interferometric measurement of a free falling retro-reflector. The Micro-g LaCoste FG5X is a free-fall gravimeter with a laser interferometer in Mach-Zehnder configuration which uses simultaneous time and distance measurements to calculate the absolute value of g. Because the instrument itself contains the necessary working standards for precise time and length measurements, it is considered independent of external references. The timing is kept with a 10 MHz rubidium oscillator with a stability of 5 ×10-10. The length unit is realized by the laser interferometer. The frequency calibrated and iodine stabilized helium-neon laser has a wavelength of 633 nm and an accuracy of 2.5 ×10-11. In 2012 the FG5-220 of the Institut für Erdmessung (IfE) was upgraded to the FG5X-220. The upgrade included a new dropping chamber with a longer free fall and new electronics including a new rubidium oscillator. The metrological traceability to measurement units of the Système International d’unités (SI unit) is ensured by two complementary and successive approaches: the comparison of frequencies with standards of higher order and the comparison of the measured g to a reference measured by absolute gravimeters defined as primary standards within the SI. A number of experiments to test the rubidium oscillator were performed. The oscillator showed a linear drift of 0.2 ×10-3 per month (= 0.3nms-2 per month) in the first 18 months of use. A jump in the frequency of 0.01 Hz (= 20nms-2 was revealed recently and the drift rate changed to -0.4 ×10-3/month. Since the upgrade of the absolute gravimeter the instrument participated in several international comparisons, which showed no significant measuring offset between the instrument prior and after the upgrade.
KW - Absolute gravimetry
KW - Frequency standard
KW - Gravimeter comparison
KW - SI units
UR - http://www.scopus.com/inward/record.url?scp=85037866638&partnerID=8YFLogxK
U2 - 10.1007/1345_2016_226
DO - 10.1007/1345_2016_226
M3 - Conference contribution
AN - SCOPUS:85037866638
SN - 9783319691695
T3 - International Association of Geodesy Symposia
SP - 69
EP - 75
BT - International Symposium on Earth and Environmental Sciences for Future Generations - Proceedings of the IAG General Assembly
A2 - Sanchez, Laura
A2 - Freymueller, Jeffrey T.
PB - Springer Verlag
T2 - International Symposium on Earth and Environmental Sciences for Future Generations, 2015
Y2 - 22 June 2015 through 2 July 2015
ER -