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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Computer Generated Hologram System for Wavefront Measurement System Calibration

Computer Generated Holograms (CGHs) have been used for some time to calibrate interferometers that require nulling optics. A typical scenario is the testing of aspheric surfaces with an interferometer placed near the paraxial center of curvature. Existing CGH technology suffers from a reduced capacity to calibrate middle and high spatial frequencies. The root cause of this shortcoming is as follows: the CGH is not placed at an image conjugate of the asphere due to limitations imposed by the geometry of the test and the allowable size of the CGH. This innovation provides a calibration system where the imaging properties in calibration can be made comparable to the test configuration. Thus, if the test is designed to have good imaging properties, then middle and high spatial frequency errors in the test system can be well calibrated. The improved imaging properties are provided by a rudimentary auxiliary optic as part of the calibration system. The auxiliary optic is simple to characterize and align to the CGH. Use of the auxiliary optic also reduces the size of the CGH required for calibration and the density of the lines required for the CGH. The resulting CGH is less expensive than the existing technology and has reduced write error and alignment error sensitivities. This CGH system is suitable for any kind of calibration using an interferometer when high spatial resolution is required. It is especially well suited for tests that include segmented optical components or large apertures.

Olczak, Gene↗
NASA NTRS2016

Global Space-Based Inter-Calibration System Reflective Solar Calibration Reference: From Aqua MODIS to S-NPP VIIRS

The MODIS has successfully operated on-board the NASA's EOS Terra and Aqua spacecraft for more than 16 and 14 years, respectively. MODIS instrument was designed with stringent calibration requirements and comprehensive on-board calibration capability. In the reflective solar spectral region, Aqua MODIS has performed better than Terra MODIS and, therefore, has been chosen by the Global Space-based Inter-Calibration System (GSICS) operational community as the calibration reference sensor in cross-sensor calibration and calibration inter-comparisons. For the same reason, it has also been used by a number of earth observing sensors as their calibration reference. Considering that Aqua MODIS has already operated for nearly 14 years, it is essential to transfer its calibration to a follow-on reference sensor with a similar calibration capability and stable performance. The VIIRS is a follow-on instrument to MODIS and has many similar design features as MODIS, including their on-board calibrators (OBC). As a result, VIIRS is an ideal candidate to replace MODIS to serve as the future GSICS reference sensor. Since launch, the S-NPP VIIRS has already operated for more than 4 years and its overall performance has been extensively characterized and demonstrated to meet its overall design requirements. This paper provides an overview of Aqua MODIS and S-NPP VIIRS reflective solar bands (RSB) calibration methodologies and strategies, traceability, and their on-orbit performance. It describes and illustrates different methods and approaches that can be used to facilitate the calibration reference transfer, including the use of desert and Antarctic sites, deep convective clouds (DCC), and the lunar observations.

Xiong, Xiaoxiong↗
DOE OSTI2021

Image plate calibration system

A calibration system for an image plate used to detect high-energy particles produced by a radioisotope includes a casing and an image plate holder disposed at least partially inside the casing. The image plate is retained by the image plate holder inside the casing. A calibration source generates energy inside the casing to prepare the image plate for detection.

Immel, Darryl R.↗
NASA NTRS2020

Bearing Anomaly for the Sentinel 6 Supplemental Calibration System

The Supplemental Calibration System (SCS) was designed to rotate an elliptical reflector for the Sentinel 6 Advanced Microwave Radiometer (AMR). By rotating the reflector, the system can perform calibrations by comparing the reflection from space to the reflection from an onboard calibration target. During the qualification testing of the SCS, a flaw was discovered that resulted in apparent brinelling of bearings that support the rotating reflector. An extensive investigation ensued to determine the root cause of the problem. Though the most likely root causes of the presumed brinelling ended up being the result of undersized bearing clamp rings and thermal mismatch, there were requirements that drove these design choices. This paper describes the design of the bearing assembly, requirements that drove the design, and documents a challenging investigation filled with ambiguous test results.

Paulsen, Gale↗
NASA NTRS2020

Bearing Anomaly for the Sentinel 6 Supplemental Calibration System

The Supplemental Calibration System (SCS) was designed to rotate an elliptical reflector for the Sentinel 6 Advanced Microwave Radiometer (AMR). By rotating the reflector, the system can perform calibrations by comparing the reflection from space to the reflection from an onboard calibration target. During the qualification testing of the SCS, a flaw was discovered that resulted in apparent brinelling of bearings that support the rotating reflector. An extensive investigation ensued to determine the root cause of the problem. Though the most likely root causes of the presumed brinelling ended up being the result of undersized bearing clamp rings and thermal mismatch, there were requirements that drove these design choices. This paper describes the design of the bearing assembly, requirements that drove the design, and documents a challenging investigation filled with ambiguous test results.

Paulsen, Gale↗
NASA NTRS1971

Attitude-referenced radiometer study. Part 2: Primary calibration system

A primary calibration system, PCS, for infrared radiometers has been developed, built, and tested. The system allows radiometers to be calibrated with less than 1 percent error for use in earth coverage horizon measurements, earth resources surveys, and synoptic meteorological measurement. The final design, fabrication and test of the PCS are reported. A detailed description of the PCS construction is presented, along with the results of a complete series of functional tests. Test to verify the source thermal characteristics, collimator reflectance, and output beam characteristics are described and their results presented.

Williamson, W. R.↗
NASA NTRS2020

Automated Noise Calibration System (VT-1000)

This paper details an automated Noise Source calibration system in development at Jet Propulsion Laboratory, California Institute of Technology (JPL). The paper begins with a discussion on Noise Figure and Excess Noise Ratio (ENR) theory, fundamentals and governing equations. As part of the fundamentals is a discussion of the system’s use of the Y-factor method to obtain accurate measurements of the Unit Under Test (UUT), and how these measurements are compared against a known ENR standard to obtain the UUT’s ENR values. There is also an in-depth discussion on uncertainty quantification for Noise Source system calibrations. The architecture of the automated calibration system is provided, which includes both the system’s hardware and software configuration. The software is written in Python 3, and provides the user detailed instruction on how to proceed, including step-by-step connection requirements. This system automates much of the measurement process, including real-time uncertainty quantification and report generation, as well as real-time feedback to the user to allow intervention if necessary. The system takes advantage of a database of results from previous measurements to compare calibration history of the ENR measurements. The automated system presented here operates over a frequency range from 10 MHz to 50 GHz, and has shown substantial time savings over traditional manual methods of performing this calibration.

Timpe, Scott↗
NASA NTRS1992

An Automated Thermocouple Calibration System

An Automated Thermocouple Calibration System (ATCS) was developed for the unattended calibration of type K thermocouples. This system operates from room temperature to 650 C and has been used for calibration of thermocouples in an eight-zone furnace system which may employ as many as 60 thermocouples simultaneously. It is highly efficient, allowing for the calibration of large numbers of thermocouples in significantly less time than required for manual calibrations. The system consists of a personal computer, a data acquisition/control unit, and a laboratory calibration furnace. The calibration furnace is a microprocessor-controlled multipurpose temperature calibrator with an accuracy of +/- 0.7 C. The accuracy of the calibration furnace is traceable to the National Institute of Standards and Technology (NIST). The computer software is menu-based to give the user flexibility and ease of use. The user needs no programming experience to operate the systems. This system was specifically developed for use in the Microgravity Materials Science Laboratory (MMSL) at the NASA LeRC.

Bethea, Mark D.↗
NASA NTRS1998

Numerical Analysis of a Radiant Heat Flux Calibration System

A radiant heat flux gage calibration system exists in the Flight Loads Laboratory at NASA's Dryden Flight Research Center. This calibration system must be well understood if the heat flux gages calibrated in it are to provide useful data during radiant heating ground tests or flight tests of high speed aerospace vehicles. A part of the calibration system characterization process is to develop a numerical model of the flat plate heater element and heat flux gage, which will help identify errors due to convection, heater element erosion, and other factors. A 2-dimensional mathematical model of the gage-plate system has been developed to simulate the combined problem involving convection, radiation and mass loss by chemical reaction. A fourth order finite difference scheme is used to solve the steady state governing equations and determine the temperature distribution in the gage and plate, incident heat flux on the gage face, and flat plate erosion. Initial gage heat flux predictions from the model are found to be within 17% of experimental results.

Jiang, Shanjuan↗
NASA NTRS1990

Reference NO2 calibration system for ground-based intercomparisons during NASA's GTE/CITE 2 mission

An NO2 calibration system, based on a permeation device and a two-stage dynamic dilution system, was designed, constructed, and characterized at the National Bureau of Standards. In this system, calibrant flow entering the second stage was controlled without contacting a metal flow controller, and permeation oven temperature and flow were continuously maintained, even during transport. The system performance and the permeation emission rate were characterized by extensive laboratory tests. This system was capable of accurately delivering known NO2 concentrations in the ppbv and sub-ppbv concentration range with a total uncertainty of approximately 10 percent. The calibration system was placed on board NASA research aircraft at both the Wallops Island and Ames research facilities. There it was employed as the reference standard in NASA's Global Tropospheric Experiment/Chemical Instrumental Test and Evaluation 2 mission in August 1986.

Fried, Alan↗
NASA NTRS2008

Positioning system for single or multi-axis sensitive instrument calibration and calibration system for use therewith

A positioning and calibration system are provided for use in calibrating a single or multi axis sensitive instrument, such as an inclinometer. The positioning system includes a positioner that defines six planes of tangential contact. A mounting region within the six planes is adapted to have an inclinometer coupled thereto. The positioning system also includes means for defining first and second flat surfaces that are approximately perpendicular to one another with the first surface adapted to be oriented relative to a local or induced reference field of interest to the instrument being calibrated, such as a gravitational vector. The positioner is positioned such that one of its six planes tangentially rests on the first flat surface and another of its six planes tangentially contacts the second flat surface. A calibration system is formed when the positioning system is used with a data collector and processor.

Finley, Tom D.↗
DOE OSTI2026

Photon Detection System Calibration for DUNE

Photon Detection System Calibration for DUNE Not scheduled 20m Conference Center (University of California, Irvine) Poster New Technologies for Neutrino Physics Poster session Speaker Denis Torres (South Dakota School of Mines and Technology) Description The Deep Underground Neutrino Experiment (DUNE) is a long baseline neutrino oscillation experiment that relies on a precise Photon Detection System (PDS) to provide accurate timing information, enhance sensitivity to low-energy and non-beam events, and support detector performance studies in liquid argon time projection chambers. Achieving these goals requires a well-understood and stable optical calibration strategy that operates reliably under cryogenic conditions. In this poster, I will present PDS calibration studies performed in ProtoDUNE, focusing on the characterization of the ultraviolet (UV) light calibration system and key optical components in the light-delivery chain. I will discuss measurements of optical fiber transmission, SMA-to-SMA connector and feedthrough interface losses, and diffuser assemblies, emphasizing wavelength dependence, attenuation, and performance under cryogenic thermal cycling and stability tests. These studies provide quantitative inputs for understanding light transport, uniformity, and long-term reliability of the PDS in large-scale liquid argon detectors, and they directly inform calibration strategies for the DUNE Far Detector.

Torres Muñoz, Denis [South Dakota Sch. Mines Tech.↗
NASA NTRS1996

Optical detector calibrator system

An optical detector calibrator system simulates a source of optical radiation to which a detector to be calibrated is responsive. A light source selected to emit radiation in a range of wavelengths corresponding to the spectral signature of the source is disposed within a housing containing a microprocessor for controlling the light source and other system elements. An adjustable iris and a multiple aperture filter wheel are provided for controlling the intensity of radiation emitted from the housing by the light source to adjust the simulated distance between the light source and the detector to be calibrated. The geared iris has an aperture whose size is adjustable by means of a first stepper motor controlled by the microprocessor. The multiple aperture filter wheel contains neutral density filters of different attenuation levels which are selectively positioned in the path of the emitted radiation by a second stepper motor that is also controlled by the microprocessor. An operator can select a number of detector tests including range, maximum and minimum sensitivity, and basic functionality. During the range test, the geared iris and filter wheel are repeatedly adjusted by the microprocessor as necessary to simulate an incrementally increasing simulated source distance. A light source calibration subsystem is incorporated in the system which insures that the intensity of the light source is maintained at a constant level over time.

Strobel, James P.↗
NASA NTRS1995

Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) onboard calibration system

The AVIRIS instrument uses an onboard calibration system to provide auxiliary calibration data. The system consist of a tungsten halogen cycle lamp imaged onto a fiber bundle through an eight position filter wheel. The fiber bundle illuminates the back side of the foreoptics shutter during a pre-run and post-run calibration sequence. The filter wheel contains two neutral density filters, five spectral filters and one blocked position. This paper reviews the general workings of the onboard calibrator system and discusses recent modifications.

Chrien, Thomas G.↗