First Experience with the Transportable MPG-2 Absolute Gravimeter
We report on design details and first results obtained with the transportable absolute gravimeter MPG-2 (“Max-Planck-Gravimeter”). It is developed as an evolution of the stationary device MPG-1, completed in 2007. The MPG-2 is built on a common scheme whe
- PDF / 861,007 Bytes
- 7 Pages / 547.087 x 737.008 pts Page_size
- 15 Downloads / 209 Views
First Experience with the Transportable MPG-2 Absolute Gravimeter S. Svitlov, C. Rothleitner, and L.J. Wang
Abstract We report on design details and first results obtained with the transportable absolute gravimeter MPG-2 (“Max-Planck-Gravimeter”). It is developed as an evolution of the stationary device MPG-1, completed in 2007. The MPG-2 is built on a common scheme where the position of a freely falling object is monitored. The setup consists of a ballistic block, an interferometer and the electronics. Free fall drops can be repeated every 10 s with the standard deviation close to 30 μgal. A one-day gravity observation gives a result with a standard deviation of the mean of less than 5 μgal. A prototype of the MPG-2 took part in the ECAG-2007. New measurements at the reference gravity station “Bad Homburg”, Germany confirmed the declared combined standard uncertainty of 50 μgal.
by fitting a freefall motion model to the measured time-distance coordinates. A comparison of different gravimeters helps to discover possible systematic errors. In this paper, we describe the MPG-2 absolute gravimeter and discuss first results obtained at different sites. The offset detected during the ECAG-2007 of (+515 ± 14) μgal was resolved by placing the ion pump about 0.3 m farther away from the ballistic block. In the specifications we introduce and explain the repeatability (5 μgal), reproducibility (25 μgal), and standard uncertainty (50 μgal). Such metrological components can be used separately, depending on a particular application, along with the reported result of measurement.
11.2 Setup 11.1 Introduction An absolute value of gravitational acceleration g is widely required in metrology, geodesy and geophysics. In an absolute gravimeter the position of a free falling test mass is monitored using an interferometer and highly precise length and time standards (Niebauer et al., 1995). The test mass contains one retro-reflector, while a second one is fixed to a pseudo-inertial reference frame. The freefall trajectory is given by timing the interference fringes generated during the test mass’s motion. Afterwards, the g value is calculated
S. Svitlov () Max Planck Institute for the Science of Light, Erlangen 91058, Germany e-mail: [email protected]
The classical freefall method is adopted for the instrument. It is developed as an evolution of the earlier completed stationary MPG-1 absolute gravimeter (Rothleitner, 2008). Figure 11.1 shows the setup of the MPG-2. It is a transportable apparatus, although still a prototype. It consists of the ballistic block with the falling body, motor and a lifting/releasing mechanism inside a vacuum chamber, plus the ion pump, a table, an interferometer, a notebook with a PCI extension, a laser, and a frequency standard (Rothleitner, 2008). The interferometer is built following the modified Mach-Zehnder “in-line system” (Niebauer et al., 1995). It is mounted on top of the Superspring (Micro-g LaCoste), which is used as the vibration isolated reference retro-reflector. The actual
Data Loading...
