Characteristics of trapped proton anisotropy at Space Station Freedom altitudes

Technical Report · Mon Oct 01 00:00:00 EDT 1990

OSTI ID:6140581

Armstrong, T W; Colborn, B L; Watts, J W

The ionizing radiation dose for spacecraft in low-Earth orbit (LEO) is produced mainly by protons trapped in the Earth's magnetic field. Current data bases describing this trapped radiation environment assume the protons to have an isotropic angular distribution, although the fluxes are actually highly anisotropic in LEO. The anisotropy of the trapped proton exposure has not been an important practical consideration for most previous LEO missions because the random spacecraft orientation during passage through the radiation belt averages out the anisotropy. Thus, in spite of the actual exposure anisotropy, cumulative radiation effects over many orbits can be predicted as if the environment were isotropic when the spacecraft orientation is variable during exposure. However, Space Station Freedom will be gravity gradient stabilized to reduce drag, and, due to this fixed orientation, the cumulative incident proton flux will remain anisotropic. The anisotropy could potentially influence several aspects of Space Station design and operation, such as the appropriate location for radiation sensitive components and experiments, location of workstations and sleeping quarters, and the design and placement of radiation monitors. Also, on-board mass could possible be utilized to counteract the anisotropy effects and reduce the dose exposure. Until recently only omnidirectional data bases for the trapped proton environment were available. However, a method to predict orbit-average, angular dependent (vector) trapped proton flux spectra has been developed from the standard omnidirectional trapped proton data bases.

• Research Organization: National Aeronautics and Space Administration, Huntsville, AL (USA). George C. Marshall Space Flight Center
• OSTI ID: 6140581
• Report Number(s): N-91-15953; NASA-CR-184061; NAS-1.26:184061; SAIC-90/1474; CNN: NAS8-37916
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ASTRONAUTS
RADIATION HAZARDS
SPACE VEHICLES
SHIELDING
TRAPPED PROTONS
ANISOTROPY
CALCULATION METHODS
COSMIC PROTONS
FLUX DENSITY
ORBITS
SOLAR ACTIVITY
THEORETICAL DATA
BARYONS
COSMIC RADIATION
DATA
ELEMENTARY PARTICLES
FERMIONS
HADRONS
HAZARDS
HEALTH HAZARDS
INFORMATION
IONIZING RADIATIONS
NUCLEONS
NUMERICAL DATA
PERSONNEL
PROTONS
RADIATIONS
VEHICLES
560151* - Radiation Effects on Animals- Man
640101 - Astrophysics & Cosmology- Cosmic Radiation