A Method for Determining Detector Efficiencies In-Situ by Variation of the Radiation Incidence Angle

1990 ◽  
Vol 122 (2) ◽  
pp. 695-704 ◽  
Author(s):  
J. Wernisch ◽  
A. Schönthaler ◽  
H.-J. August
Keyword(s):  
Incidence Angle ◽  
Radiation Incidence

scholarly journals Method for fast determination of the angle of ionizing radiation incidence from data measured by a Timepix3 detector

2021 ◽  
Vol 10 (1) ◽  
pp. 63-70
Author(s):  
Felix Lehner ◽  
Jürgen Roth ◽  
Oliver Hupe ◽  
Marc Kassubeck ◽  
Benedikt Bergmann ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Incidence Angle ◽  
Computation Time ◽  
Incident Radiation ◽  
Angle Of Incidence ◽  
Time Behavior ◽  
Calculation Algorithm ◽  
3D Geometry ◽  
Photon Event ◽  
Radiation Incidence

Abstract. This paper presents a method of how to determine spatial angles of ionizing radiation incidence quickly, using a Timepix3 detector. This work focuses on the dosimetric applications where detectors and measured quantities show significant angle dependencies. A determined angle of incidence can be used to correct for the angle dependence of a planar Timepix3 detector. Up until now, only passive dosemeters have been able to provide a correct dose and preserve the corresponding incidence angle of the radiation. Unfortunately, passive dosemeters cannot provide this information in “real” time. In our special setup we were able to retrieve the spatial angles with a runtime of less than 600 ms. Employing the new Timepix3 detector enables the use of effective data analysis where the direction of incident radiation is computed from a simple photon event map. In order to obtain this angle, we combine the information extracted from the map with known 3D geometry surrounding the detector. Moreover, we analyze the computation time behavior, conditions and optimizations of the developed spatial angle calculation algorithm.

Titan’s Ultraviolet Airglow Variability with Solar Cycle and Saturn Local Time

2020 ◽  
Author(s):  
Emilie Royer ◽  
Marielle Cooper ◽  
Joseph Ajello ◽  
Larry Esposito ◽  
Frank Crary
Keyword(s):  
Solar Cycle ◽  
Local Time ◽  
Solar Maximum ◽  
Incidence Angle ◽  
Upper Atmosphere ◽  
Particle Precipitation ◽  
Cassini Mission ◽  
Airglow Emissions ◽  
Airglow Intensity

<p>The Cassini spacecraft observed Titan’s upper atmosphere and its airglow emissions from 2005 to 2017. It is now established that the solar XUV radiation is the main source of dayglow, while magnetospheric particle precipitation principally acts on the nightside of the satellite. Nevertheless, one of the questions remaining unanswered after the end of the Cassini mission concerns the role and quantification of the magnetospheric particle precipitation and other minor sources such as micrometeorite precipitation and cosmic galactic ray at Titan. We report here on enhancements observed in Ultraviolet (UV) observations of Titan airglow made with the Cassini-Ultraviolet Imaging Spectrograph (UVIS). Enhancements are correlated with magnetospheric changing conditions occurring while the spacecraft, and thus Titan, are known to have crossed Saturn’s magnetopause and have been exposed to the magnetosheath environment. The processing and interpretation of 13+ years of airglow observations at Titan allows now for global studies of the upper atmosphere as a function of the Saturn Local Time (SLT) and the solar cycle.</p><p>Nitrogen airglow occur at about 1100 km of altitude in Titan’s upper atmosphere. Observations by the Cassini-UVIS instrument revealed the emission of the LBH band system, VK band system as well as Nitrogen atomic emission lines at 1085Å and 1493Å, as the prominent features of airglow emissions at Titan, as shown in Figures 1 and 2. Measurements were made at a wide range of solar incidence angles and Saturn Local Time (SLT), during the entire Cassini mission, allowing for the investigation of the upper atmosphere response to the magnetospheric environment and energetic particle precipitation. Additionally, observations were taken in a variety of solar condition, from solar maximum to minimum. UVIS observations of Titan around 12PM SLT (near Saturn’s magnetopause) present evidence of Titan’s upper atmosphere response to a fluctuating magnetospheric environment.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.9617eca672fe56938492951/sdaolpUECMynit/0202CSPE&app=m&a=0&c=975f92d7d9d43faa47cacd77ad47438f&ct=x&pn=gnp.elif" alt=""></p><p><strong>Figure 1.</strong> Airglow intensity as a function of the saturn Local Time (SLT), for observation taken close the Saturn’s magnetopause (12PM SLT, labelled ‘12h’) and observations taken around miadnight SLT (labelled ‘24h’). Dayglow spectra exhibit higher averaged airglow intensity than Nightglow spectra.</p><p>We present here comparisons of the spectral emissions from the dayglow (Solar incidence angle <110°) and nightglow (Solar incidence angle ≥110°) between a rayheight of 900-1200 km around noon (±1 h) and around midnight (±1 h) SLT, during solar minima and maxima conditions (Fig. 2). Results show an enhancement of the airglow brightness with increasing particle precipitation, especially at SLT close to noon (i.e. close to the magnetopause), during solar maximum and minimum. Correlation between the ratio of the V-K, LBH, and NI-1493Å emission peaks are also presented.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.2357e48772fe52168492951/sdaolpUECMynit/0202CSPE&app=m&a=0&c=2c6d843782e300fc27ec3db3de320caf&ct=x&pn=gnp.elif" alt=""></p><p><strong>Figure 2.</strong> Dayglow intensity as a function of the saturn Local Time (SLT) and solar cycle. Observations have been dispatched in four groups as a function of Titan’s orbital position within Saturn’s magnetosphere and maximum oe minimum stage of the solar cycle. Results suggest that solar maximum conditions around midgnight SLT favor the apparition of the brightest dayglow.</p><p>In the past decade, results from the Cassini-UVIS instrument greatly improved our understanding of airglow production at Titan. However, combining remote-sensing datasets, such as Cassini-UVIS data, with in-situ measurements taken by the Cassini Plasma Spectrometer (CAPS) instrument can provide us with a more rigorous assessment of the airglow contribution and correlations between data from simultaneous observations of in-situ Cassini instruments (CAPS, RPWS and MIMI) has been possible on few occasions. UVIS results present here will be put in context with results from in-situ simultaneous observations.</p><!-- COMO-HTML-CONTENT-END --> <p class="co_mto_htmlabstract-citationHeader"> <strong class="co_mto_htmlabstract-citationHeader-intro">How to cite:</strong> Royer, E., Cooper, M., Ajello, J., Esposito, L., and Crary, F.: Titan’s Ultraviolet Airglow Variability with Solar Cycle and Saturn Local Time, Europlanet Science Congress 2020, online, 21 September–9 Oct 2020, EPSC2020-415, 2020 </p>

scholarly journals An Assessment of SAPHIR Calibration Using Quality Tropical Soundings

2015 ◽  
Vol 32 (1) ◽  
pp. 61-78 ◽  
Author(s):  
G. Clain ◽  
H. Brogniez ◽  
V. H. Payne ◽  
V. O. John ◽  
M. Luo
Keyword(s):  
Radiative Transfer ◽  
Incidence Angle ◽  
Intraseasonal Variability ◽  
Sensor Data ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Water Vapor Absorption ◽  
Infrared Observation ◽  
Cross Track

AbstractThe Sondeur Atmosphérique du Profil d’Humidité Intertropicale par Radiométrie (SAPHIR) instrument on board the Megha-Tropiques (MT) platform is a cross-track, multichannel microwave humidity sounder with six channels near the 183.31-GHz water vapor absorption line, a maximum scan angle of 42.96° (resulting in a maximum incidence angle of 50.7°), a 1700-km-wide swath, and a footprint resolution of 10 km at nadir. SAPHIR L1A2 brightness temperature (BT) observations have been compared to BTs simulated by the radiative transfer model (RTM) Radiative Transfer for the Television and Infrared Observation Satellite (TIROS) Operational Vertical Sounder (RTTOV-10), using in situ measurements from radiosondes as input. Selected radiosonde humidity observations from the Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year (CINDY)–Dynamics of the Madden–Julian Oscillation (DYNAMO) campaign (September 2011–March 2012) were spatiotemporally collocated with MT overpasses. Although several sonde systems were used during the campaign, all of the sites selected for this study used the Vaisala RS92-SGPD system and were chosen in order to avoid discrepancies in data quality and biases.To interpret the results of the comparison between the sensor data and the RTM simulations, uncertainties associated with the data processing must be propagated throughout the evaluation. The magnitude of the bias was found to be dependent on the observing channel, increasing from 0.18 K for the 183.31 ± 0.2-GHz channel to 2.3 K for the 183.31 ± 11-GHz channel. Uncertainties and errors that could impact the BT biases were investigated. These can be linked to the RTM input and design, the radiosonde observations, the chosen methodology of comparison, and the SAPHIR instrument itself.

Alpha Radiation Incidence Angle Influence on Planar FDSOI nMOSFET

2019 ◽  
Vol 39 (1) ◽  
pp. 85-92
Author(s):  
Robson A. Magalhães ◽  
Paula G. Agopian ◽  
Marcilei A. Silveira ◽  
Renato C. Giacomini
Keyword(s):  
Incidence Angle ◽  
Alpha Radiation ◽  
Radiation Incidence

Microstructural Identification of SiNx Films by Real-Time Ellipsometry

1997 ◽  
Vol 472 ◽  
Author(s):  
G. Soto ◽  
E. C. Samano ◽  
R. Machorro ◽  
M. Avalos ◽  
L. Cota
Keyword(s):  
Real Time ◽  
Film Growth ◽  
Incidence Angle ◽  
Polarization State ◽  
Sample Surface ◽  
Deposition Process ◽  
Slight Variation ◽  
Si Substrates ◽  
Amorphous Si

ABSTRACTReal-time ellipsometry has shown to be a powerful tool to analyze thin films during processing. It is non-disturbing and its sensitivity lies in the submonolayer range. In fact, a slight variation in the film microstructure might result in a significant change of the polarization state of the reflected beam from the sample surface. SiNx layers have been grown on glass, quartz, KC1 and Si substrates by laser ablating a Si3N4 sintered target in vacuum and N2 environment. The film growth was monitored by real time ellipsometry at a fixed wavelength, and a fixed incidence angle. Once the deposition process is completed, the refractive index was obtained by perfoming in situ spectroellipsometric measurements in the 1.5 to 5 eV photon-energy range. The best curve fitting of the experimental data is used to find the film composition: a mixture of Si3N4, polycrystalline Si, and amorphous Si. The films composition and micro structure inferred from ellipsometric data are compared to those obtained by in-situ surface techniques and TEM, respectively.

Estimation of soil moisture from Sentinel data

2020 ◽  
Author(s):  
Stefan Krebs Lange-Willman ◽  
Henning Skriver ◽  
Inge Sandholt
Keyword(s):  
Soil Moisture ◽  
Incidence Angle ◽  
Speckle Noise ◽  
Detection Algorithm ◽  
Retrieval Algorithm ◽  
Innovation Fund ◽  
High Incidence ◽  
Land Cover Maps ◽  
The Impact

<p>The present project presents the technical implementation, testing and validation of a soil moisture retrieval algorithm in Python using C-band Sentinel-1 data at high incidence angle (∼42°). The retrieval algorithm is based on the alpha approximation, first developed by [Balenzano et al. 2011]. The alpha approximation utilizes the dense temporal coverage of the Sentinel-1 mission, assuming that changes in backscatter between subsequent acquisitions are only due to variations in soil moisture, such that vegetation and roughness can be neglected. The area used for testing the algorithm was chosen to be the region surrounding the Foulum test center for agricultural studies in Denmark, due to the availability of time series from 2018 of in situ soil moisture measurements to be used for validation. Masking of too densely vegetated areas have been performed using the cross-polarized component of the SAR backscatter, which have been validated using NDVI maps. </p><p>Auxiliary data, including land cover maps and parcel borders enable the computation of backscatter field means, significantly reducing the impact of speckle noise and thus decreasing uncertainty of the estimated soil moisture. Consequently, the results have field scale resolution (i.e. ∼0.1 km). The permittivity to soil moisture inversion is performed using a polynomial model by [Hallikainen et al. 1985], where a soil texture map provide the information necessary to obtain precise results. </p><p>Further work will aim toward applying a change detection algorithm in order to detect sudden temporal changes in vegetation and surface roughness, as the alpha approximation is inherently sensitive to such sudden changes.</p><p>The study has received partial funding from Innovation Fund Denmark, contract number: 7049-00004B (MOIST).</p>

scholarly journals Vegetation Optical Depth and Soil Moisture Retrieved from L-Band Radiometry over the Growth Cycle of a Winter Wheat

2018 ◽  
Vol 10 (10) ◽  
pp. 1637 ◽  
Author(s):  
Thomas Meyer ◽  
Lutz Weihermüller ◽  
Harry Vereecken ◽  
François Jonard
Keyword(s):  
Soil Moisture ◽  
Winter Wheat ◽  
Optical Depth ◽  
Incidence Angle ◽  
Soil Surface ◽  
Growing Season ◽  
Area Index ◽  
Vegetation Height ◽  
L Band

L-band radiometer measurements were performed at the Selhausen remote sensing field laboratory (Germany) over the entire growing season of a winter wheat stand. L-band microwave observations were collected over two different footprints within a homogenous winter wheat stand in order to disentangle the emissions originating from the soil and from the vegetation. Based on brightness temperature (TB) measurements performed over an area consisting of a soil surface covered by a reflector (i.e., to block the radiation from the soil surface), vegetation optical depth (τ) information was retrieved using the tau-omega (τ-ω) radiative transfer model. The retrieved τ appeared to be clearly polarization dependent, with lower values for horizontal (H) and higher values for vertical (V) polarization. Additionally, a strong dependency of τ on incidence angle for the V polarization was observed. Furthermore, τ indicated a bell-shaped temporal evolution, with lowest values during the tillering and senescence stages, and highest values during flowering of the wheat plants. The latter corresponded to the highest amounts of vegetation water content (VWC) and largest leaf area index (LAI). To show that the time, polarization, and angle dependence is also highly dependent on the observed vegetation species, white mustard was grown during a short experiment, and radiometer measurements were performed using the same experimental setup. These results showed that the mustard canopy is more isotropic compared to the wheat vegetation (i.e., the τ parameter is less dependent on incidence angle and polarization). In a next step, the relationship between τ and in situ measured vegetation properties (VWC, LAI, total of aboveground vegetation biomass, and vegetation height) was investigated, showing a strong correlation between τ over the entire growing season and the VWC as well as between τ and LAI. Finally, the soil moisture was retrieved from TB observations over a second plot without a reflector on the ground. The retrievals were significantly improved compared to in situ measurements by using the time, polarization, and angle dependent τ as a priori information. This improvement can be explained by the better representation of the vegetation layer effect on the measured TB.

Sign in / Sign up

Export Citation Format

Share Document