Whether your picosatellite is watching the Earth or gazing at the stars, you need to know what you're sensing. This do-it-yourself guide explains what you can measure---and the constraints on those measurements---when you're orbiting the Earth. Learn exactly what physical quantities you can measure, and how to plan your sensor loadout. The perfect follow-up to DIY Satellite Platforms (our primer for designing and building a picosatellite), this book takes you beyond just flying a camera in space and shows you what data you can gather and play with using your own personal satellite. Learn about all the sensors you can select for your mission; get acquainted with key electronic communications protocols; I2C, TTL, SPI, analog, and digital; find out how much more your instruments can "see" when they're above the atmosphere; Understand how to calibrate sensors and how to pick the signal out of the noise; determine the optimal data acquisition rate for your available bandwith; [and] look at off-the-shelf sensor hardware and CPU choices (such as Arduino).