Picture this: you walk out into the field on your property and you see a shiny silver ball on the ground in the grass. With red ribbons surrounding it and a crumpled parachute next to it. That’s what one Reddit user witnessed when they found a strange, perfectly round metallic ball in their pasture. The big question was: what is that?

It wasn’t a prop from a sci-fi movie or a leftover alien spacecraft. It was something much more terrestrial – and still cool – a radar calibration sphere!

What Is a Radar Calibration Sphere?
Radar calibration spheres are, well, just what they sound like – a calibration tool for radar systems. They are ultra-reflective, spherical, and made of either metal or metal-coated objects. The purpose of a radar calibration sphere is to provide a consistent predictable target for radar systems. Hence the need to calibrate it out in the field.

The spherical shape is very important. With an irregular or angled object, there could be different signatures radar would read depending on how the object is oriented. A sphere has a constant radar signature no matter how its oriented. That is extremely important when you want to tune a sensitive detection system. Whether that is monitoring weather, getting the location of an airplane, or collecting data for a satellite.

 

Why Did It Fall Out of the Sky?
Radar calibration spheres are generally dropped out of aircraft or balloons when testing radar systems. In this case, the object was probably released from a height where it drifted downward before slowing to settle in a vertical position with a parachute. After the test is completed, the sphere will float gently down to earth. Because that is not always possible, depending on the wind, it is not unusual to find them quite a distance from where they were launched… Perhaps they have even landed in someone’s yard or pasture.

The red ribbons in the image are the rigging for the parachute. They allow the sphere to drift in a stable floating position and to be more visible when it lands on the ground. The ribbons are there to ensure that recovery teams (or curious land-owners) will properly identify the object when it lands, after it takes its high altitude journey.

Is It Dangerous?
No, fortunately. There is nothing dangerous about radar calibration spheres. They do not have explosives, radioactive materials, or any sort of propellant. They are solid spheres and are engineered to reflect radar signals. Even though there is nothing dangerous about radar calibration spheres, it is still a good practice to inform local authorities or an aerospace agency when you find a sphere. They may want it back to be utilized in another location. Or at a minimum to confirm that it did not impact any active communications they may have.

It might also be of interest to note that several of these spheres. May also be owned by agencies such as NASA, military., or weather monitoring. So when it looks like you have found a big metallic bowling ball, remember it may be, but it may also be used for serious testing and data collection.

A Look at Today’s Technology
Finding a radar calibration sphere in your pasture is an unusual event, but an interesting reflection of radar science/aerospace testing. These spheres are quietly enabling storm monitoring, safely facilitating airplanes in our skies, and providing important information on deep space missions.

For most of us, they are simply an interesting metal ball associated with parachutes. However, under the practical plastic exterior lies a fascinating, story of precision engineering, complexities and innovations, and a reminder that no matter how ‘out there’ or rural we claim to be, we are never far from modern science.