Outline of Program Function and Outputs
In order to more accurately predict the efficiency of the telescope,
as well as the most effective combination of filters a C++ program was written
to model the filters (including the pressure windows). The program runs the source
spectrum and the blackbody curves (emitted from both the 300K and 100K pressure
windows) through all of the filters and then outputs polarimetric and photometric
measurement error, fractional increase in the loading, inband and out of band
transmission (of the source and the two blackbody curve), and the load (in ergs/cm^2)
on the first 4K filter from both blackbody curves.
The program divides the source spectrum and the blackbody curves into 400 bins with
logarithmic intervals of .01 between the wavelengths of .1 and 1000 micrometers. The
program calculates the area of the source spectrum and the blackbody curves and stores
the data in arrays (as well as outputting the data in files). The program then runs the
arrays through all the filters multiplying each data point by the corresponding
transmission for each bin and filter. Currently the program uses a rough model in order
to test its efficacy and to check for errors. In the future, the source spectrum and
transmission curves for the filters will be more accurate.
Presently the program uses a rough model of the source spectrum, based on rough
estimates of the relative intensity of the source for each wavelength. (logarithmic
scale without units)
For the blackbody curves I used Bode's equation (which is more accurate than Simpson's
which is probably overkill) to integrate the area of the curve. The blackbody curves
for both the 100K and 300K filter are almost identical (except for size) so I'm just
showing the 300K blackbody.
For both the 300K and 100K filter I made a rough model of the transmission of 1mm
quartz at each temperature. Based on my research the models may need to be revised,
because quartz seems to have varying transmission curves (probably due to random
impurities) as well as the fact that we will probably use thicker pressure windows.
The transmission curves are rather similar, but the 100K curve has higher transmissions
due to the lower temperature of the quartz.
The 300K transmission curve:
The 100K transmission curve:
The program is designed to output the throughput of the telescope using models of the
transmission curve of anywhere between one and four filters (and could allow for more
filters). Once data on prospective filters is obtained they can be entered into the
program for testing and comparison. For the purposes of testing, I used a model of a
filter with transmission leaks of T every Nth (logarithmic) bin.
I have included the outputs of two trials:
test run using no leaks
a filter with transmission leaks of 1% every fifth bin
Last updated September 7, 2000