Thoughts on Flyby Anomaly

It’s almost the time for the results of Juno’s Earth flyby. I’m considering one year as the deadline for NASA publishing and in less than three weeks, we’ll hit the deadline. My previous ideas about how to calculate an amount of flyby anomaly were wrong or inadequate. TOEBI is not in the level of explaining adequately why and with what magnitude a flyby anomaly occurs.

However, the key factor is a spacecraft’s spinning frequency. Every previous flyby anomalies can be determined by it. When a spacecraft hits the perigee it has gained approximately a half of its maximal anomalous additional velocity, no matter what’s its mass, velocity or incoming angles etc. Ok, why approximately half of its maximal anomalous additional velocity? Well, also spacecraft’s spinning plane is a factor, but in most of the cases, spinning plane has been towards Earth’s center when the perigee is hit.

Juno had its spinning plane towards Earth’s center at perigee. Measured spinning frequency at that point was \(1/30.24\) 1/s. In TOEBI, particles and stellar objects generate interaction through spinning, which effects by factor of \(f^2\), so it’s natural to expect the same in cases of flyby anomaly. Now, we get the number \(f^2 \approx 0.00109\), which is my prediction for Juno’s anomalous speed increase at perigee. But wait a minute, where are the units, m/s? Good question… I don’t know! I haven’t figured out it yet, it just works, ok.

There has been numerous flybys over time and every time the spacecraft has been spinning with its spinning plane towards Earth near the perigee, anomalous speed increase has been detected. No spinning, no flyby anomaly! And in cases of spinning spacecraft, detected speed increase matches my \(f^2\) pattern, except in cases where there has been mid flyby maneuvers or flyby occurred at too low altitude (atmosphere caused drag).

After the perigee, spacecraft is still gaining an extra acceleration (hence speed increase) due to its spinning. In most cases, after perigee speed increase is pretty much as big as speed increase gained before the perigee. Those two would be identical if spinning frequency and plane were symmetrical before and after the perigee. Unfortunately, in case of Juno, there happened something at the perigee which caused Juno to go into the safe mode and that might have caused some changes to both spinning frequency and orientation of spinning plane.

I hope, that after published NASA results I’ll get my (fulltime) chance to develop TOEBI further so that it will be capable of explaining the flyby anomaly mechanism in detail.

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