Calibration Source Research Articles

Hybrid Garfield++ simulations of GEM detectors for tokamak plasma radiation monitoring

This work presents recent efforts in optimization of Gas Electron Multiplier (GEM) detector simulations developed so far. The mentioned triple-GEM based measurement systems were already tested at the WEST project and other devices recording soft X-ray (SXR) plasma radiation in the target range of 2-15 keV. Long term plans may envisage usage of gaseous detector based SXR diagnostics in DEMO reactor for real time plasma monitoring and control, as high neutron fluxes preclude application of semiconductor-based technologies. Conditions in fusion reactors as well as in currently operating devices necessitate simulating the interactions of high-energy photons and neutrons with the detector parts, including proper handling of primary ionization electrons paths, gas mixture fluorescence and collisions with detector materials. For this use case a full-detector simulation software was created based on the already existing interface and previous results obtained so far within the group. It combines Geant4 package for interactions with solid parts of the detector, Garfield++ for electron avalanching, Heed for X-ray interaction with gas, Gmsh and Elmer for meshing and electrostatics and introduces hybrid approach to the simulation of electron drift in different manner depending on the electron position with respect to multiplication stage. To optimize the computation time software employs precomputation algorithms in later stages of the electron cascades. The expected response profiles of the triple-GEM detector, exposed to 55Fe calibration source radiation, were simulated and verified by comparing them with experimental data.

Gamma spectrometer calibration of liquid standard sources of Mix 133Ba, 137Cs and 60Co toward the measurement of 99Mo breakthrough of 99Mo/99mTc generator

The expression radionuclide in nuclear medicine is preferred than radioisotope which widely used in physics. Radionuclides have been used regularly in nuclear medicine. Their radiation provide information about the staging of a person’s specific organs and to specify what is triggering the symptoms, injury or disease to treat diseased organs or cancerous tumours in a patient called theranostic. Technetium-99m radionuclide is the most frequently used radionuclide in nuclear medicine. The quality control of technetium-99m (99m Tc) product from 99Mo/99mTc generator is crucial. One that have been highlighted in this paper is the radionuclide molybdenum-99 (99Mo) breaktrough which can be effectively measured using caliberated gamma spectrometer. The stability test of the gamma spectrometer detector is done using control chart and chi square method from 137Cs radionuclide measurement. The calibration process of liquid standard sources of mix 133Ba, 137Cs and 60Co including energy and efficiency calibration, are performed with the same geometry as Mo99 breakthrough measurement in a lead shield canister with 2.5; 4.5 and 8.5 cm distance from the HPGe detector. The result from the calibration of liquid standard sources of mix 133Ba, 137Cs and 60Co showed the required polynomial equations needed to calculate the 99Mo breakthrough of 99mTc eluted product from the 99Mo/99mTc generator.

Preliminary assessment of the radiological consequences of the hostile military occupation of the Chornobyl Exclusion Zone

The full-scale invasion of Ukraine by Russian military forces on 24 February 2022 put the radiological well-being of the people in Ukraine under unprecedented threat. Apart from the risks linked to operating nuclear power plants, there was substantial evidence of looting of facilities of all kinds, including those holding radioactive materials, as well as the scope for physical disturbance of radioactively contaminated areas and waste storage facilities. The actions of Russian military personnel invading Ukraine through the territory of the Chornobyl Exclusion Zone (the ChEZ) were of serious concern. Before its shutdown a few days after the beginning of the occupation, the automated radiation monitoring system of the ChEZ recorded sharp increases in the gamma-background in several areas which indicated some non-typical processes taking place on its territory. The State Nuclear Regulatory Inspectorate of Ukraine (SNRIU) and its technical support organisation, the Scientific and Technical Centre for Nuclear and Radiation Safety (SSTC NRS), as well as the rest of the professional nuclear community in Ukraine and worldwide, recognised the potential for movement of the radioactive contamination (reaching 101–104 kBq m−2 Cs-137 in the most of the territory) by the Russian military machinery and personnel to areas outside the ChEZ, creating locally contaminated spots along the routes taken by the invaders towards Kyiv. Certain apprehensions were caused by the inventory carried out after the liberation of the ChEZ which revealed the theft of calibration sources and radioactive samples from laboratories located in Chornobyl. As soon as this information became available to the public, it caused a wide response and anxiety, as a result of which SNRIU made a decision to conduct a radiation survey of the liberated territories in the Kyiv region. The survey was conducted between June and December 2022 by SSTC NRS specialists with the support of DSA. The scope of the survey was limited by available time and resources; however, the total route of the survey was about 840 km, and covered more than 50 settlements and a limited part of the ChEZ. The radiation survey combined the continuous gamma-dose rate measurements by the detectors installed in the laboratory vehicle and additional manual measurements at specified points. As a result of the radiation survey, no deterioration of the radiation situation was observed in the liberated territories. No contaminated objects, radiation sources, or other radioactive material removed from the ChEZ were found either. Measurements of the Cs-137 soil contamination in the ChEZ, although limited, corresponded to the results which had been obtained before the war. It can be concluded that in the surveyed territories, the direct impact on the public in the form of additional radioactive contamination removed from the ChEZ in February-March 2022 was negligible. The same applies to the radiation consequences of forest fires that occurred in the ChEZ during its occupation. However, due to the damage of the radiation monitoring system, explosive hazard, and destruction of transport infrastructure, the consequences of the occupation of the ChEZ by Russian troops will be long-term.

Phosphorus availability and corn (Zea mays L.) response to application of P‐based commercial organic fertilizers to a calcareous soil

AbstractRecycling of organic wastes for agricultural production has been recommended as a sustainable way to close the phosphorus (P) cycle. This study seeks to characterize the P forms in organic fertilizers derived from agricultural and nonagricultural source materials to understand how these organic fertilizers will affect corn growth and soil available P. Organic fertilizers including turkey litter compost (TLC), biosolid pellets (BSP), and source separated organic compost (SSO) were applied to a sandy loam soil and compared to controls that received no nutrients or chemical fertilizer. Results from sequential chemical extractions and X‐ray absorption near edge structure spectroscopy revealed that most of the P species are inorganic, with SSO and TLC containing primarily Ca‐P and Mg‐P forms, while the P in the BSP treatments was mostly associated with aluminium (Al). The two chemical fertilizer treatments had the greatest impact on corn height at the initial growth stage; however, after 42 days, corn height was similar for the organic fertilizers and chemical treatment. This initial slow response from the organic fertilizer treatments reduced the grain yield compared to chemical treatment. The results of this study suggest that priority should be given to sufficient P availability at the initial growth stage. Overall, organic fertilizer is a promising P source for grain crop production, but calibration and correlation studies are needed to ensure optimum supply of P for the initial growth stage.

Ecohydrologic model with satellite-based data for predicting streamflow in ungauged basins

Information on water availability in basins can be crucial for making decisions for effective water resource management in basins. As the operation of hydrometric stations in Korea is mainly focused on flood season and large rivers, most basins have lack or no observed data. Consequently, this complicates water resource planning and management. Remote sensing data is emerging as a powerful alternative to hydrological information in ungauged basins. This study investigated the applicability of Satellite-Remote Sensed Data (SRSD) as a source for model calibration in Prediction in Ungauged Basins (PUB) through modeling. Remote sensed leaf area index (LAI), actual evapotranspiration, and soil moisture data were used. Each SRSD was used alone to calibrate a hydrologic model to predict the daily streamflow for 28 basins in Korea. A vegetation module was added to the existing hydrologic model to use LAI. Among the SRSDs tested, the model calibrated with LAI had the most robust performance, predicting streamflow with acceptable accuracy compared to the traditional calibration based on streamflow. In particular, since the model account for vegetation actively interacting with evapotranspiration and soil moisture in the season of low flow, the LAI-calibrated model showed an advantage in improving the flow prediction performance. Although further research is required to utilize evapotranspiration and soil moisture data, the overall results of the LAI-based calibration were promising for predicting streamflow in ungauged basins where observations are scarce or absent, given that the satellite-derived LAI data were used alone without any preprocessing such as a bias correction. However, the prediction performance of the LAI-calibrated model was found to have a statistically significant relationship with local conditions. Therefore, by evaluating and improving the potential of SRSD in different region and climatic conditions, it is expected that the application of the SRSD-only calibration method can be extended to various ungauged basins.

252Cf yield calibration method for nuclear material accountancy and safeguards practitioners

Californium-252 is an isotope commonly encapsulated as a physically small but strong spontaneous fission neutron source for applications in industry, academia, and research. Within the nuclear safeguards community, a well-characterized 252Cf source is often used as an accessible alternative for plutonium in calibrations measurements, which require the absolute source strength. Current methods of source strength quantification can provide an accurate estimate, approximately 1% uncertainty under optimal conditions, but are typically costly and time consuming. An alternative method was developed to determine 252Cf source strength using passive neutron correlation counting (PNCC). The PNCC method enables institutions and facilities to perform 252Cf source calibration measurements in-house using detection systems that are common within the nuclear safeguards community. This novel method was previously successfully demonstrated using neutron multiplicity well counters. However, the previous evaluation utilized detection systems with high neutron detection efficiencies, greater than 60%. The purpose of the current study is to extend the previous evaluation and demonstrate the feasibility of the PNCC 252Cf calibration method for suite of coincidence counters with lower neutron detection efficiencies, between 15% and 35%, which are more commonly encountered in the field, as well as to provide a step-by-step guide to using the method. The neutron source used in this evaluation was previously certified by the National Institutes of Science and Technology (NIST), which provides a reference for the accuracy of the PNCC method. The present source yield calculations demonstrate excellent agreement with a NIST calibration technique and achieve a standard uncertainty below the target 1%.

Calibration and simulation of a silicon dosemeter for ambient dose equivalent in low-earth orbit space.

A particle dosemeter (PD) is a payload of NEXTSat-2 in the low-earth orbit (LEO). The absorbed dose in LEO needs to be converted into the ambient dose equivalent (H*(10)). Due to a mixed field in LEO, the calibration factors (klow and khigh) should be determined for the low-and high-linear energy transfers (LET) (below and above 1.5keV/μm), respectively. The PD was irradiated with a 137Cs source at the Korea Radiation Solution facility to obtain H*(10) and absorbed doses. However due to the lack of sources for the high-LET calibration, H*(10) and an absorbed dose were calculated by simulating PD for the high-energy neutron field at CERN-EU high-energy Reference Field. The measured klow of PD had a difference of 5.1% and 9.5% from the calculated value of PD and the measured value of Liulin detectors, respectively. However, a difference in khigh between PD and Liulin was explained by the contribution of non-neutron components to Liulin in the measurements.

Development and characterization of a high-emissivity reference blackbody radiation source with V-grooves and large aperture at low-temperature

A high-emissivity blackbody radiation source can improve the measurement level of infrared radiation temperature, which is critical for applications in high-value industries and human health monitoring. In this study, a new high-emissivity blackbody source with V-grooves and large aperture was redesigned and developed, which can be used as a radiation temperature reference source for the calibration of secondary blackbody sources and precision radiation thermometers in the temperature range from −10 ℃ to 100 ℃, including the temperature range of human body infrared radiation considered in the study of people exhibiting fever symptoms. The wavelengths of the infrared spectral radiation temperatures involved in the study were in the range of 8–14 μm. The blackbody source consisted of a blackbody cavity, a jet-stirred precision constant-temperature bath, a standard platinum resistance thermometer, a high-precision digital multimeter, a frost-proof cover, and an auxiliary test frame. The cavity was cylindrical and conical with a diameter of 60 mm, a conical top angle of 120°, and a total length of 300 mm. The V-grooves with an angle of 50° on the inner wall were coated with high-emissivity coatings. The cavity was then completely immersed in a thermostatic bath. The radiation temperature of the blackbody source was traced to the International Temperature Scale of 1990 using a standard platinum resistance thermometer, which was calibrated at fixed-points of the Ar, Hg, H2O, Sn, and Zn. The experimental results revealed that the normal effective emissivity of the blackbody measured by the thermal cavity reflectometer method was 0.999 751, which is consistent with the theoretical calculation results based on the Monte Carlo method using optical ray tracing technology. In addition, the accuracy of the radiation temperature was verified by comparing it with a reference blackbody source from the National Institute of Metrology (NIM), China. The temperature stability of the blackbody source did not exceed 0.005 ℃ within 30 min, the axial temperature uniformity of the blackbody cavity did not exceed 0.048 ℃, and the temperature uniformity at the bottom of the cavity was better than 0.053 ℃. The combined standard uncertainty of the radiation temperature of the blackbody radiation source was evaluated from 0.010 ℃ to 0.032 ℃. The novel design with 50° V-grooves allowed for the blackbody source to provide the combination of a large aperture and high emissivity, which improved radiance temperature measurements. The reliability of the new design was experimentally verified. This design provides a novel method and experimental basis for the future design of compact light-weight blackbody sources, which is useful for the development of compact spaceborne blackbody sources.

Variably polarized X-ray sources for LPD calibration

Variably polarized X-ray sources for LPD calibration

Correcting Gain Drift in TES Detectors for Future X-Ray Satellite Missions

Changes in the operating environment of transition-edge sensor (TES) microcalorimeters can cause variations in the detector gain function over time. If not corrected, this can degrade the spectral resolution, and cause systematic errors in the knowledge of the absolute energy. The non-linear nature of the TES energy scale function and the potential for multiple, simultaneous sources of drift can make effective corrections extremely challenging. Satellite instruments typically employ an on-board calibration source to provide known reference X-ray lines. This allows real-time monitoring of the detector gain stability and provides information that can be used to correct for drifts. Here we discuss progress towards demonstrating that the energy scale requirements can be met for future instruments such as Athena X-IFU. We present measurements (from ∼ 1-12 keV) on ∼ 200 pixels in a prototype X-IFU array. We use a non-linear drift correction algorithm that uses two fiducial calibration lines (5.4 keV and 8.0 keV) to track gain and interpolate a new, corrected gain between a set of three pre-calibrated gain functions that span the anticipated range of induced drifts. We demonstrate this algorithm is effective at correcting the full gain scale in the presence of multiple sources of environmental drift.

Characterisation of hydrophone sensitivity with temperature using a broadband laser-generated ultrasound source

In this work, we present a novel method for characterising the relative variation in hydrophone sensitivity with temperature, addressing a key aspect of measurements in the field of ultrasound metrology. Our study focused on a selection of miniature ultrasonic hydrophones commonly used in medical applications. The method is based on using water as a temperature-sensitive laser-generated ultrasound (LGUS) source for calibration, allowing for flexible characterisation across a wide temperature range. The measurements were performed using both the LGUS method and the established self-reciprocity method. Our results demonstrate good agreement within 5% between the two methods, validating the effectiveness of the LGUS approach. We found that the sensitivity of the tested hydrophones exhibited low temperature dependence less than −0.2% per ∘C within the studied temperature range from 17 ∘C up to 50 ∘C. The presented LGUS method offers greater flexibility than current approaches as it allows for characterisation of membrane hydrophones with small element sizes and non-electrical transducers. By combining the relative sensitivity variation obtained through the LGUS method with the standard calibration at room temperature, absolute values of hydrophone sensitivity can be determined. The expanded uncertainty of our measurements, which was evaluated at temperature intervals of 8 ∘C, was determined to be on average 10%. Our work provides valuable insights into the temperature dependence of hydrophone sensitivity and lays the foundation for further investigations in this area. The LGUS method holds promise for future enhancements, such as increased bandwidth of the LGUS source and frequency domain analysis, to explore the frequency dependency of sensitivity variation with temperature.

Optimized cyclotron production of 211At: The challenge of 210Po-characterization

The yield of 211At is currently limited by the restriction of the incident He2+-beam energy of the 209Bi(α,2n)211At reaction to ≈28 MeV avoiding the co-production of 210At with its daughter 210Po through 209Bi(α,3n)210At. In parallel, 210Po is directly produced as well through the 209Bi(α,x)210Po reaction at a energies as low as 26.7 MeV. Cross-sectional data predict a significant increase of the 211At-yield at higher energies indicating that this approach warrants optimization. The strategy of using higher energies means that potential solutions to handle 210Po during production, target processing and labelling, including the potential 210Po-related toxicity in (pre-) clinical studies have to be studied. Here we present the results of the 210Po quantification after a non-destructive target characterization.Two 25 μm thick Bi targets were irradiated at the Scanditronix MC 32, Rigshospitalet Copenhagen at 28.8 MeV and 29.8 MeV. For both targets the theoretical yield of 211At, 210At and the directly produced 210Po was estimated in a 25 layered 1 μm Bi model using the available cross-sectional data. The 211At and 210At yields were measured with a HPGe-detector 30 min post EOB. After sufficient decay Pb foils and a210Po calibration source were used to calibrate an iQID α-camera and an AMBER α-spectrometer prior to the non-destructive quantification of 210Po.Calculations predict a 28% and 1600% increased yield per μA of respectively 210At and 211At for targets irradiated at 28.8 and 29.8 MeV respectively. At the same time the 210Po activity increased by 350% up to a total activity of 24.14 kBq from which 60% is attributable to the direct reaction.Measured 211At and 210At activities show an increase of 49% and 1900% per μA for the 29.8 MeV target whereas quantification of 210Po with both α-detection systems validates the predicted activities.The results obtained in this study confirm a significantly increased yield of 211At at higher incident He2+- beam energies but also indicate the importance of directly produced 210Po, which impacts the assessment of 210Po prior to target processing.

Millimeter accuracy SLR bias determination using independent multi-LEO DORIS and GPS-based precise orbits

Satellite Laser Ranging (SLR) has become an invaluable core technique in numerous geodetic applications. SLR measurements to passive spherical satellites essentially contribute to the determination of geocenter coordinates and global scale in the International Terrestrial Reference Frame (ITRF) realizations. In addition, SLR measurements to active satellites in Low Earth Orbit (LEO) are up to now mostly used for an independent validation of orbit solutions, usually derived by microwave tracking techniques based on Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) or Global Navigation Satellite Systems (GNSS). This allows for the analysis of systematic orbit errors (e.g., originating from poorly known non-gravitational perturbations or sensor offsets) not only in the radial direction (key to satellite altimetry missions), but in three dimensions.Major obstacles to reach the millimeter accuracy and stability goals of 0.1mm/y (at decadal time scales) of the Global Geodetic Observing System (GGOS) are station-satellite measurement biases and on-ground/board coordinate offsets. Among the observatories of the International Laser Ranging Service (ILRS) a large diversity of measurement qualities exists, and the calibration of station-dependent errors is now necessary to further exploit SLR data for present and future climate-driven needs.We demonstrate that the analysis of SLR data to active LEO satellites equipped with DORIS or GNSS receivers is a promising means to characterize SLR biases and their stability. Using two independent selections of Earth observation missions in LEOs (consisting of six altimetry, three magnetic field and two gravity field satellites) with three different analysis software packages (Bernese, ZOOM, Napeos), we estimate SLR range biases for all involved tracking stations on a yearly basis. We find that for many of the stations independently estimated sets of biases agree on a few-mm level and that the inclusion of satellites from multiple missions allows rendering the bias estimation more robust and in particular less prone to geographically correlated orbit errors. This shows that microwave-derived orbits of active LEO satellites, nowadays of very high quality due to numerous advances in modeling and analysis techniques, can serve as interesting sources for SLR station calibration in demanding climate applications.

Calibration of a Micromegas-based gaseous time projection chamber using cosmic ray muons

We report the calibration of a gaseous Time Projection Chamber based on Micromegas charge readout modules with cosmic ray muons, utilizing their penetrating power and relatively uniform energy deposition per unit length. Muon events were selected through track reconstruction to characterize detector performances, such as the drift velocity, electron lifetime, detector gain, and electric field distortion. The evolution of detector performances over a 50-day data-taking cycle was measured with the muon calibration method. For instance, the drift velocity degraded from 3.40 ± 0.07 cm/μs to 3.06 ± 0.06 cm/μs without gas purification, and then recovered with gas purification. A 137Cs calibration source was also placed inside the detector as a reference for muon calibrations.

In situ measurement of relative attenuation length ofgadolinium-loaded liquid scintillator using source data at RENO experiment

We present in situ measurements of the relative attenuation length of the gadolinium-loadedliquid scintillator in the RENO (Reactor Experiment Neutrino Oscillation) detectorsusing radioactive source calibration data.We observed a steady decrease in the attenuation length of the Gd-LS in the RENO detectorsby ∼50% in about four years since the commissioning of the detectors.

Low-energy calibration of XENON1T with an internal ^{{textbf {37}}}Ar source

A low-energy electronic recoil calibration of XENON1T, a dual-phase xenon time projection chamber, with an internal {}^{37}Ar source was performed. This calibration source features a 35-day half-life and provides two mono-energetic lines at 2.82 keV and 0.27 keV. The photon yield and electron yield at 2.82 keV are measured to be (32.3,pm ,0.3) photons/keV and (40.6,pm ,0.5) electrons/keV, respectively, in agreement with other measurements and with NEST predictions. The electron yield at 0.27 keV is also measured and it is (68.0^{+6.3}_{-3.7}) electrons/keV. The {}^{37}Ar calibration confirms that the detector is well-understood in the energy region close to the detection threshold, with the 2.82 keV line reconstructed at (2.83,pm ,0.02) keV, which further validates the model used to interpret the low-energy electronic recoil excess previously reported by XENON1T. The ability to efficiently remove argon with cryogenic distillation after the calibration proves that {}^{37}Ar can be considered as a regular calibration source for multi-tonne xenon detectors.

Collaborative spatial information as an alternative data source for hydrodynamic model calibration: a Pernambuco State case study, Brazil

Collaborative spatial information as an alternative data source for hydrodynamic model calibration: a Pernambuco State case study, Brazil

Experimental and Simulation Investigation of Total Dissolved Gas Prediction in Supersaturated Water Treatment: Focusing on Source Calibration and Combining with Bubble Coalescence

Supersaturation of total dissolved gas (TDG) is a common occurrence in high dams during the spill process, which can lead to fish bubble disease and threaten aquatic organisms. As a result, many scholars have taken a keen interest in this issue. Research into the gas-liquid mass transfer mechanism has improved the accuracy of TDG prediction models. This article investigates the factors affecting TDG dissipation through laboratory experiments. Especially, the mass transfer coefficient across the bubble interface based on the slip penetration model was calibrated, and the coaxial bubble coalescence added to the coefficient was studied. The results show that the aeration rate has the most significant impact, followed by water depth, and then the aeration aperture. The TDG dissipation rate increases with the parameter β, and the parameter of 0.35 shows the highest correlation with the experimental data. Furthermore, the concentration change rate after coalescence is lower than before, suggesting that aggregation negatively impacts mass transfer. This study improves TDG concentration prediction accuracy and proposes measures for mitigating supersaturation to avoid fish bubble disease.

EMPIRICAL FORMULA FOR THE DEPENDENCE OF HPGe-DETECTOR EFFICIENCY ON ENERGY AND DISTANCE FOR SHIELDED GAMMA-RAY SOURCES

The accuracy of gamma-spectrometric measurements in the isotopic analysis of shielded nuclear materials depends on the accuracy of the detector calibration in terms of energy efficiency, which should take into account corrections related to the measurement geometry and the absorption of γ-radiation by the shield material. The results of experimental studies of the energy efficiency of the HPGe-detector measured at fixed distances between the calibration source and the detector (50 and 100 mm) in the presence and absence of an absorbing shield made of stainless steel 12X18H10T (thickness ‒ 9.6 mm) are presented. On the basis of experimental data, an empirical description of the efficiency dependence for fixed distances between the gamma radiation source and the detector in the presence of a stainless steel absorbing shield was obtained.

Single-Point Calibration for Microwave Sounders: Application to TEMPEST-D

Abstract Passive microwave sounders are critical for accurate forecasts from numerical weather prediction models. These sensors are calibrated using a traditional two-point approach, with one source typically a free-space blackbody target and the second a clear view to the cosmic microwave background, commonly referred to as “cold space.” Occasionally, one or both of these calibration sources can become corrupted, either by solar/lunar intrusion in the cold space view or by thermal instability of the blackbody calibration source. A Temporal Experiment for Storms and Tropical Systems (TEMPEST) microwave sounder instrument is currently deployed on the International Space Station (ISS) for a 3-yr mission. TEMPEST is also calibrated using a blackbody target and cold space view; however, the cold space view will be routinely obstructed by objects present on the ISS. Here we test an alternative single-point calibration methodology that uses only the blackbody calibration target. We find the brightness temperature difference between this new approach and the traditional two-point calibration approach to be <0.1 K when applied to 3 years of the TEMPEST CubeSat Demonstration (TEMPEST-D) mission data from 2018 to 2020. This approach is applicable to other microwave radiometers that experience occasional degradation of calibration sources, such as thermal effects, intrusions, or instability of noise diodes. Significance Statement Cross-track microwave sounders have relied on two distinct calibration sources, often the cosmic microwave background using a clear view to cold space and an ambient blackbody target. We have tested an alternative approach that uses a single calibration target, making the sensor robust to occasional field-of-view intrusions of the space view or alternatively simplifies the spaceborne sensor design by eliminating the need for a clear view to space. We find that the performance difference between this new approach and the traditional two-calibration source approach is indistinguishable for both microwave temperature/water vapor profiling and precipitation-rate estimation. This calibration technique can be applied to past, current, and future microwave sounders to help diagnose systematic uncertainties in sensor calibration targets.