A vacuum compatible integrating sphere was built to operate inside a thermal vacuum chamber. This paper presents the
design and test results for a 1.65 meter diameter vacuum compatible integrating sphere with a 1.0 meter diameter exit
port and approximately 10kW of internal tungsten lamps. Liquid nitrogen is used as cooling medium to remove the heat
generated by these lamps. There are no moving parts inside the vacuum chamber.
The radiance is monitored with two filter-wheel detectors, one TE-cooled silicon and one TE-cooled germanium, as well
as a TE-cooled silicon array spectrometer. All three detectors are located outside the thermal vacuum chamber and view
the sphere radiance through fiber optic cables.
The system was tested inside a thermal vacuum chamber at NASA Goddard Space Flight Center before commissioning
in the 5.5 meter thermal vacuum chamber at Space Applications Centre in Ahmedabad, India. Results of tests of radiance
uniformity, radiance levels, and radiance stability are presented. Comparisons of the filter radiometers with the array
spectrometer are also presented.
An application-specific contracted integrating sphere source of uniform spectral radiance is described. The source is used
for pre-launch test and calibration of imaging radiometers which will be used as satellite borne earth remote sensors.
The calibration source is primarily intended to serve as a transfer standard of radiance.
Design criteria for the uniform radiance source are presented. Included is a summary of the end-user specifications in
regards to spectral radiance, radiance levels of attenuation, radiance stability, and aperture uniformity. Radiometric
theory used to predict the source radiance for a specific spectral flux input is reviewed. Reasoning for the use of an
integrating sphere platform for this application and characteristic features of the source are discussed.
Calibration methods and instrumentation are described. The resultant data presented include the modeled data compared
with the measured performance. Methods of data reduction and uncertainty are addressed where applicable.