We present results of measurements obtained with a new monochromator-based
cryogenic radiometer facility at NMi/VSL. General design considerations of
the facility and associated transfer detectors are discussed. At present, S
i detectors can be calibrated between 330 nm and 1200 nm at power levels ra
nging from 5 mu W to 80 mu W. A vacuum trap detector of the reflective type
has been constructed, which accepts an f/8 optical beam in conjunction wit
h spot sizes up to 5 mm in diameter. To check the performance of the system
, the trap detector has been calibrated directly against the cryogenic radi
ometer using lasers at 488.0 nm, 543.4 nm and 632.8 nm and subsequently usi
ng the monochromator at the same wavelengths. The agreement is better than
0.02%.