Overview of the Liulin type instruments for space radiation measurement and their scientific results.

Ionizing radiation is recognized to be one of the main health concerns for humans in the space radiation environment. Estimation of space radiation effects on health requires the accurate knowledge of the accumulated absorbed dose, which depends on the global space radiation distribution, solar cycle and local shielding generated by the 3D mass distribution of the space vehicle. This paper presents an overview of the spectrometer-dosimeters of the Liulin type, which were developed in the late 1980s and have been in use since then. Two major measurement systems have been developed by our team. The first one is based on one silicon detector and is known as a Liulin-type deposited energy spectrometer (DES) (Dachev et al., 2002, 2003), while the second one is a dosimetric telescope (DT) with two or three silicon detectors. The Liulin-type instruments were calibrated using a number of radioactive sources and particle accelerators. The main results of the calibrations are presented in the paper. In the last section of the paper some of the most significant scientific results obtained in space and on aircraft, balloon and rocket flights since 1989 are presented.

[Analysis of the importance of cosmonaut's location and orientation onboard the International space station to levels of visceral irradiation during traverse of the region of the South Atlantic Anomaly].

Parametric analysis of absorbed radiation dose to the cosmonaut working in the Service module (SM) of the International space station (ISS) was made with allowance for anisotropy of the radiation field of the South Atlantic Anomaly. Calculation data show that in weakly shielded SM compartments the radiation dose to poorly shielded viscera may depend essentially on cosmonaut's location and orientation relative to the ISS shell. Difference of the lens absorbed dose can be as high as 5 times depending on orientation of the cosmonaut and the ISS. The effect is less pronounced on the deep seated hematopoietic system; however, it may increase up to 2.5 times during the extravehicular activities. When the cosmonaut is outside on the ISS SM side presented eastward, the absorbed dose can be affected noticeably by remoteness from the SM. At a distance less than 1.5 meters away from the SM east side in the course of ascending circuits, the calculated lens dose is approximately half as compared with the situation when the cosmonaut is not shielded by the ISS material.

Radiation environment monitoring for manned missions to Mars.

In this paper a radiation monitoring system for manned Mars missions is described, based on the most recent requirements on crew radiation safety. A comparison is shown between the radiation monitoring systems for Earth-orbiting and interplanetary spacecraft, with similarities and differences pointed out and discussed. An operational and technological sketch of the chosen problem solving approach is also given.

Solar cycle variations of MIR radiation environment as observed by the LIULIN dosimeter.

Measurements on board the MIR space station by the Bulgarian-Russian dosimeter LIULIN have been used to study the solar cycle variations of the radiation environment. The fixed locations of the instrument in the MIR manned compartment behind 6-15 g/cm2 of shielding have given homogeneous series of particle fluxes and doses measurements to be collected during the declining phase of 22nd solar cycle between September 1989 and April 1994. During the declining phase of 22nd solar cycle the GCR (Galactic Cosmic Rays) flux observed at L>4 (where L is the McIlwain parameter) has enhanced from 0.6-0.7 cm-2 s-1 up to 1.4-1.6 cm-2 s-1. The long-term observations of the trapped radiation can be summarized as follows: the main maximum of the flux and dose rate is located at the southeast side of the geomagnetic field minimum of South Atlantic Anomaly (SAA) at L=1.3-1.4. Protons depositing few (nGy cm2)/particle in the detector predominantly populate this region. At practically the same spatial location and for similar conditions the dose rate rises up from 480 to 1470 microGy/h dose in silicon in the 1990-1994 time interval, during the declining phase of the solar cycle. On the other hand the flux rises from 35 up to 115 cm-2 s-1 for the same period of time. A power law dependence was extracted which predicts that when the total neutral density at the altitude of the station decreases from 8x10(-15) to 6x10(-16) g/cm3 the dose increase from about 200 microGy/h up to 1200 microGy/h. At the same time the flux increase from about 30 cm-2 s-1 up to 120 cm-2 s-1. The AP8 model predictions give only 5.8% increase of the flux for the same conditions.