The low Earth orbit (LEO) environment presents unique challenges for spacecraft materials causing their progressive degradation. While ground-based simulations and mathematical models attempt to replicate these conditions, they cannot fully capture the nature and extent of material degradation in LEO. This research characterizes natural space environment effects on material stress using the Materials International Space Station Experiment Flight Facility (MISSE-FF). Building on MISSE-16, which captured temporal spectral changes in spacecraft materials, the current MISSE-22 mission evaluates mechanical property alterations in innovative materials under LEO exposure. We utilize the photoelastic effect, where mechanical stress induces birefringence, assessed through a specialized polariscope integrated within MISSE-FF. Shifts in color patterns serve as qualitative indicators of mechanical stress in thin films. Details of the MISSE-22 mission parameters, material selection criteria, payload integration testing, and pre-launch control data serving as ground truth for evaluating space-exposed materials are discussed.

Space situational awareness (SSA) demands rapid, accurate analysis of orbital objects to mitigate potential hazards to satellites. A significant challenge in this field involves characterizing objects from ground- based observations that often yield unresolved imagery. This research introduces a novel self-supervised learning approach for characterizing orbital objects using telescope-based spectral data. The self-supervised methodology offers particular value for identifying previously uncharacterized objects-a critical capability for comprehensive space situational awareness. Our approach leverages an extensive dataset of simu- lated spectral signatures from orbital objects with diverse physical properties and orbital parameters, ensuring robust and reproducible classification results. We evaluate our algorithm's effectiveness through comparative analysis against the raw spectral data. The comparison employs a novel method that detects the amount of material-composition signal within the sample. This research advances the technical foundation for improved autonomous characterization of objects in Earth orbit.

Spacecraft materials play a crucial role in safeguarding satellites from space’s harsh conditions. However, exposure to solar radiation and aggressive chemical species in the upper atmosphere alters these materials’ physical, chemical, and optical properties over time. Understanding material evolution during a mission enhances spacecraft reliability. By establishing correlations between on-orbit material performance and laboratory-based tests, accurate predictions can be made through accelerated space weather experiments. This study evaluates the effects of radiation on various modern spacecraft materials, specifically high-energy electrons, atomic oxygen, and vacuum ultraviolet radiation, in a ground-based simulated LEO environment. The focus is on assessing the impact on the Bidirectional Reflectance Distribution Function properties.

External spacecraft materials play an important role in satellite protection from the harsh space environment.Research has shown that the physical, chemical, and optical properties of matter change continuously as a result of exposure to solar radiation and aggressive chemical species produced in Earth’s upper atmosphere. Thorough knowledge of the material properties evolution throughout a planned mission lifetime helps to improve the reliability of spacecraft. Moreover, the establishment of correlation factors between true space exposure and accelerated space weather experiments at ground facilities enables accurate prediction of on-orbit material performance based on laboratory-based testing. The presented work evaluates the radiation effects of different doses of high-energy electron exposure on surface morphology, optical, and charge transport properties of two materials from the PET family, Melinex ® 454 and Mylar ® M021.

The interaction between the materials on the surface of a spacecraft and the space environment can lead to mechanical, chemical, and optical changes that affect their properties. It is crucial to comprehend how these materials respond to the different aspects of the space environment once they are in orbit and how these properties change over time. This knowledge is critical for predicting the spacecraft’s performance throughout its mission, ensuring its optimal functionality, and prolonging its lifespan. Selected polymers proposed for space applications were exposed to 95 keV electrons to simulate electron irradiation that the materials would receive in a range of different space environments. To assess the impact of electron irradiation on materials, reflectance spectra of both pristine and electron-irradiated samples were obtained and analyzed for changes in the Urbach edge. A change in the Urbach edge indicates changes in the material’s electronic structure, which can affect its electrical properties. Therefore, analyzing changes in the Urbach edge of irradiated materials can provide insight into their potential impact on the electrical conductivity of the material.

External spacecraft materials play an important role in satellite protection from the harsh space environment. Research has shown that the physical, chemical, and optical properties of matter change continuously as a result of exposure to solar radiation and aggressive chemical species produced in Earth’s upper atmosphere. Thorough knowledge of the material properties evolution throughout a planned mission lifetime helps to improve the reliability of spacecraft. Moreover, the establishment of correlation factors between true space exposure and accelerated space weather experiments at ground facilities enables accurate prediction of on-orbit material performance based on laboratory-based testing. The presented work aims to evaluate the radiation effects of low Earth orbit (LEO) environment, namely, exposure to the high-energy electrons, atomic oxygen (AO), and vacuum ultraviolet (VUV), of several modern spacecraft materials. The studied materials represent the “flight duplicates” of samples that are launched as a part of the 16th Materials International Space Station Experiment Flight Facility (MISSE-FF) mission in July 2022.

To investigate how spacecraft elements perform when exposed to the space environment, extensive studies are conducted in laboratory vacuum chambers which aim to reproduce spacelike conditions. One prevalent constituent in the space environment is energetic electron radiation. The space environment contains electrons distributed across a wide range of energies simultaneously which deposit energy and charge into spacecraft surfaces. Conventional electron guns available in the laboratory to simulate the space electron flux environment, however, are monoenergetic. Therefore, laboratory studies are often conducted in environments which are fundamentally different from the on-orbit electron flux environment. This paper presents background, prior work, and recent advances toward the development of a multi-energy electron gun which can reproduce spacelike electron fluxes in the laboratory with high fidelity in the eV to tens of keV range.

External spacecraft materials play an important role in satellite protection from the harsh space environment. Research has shown that the physical, chemical, and optical properties of matter change continuously as a result of exposure to solar radiation and aggressive chemical species produced in Earth’s upper atmosphere. Thorough knowledge of the material properties’ evolution throughout a planned mission lifetime helps to improve the reliability of spacecraft. Moreover, the establishment of correlation factors between true space exposure and accelerated space weather experiments at ground facilities enables accurate prediction of on-orbit material performance based on laboratory-based testing. The presented work aims to evaluate the radiation effects of a low-Earth-orbit environment, namely, exposure to the high-energy electrons and atomic oxygen (AO) of heritage and novel spacecraft material selection. The studied materials represent the “flight duplicates” of samples that are launched as a part of the 16th Materials International Space Station Experiment Flight Facility (MISSE-FF) mission in 2022.

The space environment is detrimental to the exterior of the spacecraft and imposes stringent requirements on spacecraft materials. Space materials are often expected to perform for 15-20 years in the harsh space environment without significant degradation of their optical, electrical, mechanical and thermal properties. Further, as commercial activities increase in the space domain, development of predictive capability for material evolution is critical for agile adaption of novel materials. Therefore, it is very important to understand the effects of the space environments on the spacecraft materials. The Materials on the International Space Station Experiment Flight Facility (MISSE-FF) has flown numerous material samples to investigate the effect of LEO space weather exposure on the performance and durability of materials and devices. As part of the MISSE-16 mission, which launched on July 15, 2022, we are flying fifteen novel and well-characterized materials in the LEO environment for a duration of six months. Changes in spectral reflectivity will be measured in real time throughout the mission with an RGB/IR camera. These time-resolved data will function as a “space-truth” reference for our team’s ongoing laboratory-based space weather-material interaction experiments. Correlation of the MISSE-16 data with extensive ground testing of duplicate samples under simulated space weather conditions will enable development of fundamental chemical models for material degradation. This paper discusses preliminary results from the ground test campaign to collect the RGB/IR images for pristine and damaged materials and the development of machine learning algorithms to extract reflectance spectra from the color images.

Successful spacecraft design and charging mitigation techniques require precise and accurate knowledge of charge deposition profiles. This paper compares models of charge deposition and transport using a venerable deep dielectric charging code, AF-NUMIT3, with direct measurements of charge profiles via pulsed electroacoustic (PEA) measurements. Eight different simulations were performed for comparison to PEA experiments of samples irradiated by 50 or 80 keV monoenergetic electrons in vacuum and at room temperature. Two materials, polyether-ether ketone (PEEK) and polytetrafluoroethylene (PTFE), were chosen for their very low conductivities so that minimal charge migration would occur between irradiation and PEA measurements. PEEK was found to have low acoustic attenuation, while PTFE has high acoustic attenuation through the sample thicknesses of 125 and [Formula: see text] for each material. The measurements were directly compared to AF-NUMIT3 simulations to validate aspects of the code and to investigate the importance of various simulation options, as well as to characterize the PEA instrumentation, measurement methods, and signal processing used. The measurement and simulation values for magnitude of charge deposition, penetration depth, and charge deposition spatial profiles are largely in agreement, though spatial and temporal distributions in incident electron flux and effects of radiation-induced conductivity (RIC) and delayed RIC during the deposition process complicate the process. This work provides an experimental validation of the AF-NUMIT3 deep dielectric charging code and insight into the accuracy and precision of the PEA method.

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Space solar arrays must survive in the hostile space environment. The most dangerous space solar array environmental interaction is spacecraft charging, which can lead to potentially disabling arcing. In this chapter we discuss why solar arrays are often the spacecraft components most likely to arc and how this is related to electrical charging of the spacecraft. The basic charging equations are given. Factors involved in charging and arcing are enumerated. How charging is related to the space plasma environment is discussed. The different types of charging are given, and how they may lead to arcing on the solar arrays. Transient arcs and sustained arcs are differentiated. We describe the effects of arcing and give examples. Standards related to charging and arcing are listed and described, and mitigation strategies (both passive and active) are surveyed. Because charging and arcing are driven by the space environment, models of the space plasma environment and charging models are listed and described. Finally, we make the case for the necessity of laboratory measurements of arcing voltage thresholds, both for primary and sustained arcs.

Space domain awareness (SDA) is becoming more important with a constantly increasing number of artificial objects in space. Astronomical reflectance spectroscopy (ARS) is a promising technique employed for remote characterization of space objects. In geosynchronous earth orbit (GEO), the chemical characteristics of a material change continuously, as it is exposed to the harsh radiation environment of several damaging species (with electrons being the primary damaging species in terms of energy deposition). These chemical modifications alter the light absorbed by and reflected from the object at certain wavelengths, resulting in a concomitant change of the measured object’s brightness and color index. By understanding the evolution of the color index of a material as a function of time on orbit, ARS can become a powerful tool for remote characterization of space objects as well as anomaly characterization and resolution. In this study, we investigate the effect of a space-simulated environment represented by high-energy (100 keV) electrons on the evolution of optical properties of several spacecraft-relevant polymer materials.

Many space environments contain energetic electrons distributed across a broad spectrum of energies which are damaging to spacecraft materials and components. To characterize degradation and ensure adequate end-of-life performance, studies are often conducted in which samples are exposed to energetic electron fluxes in vacuum chambers. However, conventional electron guns used for such testing emit electrons monoenergetically, whereas the actual space environment contains electrons across a spectrum of energies. Physical phenomena resulting from energetic electron irradiation depend strongly on the energy of the incident particles, and synergistic effects can result from the combined effects of multiple energies. Therefore, it is questionable how well many vacuum chamber experiments represent the on-orbit degradation behavior, and a clear need exists for improved laboratory simulation of space electron fluxes. This paper provides a brief review of previous studies, underscores the limitations of monoenergetic fluxes, and discusses several alternatives for simulating the space electron environment in a laboratory. Next, a concept for a novel multi-energy electron source is presented. This source presents numerous advantages over the existing techniques for laboratory simulation of space electron fluxes. Finally, Monte Carlo N-Particle (MCNP) simulations are presented for energetic electrons incident on polyimide. These simulations demonstrate the proposed multi-energy electron gun is capable of producing space-representative damage with higher accuracy than monoenergetic guns.

Ground- and space-based optical observations of space objects rely on knowledge about how spacecraft materials interact with light. In polymers, the changes in optical signature occur due to surface degradation caused by radiation induced chemical modification. This leads to altered reflectivity and deviation from a material’s expected absorption/transmission properties. The optical fingerprint of commonly used spacecraft materials changes continuously under space weather exposure. Laboratory observations have also shown that these changes in a material’s optical signature are to some degree transient. This work investigates the rate and degree of “optical healing” in vacuum and air exposure for electron damaged polyimide (PI) samples. Characterization of optical damage as a function of electron exposure and optical healing as a function of time in vacuum represents a major step toward a predictive model for optical characterization of space objects.

The harsh space environment induces local discharges (arcs) on satellite solar panels, which can cause reduced optical transmission through solar array coverglasses, thus negatively affecting long-term satellite missions. This article presents the experimental results of low-energy (4–5 keV) electron irradiation of three common types of space solar array coverglass, CMX, CMG, and fused silica at various bias voltages. The dependence of the discharge rate on the bias voltage, coverglass composition, energy of the incident electrons, vacuum exposure, and surface conductivity was investigated. It is shown that the arc frequency is inversely related to the incident electron energy. Physicochemical models of the mechanisms occurring in different types of space array coverglasses under low-energy electron irradiation are proposed to explain the experimental findings.

GPS satellites undergo surface contamination on the solar array coverglasses from repeated arcing events. Using NASA Air Force Spacecraft Charging Analyzer Program (Nascap-2 K) spacecraft charging simulation software, a GPS Block IIF satellite model was constructed and analyzed in realistic Medium Earth Orbit environments. GPS Block IIF satellites have Qioptiq CMG-type coverglasses (as do all other GPS satellites). The Nascap-2 K model with CMG coverglasses charges to high differential levels in maximum charging environments, in the range above the arcing threshold, as determined by studies at the Air Force Research Laboratory (AFRL), and so arcing is confirmed by theory. This finding agrees with onboard Los Alamos National Laboratory measurements and Arecibo observational data for GPS satellites. Other AFRL results show that CMX-type coverglasses, being more bulk-conductive, should charge less and perhaps mitigate arcing on the solar arrays. A Nascap-2 K model using CMX coverglasses is shown to charge differentially much less than CMG, and not reach levels above the arcing threshold. In the simulation, the commonly used CMG coverglass charges quickly, exceeding its arcing voltage threshold of 1500 V in about 1 h and 10 min. In comparison, CMX results indicate an ability to remain well under its arcing threshold throughout the orbit.

View Video Presentation: https://doi.org/10.2514/6.2022-0797.vid The harsh space environment imposes stringent requirements upon spacecraft materials, especially those located on exterior surfaces of space objects in low Earth orbit (LEO). As humankind moves from space exploration to space commercialization, these polymers may have to last for 15–20 years without considerable degradation of their material properties. Hence, we must understand the effects of the space environment on materials currently in use as well as on untested materials. In the presented study authors exposed several space-relevant polymers to the simulated space weather comprised by electrons and atomic oxygen irradiation. First, materials were thoroughly characterized in their pristine state to create a baseline for the ground- and space-based experiments. Next, alteration of optical, surface, and charge transport properties of the same materials were studied under space-simulated environment

The harsh space environment induces changes in optical signature of spacecraft polymeric materials which can occur due to surface degradation, leading to altered reflectivity, or due to radiation induced chemical modification, leading to an alteration of a material’s absorption/transmission. The optical character of commonly used materials change continuously under exposure to high energy electrons, a primary damaging species in geostationary Earth orbit (GEO). In this study we employed directional hemispherical reflectance (DHR) measurements to study the evolution of optical properties of several electron-irradiated PI materials during irradiation with high energy electrons. In particular, we present DHR spectra and the astronomical color index of chosen materials as a function of electron fluence to assist the spacecraft designers to understand each material’s value as a thermal control surface as a function of GEO exposure.