Space borne overhead non-imaging (non-focusing) infrared (ONIR) sensors require on-orbit calibration to
validate performance of sensor payloads. Typically this is accomplished by the use of ground based
observations including laser illumination of the calibrated sensor. This provides a-priori knowledge of the
laser characteristics and atmospheric propagation thereby providing the sensor operators a method for
deducing the true system level performance. Of concern is the need to avoid laser illumination of other
satellites to prevent inadvertent damage or temporary mission degradation. The complex predictive
avoidance process is necessarily bureaucratic and time-consuming due to the need to entertain the interests
of multiple stakeholders. Herein is described a method for mutual calibration of co-orbital ONIR sensors by
use of incoherent off-board illumination of a sample with known spectral reflectivity. The method will not
involve laser illumination, will be less threatening to neighboring spacecraft, and will not require predictive
avoidance processes.
A series of experiments was conducted in which trimethylbismuthine (TMB) was used to introduce atomic bismuth into a supersonic flow of electronically excited nitrogen fluoride, NF(a1Δ), at an elevated density of 3 x 1015 mol cm-3. Excited-state densities of Bi(2D) approximately equal to 1 x 1013 atom cm-3 and BiF(AO+) approximately equal to 4 x 1O11 mol cm-3 were achieved. After correction for mixing, these density values agreed reasonably well with values predicted by a quadratic scaling law. Simulation of the blue BiF(AO+)-BiF(XO+) emission spectrum suggests that the BiF(AO+) was in vibrational as well as rotational equilibrium at 300°C. The significance of these results for developing a supersonic BiF(AO+) laser utilizing TMB is discussed.
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