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.

Since the dawn of the Space Age, hundreds of payloads have been launched into heliocentric space. As near-Earth object (NEO) surveys search deeper for small asteroids, more artificial objects in heliocentric orbits are being discovered. We now face a challenge to identify the true nature of these objects and avoid contaminating the NEO catalog. Here, we present the methods used to characterize one such object. 2020 SO was discovered by the Pan-STARRS1 survey on 2020 September 17. Originally classified as a NEO, the object’s artificial nature became evident due to its low velocity relative to Earth and solar radiation pressure affecting its orbit about the Sun. Based on a backward propagation of its orbit, 2020 SO is thought to be a Centaur rocket body (R/B) from the launch of the Surveyor 2 mission to the Moon. We characterized 2020 SO using a range of ground-based optical and near-infrared telescopes to constrain its true nature. We find that its reflectance spectrum is consistent with that of other Centaur R/B launched during a similar time frame, and we identify 1.4, 1.7, and 2.3 μ m absorption bands consistent with polyvinyl fluoride used on the aft bulkhead radiation shield exterior of Centaur-D R/B at the time.

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.

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.

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.

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.

The harsh space environment at geosynchronous orbit (GEO) induces differential charging of spacecraft surfaces due to fluxes of high energy electrons onto and through them. Thus, satellite surfaces can charge thousands of volts with respect to each other whereas entire satellites can charge tens of thousands of volts negative of their surrounding space plasma. The ensuing electric fields can cause local discharges (arcs), endangering the normal operation of the satellite. Solar cell coverglass contamination induced by the high rate of arcing is sufficient to produce the ~1.5 percent/ year power loss in excess of radiation damage on the global positioning system (GPS) satellites. This work focuses on evaluation of a GEO space weather effect, caused by 90 keV high-energy electron radiation, on material properties of different types of commonly used in space solar cell coverglasses (CMX, fused silica, and 0214). Charge analysis performed with a GPS Block IIF NASCAP model demonstrated that the use of CMX, a high-conductivity coverglass, may help to mitigate differential charging and prevent arc-induced contamination. Finally, radiofrequency observations by the Arecibo 305 m telescope of GEO satellites with different configurations have registered abundant arcing of satellites utilizing less conductive coverglasses and no arcing on two with CMX coverglasses. It is the object of the current study to see how space weathering of different coverglass types may alter these results.

Geosynchronous orbit (GEO) weathering induces differential charging of spacecraft surfaces due to simultaneous fluxes of electrons with a wide distribution of energies onto, into, and through spacecraft surface materials. Thus, satellite surfaces can charge thousands of volts with respect to each other whereas entire satellites can charge tens of thousands of volts negative of their surrounding space plasma. The ensuing electric fields can cause local discharges (arcs) from one part of the spacecraft to another, endangering the normal operation of the satellite. Arcing on solar panels can cause reduced optical transmission through solar cell coverglasses which will lead to reduced power production negatively affecting a long-term satellite missions. This work focuses on evaluation of simulated GEO space weather effect, comprised by > 90 keV high-energy electron irradiation, on optical and charge transport properties of two different types of commonly used space solar cells coverglasses, CMX and CMG.

Artificial objects currently populating Earth orbital regimes can be distinguished by comparing remote observational data to that of optical measurements within the visible (VIS) and near infrared (NIR) spectral regions of materials obtained in the laboratory. Careful comparison of spectrally resolved observations with laboratory-based material irradiation experiments can provide a tool for remote diagnosis and anomaly resolution. However, the spectral signatures of many materials change as a function of exposure to radiation in geosynchronous Earth orbit (GEO). In order for remote characterization to be a viable characterization technique, the evolution of material optical properties (VIS-NIR) upon exposure to the GEO environment must be understood. To this end, we have studied the reflectance of several commonly used spacecraft materials including organic polymers, solar cell coverglasses, black thermal control paint, and carbon-carbon (C–C) matrix composite as a function of exposure to high energy electron irradiation in order to mimic the harsh environment of GEO. It was found that different classes of materials exhibit large variation in radiation stability resulting in the development of unique spectral characteristics.

The harsh space environment at geosynchronous orbit (GEO) induces differential charging of spacecraft surfaces due to simultaneous fluxes of electrons with a wide distribution of energies onto, into, and through spacecraft surface materials. Thus, satellite surfaces can charge thousands of volts with respect to each other, whereas entire satellites can charge tens of thousands of volts negative relative to their surrounding space plasma. The ensuing electric fields can cause local discharges (arcs) from one part of the spacecraft to another, endangering the normal operation of the satellite. Furthermore, solar cell coverglass contamination induced by the high rate of arcing is sufficient to produce the ~1.5%/year power loss in excess of radiation damage that has been observed on global positioning system (GPS) satellites. This work focuses on evaluation of a GEO space weather effect on material properties caused by irradiating different types of commonly used space solar cell coverglasses (CMX, fused silica, and Corning 0214) with >90-keV electron radiation.

The harsh radiation environment at geosynchronous Earth orbit (GEO) induces chemical changes in organic polymers, leading to alteration of optical, mechanical, and charge transport properties. This work focuses on the evaluation of laboratory-simulated GEO environmental effects on the properties of common spacecraft materials and on methods for remote diagnosis of spacecraft health for improved anomaly resolution.

Many techniques have been proposed to prevent solar array arcing on geosynchronous (GEO) satellites. All of these methods would be employed to keep differential voltages below some voltage threshold. In almost all cases, unless there are solar array string failures on orbit, there has been no way to confirm that the chosen technique actually prevented arcs, because no arc detection circuitry is typically flown. Recently, however, the radiofrequency interference (RFI) produced by arcs on solar arrays of orbiting satellites has been detected and measured by the Arecibo 305m Wm. E. Gordon radio telescope. It is clear that these emissions are from real solar array arcs because their rate follows the fluence of surface charging electrons (10-30 keV) over a typical coverglass charge-storage time, and the character of their radio spectrum is duplicated by solar array arcs in ground simulations. Additionally, in the case of Global Positioning System (GPS) satellites, the on-orbit arc rate seen at Arecibo and measured by on-board RFI detectors is sufficient to produce the observed GPS power degradation in excess of radiation damage, based on ground-based testing. Among the GEO satellites observed by the Arecibo telescope, all have proven to have frequent arcs but two, even though those should have been seen by the sensitive 305m telescope to arc as well. It is believed that the design of these active satellites precludes arcing. When the design details are examined, one in particular stands out. These satellites had coverglasses that were relatively bulk-conductive, so the maximum differential voltage and charge storage times should have been much smaller than other satellites with less conductive coverglasses. The literature about coverglass conductivity as it relates to differential charging and arcing is examined, and it is shown that the coverglasses used in these satellites should have prevented arcing, based on observed differential arc thresholds of GPS and other satellites.