The Strategic Defense Initiative (SDI) and subsequently
the Ballistic Missile Defense Organization (BMDO) of the U.S. Department of
Defense has motivated the work at NIST in support of the defense remote
sensing area. In this application the on-board sensors must detect and
measure, on parity with the radiation from the Earth, the faint signals
from small targets viewed against the cold background of space. Flux levels
at the detectors tend to be orders of magnitudes smaller in such defense
remote sensing applications than in environmental remote sensing
applications. To achieve the sensitivity required, on-board sensors are
often cooled to 77 K and below. Also, to simulate the cold-space
background, shrouds in space-simulation calibration chambers are cooled to
a low background such as 20 K using cooled helium gas. NIST’s
role has been to support pre-launch calibration activities by calibrating
blackbodies and measuring other artifacts. They are used as standards in
the sector of aerospace industry performing the pre-launch radiometric
calibrations for DoD missile defense programs. Recently NIST has developed
a portable transfer-standard radiometer (BXR) for verifying the scales
established at customer calibration facilities, analogous to those
developed for the environmental remote sensing community.
