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The UV LED mission demonstrates the precise control of the potential of electrically isolated test masses that is essential for the operation of space accelerometers and drag free sensors. Accelerometers and drag free sensors were and remain at the core of geodesy, aeronomy, and precision navigation missions as well as gravitational science experiments and gravitational wave observatories. Charge management using photoelectrons generated by the 254 nm UV line of Hg was first demonstrated on Gravity Probe B and is presently part of the LISA Pathfinder technology demonstration. The UV LED mission and prior ground testing demonstrates that AlGaN UV LEDs operating at 255 nm are superior to Mercury vapor lamps because of their smaller size, lower draw, higher dynamic range, and higher control authority. We show flight data from a small satellite mission on a Saudi Satellite that demonstrates AC charge control (UV LEDs and bias are AC modulated with adjustable relative phase) between a spherical test mass and its housing. The result of the mission is to bring the UV LED device Technology Readiness Level (TRL) to TRL 9 and the charge management system to TRL 7. We demonstrate the ability to control the test mass potential on an 89 mm diameter spherical test mass over a 20 mm gap in a drag free system configuration. The test mass potential was measured with an ultra high impedance contact probe. Finally, the key electrical and optical characteristics of the UV LEDs showed less than 7.5 percent change in performance after 12 months in orbit., Comment: 22 pages, 21 figures

Vehicle platoons are fully automated vehicles driving in close proximity of each other, where both distance keeping and steering is under automatic control. This paper is aiming at a variant of vehicle platoons, where the lateral control is using forward looking sensors, i.e. camera, radar. Such a system solution implies that the vehicle dynamics are coupled together laterally, in contrast to the classical look-down solutions. For such a platoon, lateral string stability is an important property that the controller needs to guarantee. This article proposes a method for designing such a distributed controller. It also examines the effect of model uncertainties on the lateral string stability of the platoon for the proposed method.