Minimum number of 1km circumference circles to completely cover any given area?

Hello,

I was wondering if anyone could help me with this. I'm looking into using GIS to calculate the minumum number of irrigation systems that I would need to cover an area of land.

I'm using circles with a circumference of 1km to represent the irrigation systems.

Each circle is allowed to overlap the other but I want to cover every single part of a polygon representing the area of land to be covered.

These areas of land can be several square kilometers in size but vary in shape.

Does anyone know of a routine out there that can do this for me?

Many thanks for any help :)