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This paper describes an electrostatic positioning instrument which was developed at the Jet Propulsion Laboratory to enable experimenters to conduct containerless material science experiments in space. Samples that are to be studied are electrically charged and controlled by the electrostatic force produced by a set of properly arranged electrodes. Three different types of positioners are described, i.e., the dish type, the ring type, and the tetrahedral type. In all these systems, the positioning and the damping of the sample is accomplished by a feedback control system. The advantage of this electrostatic positioning method, in comparison to the other methods, such as acoustic and electromagnetic, lies in the fact that it can operate in a high vacuum and does not require the material to be electrically conductive as long as the material can carry a certain amount of charge.

A prototype pulse-charging circuit has been developed consisting of high-voltage RF bursts superimposed onto a 60-Hz modulating field. The supply is connected to a four-electrode system that generates ac pulse corona. By selecting the burst initiation time, either positive or negative ions can be generated and transferred across an air gap of a few centimeters. The performance of the circuit has been determined by charging metal and glass spheres that have been mounted on insulated stalks. Variations have been made in the modulating field and burst characteristics to optimize the performance. Comparisons have been made between the pulse charger and inductive schemes which are available for the electrostatic levitation of objects. The pulse charger has been found to be more effective at corresponding voltages.

We have developed a simple compact electron impact laboratory source of UV radiation whose relative intensity as a function of wavelength has an accuracy traceable to the fundamental physical constants (transitions probabilities and excitation cross sections) for an atomic or molecular system. Using this laboratory source, calibrated optically thin vacuum ultraviolet (VUV) spectra have been obtained and synthetic spectral models developed for important molecular band systems of H(2) and N(2) and the n(1)P(0) Itydberg series of He. The model spectrum from H(2) represents an extension of the molecular branching ratio technique to include spectral line intensities from more than one electronic upper state. The accuracy of the model fit to the VUV spectra of H(2) and N(2) is sufficient to predict the relative spectral intensity of the electron impact source and to serve as a primary calibration standard for VUV instrumentation in the 80-230-nm wavelength range. The model is applicable to VUV instrumentation with full width at half-maximum >/= 0.4 nm. The present accuracy is 10% in the far ultraviolet (120-230 nm), 10% in the extreme ultraviolet (EUV) (90-120 nm), and 20% in the EUV (80-90 nm). The n(1)P(0) Rydberg series of He has been modeled to 10% accuracy and can be considered a primary calibration standard in the EUV (52.2-58.4 nm). A calibrated optically thin spectrum of Ar has been obtained at 0.5-nm resolution and 200-eV electron impact energy to 35% accuracy without benefit of models over the EUV spectral range of 50-95 nm. The Ar spectrum expands the ultimate range of the VUV relative calibration using this source with the four gases, He, Ar, H(2), and N(2), to 50-230 nm. The calibration of the Galileo orbiter ultraviolet spectrometer for the upcoming Jupiter mission has been demonstrated and compared to results from other methods.