# Presentation: 265281

## Description of the NIST TXR

- Joe Rice
- National Institute of Standards and Technology
- Gaithersburg, MD

## Introduction

- The Thermal-infrared Transfer Radiometer (TXR) was developed as part of a larger, multi-year calibration program between the NASA EOS Project Science Office and the NIST Optical Technology Division.
- The NIST part of any deployment of the TXR to facilities related to calibrations of NASA EOS instruments is already part of the NIST statement of work with the EOS Project Science Office, and hence does not have to funded out of individual EOS project funds.
- The host calibration facility part of such a TXR deployment would have to be funded by the individual EOS project funds.
- The TXR is a two-channel portable radiometer for providing thermal- infrared scale **verifications** of large-area calibration sources.
- The goal is to provide *in-situ* measurements of the radiance that the flight instrument actually sees during its chamber calibration.
- The TXR is continuously being characterized and its calibration improved by new facilities and measurement capabilities being developed at NIST.

## Slide 3

## TXR Anticipated Version 2 Changes

- Units:
- Inches

## Using Checksource

- Using
- Turning Mirror

## Typical TXR InSb (or scaled MCT) Pre-amp Output Signal

## NIST Water Bath Black Body

- Used for TXR calibration in ambient environmental conditions.
- Used over temperature range 15 °C to 80 °C.
- 10.8 cm diameter aperture, usually apertured down to 4 cm for TXR.

## TXR Calibration at NIST Water Bath Black Body (WBBB)

**TXR Calibration at NIST Water Bath Black Body (WBBB)**

## TXR Calibration Equation

## TXR 5-m Channel Reproducibility at NIST WBBB

**TXR 5****-********m Channel Reproducibility at NIST WBBB**

## TXR 10-m Channel Reproducibility at NIST WBBB

**TXR 10-********m Channel Reproducibility at NIST WBBB**

## TXR at Los Alamos Radiometric Calibration Chamber Facility

## Delta-Response Comparison Method

**Delta-Response Comparison Method**

**Predicted Response:**

## Component (Tc) vs. System (r)

**Slope gives mirror ******** and intercept gives ********L(bkd)**

## Delta-Delta Response Comparison Method

## Component (Tc) vs. System (r)

**Component (T****c****) vs. System (************r)**
**Slope gives mirror ******** and intercept is zero**

## Resulting comparison of SBB contact temperature Tc

**Resulting comparison of SBB contact temperature T****c**
**and SBB brightness temperature T****b**

## Final result is recommended values for

**Final result is recommended values for**
**band-integrated, chopped (SBB - LZ) radiance:**

- Planck function

## Summary of LANL Deployment Example

**Summary of LANL Deployment Example**

- TXR has successfully enabled a system level verification
-  	of the component-based scale at LANL facility.
- Mirror reflectance parameter 0.9904
- 	compares well with LANL component value of 0.989.
- Delta-background value makes sense
- 	and provides new information to LANL.
- Standard uncertainty is below 0.1 K, 2 within range,
- 	relative to NIST Water Bath Black Body.

## TXR Calibration Methods

- TXR against Water Bath Black Body
- scale derived from temperature and emissivity modelling.
- limited temperature range of source and background.
- automated and easy: will continue to play a role for reproducibility.
- TXR against Cryogenic Black Body at NIST MBIR facility.
- full temperature range of source and background.
- scale derived from temperature and emissivity modelling AND can be derived from measurements by electrical substitution radiometry.
- TXR against tunable laser-illuminated integrating sphere at a new NIST facility: the IR-SIRCUS (Spectral Irradiance & Radiance Response Calibrations with Uniform Sources)
- full range of radiance, background chopped at source
- scale derived from High Accuracy Cryogenic Radiometer, the primary standard electrical substitution radiometer at NIST.
- believed to be the best way ultimately to calibrate the TXR.

## Summary

- Some other TXR Characterization Measurements Planned at NIST

- Check-source functionality and repeatability.
- More end-to-end relative spectral response measurements.
- More relative spatial response and size-of-source effect measurements.
- Polarization sensitivity measurements.

- The TXR has been deployed successfully in chamber-mode.
- Small upgrade planned during May-July 2000, to install new can, baseplate and check-source, and reduce field of view.