Scaling and mission architecture for high-energy astrophysics

The quantitative study of the changes in the behavior of structures with scale is one of the oldest areas of physics: it was one of Galileo's "Two New Sciences". Nevertheless, it does not have the appreciation it deserves among high energy astrophysicists. While most understand the importance of collecting area and resolution, the connection between them is less well known. This matters: to make a good instrument one must exploit the applied physics, not fight against it. I will discuss counter-intuitive consequences of some well known scaling laws. I will show that for imaging instruments detector linear resolution is an under-appreciated performance driver. I will discuss the tradeoffs between modularization and integration. Attention to scaling issues has the potential to enable world class science from small instruments, increase the productivity of larger instruments, and transform extremely large instruments from impractical fantasies to practical realities.