How do I best present my skills when switching fields from electrical engineering to earth sciences?
One problem you will need to think about is if you aim for a research job within earth Sciences of a more technical job. The latter may be easier because your knowledge is certainly in demand. The former will be more difficult since you lack an Earth Science background. Note that I do not say impossible. 

Will you compete. The answer is definitely not an easy no. But, the position you will be looking for will need to be heavy on, for example, signal processing to make you of interest. Usually working on data is followed by interpretations of the data in terms of Earth Science applications. You will of course have a definite disadvantage there. Having some documented understanding of Earth Sciences will be beneficial. 

I would encourage you to find a meeting where you could meet specialists and discuss opportunities and also just see what is done out there. If you are in the US then attending the AGU (American Geophysical Union) Fall Meeting in San Francisco (December) would be a good option. In Europe the EGU (European Geophysical Union) meeting in Vienna (April) will be good. There are also more specialized meeting on Remote Sensing. A good way in could be to strike up collaborations where your expertise adds to the mix.

Building sensors. The remote sensing sensors are built by electronics experts such as yourself and not by earth Scientists within the earth Science community (departments). Earth Scientists will provide input to what specs a sensor would need but that is usually the dividing line. So the answer to the possibilities lies outside Earth Science, you most likely would be looking at space agencies or physics departments.

On the whole, I would say that your expertise is valued in Earth Science but the total lack of documented knowledge in the subject(s) will make the opportunities smaller. I need to add that Earth Science, in its widest sense is a very broad and covers many different departments/subjects which is why trying to find some persons with research profiles that attract you a good venture.