Graham S. Arnold

Absorptivity of several metals at 10.6 μm: empirical expressions for the temperature dependence computed from Drude theory

Simple expressions for the temperature-dependent absorptivity at 10.6 μm have been computed for silver, aluminum, gold, copper, lead, and tungsten by means of a straightforward application of the Drude model and experimental dc conductivity data over a wide temperature range. The results of these computations are in reasonable agreement with experimental data where such are available.

Surface mediated radical recombination luminescence: O+NO+Ni

Results of an experimental investigation of the chemiluminescence produced by the interaction of atomic oxygen and nitric oxide on a nickel foil surface are reported. Visible luminescence which depends linearly on the atomic oxygen and nitric oxide fluxes, on the substrate temperature, and on the substrate temperature history has been observed under conditions for which the three‐body gas‐phase reaction of O and NO is negligible. The intensity of the luminescence is greater than can be accounted for by the gas‐phase two‐body radiative recombination reaction of O and NO. The time, flux, and temperature dependences, along with the intensity of the emission support strongly the notion that the observed luminescence stems from excited species, most probably electronically excited NO2, formed in a surface mediated reaction.

Surface-mediated chemiluminescent reaction of O and NO

Abstract Deep-red chemiluminescence occurs when beams of O and NO react on metal surfaces. Of the metals studied (Ni, Co, Pt; Kovar, Invar, and Monel), nickel was the most effective at promoting the chemiluminescent reaction. The rate depends inversely on the surface temperature. The reaction rate appears to be controlled by the flux of NO to the surface, and does not depend strongly on the NO beam temperature. These behaviors indicate that the chemiluminescence arises not from a gas-phase reaction near the surface, but from a surface-mediated reaction of O and NO to produce electronically excited gas-phase NO 2 , most probably of the Langmuir—Hinshelwood variety.

Spacecraft contamination model development

The quantitative prediction of on-orbit molecular contamination effects is a difficult task that must rely on substantially simplifying assumptions about the rates and mechanisms of contamination production, transport, and deposition processes. Therefore, there is clearly room for a diversity of approaches within the spacecraft design community for the execution of contamination sources and effects analyses. This paper provides the initial description of the approach being taken for the development of a new contamination prediction code. In this development we intend to exploit the growing ASTM E1559 data base for outgassing and desorption measurements and to incorporate physical, kinetic models of condensation and photochemical deposition that are still sufficiently simple as to admit to successful parameterization.

Optical effects of photochemically deposited contaminant films

Two aromatic hydrocarbons bibenzyl (BB) and dodecahydrotriphenylene (DTP) have been studied in an ongoing contaminant effects measurement program. Photochemical deposition of these molecules did not proceed quickly under conditions which result in the deposition of dark tenacious films from phthalate siloxane and alkene precursor molecules. Additional measurements show that DTP probably does not deposit photochemically at a substantial rate because the quantum yield for photodeposition is small not that a DTP molecule does not reside on the surface long enough to absorb light. The initial sticking coefficient of DTP appears to depend on surface temperature. Films of DTP scatter visible and near-ultraviolet light very efficiently which is consistent with the observed heats of vaporization and desorption for this molecule. 1.

Spacecraft Environment and Effects Monitoring Instrumentation for Small Satellites

Future satellite systems will be required to survive and function in the space environment for much longer durations(10‐15 years) than their present counterparts to achieve greater cost effectiveness. Therefore, the characterization of orbitalspaceenvironment and itseffectson spacecraft systemshavereceived considerableattention in the recent years. Instrumentation is described for long-term measurement of key physical parameters characterizing the low-Earth-orbit environment and its effects on degradation of spacecraft materials and solar arrays. These measurements enable active, real-time monitoring of the spacecraft environment and the health of spacecraft and payload systems. The instrumentation, called Space Active Modular Materials Experiments, is designed to be compact, low power, and lightweight. It is ideally suited for applications to small satellites, especially those designed for long-term, autonomous operation.

Space active modular materials experiment

The Ballistic Missile Defence Organization is flying the Space Active Modular Materials Experiments (SAMMES), test of contamination and space environment effects on materials on board the Space Test Research Vehicle-2. This paper describes the experiment architecture, the instruments, and the sample suite. Notional descriptions of operations are provided to highlight the objectives and capabilities of SAMMES.

Progress on spacecraft contamination model development

This paper provides a progress report on the development of a new contamination prediction code, the Aerospace Satellite Contamination Model Evaluator (ASCME). In this development, we intend to exploit the growing ASTM E1559 database for outgassing and desorption measurements and to incorporate realistic physical and kinetic models of condensation and photochemical deposition.