alt Hacker NewsHow did you manage meaningful attitude control with only torque rods? They would need to big (read: heavy) to be useful — was this just stabilising in inertial frame or active pointing? Mag dipoles in chassis and components tend to lock tumbling satellites into the Earth’s magnetic field. Did you see this? Or did you see atmospheric drag dominate at this altitude?
I'm AyJay, Topher's co-founder and Albedo's CTO. We'll actually be publishing a paper here in a few weeks detailing how we got 3-axis torque rod control so you can get the real nitty gritty details then.
We got here after stacking quite a few capabilities we'd developed on top of one another and realizing we were beginning to see behavior we should be able to wrap up into a viable control strategy.
Traditional approaches to torque rod control rely on convergence over long time horizons spanning many orbits, but this artificially restricts the control objectives that can be accomplished. Our momentum control method reduced convergence time by incorporating both current and future magnetic field estimates into a special built Lyapunov-based control law we'd be perfecting for VLEO. By the time the issue popped up, we already had a lot of the ingredients needed and were able to get our algorithms to control within an orbit or two of initialization and then were able to stay coarsely stable for most inertial ECI attitudes albeit with wide pointing error bars as stated in the article. For what we needed though, it was perfect.