Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.cosmos.ru/conf/2009elw/presentations/presentations_pdf/session2/podzolko_getselev_ELW.pdf Äàòà èçìåíåíèÿ: Mon Apr 20 20:24:04 2009 Äàòà èíäåêñèðîâàíèÿ: Sat Oct 17 09:32:04 2009 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: solar cycle

Charged Particle Fluxes and Radiation Doses in Earth-Jupiter-Europa Spacecraft's Trajectory
M. V. Podzolko1, I. V. Getselev1, Yu. I. Gubar1, I. S. Veselovsky1,2, A. A. Sukhanov2
1

Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Russia 2 Space Research Institute (IKI), Russian Academy of Sciences, Moscow, Russia

­ Models of Jupiter's radiation belts and satellite experiments near Jupiter ­ Charged particle fluxes and radiation doses in Europa orbit ­ Charged particle fluxes and radiation doses during the gravity assists near Jupiter ­ Radiation environment in the interplanetary part of the trajectory ­ Proposals for radiation environment control during the mission ­ Conclusions, discussion


Models of Jupiter's radiation belts
N. Divine, Jupiter Radiation Belt Models, Techn. Mem. 33-715, 1974, 13 p. /1st model, used Pioneer 10 data/ R. W. Fillius, C. E. McIlwain, A. Mogro-Campero, Radiation Belts of Jupiter: A Second Look, Science, v. 188, 1975, p. 465­467. /An update of the model, using Pioneer 11 data/ N. Divine, H. B. Garrett, Charged Particle Distributions in Jupiter's Magnetosphere, J. Geophys. Res., v. 88, No 9, 1983, p. 6889­6903. /Model, based on the data from Pioneer 10, 11 and Voyager 1, 2/ M. H. Acuna, N. F. Ness, The main magnetic field of Jupiter, J. Geophys. Res., 81, 1976, p. 2917­ 2922. /The "O4" Jupiter's magnetic model, 15 Gauss coefficients/ I. V. Getselev, Yu. I. Gubar et al., Radiation Conditions of the Spacecraft Flight in Jupiter's NearPlanetary Space, MSU, VINITI No 4636-84, 1984. (in Russian). I. V. Getselev, Yu. I. Gubar et al., Model of the Radiation Environment of Jupiter's Artificial Satellites, MSU, VINITI No 8970B, 1985. (in Russian). Yu. I. Gubar, A. R. Mozzhukhina, I. S. Veselovsky, The Expected Radiation Doses for the Flight of S/C "Solar Probe" through the Jovian Magnetosphere, Proc. 1st US-Russian Scientific Workshop on FIRE Environment, SRI, Moscow, 1995, p. 213­215. /Values obtained using Getselev-Gubar model agree with NASA computations/ H. B. Garrett, S. M. Levin, S. J. Bolton, A Revised Model of Jupiter's Inner Electron Belts: Updating the Divine Radiation Model, Geophysical Research Letters, v. 32, L04104, 2005, 5 p. /A revision of Divine-Garrett model for high-energy electrons at L < 4 from Galileo and synchrotron observations/


Magnetosphere and charged particles satellite measurements at Jupiter
mission time orbit Fly-by at 130 ths. km from Jupiter (2.8 RJ) experiments doses 5·105 rad electrons and 1·106 rad protons on the surface, 4.5·105 rad at 3 mm Al 1.3·105 rad electrons, 3·105 rad protons on the surface, 1.2·105 rad at 3 mm Al 5·105 rad

Pioneer 10 Dec. 1973

Pioneer 11 Dec. 1974

Fly-by at 43 ths. km (1.6 RJ), high incl. orb. Fly-by at 207 ths. km (4 RJ) Fly-by at 570 ths. km (9 RJ) Fly-by at 378 ths. km (6.3 RJ), high incl. orb. 35 highly elliptical orbital segments with r typically 6­11 RJ Fly-by at 10 mln. km (140 RJ)

Magnetic field, electrons: 0.06 to >35 MeV, protons: 0.6 to >80 MeV

Voyager 1 Voyager 2 Ulysses

March 1979 July 1979 Feb. 1992

Magnetic field, low-energy particles, electrons: 3­110 MeV, ions: 1­500 MeV/nucl Magnetic field, energetic particles

estim. 6·104 rad (inside?)

Galileo

1995­2003

Designed for 150 krad at 2.2 g/cm2, sustained Magnetic field, electrons: 15 keV to >11 eV, >650 krad; "remarkably Ions: 10 keV to 200 MeV/nucl healthy", but damaged some electronic systems Magnetic field sync. w/Galileo, high-energy electrons (radiation spectrometer)

Cassini

Nov. 2000


Charged particle flux and radiation dose equatorial profiles at Jupiter
10 10
9 8

> 0.2 MeV

10
7

6

f , cm-2s-1

10 10 10 10 10

>2

6

5

4

> 30

Dose, rad/day

e

> 10

10

5

0.27 g/cm
4

2

10

1 2.2 5

3

2

4

6

8

10

12

14

16

L
10 10
8

10

3

7

> 2 MeV

10

2

2

4

6

8

10

12

14

16

f , cm-2-1

10 10 10 10

6

L, L J R
> 10

5

Amalthea

Io

Europa

Ganymede

p
4

> 30

3

2

4

6

8

10

12

L

Equatorial profiles of the integral fluxes of E >0.2, >2, >10 and >30 MeV electrons and E >2, >10 and >30 MeV protons at Jupiter.

Equatorial profiles of radiation doses under 0.27, 1, 2.2 and 5 g/cm2 shielding near Jupiter.


Calculated radiation doses in Europa orbit: high hazard
10
9

10

7

10

Radiation dose, rad/day

Electron flux, 1/(cm2s)

8

10

6

electrons protons total Renard et al., 04

10

7

10

5

10

6

10

4

10

5

10

3

10

4

10

-1

10

0

10

1

10

2

10

2

Energy, MeV

10

2

10

-2

10

-1

10

0

g/cm 10

1

2

Electron integral spectra in Europa orbit
10
8

10

-1

10

0

10

1

mm Al

Proton flux, 1/(cm2s)

10 10 10 10 10 10

7

Doses under various shielding from electrons (dashed line), protons (dash-dot line) and total dose (solid line); also the doses from Renard et al. (2004) are given (triangles).

6

5

Total 2-month doses in Europa orbit (at 9.5 RJ)
g/cm2 0.00
10
0

4

3

rad 8.5·10 1.0·10 1.5·10 7.4·10
8 8 7 6

g/cm2 1.0 2.2 5.0 10.0

rad 2.2·10 8.8·10 2.4·10 4.5·10
6 5 5 4

2

10

1

10

2

0.01 0.10 0.27

Energy, MeV

Proton integral spectra in Europa orbit


Average fluxes of electrons near Europa
10
6

Dose, rad/day oa, pa/cy, /c2

10

5

10

4

10

3

10

-2

Shiel a a g/cm2 Toding,, /c2

10

-1

10

0

10

1

Mean doses with and without taking into account Europa influence. Mean 2-month electron fluxes taking into account Europa influence (C. Paranicas et al., Europa's Near-Surface Radiation Environment, Geophys. Res. Letters, v. 34, 2007).

Total 2-month doses in Europa orbit
g/cm2 1.0 2.2 5.0 10.0 w/o Europa 2.2·10 8.8·10 2.4·10 4.5·10
6 5 5 4

with Europa 7.4·10 2.9·10 8.1·10 1.5·10
5 5 4 4


Factors that determine charged particle flux reduction near Europa
­ "directly" blocking of the particles by Europa;
It depends on the latitude, more exactly -- from the angle between the force line and the surface.

­ the ratio between the drift speed relative to Europe, and the bounce period;
E.g. 30 MeV electron flux on the surface is equal to zero, 5­30 MeV electrons do not reach the leading side.

­ distortion of Jupiter's magnetic field near Europa; ­ presence of the electric field; ­ difference of Europa orbit plane from the plane of Jupiter's magnetic equator; ­ atmosphere and ionosphere of Europa; ­ presence of the electric field; ­ the exact information about the geometry and the thickness of the shielding
proton drift flux tube leading center

field moving electron drift

r pite Ju


Dependence of electron flux reduction from the surface point latitude

Electron flux reduction, times

0.5 100 keV 0.2

5 MeV

0.1

0.05

10

20

30

40

50

60

70

80

90

Europa latitude, degrees

Dependency of the 100 keV (thin curve) and 5 MeV (bold curve) Europa surface from the latitude (more exactly -- from the angle of the surface). The type of the dependence is the same for both en two curves result from the difference of the pitch-angle distributions energies over 5­10 MeV the type of the dependency will somewhat

electron flux reduction on the magnetic field line with ergies; difference between for these energies. But for differ.


Gravity assists near Jupiter and its Galilean satellites
We consider the gravity assists contain the next stages: ­ 1st fly-by near Jupiter, firing the engine in the pericenter and coming to high-elliptical orbit; ­ 2nd firing the engine in its apocenter, to turn the orbit plane to Jupiter's equatorial plane, and to rise the pericenter to the orbit of Io or Ganymede; ­ several gravity assists at Galilean satellites to lower spacesraft orbit to the orbit of Europa; ­ and finally 3rd impulse by the engine and coming to the orbit around Europa.

The problem is: to optimize both the fuel consumption and the radiation dose.


Dependence of doses and impulses on the 1st fly-by from pericenter distance
70 2.1

Dose a a 2.2 /c2, , d o under 2.2 g/cm2 kra

dv + d dv ( anymede), /c dvp + va(Gae), km/s a

50 30 20

i = 0, 20, 30, 40° ­1/2 sin(i) = c·r

2 1.9 1.8 1.7 1.6 1.5 1.4 1.3 2

i = 40, 30, 20, 0° ­1/2 si n(i) = c·r

10 7 5 2 3 4 5 6
J

7

8

9

3

4

5

6
J

7

8

9

r ,R


r ,R


30

1.6 i = 0, 20, 30, 40° ­1/2 sin(i) = c·r 1.5 i = 40, 30, 20, 0° ­1/2 sin(i ) = c·r

Dose a a 5 5/c2, , krad o under g/cm2

dv p + dva(I), m/s dv + dva( o), k /c
2 3 4 5 6
J

20

1.4 1.3 1.2 1.1 1 0.9

10 7 5 3 7 8 9

0.8

2

3

4

5

6

r ,R


r ,R


J

Doses on the 1st fly-by under 2.2 (top) and 5 g/cm2 (bottom) depending on the pericenter distance r for the inclination i = 0, 20, 30, 40° and ncli sin(i) = c·r ­1/2.

g/cm2

Sum of the impulses dvp + dva in pericenter and apocenter of the 1st circuit for the next curcuit near Ganymede (top) and Io (bottom) depending on r for i = 0, 20, 30, 40° and sin(i) = c·r ­1/2. and


Parameters of different variants of gravity assists near Galilean satellites

t gravity assists scheme 1. IIIIIIIIIIGGGE 2. IIIIIIIIIIGGGEGEGE 3. IIIIIIIIIIGGGEGEGEGE 11. GGGGGGE 12. GGGGGGGGIIGGGGE 13. GGGGGGGIIGGGE 15. GGGGGEEGE 16. GGGGGE days 347 358 364 293 390 347 40 2 335

dvi1

dvi2

dose, except 1st fly-by, krad 1 g/sm2 2.2 803 853 876 25 731 504 445 25 5 364 376 382 5 273 197 10 7 5 10 94 96 98 1.2 63 46 22 1.2

t

rad belt

km/s 1.410 1.081 1.080 1.620 1.292 1.292 1.091 1.620 2.569 2.073 2.070 2.857 2.339 2.339 2.090 2.860

days 71 82 88 14 99 66 107 14

1487 1642 1717 103 1599 1048 1433 103


Cosmic ray protons in the interplanetary space during the mission
The mission will star in 2017­2020. The 24th cycle maximum will be in 2011­2012, thus the flight will mainly take place during the quiet Sun.
­1

10 10

11 10 9 8 7 6 5 4

f p, 1/(cm2MeV)

10 10 10 10 10

F(>1 MeV), 1/(cm·ste F (>10 0 MeV), c m­22·sr) r

1010

20, 21, 22, 23,

1968/ 1979/ 1989/ 2000/

11 12 6 4

109

10

10

0

10

1

10

2

10

3

10

4

Energy, MeV
108

Total differential interplanetary proton fluxes for -4 -3 -2 -1 0 1 2 3 4 5 6 7 "EVEEJ" variant of trajectory; start in 2017, reach Y"Year" relative to the solar maximum um ear relati ve to the solar maxi m Jupiter in 2022, last 5.6 year. In the active cycle phase 1-year cosmic ray proton 1) Thin solid line -- upper estimate, using simple fluences are higher, and in the passive -- lower, model (Podzolko, Getselev, 2005) of the total solar than threshold level, correspond to overall p = 0.5. and galactic proton flux in Earth's orbit. 2) Bold line -- prediction, using (Nymmik, 1999) for SCR solar, and (ISO 15390, 2004) for galactic Total doses for the interplanetary path, rad protons. Time relative to the beginning of the cycle g/cm2 prediction upper est. and the distance from the Sun have been taken 1 3 1.0 3.8·10 1.2·10 into account; "typical" solar cycle was considered.
2.2 5.0 10.0 1.5·10 9.1·10 7.5·10
1 0 0

5.5·10 2.5·10 1.3·10

2 2 2

"Galileo" was launched on October 18, 1989, right during the 22rd cycle maximum. Received 50 krad under 2.2 g/cm2 during the interplanetary flight.


Solar wind and interplanetary magnetic field during the mission
Main parameters are solar wind proton density and speed, temperature, magnitude of the magnetic field and its components. The density and Bx depends from the heliocentric distance as R­2, other ­ as R­1. Speed and temperature can be considered constant with 10% accuracy from 1 AU to Jupiter's orbit (5.2 AU). The mean parameters depends on solar cycle phase within 20%. Coronal mass ejections and shockwaves in heliosphere weaken and slow down somewhat with increase of R. The slowing is that faster, the higher the disturbance is. For the estimation purposes within the first tens % we may consider the speed being constant In Earth's orbit times vary from 1 day to 1 week, for Jupiter ­ from 1 week to 1 month. For accurate computations the MGD-modeling should be used. For the medium-term forecasts we suggest to use irregularity of the heliolongitude distribution of particle sources on the Sun. In particular we discover a continuous (80­170°) "passive longitudes" interval, that is stable and keeps very "quiet" during the last 5 solar cycles.
8 6

t, days

4 2 0

500

1000

1500

Vsw, km/s


Cosmic ray protons in the interplanetary space during the mission
1. Control of the radiation onboard spacecraft: Spectrometer of Linear Energy Transfer (SLET) ­ dosimetry; ­ model of LET and dose distribution for Jupiter from simultaneous multisatellite measurements! ­ need LET spectra to estimate the Single Event Effects (SEE) frequency; ­ inverse task: discover or verify particles spectra from the measured LET spectra
mass power telemetric information 500 g 0.5 W 250 KB/day

2. Radiation in the interplanetary space: studying the spectra and the dynamics of charged particle fluxes (electrons, protons and Helium ions) on the interplanetary path, in Jupiter's near-planetary region and in Europa orbit: Spectrometer of Charged Particles (SCP)
registered particles mass power telemetric information electrons: 0.1­4 MeV, protons, He: 1­30, >500 MeV/nucl 3 kg 4W 1 MB/day


Conclusions, discussion
­ The main radiation hazard during the mission comes from Jupiter's radiation belts. Most of the radiation dose will be received by the spacecraft in Europa orbit and on its surface. ­ The factors have been defined, that affect the charged particle flux reduction near Europa and on its surface; they should be taken as the entry parameters for constructing the detailed model of particle fluxes near Europa. ­ Gravity assists near Jupiter and its Galilean satellites is also connected with serious radiation hazard. We conclude, that both for the energy consumption issue and for the radiation safety it is optimal to make the 1st gravity assist near Jupiter with the pericenter closer than ~150 thousand km and an inclination of 40° or higher. For the rest of the gravity assists we suggested to use Ganymede, and make the final path between Ganymede and Europe as short, as possible. ­ The doses on other parts of the trajectory will be considerably smaller. ­ Proposals have been made on monitoring the radiation environment at all stages of the flight. ­ Possibly the main conclusion: working on Europa Lander project we have to solve the complex optimization task, simultaneously taking into account many factors: radiation, energy consumption, limits on the size and weight of the scientific equipment, data transfer and so on. ­ The question of improving the models of Jupiter's radiation belts and magnetic field etc. is still actual.