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The magnetic gradient tensor is the spatial rate of change of the magnetic vector along the three axes of the Cartesian coordinate system. It is particularly suitable for aeromagnetic surveys because it is relatively insensitive to temporal changes and regional variations of the geomagnetic field. However, the complexity of the flight environment and defects in the existing calibration methods for airborne magnetic tensor gradiometers cannot guarantee the measurement accuracy of tensor data. Research shows that the generalized Hilbert transform can convert total-field gradients, measured over an extensive survey area, into the magnetic gradient tensor components, so a high-precision total-field gradiometer can be employed to calibrate a magnetic tensor gradiometer, using a generalized Hilbert transform calibration method (GHTCM). However, practical survey conditions cannot meet the requirements of the generalized Hilbert transform, which degrades the accuracy of GHTCM. Based on the theory of the generalized Hilbert transform, we first analyze the error sources and error mechanisms of the GHTCM according to the differences between real and ideal survey conditions and then build models to design an appropriate evaluation algorithm for the accuracy of the GHTCM. Simulation experiments based on the open-source flight simulator, FlightGear, and a practical flight experiment are designed. The results indicate that the proposed method can correctly evaluate the accuracy of the GHTCM. This evaluation algorithm is the basis of obtaining the high-precision calibration data for practical airborne magnetic gradient tensor in the survey. [ABSTRACT FROM AUTHOR]

The Advanced Microwave Sounding Unit-A (AMSU-A) on the Meteorological Operations Platform A (METOP-A) Satellite was successfully launched in October 2006. The AMSU-A, which was provided by NOAA, is one of a new generation of total-power microwave radiometers which have been flown on the NOAA-15 to NOAA-18 Satellites since May 1998. A systematic postlaunch calibration and validation (cal/val) of the instrument performance was conducted with on-orbit data. A brief report of the postlaunch assessment of the instrument performance is presented in this paper. Scan-by-scan examination of the radiometric calibration counts is employed to confirm normal functioning of the instrument and to detect any anomalous events, such as lunar contamination (LC) in the space radiometric counts, which are detected, flagged, and corrected using an algorithm for detection and correction of LC in AMSU-A data. The correction algorithm provides a practical approach for scan-by-scan correction of the LC in AMSU-A data and improves the accuracy of operational calibration of the NOAA Level 1B data. The long-term trends of the space and warm calibration counts, channel gains, and housekeeping temperature sensors are monitored. Temperature sensitivity (or NEΔT) values for individual channels are also examined. The monthly mean angular distributions of brightness temperatures from the METOP-A and NOAA-15, -16, and -18 over the tropical ocean region of 20° S-20° N are obtained and theoretically modeled to demonstrate that the ocean can be used as a cold reference calibration target. The establishment of a natural Earth calibration target is an important addition to the few tools available to date for cal/val of spaceborne microwave radiometers. The measured ocean brightness temperatures from the four satellites provide eight measurements across the diurnal time for a unique opportunity of studying the diurnal variation of ocean brightness temperatures which show a pattern of daytime cooling and nighttime warming. [ABSTRACT FROM AUTHOR]

The National Oceanic and Atmospheric Administration (NOAA)-18 Polar-orbiting Operational Environmental Satellite (POES) was successfully launched with the fourth Advanced Microwave Sounding Unit-A onboard in May 2005. After launch, a systematic postlaunch calibration and validation of the instrument performance was conducted with on-orbit data. A brief report of the initial assessment of the instrument performance is presented in this paper. Scan-by-scan examination of the radiometric calibration counts is employed to confirm normal functioning of the instrument and to detect any anomalous events, such as lunar contamination in the space radiometric counts, which are accurately detected, flagged, and corrected using a physical model of lunar surface temperature and antenna patterns derived from on-orbit data. The long-term trends of the space and warm calibration counts, channel gains, and housekeeping temperature sensors are monitored. Temperature sensitivity (or the noise-equivalent ΔT) values for individual channels are also monitored since launch. The long-term temporal trends of the monthly averages and angular distributions of brightness temperature measurements from the NOAA-16 and -18 over the Amazon rain forest region are obtained and compared to demonstrate that the Amazon rain forest can be used as a hot reference calibration target. The establishment of a land calibration target is an important addition to the few tools available to date for calibration and validation of spaceborne microwave radiometers. [ABSTRACT FROM AUTHOR]

We have tested the use of a supercontinuum laser source in laser-based spectral backscatter measurement. The calibration and first results with the prototype instrument are presented with a discussion of improvements and applications in laser-based hyperspectral remote sensing and laboratory measurements. This technique enables the spectral study of the backscatter effects and the calibration and test measurements for the purpose of airborne laser measurement. We also explore the prospect of using a supercontinuum laser source in a broadband (hyperspectral) lidar [ABSTRACT FROM PUBLISHER]

Accurate documentation of instrument calibration saves time and money in the completion of construction projects. There are thousands of newly arrived instruments that must be checked and calibrated and then documented prior to installation in new plants. Such an extended effort was not necessary at the recently completed Front Range Power Station, a 480-MVV combined cycle power plant constructed by The Industrial Company (TIC) near Colorado Springs, Colorado. Instead, one technician printed out calibration certificates in an orderly fashion for more than 60 turnover packages. Ultimately, more than 1,200 HART (highway addressable remote transducer) and conventional devices were documented, and not a single calibration document was subsequently questioned or returned. Even better, no additional costs were incurred for recalibrating the instruments or reworking the documentation, providing an estimated savings of up to US$50,000 in avoided costs. These savings - and the accurate documentation that made them possible - were accomplished through the use of a software tool, the AMS Suite: Intelligent Device Manager software created by Emerson Process Management. This package was originally designed to help end users reduce instrument startup and maintenance costs by accessing diagnostic information from smart field instruments. The database that functions as an integral part of this predictive maintenance technology is also suitable for use by instrument technicians, making instrument calibration easier by saving them time before and after the actual testing and calibration. Furthermore, a record is automatically generated every time an instrument is calibrated or a configuration parameter is changed. Loaded into a PC in a control room or maintenance shop, this software communicates with smart field instruments on the control network, capturing diagnostic information generated by those devices. The massive amount of data obtained in this way is integrated into a single database, organized, processed, and presented on the PC monitor for use by engineers and technicians to streamline and simplify their work. [ABSTRACT FROM PUBLISHER]