Space Environment Exposure Research Articles

Commercial optical coatings in space

The use of commercial optical coatings for space applications for the aptly named “New Space” missions is a state-of-the-art trend. These products are generally less costly and time-consuming in their production and therefore, there is a much wider range of optical coatings available compared to custom-made products. However, the reliability of commercial manufacturing processes is a key concern. Additionally, the resistance of commercial products against space environmental degradation mechanism at operating temperatures needs to be evaluated. In this study, seven commercial products with multi-layer thin film optical coatings consisting of filters, mirrors and windows have been selected from various manufacturers and the results with regards to process verification and space environmental exposure testing are presented. The impact of space environmental effects on the optical performance of the coatings is evaluated, with particular emphasis on the performance at cryogenic temperature. Finally, guidelines and precautions for use of commercial optical coatings for space applications.

Shape Adjustment and Experimental Study of a Shape Memory Cable (SMC) Structure.

Large deployable cable net antennas have attracted extensive attention worldwide because of their simple structure and high storage ratio. The cable net structure is affected by long exposure in a harsh space environment during satellite operation, resulting in large thermal deformation and stress relaxation, which leads to a degradation of antenna performance. To address the thermal deformation of the cable net structure, a shape memory cable (SMC) net structure model was proposed with surface accuracy as the research objective. Specifically, we aimed to utilize its phase transition characteristics to adjust the thermal deformation of cable net structure and improve its surface accuracy. A shape memory cable net structure model with a diameter of 2.2 m was built, and a normal temperature experiment and high- and low-temperature experiments were carried out. High- and low-temperature test refers to environmental simulation testing of shape memory cable net structures under high- and low-temperature conditions. This was done to determine whether the adjustment method for surface accuracy meets the requirements. The results showed that the shape memory alloy wire has a relatively stable ability to adjust the surface accuracy of the cable net structure at room temperature. During temperature cycling, the thermal deformation of the shape memory cable net structure is slight, and the surface accuracy is good. Compared with ordinary cable net structures, the shape memory cable net structure has improved surface accuracy by 44.4% and 45.2% at high and low temperatures, respectively. This proved the effectiveness of the method for adjusting surface accuracy. These experimental results offer guiding significance for engineering applications.

Space Environment Exposure Effects on Ceramic Coating for Thermal Protection Systems

Carbon/carbon (C/C) structures are widely considered for space thermal protection systems (TPSs), being able to withstand critical reentry conditions thanks to an excellent thermal stability. In low-Earth-orbit long-time missions, however, the TPS effectiveness is significantly lowered due to the surfaces’ prolonged staying within the harsh space environment. In particular, the detrimental oxidation due to thermal cycles and atomic oxygen (AtOx) exposure greatly affects the TPS integrity, thus leaving the spacecraft’s outer surface less protected during reentry. A great effort is thus made for testing solutions based on advanced coatings aimed at preserving TPS materials from oxidation. In the present work, ceramic coatings are evaluated by measurements of the thermal expansion coefficient and AtOx erosion rate. The specimens tested are C/C substrates on which commercial refractory varnishes are applied. Silicon carbide and aluminum and zirconium oxides are the basic ceramic constituents, and the effect of silica nanoparticles’ inclusion on the coating performances is also evaluated. A phenomenological modeling is then introduced to approach the relationship between erosion mechanism due to AtOx impact and surface energy variation induced by thermal cycles; such analysis highlights the importance of considering the combined action of different aging factors, in order to achieve a reliable interpretation of the space environment’s effect on spacecraft structures and subsystems.

Strategies for Determining Electron Yield Material Parameters for Spacecraft Charge Modeling

AbstractAccurate modeling of spacecraft charging is essential to mitigate well‐known and all‐too‐common deleterious and costly effects on spacecraft resulting from charging induced by interactions with the space plasma environment. This paper addresses how limited availability of electron emission and transport properties of spacecraft materials—in particular, secondary electron yields—and the wide ranges measured for such properties pose a critical issue for modeling spacecraft charging. It describes a materials charging database for electron emission properties under development, which facilitates more accurate spacecraft charge modeling when used in concert with the strategies outlined herein. These data and techniques provide tools for more accurate material selection, increased confidence in charge models, and a concomitant decrease in mission risk. They also allow better customization of models in response to prolonged space environment exposure and specific mission requirements, which may evolve materials properties.

Space Environment Exposure Test for Highly Functional Thermal Control Materials

Space Environment Exposure Test for Highly Functional Thermal Control Materials

Shape Memory Polymer Composites for Long-Term Exposure to Space Environment

Shape memory polymer composite (SMPC) samples for long-term exposure in Space environment have been designed and tested. SMPC laminates consisted of two carbon fiber reinforced (CFR) plies and a SMP interlayer. Samples were manufactured by prepreg lamination and molding with subsequent thermomechanical processing for shape change. Commercial raw materials were selected both for CFR plies and SMP interlayer. Differential scanning calorimetry and dynamic mechanical analysis have been used to evaluate the thermo-mechanical behavior of the SMPC laminate in comparison with the neat CFR laminate and the SM epoxy resin of the interlayer. Results show that the hybrid nature of the SMPC laminate is responsible for their good shape memory behavior. A small disk with a simple shape change has been prepared to be integrated in the MISSE-FF platform for long-term exposure to Space environment. Recovery tests under IR light exposure highlighted the optimal functional behavior of this kind of sample. Copyright © VBRI Press.

Response of RF-sputtered MoS2 composite films to LEO space environment

The rf-sputtered MoS2-Au composite films were exposed in real low earth orbit (LEO) space environment by a space environment exposure device (SEED) aboard China Shenzhou-7 manned spaceship. The ability of the composite films resistant to atomic oxygen (AO) was investigated using X-ray photoelectron spectroscope (XPS), X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) equipped with an X-ray energy dispersive spectroscopy (EDS). The results showed that the microstructure of the composite film was densified because the growth of MoS2 platelets was suppressed to some content due to the addition of Au, although it was still characterized by a typical dendrite-like morphology. No obvious change in the morphology, phase structure, element composition and friction property was observed from the space exposed and non-exposed composite films, indicating that the composite film exhibited a better anti-oxidation ability as exposed in LEO environment. The improved anti-oxidation ability was attributed to the more compact microstructure and a passivation effect that the dangling bonds at the edge planes of MoS2 platelets were probably occupied by the partial doping atoms.

The structure and composition of samples made of carbon-fiber-reinforced plastic KMU-4l exposed for 12 years on the exterior surface of the International Space Station: 2. Microstructure and surface composition

The experimental data on macrostructure, composition, and weight losses of unique KMU-4l carbon-fiber-reinforced plastic samples with surface modified by fiberglass fabric subjected to long-term exposure (12 years) in space environment as a part of Komplast 10-1 panels on the exterior surface of the functional cargo unit of the International Space Station are presented in the paper. Research results are obtained for the first time by methods of visual examination, gravimetric analysis, digital photography, optical microscopy, and energy-dispersion X-ray spectroscopy. It is shown that the studied macrostructural characteristics, mass loss, and elemental composition of modified carbon-fiber-reinforced plastic differ insignificantly for the reference and exposed test samples, i.e., the composite materials are characterized by stable macrostructural, physical, and chemical properties.

Gene expression of rice seeds surviving 13- and 20-month exposure to space environment

Rice seeds were exposed outside of the international space station to assess the risk of space environment exposure on gene expression associated with seed germination. The germination percentages of the space-stored and ground-stored seeds exposed for 13 months were 48 and 96% respectively. Those for 20 months were 7 and 76%, respectively. Germination was defined 3 days after imbibition, except for the space-stored seeds exposed for 20 months, which germinated 5 days after imbibition. Subsequent RNA-seq analyses of the dry seeds, germinated seeds, and roots and shoots of seedlings revealed that the mutation rates of mRNA sequences were not significantly different between space-stored and ground-stored samples exposed for 13 months and 20 months. In all, 4 and 16 transcripts of glycolysis-related genes were increased in the germinated seeds after 13-month and 20-month exposure, respectively. Also, 2 and 39 transcripts of long-lived mRNA required for germination were decreased more than 2-fold in the dry seeds after 13-month and 20-month exposure, respectively. These results suggest that damage to long-lived mRNA in seeds by a space environment delays and reduces germination.

Study on Secondary Arcing Occurrence on Solar Panel Backside Wires With Cracks

Space environment exposure may create cracks on solar panel backside wires. In terms of the wiring design of the solar array backside, environmental constraints applied on each wire are identical. Thus, the probability of two adjacent wires having cracks facing each other is very high. This configuration presents a risk of secondary arc occurrence, which can lead to a destructive process such as arc tracking. In order to determine in which conditions electrostatic discharges (ESDs) can lead to an arc, we have carried out an experimental study on solar panel backside-like samples. We have tested different types of wires presenting artificial mechanical cracks or space simulation aging cracks, set on a solar panel backside coupon. The wires are connected to a secondary arc test setup including a solar array simulator (SAS) set to different current values. As both direct and inverted potential gradient (IPG) charging are theoretically possible on geostationary orbit and low earth orbit, we have carried out, in the JONAS vacuum chamber (ONERA facility), both charging types. Direct charging was achieved with an electron gun and IPG with a plasma source. Results are presented for the two types of charging, different types of wires, and different SAS current values. They show that, in direct charging conditions, ESD propagates along the wires but the plasma density is too weak to provoke an arc. In IPG situation, ESDs are able to trigger different arc types, such as nonsustain arc, temporary sustain arc, and permanent sustain arc, depending on SAS current values.

LEO space environment exposure resistant behavior of Ag–Cu films

Ag–Cu films, deposited by arc ion plating and composed of face-centered cubic (fcc) Ag and AgCu alloy phases, had been exposed for 43.5h in low earth orbit (LEO) space environment by a space environment exposure device (SEED) aboard the China Shenzhou-7 manned spaceship. The structure, morphology, composition and tribological property of the Ag–Cu films after the space environment exposure (SEE) were investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscope (XPS) and ball-on-disk tribometer, respectively. After the SEE, the surface layer of Ag–Cu film was partially oxidized to Ag2O, in which the Ag2O content was decreased from the surface to inner and the Cu element was absent. Furthermore, the exposed Ag–Cu film surface became color and exhibited lots of fine particle-like protuberances, but cracking and flaking phenomena that were common for the exposed Ag film, were not observed. Overall, the influence of space exposure on Ag–Cu film was slight compared to the pure Ag film. Sliding friction tests revealed that for the exposed Ag–Cu film, the friction coefficient was stable and the mean value was almost equivalent to one of the non-exposed Ag–Cu film.

Effects of space environmental exposure on photoemission yield of polyimide

As photoemission plays a key role in surface potential of spacecraft materials in sunlight, the photoemission yield of spacecraft used polyimide film is required for surface potential analysis. To reveal the space environmental effects on the photoemission, the ground based degradations of polyimide film due to 500 keV electrons and 50 keV protons irradiation with 4 different fluences respectively, ultraviolet irradiation with 5 different doses, and atomic oxygen beam erosion with 2 different fluences were conducted separately. By using a developed measuring system, we measured the photoemission yield of the virgin and the 4 kinds of degraded polyimide films respectively and compared the results. It is inferred that, the variation of photoemission yield was obvious after electrons, protons and ultraviolet irradiation but slight for atomic oxygen erosion. The variation of photoemission yield has been explained from the viewpoint of surface reflectance, roughness, and the free radical concentration of the exposed samples. Besides, the Monte-Carlo analysis software Casino and SRIM were used to analysis the distribution and stopping power of electron and proton respectively. It is considered that, the degradation mechanism is the multiple effects of reflectance, free radicals and so forth.

Changes in the composition, structure and friction property of sputtered MoS2 films by LEO environment exposure

Radio frequency-sputtered MoS2 films had been exposed for 43.5h in real low earth orbit (LEO) space environment by a space environment exposure device (SEED) aboard China Shenzhou-7 manned spaceship. The composition, morphology, phase structure and friction property of the exposed films were investigated using X-ray photoelectron spectroscope (XPS), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray energy-dispersive spectroscopy (EDS) and ball-on-disk tribometer. XRD and EDS results revealed that the as-deposited MoS2 films were characterized by a MoSxOy phase structure, in which x and y values were determined to be ∼0.65 and 1.24, respectively. XPS analysis revealed that due to space atomic oxygen attack, the film surface was oxidized to MoO3 and MoSxOy with higher O concentration, while the partial S was lost. However, the affected depth was restricted within the surface layer because of protective function of the oxidation layer. As a result, the friction coefficient only exhibited a slight increase at initial stage of sliding friction.

Space Systems Design for Research on the Interaction of Osteoblast-like Cells and Biomaterials (Hydroxyapatite Particles and Titanium) in Microgravity Environment

Microgravity and ionizing radiations are some of the special condition that characterize the space environment. These conditions cause major changes in human bodies, or in biomedical samples; in particular, the bone tissue in microgravity conditions, lack of mechanical loading which is one of the main stimulus to bone remodelling needed, loose elasticity and toughness.In 2014 a cooperation between GAUSS srl. (Group of Astrodynamic for the Use of Space System, Rome, Italy), the University of Brasilia (UnB, Brasilia, Brazil) and the State University of São Paulo (UNESP, Botucatu, São Paulo, Brazil) has been started to study in orbit the effects of the exposure of osteoblast-like cells, responsible to forming-up a new bone, to gold standard biomaterials (hydroxyapatite particles and titanium).Biomaterials are artificial materials, with potential biocompatibility. They are more used in regenerative medicine to support cells behaviour to repair the damage. Nowadays, this field of medicine requires collaboration among engineers, biologists, chemists to create and test new biomaterials and to investigate what might be the best to use to enhance the performance during the repair of the damage. By now, in a field so critical to human health and biomaterial development, it is very important to explore and exploit new research pathways and hence, it is clear that the exposition of osteoblast-like cells to biomaterials under reduced gravity conditions certainly will induce changes in cell adhesion, growth and differentiation of those cells. Each experiment will use the microgravity environment to conduct experimentation that could produce tremendous health benefits for humankind such as advancements in biomaterial screening, tissue engineering/regeneration, cell replacement therapy. Therefor the main goal of this project is to investigate potential effects of the space environment exposure on osteoblast-like cells and biomaterials through an autonomous space system, designed and manufactured specifically for this goal. Specifically, this paper describes the engineering solutions to design and manufacturing autonomous space system that can allow to keep alive and to study these kinds of cells.

Novel Fluorine-containing Trisilahydrocarbon Lubricants and Their Antiatomic Oxygen Irradiation under Simulated Space

Abstract The novel fluorine-containing trisilahydrocarbon lubricants with methyl and 3,3,3-trifluoropropyl substituents (named SiFCH) were synthesized. Importantly, as potential aerospace lubricants, their chemical, physical, and tribological properties under simulated atomic oxygen (AO) exposure in space environment were investigated by a laboratory-built simulation multifunctional space tribo-tester system. The results showed that the SiFCH synthetic oils possess good physical properties and favorable tribological performance, which are superior to that of multi-alkylated cyclopentanes (MACs) in terms of frictional reduction and antiwear capacity under vacuum.

Changes in the structure and tribological property of Ag film by LEO space environment exposure

Ag films, deposited by arc ion plating, had been exposed for 43.5h in real low earth orbit (LEO) space environment by a space environment exposure device (SEED) aboard the China Shenzhou-7 manned spaceship. The structure, morphology, composition and tribological property of the Ag films after the space environment exposure (SEE) were investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscope (XPS) and ball-on-disk tribometer, respectively. Depth XPS and XRD analysis revealed that after the SEE, the surface layer of Ag films was partially oxidized to Ag2O, the cracking and flaking phenomena could be observed from the film surface by FESEM, and so the Ag films lose its metallic shine and became gray. As a result, the tribological performance was deteriorated and the high/unstable friction was obtained.

Degradation of thermal control materials under a simulated radiative space environment

A spacecraft with a passive thermal control system utilizes various thermal control materials to maintain temperatures within safe operating limits. Materials used for spacecraft applications are exposed to harsh space environments such as ultraviolet (UV) and particle (electron, proton) irradiation and atomic oxygen (AO), undergo physical damage and thermal degradation, which must be considered for spacecraft thermal design optimization and cost effectiveness. This paper describes the effect of synergistic radiation on some of the important thermal control materials to verify the assumptions of beginning-of-life (BOL) and end-of-life (EOL) properties. Studies on the degradation in the optical properties (solar absorptance and infrared emittance) of some important thermal control materials exposed to simulated radiative geostationary space environment are discussed. The current studies are purely related to the influence of radiation on the degradation of the materials; other environmental aspects (e.g., thermal cycling) are not discussed. The thermal control materials investigated herein include different kind of second-surface mirrors, white anodizing, white paints, black paints, multilayer insulation materials, varnish coated aluminized polyimide, germanium coated polyimide, polyether ether ketone (PEEK) and poly tetra fluoro ethylene (PTFE). For this purpose, a test in the constant vacuum was performed reproducing a three year radiative space environment exposure, including ultraviolet and charged particle effects on North/South panels of a geostationary three-axis stabilized spacecraft. Reflectance spectra were measured in situ in the solar range (250–2500nm) and the corresponding solar absorptance values were calculated. The test methodology and the degradations of the materials are discussed. The most important degradations among the low solar absorptance materials were found in the white paints whereas the rigid optical solar reflectors remained quite stable. Among the high solar absorptance elements, as such the change in the solar absorptance was very low, in particular the germanium coated polyimide was found highly stable.

Air-Induced Recovery of Proton-Exposed Space Materials

T HE fact that materials degrade in space-radiation environments has been studied for decades [1–19] and continues to be an issue of significant importance for space-based systems. Consequently, ground-based simulation of space environmental effects remains an invaluable method for ensuring the performance of any orbital asset, particularly as newmaterials, coatings, and processes are introduced. High-fidelity simulation of space environmental effects requires accurate definition and modeling of the orbital mission exposure, appropriate calculation of the absorbed radiation dose as a function of material thickness, proper simulation of this dose-depth profile in the laboratory, and precise characterization of test-induced changes in material properties. When performing material characterization, in vacuomeasurements are absolutely essential to avoid atmospheric effects on tested materials. Failure to do this can lead to results that are skewed by the too-often-overlooked dynamic of air-induced recovery of radiation-induced degradation, also known as bleaching. For some materials, ignoring the effects of bleaching can easily lead to a significant under estimation of radiation-induced losses and an inaccurate prediction of on-orbit performance. Bleaching is known to occur primarily for thermal control materials [20], and recent work by The Aerospace Corporation has added to the evidence that somematerials, which have been degraded from exposure to simulated space environments, display air-induced recovery behavior. In particular, samples of silverized Teflon, aluminized Kapton, and Z-93P ceramic white paint that were exposed to simultaneous ultraviolet (UV) and electron radiation in a test designed to simulate the conditions present at geosynchronous Earth orbit (GEO) exhibited noticeable bleaching upon subsequent exposure to air. In each case, a portion of the test-induced optical losses was recovered after a brief period ( 2 min) of air exposure. The behavior is material-specific, exhibiting differences in affected spectral region and magnitude of change. The recovery can occur rapidly or over long timescales, with the rate of recovery appearing to depend on material porosity and/or ambient temperature. The spectral response of the three materials is exemplified in Fig. 1. Although air-induced bleaching of optical degradation in some thermal control materials is relatively common, and the effect is not typically observed for materials that are more resistant to the effects of space-radiation exposure, such as solar-cell coverglass.Additional data generated by The Aerospace Corporation, however, indicated that certain coated coverglass materials, namely, those with thin-film coatings of magnesium fluoride (MgF2) and indium tin oxide (ITO), might also be susceptible to bleaching. In another recent GEO simulation, samples of MgF2/ITO-coated 0214 coverglass (0214 refers to the manufacturer-specific type of coverglass substrate) exhibited slight, yet discernible, air-induced recovery of spectral transmittance following simultaneous exposure to UV and electron radiation. Figure 2 shows the material’s spectral response to a short ( 2 min) postirradiation air exposure. Primarily, because of facility limitations, proton exposures at The Aerospace Corporation historically have been performed, usually precedingUV/electron irradiation, in a separate exposure facility: the low-energy accelerator facility (LEAF). The LEAF has a vacuum chamber attached to a linear ion accelerator; the accelerator’s beam is passed through a 30 deg magnetic turn to select the appropriate ion species, and the beam is rastered across the exposure target. The LEAF lacks in vacuo optical measurement capability; thus, air exposure is unavoidable when characterizing proton-induced material changes. Because of this, it is unknown whether, or to what degree, bleaching occurs for proton-irradiated coverglass materials, although it seems reasonable to suspect that somematerials degraded by proton exposure would also exhibit air-induced recovery. Given the apparent bleaching ofUV/electron-induced degradation in MgF2/ITO-coated coverglass and the lack of in vacuo optical measurement capability of the LEAF, this research effort was undertaken to investigate the air-induced response of protonirradiated space materials. Making this possible is The Aerospace Corporation’s newest space environmental effects exposure facility, which had already possessed in vacuo optical measurement capability and now features a variable-energy proton flood gun. This recently enhanced facility makes possible measurements of protonirradiated materials that are free from atmospheric effects and allows Received 21 September 2011; revision received 5 December 2011; accepted for publication 9 January 2012. Copyright © 2012 by The Aerospace Corporation. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. All rights reserved. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0022-4650/12 and $10.00 in correspondence with the CCC. Research Scientist, Materials Science Department, Space Materials Laboratory, 2310 East El Segundo Boulevard, M2-248. Distinguished Scientist, Space Materials Laboratory, 2310 East El Segundo Boulevard, M2-248. JOURNAL OF SPACECRAFT AND ROCKETS Vol. 49, No. 4, July–August 2012

Electrostatic Discharge Testing of Multijunction Solar Array Coupons After Combined Space Environmental Exposures

A set of multijunction GaAs/Ge solar array test coupons provided by Space Systems/Loral was subjected to a sequence of five-year increments of combined space environmental exposure tests. The test coupons capture an integrated design intended for use in a geosynchronous (GEO) space environment. A key component of this test campaign is performing electrostatic discharge (ESD) tests in the inverted gradient mode. The protocol of the ESD tests is based on the ISO standard for ESD testing on solar array panels [ISO-11221]. The test schematic in the ISO reference has been modified with Space System/Loral designed circuitry to better simulate the on-orbit operational conditions of its solar array design. Part of the modified circuitry is to simulate a solar array panel coverglass flashover discharge. All solar array coupons used in the test campaign consist of four cells constructed to form two strings. The ESD tests are performed at the beginning-of-life (BOL) and at each five-year environmental exposure point. The space environmental exposure sequence consists of ultraviolet radiation, electron/proton particle radiation, thermal cycling, and xenon ion thruster plume erosion. This paper discusses the coverglass flashover simulation, the ESD test setup, and the importance of the electrical test design in simulating the on-orbit operational conditions. Results from fifth-year testing are compared to the baseline ESD characteristics determined at the BOL condition.

Combined Space Environmental Exposure Test of Multijunction GaAs/Ge Solar Array Coupons

The purpose of this test program is to understand the changes and degradation of the space solar array panel components, including its electrostatic discharge (ESD) mitigation design features in their integrated form, after multiple years (up to 15) of simulated Earth geosynchronous (GEO) space environment. A set of multijunction GaAs/Ge solar array test coupons was subjected to five-year increments of combined environmental exposure tests. These tests consisted of the following: simulated ultraviolet (UV) radiation, ESD, electron/proton particle radiation, thermal cycling, and simulated ion thruster exposures. The solar radiation simulation was produced using a mercury-xenon lamp with wavelengths in the UV spectrum ranging from 230 to 400 nm. The ESD test was performed in the inverted-gradient mode using a low-energy electron (3-6 keV) beam exposure. The ESD test also included a simulated panel coverglass flashover for the primary arc event. The electron/proton radiation exposure included 1.0-MeV electrons, 100-keV electrons, and 40-keV protons. Thermal cycling included simulated transient Earth eclipse for satellites in geosynchronous orbit. With the increasing use of ion thruster engines on many satellites, the combined environmental exposure test also included ion thruster exposure to determine the impact on solar array performance, as well as the ion thruster interaction to ESD events. Before and after each increment of combined environmental exposures, the coupons underwent visual inspection using high power magnification and electrical tests that included characterization by large-area pulse solar simulator, dark I -V, insulation resistance, and electroluminescence. This paper discusses the test objective, test methodologies, and preliminary results after five and ten years of simulated combined environmental exposure tests.