DoD also supported the development of the water bath blackbody and various fixed-point blackbodies
to provide source-based radiometric scales.
However, it would imply that arbitrary cavities are not necessarily blackbodies
and that the universality of the constants h and k does not hold [13-18, 20-24,24-26].
The characterization of integrating spheres and blackbodies
using SI traceable standards at NIST has been the hallmark of interaction between NIST and NASA for many of the EOS instruments including the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and the Moderate Resolution Imaging Spectroradiometer (MODIS) pre-launch sensor level calibrations.
This remains a significant departure from the other laws of thermal emission [3-6] which have been confirmed through the construction of laboratory blackbodies
The Optical Technology Division (OTD) at the National Institute of Standards and Technology (NIST) has been developing techniques to calibrate heat-flux sensors using thermal radiation from high-temperature blackbodies
In truth, Planck's equation was only valid for laboratory blackbodies
constructed from highly absorbing materials.
An exploratory study at the National Institute of Standards and Technology (NIST) with a commercial ellipsoidal radiometer showed that the responsivity could be a function of the view-angle when viewing finite aperture blackbodies
At the same time, it implies that all materials used to assemble blackbodies
will act as Lambertian emitters/reflectors.
In the laboratory, blackbodies
are specialized, heated, and opaque enclosures, whose internal radiation is determined by the Planckian function [2, 3].
These materials are known to be very good physical examples of blackbodies
in the laboratory [18-21].
It includes skill-building, problem-solving laboratory experiments and lectures on radiometry fundamentals, emissivity, blackbodies
, the signal measurement equation, the temperature measurement equation and NIST temperature calibration services.
The mechanism is allowed, because laboratory blackbodies
are known to possess a small hole in their outer walls through which radiation is typically sampled.
For indium, tin, aluminum, silver, gold, or copper reference blackbodies
, the cavity and the crucible are machined from high-purity, high-density graphite.
But, laboratory blackbodies
are known to be extremely complex devices, typically involving the use of specialized nearly perfectly absorbing' materials over the frequencies of interest.
For a variety of reasons this project did not achieve the desired results, but by building on the experience gained by Ginnings and Reilly, Yokley built a cryogenic radiometer system at NBS in the mid-1970s to measure the radiation temperature of low-temperature blackbodies
used in a low-background environment (20, 21).