Albert C. Whittlesey

Modeling of the Jovian Auroral Environment and Its Effects on Spacecraft Charging

A well-known concern for polar orbiting spacecraft at the Earth is spacecraft charging due to the aurora. Studies of Jupiter reveal the presence of a variety of similar auroral phenomena. In particular, three regions have been identified-a narrow auroral zone at high latitudes, a complex and variable environment over the poles, and auroralike features associated with the main jovian moons and their magnetic flux tubes. These auroral structures are, like their earthly counterparts, expected to be sources of charging. This paper reviews the observational data and models of the jovian aurora zone and polar regions. In combination with models of the jovian plasma environment, the ambient charging currents are then computed with the intention of providing realistic estimates of spacecraft potentials at Jupiter. These are of particular importance to the Juno mission as it is a Jupiter polar orbiter and will pass through the jovian auroral zones near the planet. Of special concern, unlike previous missions to Jupiter, Juno will utilize large solar arrays. While previous missions (e.g., the Voyagers and Galileo) utilized RTGs and were carefully designed to avoid differential surface charging, the Juno missions solar arrays may make it more sensitive to surface charging. Although the jovian aurora is a possibly serious threat to Juno and similar missions, as will be discussed, an understanding of the environment and proper mitigation techniques should limit their effects.

Spacecraft charging - An update

Twenty years after the landmark SCATHA program, spacecraft charging and its associated effects continue to be major issues for earth-orbiting spacecraft. Since the time of SCATHA, spacecraft charging investigations were focused primarily on surface effects and spacecraft external surface design issues. Today, however, a significant proportion of spacecraft anomalies are believed to be caused by internal charging effects (charging and ESD events internal to the spacecraft Faraday cage envelope). This review will, following a brief summary of the state of the art in surface charging, concentrate on the problems introduced by penetrating electrons (“internal charging”) and related processes (buried charge and deep dielectric charging). With the advent of tethered spacecraft and the deployment of the International Space Station, low altitude charging has taken on a new significance as well. These and issues tied to the dense, low altitude plasma environment and the auroral zone will also be briefly reviewed.

The Jovian Charging Environment and Its Effects—A Review

Several space missions are being considered for Jupiter. These range from the recently launched Juno mission to possible joint NASA and ESA missions to Europa and Ganymede. Although the direct effects of radiation dose are normally considered the most pressing design issue for these missions, spacecraft charging, through surface charging, vxB, and, more importantly, internal charging, is also a key design concern. This paper reviews the current state of understanding of the jovian charging environment including the background plasma, high-energy electrons, and magnetic field. In conjunction with these environments, we will also review the range of effects to be expected in response to these environments. These effects need to be carefully considered in parallel with radiation effects in the design of the planned missions if they are to survive in the extremely challenging jovian environment.

Spacecraft charging requirements and engineering issues

An effort is currently underway to recast and combine two NASA guidelines for mitigating the effects of spacecraft charging and electrostatic discharge on spacecraft. The task has the goal of taking the existing NASA guidelines for preventing surface electrostatic charging, NASA-TP-2361 (Purvis et al., 1984), and internal electrostatic charging, NASAHDBK 4002 (Whittlesey, 1999), and bringing them up to date with recent laboratory and onorbit findings. This paper will describe the status of those on-going efforts to combine and update the two guidelines. Reasons for the upgrades will be presented, including new subject material for which there is now a greater understanding or a greater need which changes satellite design procedures, or both. There will be an emphasis on the proposed contents and on the differences and similarities between surface and internal charging mitigation techniques. In addition, the mitigation requirements that can be derived from the combined handbook will be discussed with emphasis on how they might affect the engineering design and testing of future spacecraft.

Book review [review of "Guide to Mitigating Spacecraft Charging Effects" (Garrett, H.B. and Whittlesey, A.C.; 2012)]

This is the first time that I have faced the topic described by the title of this book. As a consequence, my reading of this well written text has been guided more by my own curiosity on a new field related to EMC than by the wish to deepen my knowledge of the subject.