Spectrally resolved infrared (IR) and far infrared (FIR) radiances measured from orbit with extremely high absolute
accuracy are a critical observation for future climate benchmark missions. For the infrared radiance spectra, it has been
determined that a measurement accuracy, expressed as an equivalent brightness temperature error, of 0.1 K (k = 3)
confirmed on orbit is required for signal detection above natural variability for decadal climate signatures [1, 2].
The challenge in the sensor development for a climate benchmark measurement mission is to achieve ultra-high
accuracy with a design that can be flight qualified, has long design life, and is reasonably small, simple, and affordable.
The required simplicity is achievable due to the large differences in the sampling and noise requirements for the
benchmark climate measurement from those of the typical remote sensing infrared sounders for weather research or
operational weather prediction.
The University of Wisconsin Space Science and Engineering Center, with funding from the NASA Instrument Incubator
Program (IIP), developed the Absolute Radiance Interferometer (ARI), which is designed to meet the uncertainty
requirements needed to establish spectrally resolved thermal infrared climate benchmark measurements from space. The
ARI is a prototype instrument designed to have a short upgrade path to a spaceflight instrument.
Recent vacuum testing of the ARI, conducted under funding from the NASA Earth Science Technology Office, has
demonstrated the capability to meet the 0.1 K (k = 3) uncertainty requirement on-orbit. An overview of the instrument
design and summary of the radiometric performance verification of the UW-SSEC ARI will be presented.