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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

The throughput calibration of the VERITAS telescopes

Context. The response of imaging atmospheric Cherenkov telescopes to incident γ -ray-initiated showers in the atmosphere changes as the telescopes age due to exposure to light and weather. These aging processes affect the reconstructed energies of the events and γ -ray fluxes. Aims. This work discusses the implementation of signal calibration methods for the Very Energetic Radiation Imaging Telescope Array System (VERITAS) to account for changes in the optical throughput and detector performance over time. Methods. The total throughput of a Cherenkov telescope is the product of camera-dependent factors, such as the photomultiplier tube gains and their quantum efficiencies, and the mirror reflectivity and Winston cone response to incoming radiation. This document summarizes different methods to determine how the camera gains and mirror reflectivity have evolved over time and how we can calibrate this changing throughput in reconstruction pipelines for imaging atmospheric Cherenkov telescopes. The implementation is validated against seven years of observations with the VERITAS telescopes of the Crab Nebula, which is a reference object in very-high-energy astronomy. Results. Regular optical throughput monitoring and the corresponding signal calibrations are found to be critical for the reconstruction of extensive air shower images. The proposed implementation is applied as a correction to the signals of the photomultiplier tubes in the telescope simulation to produce fine-tuned instrument response functions. This method is shown to be effective for calibrating the acquired γ -ray data and for recovering the correct energy of the events and photon fluxes. At the same time, it keeps the computational effort of generating Monte Carlo simulations for instrument response functions affordably low.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1996

Calibration of Hot Wire Anemometers. (Latest Citations from the Aerospace Database)

The bibliography contains citations concerning calibration methods and measurement correction schemes for hot wire anemometers. Coverage includes static and dynamic calibration of sensors having single, multiple, cross, and ring wire configurations. Correction methods to account for yaw angle, low-velocity flow, microgravity, wall proximity, and highly fluctuating turbulence, velocity, or temperature are covered. Correction methods are also referenced for installations having multiple sensors. Hot film and laser anemometers, and the use of anemometers in specific industrial and aerospace applications are extensively covered in separate biblographies. (Contains 50-250 citations and includes a subject term index and title list.)

HOT WIRE ANEMOMETERS↗
NASA NTRS2004

Aquarius Instrument Science Calibration During the Risk Reduction Phase

This final report presents the results of work performed under NASA Grant NAG512726 during the period 15 January 2003 through 30 June 2004. An analysis was performed of a possible vicarious calibration method for use by Aquarius to monitor and stabilize the absolute and relative calibration of its microwave radiometer. Stationary statistical properties of the brightness temperature (T(sub B)) measured by a low Earth orbiting radiometer operating at 1.4135 GHz are considered as a means of validating its absolute calibration. The global minimum, maximum, and average T(sub B) are considered, together with a vicarious cold reference method that detects the presence of a sharp lower bound on naturally occurring values for T(sub B). Of particular interest is the reliability with which these statistics can be extracted from a realistic distribution of T(sub B) measurements that would be observed by a typical sensor. Simulations of measurements are performed that include the effects of instrument noise and variable environmental factors such as the global water vapor and ocean surface temperature, salinity and wind distributions. Global minima can vary widely due to instrument noise and are not a reliable calibration reference. Global maxima are strongly influenced by several environmental factors as well as instrument noise and are even less stationary. Global averages are largely insensitive to instrument noise and, in most cases, to environmental conditions as well. The global average T(sub B) varies at only the 0.1 K RMS level except in cases of anomalously high winds, when it can increase considerably more. The vicarious cold reference is similarly insensitive to instrument effects and most environmental factors. It is not significantly affected by high wind conditions. The stability of the vicarious reference is, however, found to be somewhat sensitive (at the several tenths of Kelvins level) to variations in the background cold space brightness, T(sub c). The global average is much less sensitive to this parameter and so using two approaches together can be mutually beneficial.

Ruf, Christopher S.↗
NASA NTRS2019

Uncertainties for Pre- and Post-Launch Radiometric Calibration of Imaging Spectrometers for Multi-Sensor Applications

An important aspect to using imaging spectrometer data is the radiometric characterization and calibration of the sensors and validation of their data products and doing so with error budgets with known traceability. The radiometric accuracy of a given sensor is important for demonstrating the expected quality of data from the sensor. Known traceability allows data from multiple sensors to be directly comparable as will become more important in the near future with the expected launches of multiple imaging spectrometers from multiple countries, agencies, and commercial entities. The current work describes the state of pre- and post-launch radiometric absolute and relative uncertainties and their role in harmonising on-orbit data. Examples of prelaunch uncertainties based on the calibration of EnMAP and the calibration planned for the CLARREO Pathfinder Mission are presented highlighting recent work in the area of detector-based approaches using tunable laser sources. Post-launch calibration approaches for Pathfinder, EnMAP, CHIME, and DESIS including traditional vicarious calibration methods and the challenges of working with commercial data are presented. The vicarious calibration discussion relies on the example of the recently-available RadCalNet data to describe typical methods and challenges that will be faced when harmonising data between imaging spectrometers as well as with multispectral sensors.

Thome, K.↗
DOE OSTI2025

CaliQEC: In-situ Qubit Calibration for Surface Code Quantum Error Correction

Quantum Error Correction (QEC) is essential for fault-tolerant, large-scale quantum computation. However, error drift in qubits undermines QEC performance during long computations, necessitating frequent calibration. Conventional calibration methods disrupt quantum states, requiring system downtime and rendering in situ calibration impractical. To address this challenge, we propose QECali, a novel framework that enables in situ calibration for surface codes. Our evaluation demonstrates that QECali introduces modest qubit overhead and negligible increases in execution time, offering the first practical solution for in situ calibration in surface code based quantum computation.

Fang, Xiang [University of California, Santa Barba↗
DOE OSTI2023

The Dark Energy Survey Six-Year Calibration Star Catalog

This Technical Note presents a catalog of calibrated reference stars that was generated by the Forward Calibration Method (FGCM) pipeline (arXiv:1706.01542) as part of the FGCM photometric calibration of the full Dark Energy Survey (DES) 6-Year data set (Y6). This catalog provides DES grizY magnitudes for 17 million stars with i-band magnitudes mostly in the range 16 < i < 21 spread over the full DES footprint covering 5000 square degrees over the Southern Galactic Cap at galactic latitudes b < -20 degrees (plus a few outlying fields disconnected from the main survey footprint). These stars are calibrated to a uniformity of better than 1.8 milli-mag (0.18%) RMS over the survey area. The absolute calibration of the catalog is computed with reference to the STISNIC.007 spectrum of the Hubble Space Telescope CalSpec standard star C26202; including systematic errors, the absolute flux system is known at the approximately 1% level. As such, these stars provide a useful reference catalog for calibrating grizY-band or grizY-like band photometry in the Southern Hemisphere, particularly for observations within the DES footprint.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1986

Variations in in-flight absolute radiometric calibration

Variations in the in-flight absolute radiometric calibration of the Coastal Zone Color Scanner and the Thematic Mapper (TM) are reviewed. At short wavelengths, the sensors show a gradual reduction in response, while in the mid-IR the TM shows oscillatory variations. One set of measurements made at White Sands, New Mexico shows anomalous results in TM bands 2 and 4. The results of a reflectance-based and a radiance-based calibration method at White Sands are described. An analysis of the radiance-based method shows the value of such measurements from helicopter altitudes for calibration.

Slater, Philip N.↗
NASA NTRS1984

Method and apparatus for precision control of radiometer

A radiometer controller of a radiation detector is provided with a calibration method and apparatus comprised of mounting all temperature sensitive elements of the controller in thermostatically controlled ovens during calibration and measurements, using a selected temperature that is above any which might be reached in the field. The instrument is calibrated in situ by adjusting heater power (EI) to the receptor cavity in the radiometer detector to a predetermined full scale level and is displayed by a meter.

Estey, R. S.↗
DOE OSTI2026

Long-term thermal stability and calibration of Type-II fiber Bragg grating array inscribed in radiation-hardened fibers

This paper investigates the long-term thermal stability of Type-II fiber Bragg grating (FBG) arrays, inscribed by femtosecond laser in radiation-hardened fiber, for potential applications as multiplexed sensors in high-temperature energy systems. The thermal stability of FBG sensors was assessed through 16 thermal cycles from room temperature (RT) to 750 ℃ about two months, involving 100 FBG sensors. The results show that the absolute temperature drift of FBG sensors can be reduced to less than 0.4 pm/day after 54 h thermal annealing process at a constant temperature of 800 ℃. As temperature sensors, the FBGs demonstrated stable performance, achieving a standard deviation (STD) of 1.8 pm (corresponding to a temperature resolution of 0.118 ℃) post-annealing. Repeated thermal cycles revealed a random drift of 2.3 pm in the FBG wavelength at RT. Polynomial fitting was explored as a calibration method to convert FBG wavelength shifts into absolute temperature measurements. By optimizing calibration temperature points (RT, 200 ℃, 400 ℃, and 750 ℃), the study shows that cubic polynomial calibration using four points yields an average R2 of 0.9997 and an RMSE of 3.58 ℃ across the entire temperature range (RT to 750 ℃). This approach represents an 11.53-fold improvement over empirical slope calibration and a 1.34-fold improvement over four-point piecewise fitting. The findings indicate that Type-II FBGs inscribed in radiation-hardened fibers can function as accurate temperature sensors, with performance on par with or exceeding that of thermocouples. With their multiplexing capability, robust signal transmission over long lead cables, and immunity to electromagnetic interference, FBG sensors offer a promising alternative to traditional electronic sensors for energy system monitoring.

Dominguez-Ontiveros, Elvis [ORNL] (ORCID:000000018↗
NASA NTRS2014

Radiometric Calibration Techniques for Signal-of-Opportunity Reflectometers

Bi-static reflection measurements utilizing global navigation satellite service (GNSS) or other signals of opportunity (SoOp) can be used to sense ocean and terrestrial surface properties. End-to-end calibration of GNSS-R has been performed using well-characterized reflection surface (e.g., water), direct path antenna, and receiver gain characterization. We propose an augmented approach using on-board receiver electronics for radiometric calibration of SoOp reflectometers utilizing direct and reflected signal receiving antennas. The method calibrates receiver and correlator gains and offsets utilizing a reference switch and common noise source. On-board electronic calibration sources, such as reference switches, noise diodes and loop-back circuits, have shown great utility in stabilizing total power and correlation microwave radiometer and scatterometer receiver electronics in L-band spaceborne instruments. Application to SoOp instruments is likely to bring several benefits. For example, application to provide short and long time scale calibration stability of the direct path channel, especially in low signal-to-noise ratio configurations, is directly analogous to the microwave radiometer problem. The direct path channel is analogous to the loopback path in a scatterometer to provide a reference of the transmitted power, although the receiver is independent from the reflected path channel. Thus, a common noise source can be used to measure the gain ratio of the two paths. Using these techniques long-term (days to weeks) calibration stability of spaceborne L-band scatterometer and radiometer has been achieved better than 0.1. Similar long-term stability would likely be needed for a spaceborne reflectometer mission to measure terrestrial properties such as soil moisture.

calibrating↗
NASA NTRS2021

Derivation of the final OSIRIS-REx OVIRS in-flight radiometric calibration

The OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS) operates over the ∼0.4- to 4.3-μm wavelength range. Radiometric calibration over this broad range requires the use of multiple calibration sources. Initial OVIRS in-flight calibration coefficients were previously computed using ground calibration from visible integrating sphere and IR blackbody sources, cross-calibrated with Earth-observing satellites for visible wavelengths, and adjusted using the spectrum of the OSIRIS-REx mission’s target body, asteroid (101955) Bennu. As part of the final in-flight calibration, we determined that the best calibration method removes out-of-band IR signal leakage prior to radiometric calibration and updated the calibration coefficients accordingly. These final calibration coefficients work well for data where the field of view is filled, and we document the possible artifacts in underfilled spots.

Amy A. Simon↗
DOE OSTI2023

Time-walk and jitter correction in SNSPDs at high count rates

Superconducting nanowire single-photon detectors (SNSPDs) are a leading detector type for time correlated single photon counting, especially in the near-infrared. When operated at high count rates, SNSPDs exhibit increased timing jitter caused by internal device properties and features of the RF amplification chain. Variations in RF pulse height and shape lead to variations in the latency of timing measurements. To compensate for this, we demonstrate a calibration method that correlates delays in detection events with the time elapsed between pulses. The increase in jitter at high rates can be largely canceled in software by applying corrections derived from the calibration process. We demonstrate our method with a single-pixel tungsten silicide SNSPD and show it decreases high count rate jitter. The technique is especially effective at removing a long tail that appears in the instrument response function at high count rates. At a count rate of 11.4 MCounts/s, we reduce the full width at 1% maximum level (FW1%M) by 45%. The method, therefore, enables certain quantum communication protocols that are rate-limited by the FW1%M metric to operate almost twice as fast.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2010

TPSAS-NF1676L-10863-DND

One important aspect of successful climate monitoring is satellite calibration. There is at least a 25-year of operational geostationary (GEO) record available for climate studies, if properly calibrated. The Global Space-based Inter-Calibration System (GSICS) project is another effort to provide the climate community consistent calibration across multiple platforms. Also, the Clouds and the Earth's Radiant Energy System (CERES) project, provides consistent GEO retrieved cloud properties and derived broadband fluxes across multiple platforms. This year GSICS is focusing on geostationary visible channel calibration. The GSICS strategy is to use multiple approaches, such as cross-calibrating the GEO radiances against MODIS as a reference, deep convective clouds as bright stable targets, deserts, sun-glint, stars, moon and other model based calibration methods. Each of these methods is independent of each other and can assess the stability of the GEO visible instrument with differing uncertainties. This study focuses on the inter-calibration of the GEO radiances against MODIS as a reference by using collocated, and coincident ray-matched radiances. The advantage of the ray-matching technique is that it provides a full dynamic range of radiances to check the linearity of the GEO visible instrument. This presentation will focus on the technique, some error analysis, comparisons with other methods, and an approach to inter-calibrate historical GEOs before MODIS.

D R Doelling↗
NASA NTRS2007

General Matrix Inversion Technique for the Calibration of Electric Field Sensor Arrays on Aircraft Platforms

A matrix calibration procedure has been developed that uniquely relates the electric fields measured at the aircraft with the external vector electric field and net aircraft charge. The calibration method can be generalized to any reasonable combination of electric field measurements and aircraft. A calibration matrix is determined for each aircraft that represents the individual instrument responses to the external electric field. The aircraft geometry and configuration of field mills (FMs) uniquely define the matrix. The matrix can then be inverted to determine the external electric field and net aircraft charge from the FM outputs. A distinct advantage of the method is that if one or more FMs need to be eliminated or deemphasized [e.g., due to a malfunction), it is a simple matter to reinvert the matrix without the malfunctioning FMs. To demonstrate the calibration technique, data are presented from several aircraft programs (ER-2, DC-8, Altus, and Citation).

Mach, D. M.↗
DOE OSTI2024

Toadstool Deep Learning Framework

SAND2025-11741O Toadstool is a deep learning framework and support library that provides PyTorch boiler plate training and testing loops. This enables the user to remember parts and customize a callback interface. Toadstool also provides useful callbacks and other methods for deep learning experimentation. The framework also implements publicly available temperature and calibration methods, model initialization methods, learning rate schedulers, and model evaluation methods. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Heidbrink, Scott↗
DOE OSTI2017

Vibrational Spectroscopy for the Determination of Ionizable Group Content in Ionomer Materials

An approach based on vibrational spectral measurements is described for determining the ionizable group content of ion conducting polymer membrane materials. Aimed at supporting the assessment of membrane stability and wear characteristics, performance is evaluated for attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy, confocal Raman microscopy, and ATR FT-IR microscopy using perfluorinated ionomer membrane standards. One set of ionomer standards contained a sulfonic acid ionizable group and the other a sulfonyl imide group. The average number of backbone tetrafluoroethylene (TFE) units separating the ionizable-group containing side chains was in the range of 7.2–2.1 (sulfonic acid set) and 10.5–4.6 (sulfonyl imide set). A poly(tetrafluoroethylene) (PTFE) sample was included as a blank, representing the limit of zero ionizable group (and maximum TFE) content. Calibration relationships were derived from area-normalized vibrational spectra. For all three methods, calibration models applied to independent spectral measurements of samples predicted the ratio of backbone TFE groups to ionizable groups in the repeat unit ( m) with a standard error of ≤ ±0.3. The confocal Raman and ATR FT-IR microscopy techniques achieved ideal blank responses and the lowest prediction errors, down to m ± 0.1 at the 90% confidence level. With its relative simplicity, low sample size requirements, and potential for quantitative micron-scale spatial mapping of the ionizable group content within a membrane, the approach has application to advancing materials development, including exploratory synthesis, durability and wear assessment, and in situ studies of membrane process.

Korzeniewski, Carol↗
DOE OSTI2017

Non-negative Matrix Factorization for Self-calibration of Photometric Redshift Scatter in Weak-lensing Surveys

Photo- z error is one of the major sources of systematics degrading the accuracy of weak-lensing cosmological inferences. Zhang et al. proposed a self-calibration method combining galaxy–galaxy correlations and galaxy–shear correlations between different photo- z bins. Fisher matrix analysis shows that it can determine the rate of photo- z outliers at a level of 0.01%–1% merely using photometric data and do not rely on any prior knowledge. In this paper, we develop a new algorithm to implement this method by solving a constrained nonlinear optimization problem arising in the self-calibration process. Based on the techniques of fixed-point iteration and non-negative matrix factorization, the proposed algorithm can efficiently and robustly reconstruct the scattering probabilities between the true- z and photo- z bins. The algorithm has been tested extensively by applying it to mock data from simulated stage IV weak-lensing projects. We find that the algorithm provides a successful recovery of the scatter rates at the level of 0.01%–1%, and the true mean redshifts of photo- z bins at the level of 0.001, which may satisfy the requirements in future lensing surveys.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1988

The absolute radiometric calibration of the advanced very high resolution radiometer

The need for independent, redundant absolute radiometric calibration methods is discussed with reference to the Thematic Mapper. Uncertainty requirements for absolute calibration of between 0.5 and 4 percent are defined based on the accuracy of reflectance retrievals at an agricultural site. It is shown that even very approximate atmospheric corrections can reduce the error in reflectance retrieval to 0.02 over the reflectance range 0 to 0.4.

Slater, P. N.↗