High Dose Rates by Relativistic Electrons: Observations on Foton M2/M3 satellites and on International Space Station

Size: px

Start display at page:

Download "High Dose Rates by Relativistic Electrons: Observations on Foton M2/M3 satellites and on International Space Station"

Preston Burke
5 years ago
Views:

1 High Dose Rates by Relativistic Electrons: Observations on Foton M2/M3 satellites and on International Space Station Ts. Dachev 1, B. Tomov 1, Yu.. Matviichuk 1 1, Pl.. Dimitrov 1 1 N. Bankov 2 1 Solar-Terrestrial Influences Laboratory,, BAS 2 Space research institute Bulgarian Academy of Sciences,, 1113 Sofia, Bulgaria tdachev@bas bas.bg

2 Introduction Relativistic electron precipitations (REP) are observed since many years. First of them are those reported in 1972 by Brown and Stone and Imhov et al. in 1986 and Most comprehensive study of the long term observations of REP using the MeV electron data from the SAMPEX satellite during is made by Zheng et al. in In the book Radiation and the International Space Station: Recommendations to Reduce Risk,, US National Research Council published in 2000 the total dose of astronaut, which is spending 6 hours on Extra Vehicular Activity (EVA) inside of REP, is estimated. The conclusion is that the dose will be great enough to force an astronaut over the short term limit for skin and eyes.. One of the recommendations (3b on page 37) is: As soon as possible, JSC should install an electron dosimeter and an ion dosimeter outside the ISS that can return data in real time to Space Radiation Analysis Group (SRAG) at the Johnson Space Center 2

Haeder, University of Erlangen, Germany Detector of 256 Channels LET spectrometer 4 Channels UV

3 R3D-B2/B3 instruments for ESA Biopan 5/6 facilities were successfully y flown outside of Foton M2/M3 satellites in June 2005 and September The spectrometers are mutually developed with Prof. D.-P. Haeder, University of Erlangen, Germany Detector of 256 Channels LET spectrometer 4 Channels UV spectrometer UV-C channel UV-B channel UV-A channel PAR channel Size: 82x57x25 mm Weight: : 1291 g Consumption: 84 mw 3

4 R3DE instrument, which is apart of the EXPOSE facility is working continuously on the EuTEF facility of Columbus module on International space station since February 20 th Z R3DE EuTEF EXPOSE 4

5 0.9<L<1.1 Gmag=0.21 Gauss (SAA) L>2.8 Magnetic Equator + Foton M2, R3D-B2; June 2005; D>50 µgy/h Latitude (deg) Latitude (deg) Geographic positions of the selecting procedures and radiation sources g/cm2 + Foton M3, R3D-B3; Sept. 2007; D>50 µgy/h Latitude (deg) Latitude (deg) >20 g/cm Longitude (Deg) 0.81 g/cm2 + Foton M3, Liulin-Ph.; Sept. 2007; D>50 µgy/h Latitude (deg) Latitude (deg) Longitude (Deg) Longitude (Deg) + ISS, Liulin E094 D#3; July 2001; D>50 µgy/h 1.75 g/cm Longitude (Deg) Longitude (Deg) + ISS, R3DE; EuTEF, Feb.-Mar. 2008; D>0 µgy/h >5 g/cm Longitude (Deg) WRMISS 5

6 Descending crossing of SAA by Foton M2 satellite Inner proton maximum Gap electrons and bremsshtrahlung Outer belt electrons Latitude (deg) Longitude (deg) 6

Sequence of Foton M3 60 seconds data with observations of other radiation belt relativistic electrons and SAA region SAA SAA SAA On the energy-time 3D diagram the relativistic (>1 MeV) electron

7 Sequence of Foton M3 60 seconds data with observations of other radiation belt relativistic electrons and SAA region SAA SAA SAA On the energy-time 3D diagram the relativistic (>1 MeV) electron bursts are seen with red color bars in the upper panel and with black bars above 500 counts per minute in the lower panel. In this case the R3D-B3 spectra in Northern N and Sothern S hemisphere are relatively short and reach up to 50 th channel; S N S N S N S N S N S The 3 cases of crossing of inner radiation belt in the region of SAA are shown with labels SAA.. The spectra in SAA are much wider reaching even the 256 th channel. 7

Example of observation of relativistic electrons with R3DE instrument on ISS on 28 February 2008 Relativistic (>1 MeV) electron bursts with maximum duration few minutes was observed by us first at

8 Example of observation of relativistic electrons with R3DE instrument on ISS on 28 February 2008 Relativistic (>1 MeV) electron bursts with maximum duration few minutes was observed by us first at the Foton M2 satellite behind 1.75 g/cm 2 shielding. The maximmum dose observed is 304 µgy/h at 280 km altitude. At Foton M3 satellite behind 0.71 g/cm 2 shielding the maximmum dose observed is 2314 µgy/h at 295 km altitude. At the EuTEF platform of Columbus module at ISS with R3DE instrument behind less than 0.4 g/cm 2 shielding the maximmum dose is µgy/h at 361 km altitude. The flux of electrons reach 8363 cm - 2 s

9 REP observed on ISS on 5th of March 2008 between 14:27 and 14:46 hour 9

10 Different radiation sources seen in Foton M3 data with lid open/closed Foton M3; R3D-B3 September D/F (ngy cm^2/event) 1E+1 When the lid of Biopan 6 is closed (~5.8 g/cm2) only protons from the region of SAA and GCR penetrate down to the detector of R3D-B3 Lid open (0.81 g/cm^2) Lid closed (~5.8 g/cm^2) 1E+0 ORB electrons Dose (ugy/h) 1E+3 When the lid is open (0.81 g/cm2), because of lower shielding relativistic electrons with energy above 1 MeV start to penetrate to the detector also 1E+2 1E+1 1E+0 ORB Flux (cm^-2 s^-1) 1E+3 SAA 1E+2 GCR 1E+1 1E The GCR dose and flux for L> are higher (11.12 µgy/h) when lid is closed (11.04 µgy/h), because the secondary's and neutrons produced in the shield L value WRMISS

11 Comparison of data obtained at Foton M3By R3D-B3 instrument outside and Liulin-Photo instrument inside the capsule 11

12 Altitude (km) UT (hours) Main characteristics of the measurements by R3DE in geographic coordinates, in which the dose is more than 0 mgy/h in period 20 February- 20 March R3DE; EuTEF, Columbus; ISS 20 Febr March, 2008 Dose>0 ugy/h Descending data are clustered around evening UT, while ascending around morning UT. Small difference in the averaged altitude of SAA data in descending (353 km) and ascending (351 km) orbits can t describe the large (with 56 mgy/h) averaged descending doses Dose (ugy/hour) Places of observations of relativistic electrons are separated in narrow latitudinal range equatorialward from magnetic poles Longitude (deg.) The calculated values of the incident proton energies in SAA region fall down from about 60 MeV at the west edge of the anomaly to MeV at the east edge. Very high doses (Up to 19 mgy/h) in the regions equatorialward from magnetic poles are generated by relativistic (>1 MeV) electrons, which seems to be the first observation of them at ISS. Descending Ascending Inc. energy (MeV) D/F (ngy cm^2/p.) Latitude (deg.) WRMISS 12

distribution of the dose data 20 February-20 March 2008

13 ISS and Foton M3 global distributions of the averaged dose in pixels Long=,, Lat=5 R3DE, EuTEF, ISS global distribution of the dose data 20 February-20 March 2008 R3D-B3, Foton M3 global distribution of the dose data September

Comparison of the observed doses at 3 satellites 1E+5 1E+4 Foton M2; 1-12 June 2005; 1.85 g.cm^-2 90 70 50 ORB ORB 1E+3 1E+2 1E+1 Latitude 30 - -30-50 Dose (ugy.

14 Comparison of the observed doses at 3 satellites 1E+5 1E+4 Foton M2; 1-12 June 2005; 1.85 g.cm^ ORB ORB 1E+3 1E+2 1E+1 Latitude Dose (ugy.h^-1) 1E+0 1E+5 1E+4 1E+3 1E+2 1E+1 1E+0 1E+5 1E+4 1E+3 1E+2 1E+1 Foton M3; Sept. 2007; 0.71 g.cm^-2 ISS; 20 Feb March 2008; 0.41 g.cm^ Longitude High doses are regularly observed on Foton M2/M3 satellites in the Southern hemisphere at latitudes above the inclination oof ISS The REP on ISS are rare and very sporadic. Till the whole operation period of the R3DE instrument on ISS between February and July 2008 we have only 8 events when the doses are above 2000 µgy.h -1 1E L value 14

15 Comparison of doses obtained on ISS and Foton M2/3 with Oulu neutron monitor data 6.14 µgy/h 14.6 µsv/h 7.38 µgy/h 16 µsv/h 12 µgy/h 29.4 µsv/h.3 µgy/h 27.2 µsv/h Foton M3 Solar minimum GCR doses in low earth orbit rise twice during the solar maximum, while neutron component on Earth surface rise up only with w % 15

16 Conclusions If we will consider that the danger for the astronauts being on EVA relativistic electrons events are with dose above 500 µgy.h -1 than for the period 22 February 18 March 2008 we collect totally 132 seconds intervals, which is only 22 minutes. From other hand this observations are made in very low solar activity. The long period observations with SAMPEX satellite and others show increase of the REP observations when the solar activity is larger. This confirm another time the necessity of permanent active monitoring of the ISS radiation environment. 16

Simultaneous Investigation of Galactic Cosmic Rays on Aircrafts and on International Space Station

Simultaneous Investigation of Galactic Cosmic Rays on Aircrafts and on International Space Station T. Dachev(1), F. Spurny(2), G. Reitz(3), B.T. Tomov(1), P.G. Dimitrov(1), itrov(1), Y.N. Matviichuk(1)