(LDEF) Archive System
NASA Langley Research Center
Hampton, Virginia
Ionizing Radiation Results
 |
Langley Home Page |
 |
Space Environments &Technology Archive System Home Page |
 |
Space Environments &Effects Home Page |
 |
NASA Home Page |
|
If you would like to receive further information on SETAS, or have suggestions on what information you would like to see accessible through this archive, please fill out the SETAS request form.
SETAS Request Information |
|
Responsible Parties:
Page Content: William H. Kinard Page Construction: Thomas H. See |
The ionizing radiation measurements of the LDEF satellite have produced results that further all aspects of the radiation field. New understandings and new questions have arisen due to the LDEF measurements. The affected areas are:
Trapped Proton and Neutron Flux- Early measurements have clearly shown the presence of an east-west flux anistropy for trapped protons in the South Atlantic Anomaly (SAA) in both activation and dosimetric measurements.
- Effects of trapped proton directional properties have been measured and a new proton directional model has been tested.
- Good quality activation versus depth profiles in steel for some isotopes have been obtained and some capability in distinguishing between the proton and neutron fluxes has been achieved.
- An east-west asymmetry in the dose is observed which is not predicted by the standard calculation methods.
- On the west trailing side of the LDEF mission accumulated radiation doses exceeded the annual crew dose limit at shielding of less than 5 cm aluminum. This was influenced by LDEF initial altitude (470 km) and solar minimum conditions for most of the mission.
- Westside LDEF radiation dose data have been used to establish Space Station radiation requirements for parts.
- The highest part of the LET spectrum has been measured with unprecedented statistics and exceeds predictions about 1000 MeV cm2/g. The high LET component is attributed to a combination of elastic recoil ions and inelastic collision products produced by the South Atlantic Anomaly.
- Co, Fe, Mn, Cr and Ti cosmic rays have been discovered near 600 MeV/nucleon. This unexpected result may indicate either a new cosmic ray component or partially ionizing solar flare particles.
- The LDEF Cosmic Ray experiments will measure about 20 actinide (Th, U, etc.) nuclei (Z > 65) in the galactic cosmic rays. The current total for previous space flights (Skylab, Ariel and HERO-3) is 3. The LDEF experiments will measure the UH GCR with unprecedented statistics and resolution.
- Significant activities of 7Be (half life 53 days) confined to leading surfaces of LDEF.
- This 7Be activity is presumed to be of atmospheric origin, apparently from the stratosphere, and unrelated to nuclear activation of the spacecraft. The quantity is larger than simple diffusion would predict and is of interest in atmospheric transport studies.
- AP8 Proton Model Flux level is low (tentative).
- AE8 Electron Model Flux is too high at very thin shielding (tentative).
 | LDEF Archive System Home Page |