Point the Way to the International Space Station with This DIY Orbit Tracker

Given the International Space Station’s host of superlatives (i.e. most expensive man made structure, largest artificial body in Earth’s orbit, longest functioning habitable satellite, greatest engineering accomplishment of all time, coolest flying space laboratory, etc.), you’d think that it would be on our minds constantly. Yet many of us go hours, even days, without thinking about it once.

There’s a growing movement of people who believe that our space agencies are underfunded because humanity is just not paying enough attention to our present accomplishments and future plans in space exploration. Well, I know one way to direct attention to something. Point at it.

This is the first prototype of the International Space Station Orbit Tracking Pointer. The pointer is controlled by an ST Microelectronics Nucleo F401, an “Arduino-compatible” microcontroller development board with an 84 MHz clock and 512 KB of memory. The board performs the orbital propagation and coordinate system transformations using a ported version of the SGP4 model.

A stepper motor controls the azimuth and a servo controls the elevation. After powering up, the pointer goes through a quick range-of-motion routine and then starts its one job: pointing at the ISS. The Station orbits the earth every 90 minutes so the speed of motion is roughly on the order of a minute hand on a clock: slow enough that it’s not really interesting to watch, but fast enough that it’s in a new place every time you glance over.

This is a prototype so it does have some limitations: the pointer must be initialized at true north before powering up, and the orbital parameters for the ISS are hard-coded into the development board so the pointer will lose accuracy over time if not updated. Ideally the system would be able to download the latest and greatest orbital parameters on a regular basis and update itself.

I’ve got lots of ideas for extensions of this design, including trophies for aerospace-related awards, keeping track of cubesats in high school classrooms, amateur radio antenna mounts, a children’s museum exhibit where you can select between satellites, planets, and landmarks to point at, and even making a huge one as an outdoor art installation.

For this prototype, though, I just wanted it to simply point. For me, it serves as a reminder that the world’s full of incredible things if you just know what direction to look.