A Sensitivity Analysis Using Pyradi, for Ophelia and Skyla

This article is devoted to PyRadi, which is an infrared modeling toolkit written for Python. Python is a computer language similar to MATLAB which runs on most computer systems and is completely free.

PyRadi is useful because it simplifies the process of designing and evaulating infrared vision systems. Infrared vision systems are able to detect heat signatures of life on Earth, and in other places. Additionally they can also detect many naturally occuring phenomena such as bacteria in the ocean which help our planet support life.

In my experience, infrared systems can be used for remote sensing, which means that they are deployed in space and used to observe the Earth. NASA has a mission similar to this called VIIRS which monitors ocean algae populations and tracks the rate at which they bloom.

PyRadi is completely open ended and can be played with and modified by anyone with internet access. I have been doing this for years.

Here is a summary some of the things you can do with Pyradi.

WHen you want to design a system for seeing infrared radiation, whether on the Earth or moon or both, you need to determine the performance as you generate your design. This is because the performance helps you understand how well your design will work, efficiently.

PyRadi helps with this. If you give it some information about the source of infrared light (just a rough light curve, not too hard to find for most objects), and some other basic information about your system (i.e. telescope, etc) then PyRadi will show you its guess at the performance. This is measured by the amount of signal that your system will be able to receive from it’s target or source.

Here is some output from PyRadi.

Two graphs showing output from PyRadi!

The first graph shows several curves which can be thought of as components of a transfer function, as commonly used in control theory. For anyone who doesn’t know this already, a transfer function is represented as a product of several smaller functions. It is part of the solution to a differential equation, which is the basic mathematical model of a system that evolves with respect to time (i.e. dynamical system).

Here is an example:

In this figure, the box labeled Plant is the portion of the system which we are interested in studying or modeling. The “transfer function” is basically all of the interesting aspects of the physical system which we care about. In the case of Pyradi, it includes the following:

  • Source basic radiant properties
  • Source emisivity or tendancy to illuminate debris
  • Intervening atmosphere
  • Optics passivity
  • Camera sensitivity
  • etc.

In summary, the PyRadi enables you to do what is called a Sensitivity Analysis of your experiment.

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