Radiometer Research Articles

On the Estimation of Land Surface Parameters by Using FY-3A Microwave Radiometer Imager(MWRI)

FY3 is new generation polar orbit meteorological satellite of China plan to launch in 2006. There is total of 11 different remote sensing sensor onboard it, design to get the geophysical parameters of atmosphere, land, and ocean surfaces at the same time all day and night and in all weather conditions. The MWRI is a 10-channel five-frequency linearly polarized, passive microwave radiometer imager system onboard the FY3, which measures atmospheric, ocean, and terrain microwave brightness temperatures at 10.65, 18.7, 22.3, 36.5, and 89 GHz. In this paper, in order to derive surface temperature and soil moisture from the MWRI data, a new developed microwave RT model, AIEM was used to simulate the microwave emission characteristic of bare soil, and an new surface soil moisture inversion algorithm was established, which is only need the 10.65GHz V and H channel data. Applying the algorithm to AMSR-E orbit data, which is very similar with the FY3/MWRI, the daily globe soil moisture and surface temperature distribution was derived.

Evaluation of light curing units used for polymerization of orthodontic bonding agents.

This study evaluated the light intensity of various light curing units, the effect of distance of the light guide, and the validity of a tapered light guide. Light curing units tested included (1) four blue light-emitting diode curing units, Lux-O-Max, LEDemetronl, Ortholux LED, and The Cure; (2) two tungsten-quartz halogen curing units, Optilux 501 and Co-bee; and (3) one plasma arc curing unit, Apollo95E. The Optilux 501 was also evaluated for combinations of normal mode and boost mode and Standard tip and Turbo tip light guide. The spectral output of each unit was measured from 300 to 600 nm with a spectroradiometer. The light intensities at distances of zero, five, 10, 15, and 20 mm were determined with the radiometer. The peak value of Ortholux LED and The Cure surpassed that of Apollo95E. The light intensity significantly decreased with distance. Although The Cure showed a higher light intensity than the LEDemetron1 at zero-mm distance, the light intensity of the LEDemetron1 was higher than that of The Cure at five to 20 mm, resulting in no significant difference. The boost mode increased light intensity at any distance. Although the Turbo tip enhanced light intensity at zero-mm distance, reduction of light intensity by Turbo tip was demonstrated at five- to 20-mm distance.

‘Daleks’ and ‘Whirligig’ used to uncover the fate of intercepted light by an apple tree canopy

Canopy light interception and distribution has a major influence on CO2 fixation and the growth and productivity of fruit trees. Spatial and temporal variations in microclimate alter the gas exchange from the leaves and other organs (fruit, branch, etc.). The variable nature of the light environment within the tree crown, and other factors such as leaf age and various stresses (water, diseases, pests) can often impair our ability to extrapolate whole-canopy net carbon exchange (NCE) and transpiration from a small sample of single-leaf measurements. This paper compares two methods for estimating whole-canopy gas exchange. An open-top, through-flow whole-canopy cuvette (Wunsche & Palmer, 1997, HortScience, 32:653-658) was used to enclose the above-ground portion of a 4 year-old apple tree (Malus domestica Borkh. cv. `Braeburn? on M.9 rootstock). NCE and transpiration from the whole canopy was measured over a one week period in mid-season. Measurements of light interception were made on a neighbouring apple tree of the same age and of a similar growth habit using a `whole-plant? radiometer known as the Whirligig (McNaughton et al., 1992, Plant Cell Environ., 17:1061-1068). Data from the Whirligig were used to estimate the distribution of PAR radiation over the total leaf area of the tree. This PAR distribution was then combined with leaf stomatal conductance and leaf net photosynthesis response functions to estimate the rates of whole-canopy NCE and transpiration. The Whirligig calculations of transpiration were in good agreement with data from the whole-canopy cuvette, and with independent measurements of sap flow recorded using heat-pulse sensors located in the trunk of the cuvette tree. The Whirligig estimates of NCE were also comparable to values obtained from the whole-canopy curvette. We conclude that both instruments provide an integrated approach for whole-plant productivity studies

The multi-band reflector antenna of the double-polarization scanning radio aerospace radiometer

The paper describes a 13-channel reflector antenna operating in six subbands of wavelengths from 3 mm to 4.5 cm in two orthogonal linear polarizations for the scanning aerospace radiometer.

Accurate radiometers should measure the output of the Sun

Accurate radiometers should measure the output of the Sun

The multichannel scanning antenna system of the EHF radiometer complex for space vehicles

The paper considered the design and operating principle of the mechanical scanning antenna system for the satellite multichannel radiometer complex possessing high manufacturing adaptability and not needing additional elements for statistical and dynamic balancing.

低キュリー温度磁性膜の作製と広帯域光センサへの応用

Photographic devices utilizing the pyroelectric effect have already been put to practical use. A wide-range photosensor (WRP) is a detector system using the pyromagnetic effect of a low-Curie-temperature magnetic film (LMF) with 1 μm. thickness. When light is directed onto the WRP, the latter absorbs its energy, which causes a magnetization change in the WRP. This change can be read out by a magnetoresistance element and converted into a voltage. The WRP emits a pulse in response to light with a wide range of wavelengths, from visible to invisible, and its peak value depends on the light intensity. Therefore, the WRP can be used in a radio meter and magnetic light remote control, as well as for magnetic infrared communication. This paper describes the preparation of the LMF, Hie construction of the WRP, and the light response characteristics.

Full-wave detection against half-wave detection in radiometry

Half-wave detection which is used in practice in radiometers does not allow the achievement of potential sensitivity. A comparison of the output signal-to-noise ratios for both full-wave and half-wave detectors shows that considerable gain could be obtained with the full-wave detector.

Measurement of Thermal Properties of SiC/C Functionally Gradient Materials by Laser Flash Method

Laser flash technique was applied to measure thermal properties of FGM made by a CVD method. System stability and reproducibility of this measuring system were proved and calibrated with glassy carbon used as reference material. Specimens was prepared by cutting FGM diagonally. Measurements were performed for a wide range of temperatures up to 1500K. Relative heat capacity of the FGM specimen was scattered with in 13% at room temperature and at high temperature above 1200K, and 3% at medium temperature range. On the other hand, thermal diffusivity data showed excellent reproducibility and stability through the whole temperature range. In conclusion, the multi-target radiometer can be applied to measure the thermal properties of non homogeneous materials like FGM.

Evaluación técnica de 5 marcas de concentradores de O2. Proyecto Asturias

To check the technical specifications of 5 O2 concentrators pertaining to 5 different brands: Mark 4, Zefir, Puritan-Bennet, Drager and MHF prototype. The concentrators worked continuously for 37 days. External filters were cleaned after 400 hours and measurements were taken when theoretical flows were between 1 and 3 l/min. One-way analysis of variance and Scheffe's method were used to compare the different brands. Flow measurements were taken with Costrema and Drager debitmeters. O2 concentrations were measured with Drager, Cepo and Oxidig oximeters. Emitted sound was measured with Cel, Spyri Ag Thun, Bruel Kjaer and General Radio meters. Electrical consumption was determined with a Siemens counter. All the concentrators produced flows that were under theoretical values, though the Zefir and MHF models came the closest. Accuracy and precision of flow varied from 1% to -32%, and from 1.1% to 11.7%, respectively. The value of 4 expressing linearity of flows oscillated between 0.959 and 0.991. When flow was 2 l/min or less, all achieved O2 concentrations greater than 90%, but this level was reached only by the Drager and MHF concentrators when flows were 3 l/min. With the exception of the MHF prototype, all the models emitted noise over 50 dB, the Drager machine being the noisiest. Electrical consumption was similar in all models. O2 concentrators can be recommended as sources of oxygen supply, but they have their limitations. Improvements must be made in accuracy of flow and monitoring of the apparatus ability to concentrate; noise must be reduced as well.

Prediction of interference by modeling a radio interference meter

A method of predicting interference by modeling a radio-interference meter which satisfies the requirements of the CISPR is considered. The quasi-peak voltages of the radio interference is determined by analyzing the transmission of the interference signal through a channel consisting of a bandpass filter, a quasi-peak detector and an indicator instrument. The peak, mean and root mean square radio-interference voltages are calculated from the envelope at the output of the bandpass filter. Examples of the calculation of the radio-interference voltage for different forms of detectors in the measuring instrument are given.

Dinámica de la pluma de turbidez del Canal del Dique en la Bahía de Cartagena

Se estudian cuatro imágenes de satélite SPOT, del área de la Bahía de Cartagena de Indias, tomadas por el radiómetro Alta Resolución Visible (ARV) operando en modo multiespectral y con fechas: 27 de marzo de 1986, 10 de noviembre de 1987, 7 de marzo de 1990 y 20 de diciembre de 1990.
 Cada imagen fue corregida radiométricamente en término de reflectancia dispersa y calibrada con base en la concentración de sólidos en suspensión medidos en NTU.
 Los mapas temáticos de isolíneas obtenidos se han incluido en la base de datos que el Centro de Investigaciones Oceanográficas e Hidrográficas administra en ambiente SIG, como nuevos datos para el programa del centro de acopio, procesamiento, análisis y distribución concerniente a la zona costera del Caribe colombiano.
 Estas imágenes muestran los diferentes comportamientos de las masas de agua a través de los sedimentos en suspensión. Se obtuvo una tipificación de las situaciones que se presentan. Los resultados obtenidos son de interés para la calibración de Modelos Matemáticos de la dinámica de la Bahía de Cartagena de Indias; así como su aplicación en la formulación de planes de contingencia en situaciones de algún tipo de contaminación.

MICROWAVE REMOTE SENSING OF ATMOSPHERIC PROPERTY AND WEATHER PROCESS

In this paper, the principle and test of remote sensing of atmospheric property and weather process with 5mm (52.9Ghz, 54.5GHz), 1.35cm (22.235GHz) and 8mm (35,3 GHz) radio- meters are described. The assessment of the ability of remote sensing of atmospheric tem- perature, humidity, liquid water content of clond in all weather (except rain) has been discussed. The efficiency of remote sensing of the atmospheric sounding has been proved by the field experiment. The field experiment results show that it could meet the need of atmospheric sounding in clear and cloudy weather. To monitor the weather, such as the change of air mass, the process of precipitation and the disturbance of microscale and mesoscale weather, the signal reveals itself significantly in the atmospheric microwave radiation. The effect could be used in the nowcasting and artificial precipitation area.

STUDIES ON EFFECTS OF NONLINEAR FEATURES OF CAPILLARY-GRAVITY WAVE SPECTRA ON MICROWAVE EMISSIVITY OF SEA SURFACE

Based on the results of oceanic microwave remote sensing and the dynamics of ocean waves as well as in situ measurements, the effects of nonlinear features of slope spectra of the sea surface at the low sea state on microwave emissivity are studied. It is revealed that the Bragg scattering effect of capillary-gravity waves of the sea surface on microwave influences not only the scattering measurements dara, but also the microwave emission. The effects reflect that there is a trough on the curve of changes in microwave emissivity of vertical polarization with frictional velocity, u*, on the sea surface. The measurement results also indicate changes in microwave emissivity with the wind direction. This fact also proves that the directionality of capillary-gravity waves influences not only the scattering measurements, but also emission. Based on these results, the possibility of measuring the spectra of capillary-gravity waves using a multifrequeney microwave radiometer is presented. It is pointed out that when the physical parameters besides the wind field are measured with microwave radiometry, it is neocessary to correct the effects of sea surface roughness or choose the measurement circumstances to keep away from the influence of the sea state.

Running Crooke’s radiometer backwards

It is pointed out that the direction in which a Crooke’s radiometer rotates can be controlled by changing the temperature of its surroundings. (AIP)

Intercomparison between silicon and blackbody-based radiometry using a silicon photodiode/filter radiometer

Intercomparison between silicon and blackbody-based radiometry using a silicon photodiode/filter radiometer

STUDY ON OPTICAL REMOTE SENSING ATMOSPHERIC AEROSOL AND WATER VAPOUR CONTENT

With the multichannel radiometer of visible and infrared band, ground-based observationsof the intensity of solar spectrum and the atmospheric optical thickness have been made andthe method of remote sensing atmospheric aerosol and water vapour content have been studied.With the radiometer(seven channels of 0.5--1.06μ), observations have been made for morethan one year in Beijing. The atmospheric water vapour content obtained from remote sensingis in accord with that from radiosonde data. In this paper, the characteristics of atmosphericaerosol and total water vapour content are discussed, and the influences of aerosol and thewater vapour on the atmospheric optical thickness and the relationship between them in thewater absorption region are also treated with.

Magnetic Field for Radiating and Receiving Loops Placed on Parallel Planes

In the calibration of radio receivers and field-intensity meters, a radiating loop and a receiving loop under test are mainly located either in a coaxial or coplane to each other. A formula to obtain the average magnetic-field strength incident on a receiving loop is derived for the case where the radiating and receiving loop antennas have a certain deviation on a parallel plane from the coaxial or coplanar alignment of the loops. In order to expand the uniform region of the magnetic field around the test point, the distribution of the magnetic field is investigated by using this formula for some alignments where the four (or less) radiating loops and a receiving loop lie on parallel planes to each other. It is obvious that the uniform regions are improved by factors of about 10 or 16 by increasing a radiating loop to two or four loops, respectively.

Standardization of techniques for testing neutron radiometers

Standardization of techniques for testing neutron radiometers

Limiting sensitivity of a modulated radiometer

Limiting sensitivity of a modulated radiometer