The design of the optics is such that the rays from 0 degrees to 3.6 degs ? come from the outside world through the filter. The rays from 3.6 degrees to 9 degs ? will come from the blackened area of the optics holder. The rays from 9 degrees to 180 degrees will come from the blackened area of the chip holder. Attempting to model the first three factors we make the following assumptions:
Region 1/2 angle Solid Angle Temperature
(degs) (ster) (K)
chip holder
optics
filter
Using
Integrated photon flux from lambda=0 to 2.7 microns Temp Photon Number Flux Kelvin photons/m^2/sec/steradian 100 4.234e+00 120 3.690e+04 140 2.470e+07 160 3.317e+09 180 1.522e+11 200 3.292e+12 220 4.114e+13 240 3.405e+14 260 2.051e+15 280 9.622e+15 300 3.695e+16The background that passes through the filters depends on the passband of the filters.
Integrated photon flux from lambda=0 from 300K Black Body Lambda Photon Number Flux microns photons/m^2/sec/steradian 0.900 1.2e+02 1.000 2.0e+04 1.100 1.3e+06 1.200 4.1e+07 1.300 7.5e+08 1.400 9.1e+09 1.500 7.8e+10 1.600 5.1e+11 1.700 2.6e+12 1.800 1.1e+13 1.900 4.1e+13 2.000 1.3e+14 2.100 3.8e+14 2.200 9.7e+14 2.300 2.3e+15 2.400 5.1e+15 2.500 1.0e+16 2.600 2.0e+16 2.700 3.7e+16
Integrating this over the filter bandpasses we have the following:
Filter range photonflux
microns photons/m^2/steradian
J 1.16-1.32 1.3e+09
H 1.48-1.77 7.8e+12
Ks 2.0 - 2.3 2.2e+15
none - 2.55 1.5e+16