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USGS2003

Using absolute gravimeter data to determine vertical gravity gradients

The position versus time data from a free-fall absolute gravimeter can be used to estimate the vertical gravity gradient in addition to the gravity value itself. Hipkin has reported success in estimating the vertical gradient value using a data set of unusually good quality. This paper explores techniques that may be applicable to a broader class of data that may be contaminated with "system response" errors of larger magnitude than were evident in the data used by Hipkin. This system response function is usually modelled as a sum of exponentially decaying sinusoidal components. The technique employed here involves combining the x0, v0 and g parameters from all the drops made during a site occupation into a single least-squares solution, and including the value of the vertical gradient and the coefficients of system response function in the same solution. The resulting non-linear equations must be solved iteratively and convergence presents some difficulties. Sparse matrix techniques are used to make the least-squares problem computationally tractable.

Metrologia↗

USGS2006

Set standard deviation, repeatability and offset of absolute gravimeter A10-008

The set standard deviation, repeatability and offset of absolute gravimeter A10-008 were assessed at the Walferdange Underground Laboratory for Geodynamics (WULG) in Luxembourg. Analysis of the data indicates that the instrument performed within the specifications of the manufacturer. For A10-008, the average set standard deviation was (1.6 0.6) ??Gal (1Gal ??? 1 cm s -2), the average repeatability was (2.9 1.5) ??Gal, and the average offset compared to absolute gravimeter FG5-216 was (3.2 3.5) ??Gal. ?? 2006 BIPM and IOP Publishing Ltd.

Metrologia↗

USGS2009

Absolute stellar photometry on moderate-resolution FPA images

An extensive database of star (and Moon) images has been collected by the ground-based RObotic Lunar Observatory (ROLO) as part of the US Geological Survey program for lunar calibration. The stellar data are used to derive nightly atmospheric corrections for the observations from extinction measurements, and absolute calibration of the ROLO sensors is based on observations of Vega and published reference flux and spectrum data. The ROLO telescopes were designed for imaging the Moon at moderate resolution, thus imposing some limitations for the stellar photometry. Attaining accurate stellar photometry with the ROLO image data has required development of specialized processing techniques. A key consideration is consistency in discriminating the star core signal from the off-axis point spread function. The analysis and processing methods applied to the ROLO stellar image database are described. ?? 2009 BIPM and IOP Publishing Ltd.

Metrologia↗

USGS2011

Final report on the Seventh International Comparison of Absolute Gravimeters (ICAG 2005)

The Bureau International des Poids et Mesures (BIPM), Sevres, France, hosted the 7th International Comparison of Absolute Gravimeters (ICAG) and the associated Relative Gravity Campaign (RGC) from August to September 2005.;ICAG 2005 was prepared and performed as a metrological pilot study, which aimed:;(1) To determine the gravity comparison reference values;;(2) To determine the offsets of the absolute gravimeters; and;(3) As a pilot study to accumulate experience for the CIPM Key Comparisons.;This document presents a complete and extensive review of the technical protocol and data processing procedures. The 1st ICAG-RGC comparison was held at the BIPM in 1980-1981 and since then meetings have been organized every 4 years.;In this paper, we present an overview of how the meeting was organized, the conditions of BIPM gravimetric sites, technical specifications, data processing strategy and an analysis of the final results. This 7th ICAG final report supersedes all previously published reports.;Readings were obtained from participating instruments, 19 absolute gravimeters and 15 relative gravimeters. Precise levelling measurements were carried out and all measurements were performed on the BIPM micro-gravity network which was specifically designed for the comparison.

Metrologia↗

USGS2022

Final report on pilot study CCQM-P211: Carbon isotope delta measurements of vanillin

This pilot study was conducted in parallel to the key comparison CCQM-K167. Vials containing 0.25 mg of vanillin were prepared at NRC and distributed to four participating institutes. Institutes could choose any suitable reference materials and methodology to perform carbon isotope delta measurements. Participants reported analysis details, and a carbon isotope delta value and associated uncertainty for the vanillin sample. Each of the carbon isotope delta results of vanillin were compared to the KCRV established from CCQM-K167, and metrological compatibility to the KCRV was determined. Three expert laboratories participated in this study, and their reported results serve as a benchmark to compare the performance of all other participants to these world-class institutes.

Metrologia↗