Effect of juno's solar panel bending on gravity measurements

Juno’s radio science experiment has provided the most accurate measurement of Jupiter’s gravity field to date, thanks to very low noise Doppler data that result in an accuracy on Juno’s radial velocity as low as 0.01 mm/s at an integration time of 60 seconds. In order to translate such accuracy to uncertainties on the gravity field determination, any instrumental effect must be ruled out. When approaching the pericenter of its highly-elliptical orbit around Jupiter, Juno experiences an increase in temperature due to Jupiter's albedo and infrared emission. The higher temperature bends the solar panels, which in turn move the spacecraft’s main body. During a gravity-dedicated pericenter passage, Juno's high-gain antenna points toward the Earth, resulting in a motion which is almost entirely along the line of sight. Here we present a simple model to predict the amplitude of this effect, as well as the resulting Doppler signature during a typical Juno's tracking passage. We show that the effect on Juno’s measurements is small, peaking at about 0.002 mm/s (five times below the noise level), while numerical simulations confirm that this effect does not affect the determination of Jupiter’s gravitational field.