The JPL Proton Fluence Model: An Update
The development of new technologies and the miniaturization of sensors bring new requirements for our ability to predict and forecast hazardous space weather conditions.
solar events spacecraft environments↗
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Spacecraft Charging: Hazard Causes, Hazard Effects, Hazard Controls
Spacecraft flight environments are characterized both by a wide range of space plasma conditions and by ionizing radiation (IR), solar ultraviolet and X-rays, magnetic fields, micrometeoroids, orbital debris, and other environmental factors, all of which can affect spacecraft performance. Dr. Steven Koontz's lecture will provide a solid foundation in the basic engineering physics of spacecraft charging and charging effects that can be applied to solving practical spacecraft and spacesuit engineering design, verification, and operations problems, with an emphasis on spacecraft operations in low-Earth orbit, Earth's magnetosphere, and cis-Lunar space.
cis-lunar space↗
Radiation and Internal Charging Environments for Thin Dielectrics in Interplanetary Space
Spacecraft designs using solar sails for propulsion or thin membranes to shade instruments from the sun to achieve cryogenic operating temperatures are being considered for a number of missions in the next decades. A common feature of these designs are thin dielectric materials that will be exposed to the solar wind, solar energetic particle events, and the distant magnetotail plasma environments encountered by spacecraft in orbit about the Earth-Sun L2 point. This paper will discuss the relevant radiation and internal charging environments developed to support spacecraft design for both total dose radiation effects as well as dose rate dependent phenomenon, such as internal charging in the solar wind and distant magnetotail environments. We will describe the development of radiation and internal charging environment models based on nearly a complete solar cycle of Ulysses solar wind plasma measurements over a complete range of heliocentric latitudes and the early years of the Geotail mission where distant magnetotail plasma environments were sampled beyond X(sub GSE) = -100 Re to nearly L2 (X(sub GSE) ~-236 Re). Example applications of the environment models are shown to demonstrate the radiation and internal charging environments of thin materials exposed to the interplanetary space plasma environments.
Minow, Joseph I.↗
A study of spacecraft charging due to exposure to interplanetary protons
The interplanetary space environment is composed mostly of plasma from the solar wind and high energy protons from solar events such as coronal mass ejections. Satellites orbiting Earth are shielded to some degree from these events by the Earth's magnetic field but spacecraft traveling between planets are exposed to these solar protons directly. A major concern for spacecraft is internal electrostatic discharge (IESD), a form of spacecraft charging. The majority of research regarding IESD has been concerned with the electrons in the space environment around the Earth and at Jupiter; little research has been done on the charging of spacecraft in interplanetary space due to solar event protons. This paper reviews the work done so far on IESD due to protons and provides a possible example of an anomaly due to a proton induced discharge in interplanetary space on the Galileo spacecraft.
proton↗
The International Space Station Space Radiation Environment: Avionics Systems Performance in Low-Earth Orbit Single Event Effects (SEE) Environments
Single event effects (SEE) are those errors, anomalies, or failures in microelectronic devices caused by the passage of a single energetic charged particle through the device. Spacecraft SEE environments consist primarily of energetic charged particles; both primary particles originating in the natural environment and secondary particles (including secondary neutrons) produced by nuclear reactions of primary particles with spacecraft materials. The energetic charged particle components (electrons, protons, and atomic nuclei) of the spacecraft SEE environment include galactic cosmic rays (GCR), and planetary radiation belt charged particles, as well as solar energetic particle event (SPE) charged particles. The International Space Station (ISS) orbital altitude and inclination (~350 km to ~420 km at 51.6o inclination) results in a spacecraft SEE environment that varies dramatically with the location in Earth?s geomagnetic field. Geomagnetic GCR shielding diminishes with distance from the geomagnetic equator. Near + 51.6o latitude the ISS GCR environment has a high degree of similarity to the interplanetary GCR environment in cis-Lunar space.SEE environments supporting ISS avionics systems design, development, test, and verification are documented in SSP-30512, Space Station Ionizing Radiation Design Environment. Comparisons of overall ISS avionics systems in-flight performance with pre-flight verification report predictions have been previously reported and meet or exceed expectations in all cases.In this paper we report the results of more detailed investigations of the effects of geographic location, altitude, solar cycle, and shielding mass effects on the in-flight SEE performance of the ISS command and data handling system during the past 17 years. In addition, we report on the preflight testing and in-flight performance of the commercial-off-the-shelf lap top computers used on ISS. Finally, we present an assessment of ISS as an avionics SEE test and flight demonstration platform for exploration hardware destined for the cis-lunar or other inner solar system environments.
International Space Station↗
The Space Radiation Environment as it Relates to Electronic System Performance: Or Why Not to Fly Commercial Electronic Components in Space
This viewgraph presentation offers an overview of the space radiation environment, primarily in near-Earth environments such as Low Earth Orbit (LEO). The presentation describes the Halloween solar event of 2003 as an example of how solar activity can affect spacecraft electronic systems. The lunar radiation environment is also briefly summarized.
Barth, Janet L.↗
Using Space Weather Variability in Evaluating the Environment Design Specifications for NASA'S Constellation Program
Spectral models of solar particle events and trapped radiation belts are necessary for the design requirements of total ionizing radiation dose, single event effects, and spacecraft charging. Space radiation and plasma environment specifications for hardware design are necessarily conservative to assure system robustness for a wide range of space environments.
Coffey, Victoria N.↗
Probabilistic Assessment of Risks from Solar Energetic Particle Events
Solar energetic particle events pose a radiation hazard for space crews and a risk of harmful radiation effects in spacecraft electronics. To assess these risks, engineers need to know the worst-case environment that they must plan for or design to withstand. Depending on the application, engineers may need to know the instantaneous worst-case environment, the radiation environment that accumulates during one solar particle event or the cumulative worst-case environment for their entire mission. Also, depending on their application, they will need to know this environment at a confidence level which they will specify. We will present a probabilistic model for the peak fluxes, event-integrated fluences and mission-integrated fluences for solar protons and heavy ions. The model will provide these worst-case environments at user-specified confidence levels. Examples of the use of this model will also be shown.
Adams, James H., Jr.↗
Spacecraft Natural Thermal Environments
During this U.S. Spacesuit Knowledge Capture Program event, Dr. Eugene Ungar presented the background on the Earth and Moon solar, albedo, and outgoing longwave radiation (OLR) natural thermal environment parameters. He reviewed the interrelationship of the parameters and explore the physically correct method of combining them. Dr. Ungar also presented a sample analysis of a representative case.
Eugene K Ungar↗
Oh! I Slipped the Surly Bounds of Earth....and Ran into Space Weather!
Over the past decade the concept of space weather has been introduced and matured in both the scientific community and popular press. Likewise the concept of space climatology recently also is being advanced. Closely linked to these concepts are their impacts on ground- and space-based technological systems; one such system commonly mentioned is manned space flight exemplified by the Space Shuttle and International Space Station (ISS). From a manned space flight perspective, space weather and space climatology have significant effects on the amount of radiation exposure received by humans in space from the ambient high-energy charged particles present in interplanetary space and trapped in the geomagnetosphere. Whereas the impact of space weather for most technological systems is usually discrete and well correlated in time, the principle impact of space weather and space climatology is to increase the probability of latent cancer formation in thetraveler cohort. In this regard, while space weather may be the dominating factor for a given mission, over the life of a long-term program such as the Space Shuttle or ISS space climatology is the controlling factor of latent cancer risk. Human radiation exposure enhancements associated with space weather disturbances has been a concern among scientist and mission controllers since the inception of manned spaceflight nearly forty years ago. This led NASA to develop, in conjunction with the Environmental Science Services Administration s Space Disturbance Forecast Center and the USAF/AWS, the Solar Particle Alert Network (SPAN)-the foundation of an initial U.S. space weather monitoring and forecasting service. Since Apollo, routine space flight operations have evolved to include the use of space weather and climatology data provided through a world-wide network of operational space weather data services to predict and recommend actions to minimize astronaut radiation exposures. NASA Space Radiation Analysis Group (SRAG) flight controllers use real-time space weather data to detect and assess the impact of solar particle events, outer electron belt enhancements, the formation of pseudo-stable additional trapped radiation belts, and the solar cycle modulation of trapped radiation belts and galactic cosmic rays. Energetic particle data from GOES spacecraft are automatically ingested from NOAA Space Environment Center data servers and used to drive a model for the estimating the exposure to astronauts from solar particle events. While adequate for current manned space flight support, the existing operational space weather support system requires improvements to address the anticipated evolution in both the character of manned missions as well as space flight operations management. Necessary space weather data improvements include: reliably available (near) real-time space weather data on a fixed schedule via redundant access methods that support autonomous data acquisition by computer systems behind enterprise firewalls; and rapid transition of promising research sensors into operational systems.
Golightly, Michael J.↗
Space Environment Effects: Model for Emission of Solar Protons (ESP): Cumulative and Worst Case Event Fluences
The effects that solar proton events have on microelectronics and solar arrays are important considerations for spacecraft in geostationary and polar orbits and for interplanetary missions. Designers of spacecraft and mission planners are required to assess the performance of microelectronic systems under a variety of conditions. A number of useful approaches exist for predicting information about solar proton event fluences and, to a lesser extent, peak fluxes. This includes the cumulative fluence over the course of a mission, the fluence of a worst-case event during a mission, the frequency distribution of event fluences, and the frequency distribution of large peak fluxes. Naval Research Laboratory (NRL) and NASA Goddard Space Flight Center, under the sponsorship of NASA's Space Environments and Effects (SEE) Program, have developed a new model for predicting cumulative solar proton fluences and worst-case solar proton events as functions of mission duration and user confidence level. This model is called the Emission of Solar Protons (ESP) model.
Xapsos, M. A.↗
Space Environment Effects: Model for Emission of Solar Protons (ESP)--Cumulative and Worst-Case Event Fluences
The effects that solar proton events have on microelectronics and solar arrays are important considerations for spacecraft in geostationary and polar orbits and for interplanetary missions. Designers of spacecraft and mission planners are required to assess the performance of microelectronic systems under a variety of conditions. A number of useful approaches exist for predicting information about solar proton event fluences and, to a lesser extent, peak fluxes. This includes the cumulative fluence over the course of a mission, the fluence of a worst-case event during a mission, the frequency distribution of event fluences, and the frequency distribution of large peak fluxes. Naval Research Laboratory (NRL) and NASA Goddard Space Flight Center, under the sponsorship of NASA's Space Environments and Effects (SEE) Program, have developed a new model for predicting cumulative solar proton fluences and worst-case solar proton events as functions of mission duration and user confidence level. This model is called the Emission of Solar Protons (ESP) model.
Xapsos, M. A.↗
Interplanetary energetic particle observations of the March 1989 events
The IMP-8 spacecraft placed in an elongated orbit of approximately R(sub E) x R(sub E) orbit around the Earth was the only monitor of the energetic particle environment of the near interplanetary space during the period of the solar particle events associated with the Active Region 5395 in March 1989. Measurements of energetic ion and electron intensities were obtained in a series of channels within the energy range: 0.3 to 440 MeV for photons, 0.6 to 52 MeV/nuc for alpha particles, 0.7 to 3.3 MeV/nuc for nuclei with Z greater than or equal to 3, 3 to 9 MeV/nuc with Z greater than or equal to 20, and 0.2 to 2.5 MeV for electrons. The responses of selected energy channels during the period 5 to 23 March 1989 are displayed. It is clearly noted that the most prominent energetic ion intensity enhancements in that time interval were associated with the interplanetary shock wave of March 13 (07:42 UT) as well as that of March 8 (17:56 UT), which have distinct particle acceleration signatures. These shock waves play a major role in determining the near Earth energetic ion intensities during the above period by accelerating and modulating the ambient solar energetic particle population, which was already present in high intensities in the interplanetary medium due to the superposition of a series of solar flare particle events originating in AR 5395. The differential ion intensities at the lowest energy channel of the CPME experiment, which were associated with the March 13 shock wave, reached the highest level in the life of the IMP-8 spacecraft at this energy. At high energies, the shock associated intensity peak was smaller by less than a factor of 3 than the maxima of solar flare particle intensities from some other major flares, in particular from those with sites well connected to the Earth's magnetic flux tubes.
Sarris, E. T.↗
Sub-GLE Solar Particle Events and the Implications for Lightly-Shielded Systems Flown During an Era of Low Solar Activity
Many of the large space missions must be very rigorous in their designs to reduce risk from radiation damage as much as possible. Some ways of reducing this risk have been to build in multiple redundancies, purchase/develop radiation hardened electronics parts, and plan for worst case radiation environment scenarios. These methods work well for these ambitious missions that can afford the costs associated with these meticulous efforts. However, there have been more small spacecraft and CubeSats with smaller duration missions entering the space arena, which can take some additional risks, but cannot afford to implement all of these risk-reducing methods. Therefore, one way to quantify the radiation exposure risk for these smaller spacecraft would be to investigate the radiation environment pertinent to the mission to better understand these radiation exposures, rather than always designing to the infrequent, worst-case environment. In this study, we have investigated 34 historical solar particle events (1974-2010) that occurred during a time period when the sun spot number (SSN) was less than 30. These events contain Ground Level Events (GLE), sub-GLEs, and sub-sub-GLEs(sup 1-3). GLEs are extremely energetic solar particle events (SPEs) having proton energies often extending into the several GeV range and producing secondary particles in the atmosphere, mostly neutrons, observed with ground station neutron monitors. Sub-GLE events are less energetic, extending into the several hundred MeV range, but without producing detectable levels of secondary atmospheric particles. Sub-sub GLEs are even less energetic with an observable increase in protons at energies greater than 30 MeV, but no observable proton flux above 300 MeV. The spectra for these events were fitted using a double power law fit in particle rigidity, called the Band fit method. The differential spectra were then input into the NASA Langley Research Center HZETRN 2005, which is a high-energy particle transport/dose code, to determine the dose in various thicknesses of aluminum, representing the spacecraft. This paper will detail the absorbed dose results of each of these environments, as well as analyze the data to better understand the doses over small thicknesses that are more relevant to small spacecraft and satellites, such as CubeSats. In addition, we will discuss the implications of these data and provide some recommendations that may be useful to spacecraft designers of these smaller spacecraft/CubeSat-type missions.
Atwell, William↗
Solar Particle Events Observed by the Odyssey MARIE Instrument at Mars: Dose and Model Calculations
One of the primary concerns prior to human exploration of Mars is the need to accurately characterize the charged particle radiation environment both for the surface stay, and for the transit period to and from the planet. The Odyssey spacecraft, currently in Mars orbit includes a charged particle radiation detector, MARIE, which can measure particle fluxes with energies above approx. 30 MeV and charges between 1 and 10. Two classes of particles are of particular interest: the Galactic Cosmic Rays, (GCR), and those charged particles associated with Solar Particle Events, (SPE). The GCR are present continuously throughout the solar activity cycle, and their numbers vary inversely with the level of solar activity. They are characteristically more energetic than those particles originating from solar activity, and hence less influences by the solar magnetic field.
Cleghorn, T. F.↗
Large-scale Coronal Dimming Foreshadowing a Solar Eruption on 2011 October 1
Understanding large-scale solar eruptions requires detailed investigation of the entire system's evolution, including the magnetic environment enveloping the source region and searches for precursor activity prior to event onset. We combine stereoscopic observations from the Solar Dynamics Observatory (SDO) and STEREO-B spacecraft for several hours before a filament ejection, M1.2-class eruptive flare, and coronal mass ejection (CME) originating in NOAA active region (AR) 11305 on 2011 October 1. Two episodes of significant preeruption coronal dimming that occurred well to the southeast of the ejected filament are identified. The CME subsequently took off with a substantial component of velocity toward the dimming, which became very pronounced during eruption. We used SDO/Helioseismic and Magnetic Imager (HMI) data to reconstruct the magnetic environment of the system and found that it contains a null point near the dimming region. AR 11305 had quite complex connections to nearby ARs 11302 and 11306, as well as to other regions of decayed AR flux. The intensifying and spatially expanding precursor dimming was accompanied by southeastward rising motions of loops toward the null point and northeastward and southwestward motions of loops retracting away. These motions and the dimming are consistent with persistent magnetic reconnection occurring at the null point as it moved upward and southeastward, thereby removing a strapping magnetic field high above AR 11305. Eventually, the filament was ejected explosively toward the null point. We conclude that the breakout model for solar eruptions provides a compelling account of this event. Furthermore, we conjecture that preeruption dimmings may be much more frequent than currently recognized.
solar flares↗
BioSentinel: Mission Development of a Radiation Biosensor to Gauge DNA Damage and Repair Beyond Low Earth Orbit on a 6U Nanosatellite.
We are designing and developing a "6U" (10 x 22 x 34 cm; 14 kg) nanosatellite as a secondary payload to fly aboard NASA's Space Launch System (SLS) Exploration Mission (EM) 1, scheduled for launch in late 2017. For the first time in over forty years, direct experimental data from biological studies beyond low Earth orbit (LEO) will be obtained during BioSentinel's 12- to 18- month mission. BioSentinel will measure the damage and repair of DNA in a biological organism and allow us to compare that to information from onboard physical radiation sensors. In order to understand the relative contributions of the space environment's two dominant biological perturbations, reduced gravity and ionizing radiation, results from deep space will be directly compared to data obtained in LEO (on ISS) and on Earth. These data points will be available for validation of existing biological radiation damage and repair models, and for extrapolation to humans, to assist in mitigating risks during future long-term exploration missions beyond LEO. The BioSentinel Payload occupies 4U of the spacecraft and will utilize the monocellular eukaryotic organism Saccharomyces cerevisiae (yeast) to report DNA double-strand-break (DSB) events that result from ambient space radiation. DSB repair exhibits striking conservation of repair proteins from yeast to humans. Yeast was selected because of 1) its similarity to cells in higher organisms, 2) the well-established history of strains engineered to measure DSB repair, 3) its spaceflight heritage, and 4) the wealth of available ground and flight reference data. The S. cerevisiae flight strain will include engineered genetic defects to prevent growth and division until a radiation-induced DSB activates the yeast's DNA repair mechanisms. The triggered culture growth and metabolic activity directly indicate a DSB and its successful repair. The yeast will be carried in the dry state within the 1-atm P/L container in 18 separate fluidics cards with each card having 16 independent culture microwells, with integral microchannels and filters to supply nutrients and reagents, confine the yeast to the wells, and enable optical measurement. The measurement subsystem will monitor each subgroup of culture wells continuously for several weeks, optically tracking DSBtriggered cell growth and metabolism. BioSentinel will also include physical radiation sensors based on the TimePix sensor, as implemented by JSC's RadWorks group, which record individual radiation events including estimates of their linear-energytransfer (LET) values. Radiation-dose and LET data will be compared directly to the rate of DSB-and-repair events measured by the S. cerevisiae biosentinels. The spacecraft bus will operate in a deep space environment with functions that include command and data handling, communications, power generation (via deployable solar panels) and storage, and attitude determination-and-control system with micropropulsion. Development of the BioSentinel spacecraft will mature and prove multiple nanosatellite advances in order to function well beyond LEO: Communications from distances of ≥ 500,000 km; Autonomous attitude control, momentum management, and safe mode of nanosatellites in deep space; Shielding-, hardening-, design-, and software-derived radiation tolerance for electronics; Reliable functionality for 12 - 18 months of key subsystems for biofluidics, memory, communications, power, etc.; Close integration of living biological radiation event monitors with miniature physical radiation spectrometers; Biological measurement of solar particle events beyond Earth orbit In addition to providing the first biological results from beyond LEO in over 4 decades, BioSentinel will provide an adaptable small-satellite instrument platform to perform a range of human-exploration-relevant measurements that characterize the biological consequences of multiple outer space environments. BioSentinel is being developed under NASA's Advanced Exploration Systems program.
DNA damage↗
Near-Earth Space Radiation Models
Review of models of the near-Earth space radiation environment is presented, including recent developments in trapped proton and electron, galactic cosmic ray and solar particle event models geared toward spacecraft electronics applications.
Xapsos, Michael A.↗