The NPL Gonio RAdiometric Spectrometer System (GRASS)

Increasingly satellites have the capability and requirement to measure surfaces at multiple angles, and additionally, due to the variations in slope angle and aspect, few remotely sensed data sets are immune to multi-angular effects. Since such measurements need to be calibrated or at least validated against real ground data we need to improve the accuracy of multi-angular field measurements. A new instrument has been designed, in conjunction with the Natural Environmental Research Council (UK) Field Spectroscopy Facility (FSF) and the University of Southampton for this purpose. The GonioRAdiometric Spectrometer System (GRASS) has been developed at the National Physical Laboratory, which provides quasi-simultaneous, multi-angle, multi-spectral measurements of Earth surface reflected sunlight to support vicarious calibration of satellite sensors operating in the optical region. The instrument will ultimately be available for use by UK researchers through the FSF to provide data to develop a better understanding of the anisotropy of natural targets, which can be used to reduce errors in climate modelling. It will also be utilised for the characterisation of “reference standard” test sites

Unshielded use of thin-film Nb dc superconducting quantum interference devices and integrated asymmetric gradiometers for nondestructive evaluation

Novel nondestructive evaluation measurements made using niobium dc superconducting quantum interference devices with integrated asymmetric first-order gradiometers are described. Comparative theoretical and experimental studies of their spatial response have been described, and it is shown that the gradiometric response makes operation possible in an unshielded and electromagnetically noisy environment. As a demonstration of their capabilities, subsurface defects in a multilayer aluminum structure have been located and mapped using induced eddy currents at 70 Hz, with no magnetic shielding around the specimen or cryostat