SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 14 - JULY 18, 2006

93 SPACE RADIATION
Includes cosmic radiation; and inner and outer Earth radiation belts.

For biological effects of radiation on plants and animals see 51 Life Sciences; on human beings see 52 Aerospace Medicine.

For theory see 73 Nuclear Physics.

20060019230 NASA Stennis Space Center, Stennis Space Center, MS, USA

Radiometric Characterization of the IKONOS, QuickBird, and OrbView-3 Sensors

Holekamp, Kara; [2006]; 42 pp.; In English; JACIE Civil Commercial Imagery Evaluation Workshop, 14-16 Mar. 2006, Laurel, MD, USA; Original contains color and black and white illustrations Contract(s)/Grant(s): NNS04AB54T Report No.(s): SSTI-2220-0076; No Copyright; Avail.: CASI: A03, Hardcopy

Radiometric calibration of commercial imaging satellite products is required to ensure that science and application communities can better understand their properties. Inaccurate radiometric calibrations can lead to erroneous decisions and invalid conclusions and can limit intercomparisons with other systems. To address this calibration need, satellite at-sensor radiance values were compared to those estimated by each independent team member to determine the sensor's radiometric accuracy. The combined results of this evaluation provide the user community with an independent assessment of these commercially available high spatial resolution sensors' absolute calibration values. Author

Radiometric Resolution; Spatial Resolution; Imaging Techniques; Calibrating; Radiometers; High Resolution

20060019231 Science Systems and Applications, Inc., Bay Saint Louis, MS, USA

Emerging Techniques for Vicarious Calibration of Visible Through Short Wave Infrared Remote Sensing Systems

Ryan, Robert E.; [2006]; 39 pp.; In English; 2006 EO/IR Calibration and Characterization Workshop, 7-9 Mar. 2006, Logan, UT, USA; Original contains color and black and white illustrations Contract(s)/Grant(s): NNS04AB54T Report No.(s): SSTI-2220-0077; No Copyright; Avail.: CASI: A03, Hardcopy

Simple field-portable white light LED calibration source shows promise for visible range (420-750 nm) 1) Prototype demonstrated \h0.5% drift over 10-40 C temperature range; 2) Additional complexity (more LEDs) will be necessary for extending spectral range into the NIR and SWIR; 3) LED long lifetimes should produce at least several hundreds of hours or more stability, minimizing need for expensive calibrations and supporting long-duration field campaigns; and 4) Enabling technology for developing autonomous sites.

Derived from text Remote Sensing; Infrared Detectors; Light Emitting Diodes; Calibrating; Autonomy; Light Sources

20060020700 NASA Johnson Space Center, Houston, TX, USA

Induction of micronuclei in human fibroblasts across the Bragg curve of energetic heavy ions

Hada, Megumi; Rusek, Adam; Cucinotta, Francis A.; Wu, Honglu; [2006]; 1 pp.; In English; 53rd Annual Meeting Radiation Research Society, 5-8 Nov. 2006, Philadelphia, PA, USA; Copyright; Avail.: Other Sources; Abstract Only

The space environment consists of a varying field of radiation particles including high energy ions, with spacecraft shielding material providing the major protection to astronauts from harmful exposure. Unlike low-L or X-rays, the presence of shielding does not always reduce the radiation risks for energetic charged particle exposure. Although the dose delivered by the charged particle increases sharply as the particle approaches the Bragg peak, the Bragg curve does not necessarily represent the biological damage along the particle traversal. The 'biological Bragg curve' is dependent on the energy and the type of the primary particle, and may vary for different biological endpoints. To investigate 'biological Bragg curves', we analyzed micronuclei (MN) induction along the particle traversal of Si and Fe ions at incident energies of 300 MeV/nucleon and 1 GeV/nucleon. A quantitative biological response curve did not reveal an increased yield of MN at the location of the Bragg peak. However, the ratio of mono-to bi-nucleated cells, which indicates inhibition in cell progression, increased at the Bragg peak location. These results confirm the hypothesis that 'over kill' at the Bragg peak will affect the outcome of other biological endpoints. Author

Heavy Ions; Fibroblasts; Energetic Particles; Charged Particles; Bragg Angle; Spacecraft Shielding; Biological Effects

20060020736 NASA Johnson Space Center, Houston, TX, USA

Visual Risk Assessment of Space Radiation Exposure for Future Space Exploration Missions

Hussein, Hesham F.; Kim, Myung-Hee; Cucinotta, Francis A.; [2006]; 1 pp.; In English; IEEE 2006 Nuclear Science Symposium, 29 Oct. - 4 Nov. 2006, San Diego, CA, USA; No Copyright; Avail.: Other Sources; Abstract Only

Protecting astronauts from space radiation exposure during an interplanetary mission is an important challenge for mission design and operations. If sufficient protection is not provided near solar maximum, the risk can be significant due to exposure to sporadic solar particle events (SPEs) as well as to the continuous galactic cosmic radiation (GCR). Polyethylene shielded 'storm shelters' inside spacecraft have been shown to limit total exposure from a large SPE to a permissible level, preventing acute risks and providing a potential approach to fulfill the ALARA (as low as reasonably achievable) requirement. For accurate predictions of radiation dose to astronauts involved in future space exploration missions, detailed variations of radiation shielding properties are required. Radiation fluences and doses vary considerably across both the spacecraft geometry and the body-shielding distribution. A model using a modern CAD tool ProE(TradeMark), which is the leading engineering design platform at NASA, has been developed to account for these local variations in the radiation distribution. Visual assessment of radiation distribution at different points inside a spacecraft module and in the human body for a given radiation environment are described. Results will ultimately guide in developing requirements for maximal protection for astronauts from space radiation. Author

Astronauts; Radiation Shielding; Continuous Radiation; Exposure; Galactic Radiation; Protection; Radiation Dosage; Radiation Distribution; Solar Activity Effects; Extraterrestrial Radiation

20060021461 NASA Langley Research Center, Hampton, VA, USA

The Projection of Space Radiation Environments with a Solar Cycle Statistical Model

Kim, Myung-Hee; Cucinotta, Francis A.; Wilson, John W.; [2006; 1 pp.; In English; 36th COSPAR Scientific Assembly Meeting, 16-23 Jul. 2006, Beijing, China; No Copyright; Avail.: Other Sources; Abstract Only

A solar cycle statistical model has been developed to project sunspot numbers which represent the variations in the space radiation environment. The resultant projection of sunspot numbers in near future were coupled to space-related quantities of interest in radiation protection, such as the galactic cosmic radiation (GCR) deceleration potential (f) and the mean occurrence frequency of solar particle event (SPE). Future GCR fluxes have been derived from a predictive model, in which GCR temporal dependence represented by f was derived from GCR flux and ground-based Climax neutron monitor rate measurements over the last four decades. Results showed that the point dose equivalent inside a typical spacecraft in interplanetary radiation fields was influenced by solar modulation up to a factor of three. One important characteristic of sporadic SPEs is their mean frequency of occurrence, which is dependent on solar activity. Projections of future mean frequency of SPE occurrence were estimated from a power law function of sunspot number. Furthermore, the cumulative probabilities of SPE during short-period missions were defined with the continuous database of proton fluences of SPE. The analytic representation of energy spectra of SPE was constructed by the Weibull distribution for different event sizes. The representative exposure level at each event size was estimated for the guideline of protection systems for astronauts during future space exploration missions. Author

Sunspots; Solar Cycles; Solar Activity; Radiation Distribution; Interplanetary Magnetic Fields; Extraterrestrial Radiation; Galactic Radiation; Exposure

Source: NASA