# Measuring and analyzing the tumble of space debris

How well or accurately can we measure the tumble of space debris?

I know that we can make ground-based measurements based on light curve data acquired by telescopes. Can tumble be measured from radar data?

What percentage of space debris do we already have tumble data for?

Primarily, I am wondering if there are currently any space-based methods for analyzing tumble.

• related in Astronomy SE: DAMIT how do they get 3D shape and rotational trajectory of a tumbling asteroid from photometry? but of course different; as you point out radar reflections will be different than light since the wavelengths can be of order the same size as macroscopic features on the object. cf. Star-shaped artifacts in SAR images of the “Suez Canal traffic jam seen from space”
– uhoh
Jun 20 at 9:47
• @Uwe I don't think tumbling is necessarily periodic, though I'm sure you can probably still figure out the motion making assumptions about the shape and reflectivity and gauging the principal moments of inertia. Jun 22 at 16:38
• @RogerWood If there is conservation of angular momentum, how tumbling may be non periodic ?
– Uwe
Jun 22 at 20:36
• @Uwe I don't underand this very well, but, despite the conservation of angular momentum and rotational energy, the axis of rotation can still wander around within the body and the rpm can change (see Tennis Racket Theorem). The wandering around with respect to the body is called the "polhode" and it is periodic. But the wandering around of the axis with respect to fixed space (the "herpolhode") is not generally periodic. See also en.wikipedia.org/wiki/Poinsot%27s_ellipsoid Jun 23 at 2:32
• I did some more digging. It seems the best tumble/rotational data comes from AIUB in Switzerland. They have a database of light curves for about 400 pieces of space debris throughout LEO, HEO, and GEO. They also catalogue some GLONASS objects. Silha et. al did a phenomenal study on it. Here's the link: sciencedirect.com/science/article/pii/S027311771730786X#b0025 Jun 23 at 12:32