MISSION PLAN - PDS Small Bodies Node

Solar flare contribution is given as the flux at 1 AU with a required 1/r 2 to 1/r 2.5 scaling
factor for other distances from the sun. The galactic cosmic ray (GCR) contribution is
independent of the spacecraft location.
Probability of Large Solar Events: The probability of encountering a 90% to 99%
magnitude solar flare, particularly during the comet flyby, is of interest for the spacecraft
design team. The probabilities are estimated by D.R. Croley (JPL IOM 5052-96-304)
using the model developed by Feynman et al. at JPL. The predicted mean times between
flares of 90%, 95% and 99% magnitude are given in Table 2.3-6. The table also gives the
derived probability of seeing these flares during the 12 hour period around the flyby.
Table 2.3-6 Probability of Large Solar Flares
Flare Magnitude >90% >95% >99%
Mean time (*solar- max years) ~1.4 ~2.8 ~16.9
Probability of occurrence during the
~1E-3 ~5E-4 ~8E-5
12-hrs of the flyby
*Solar-max years=~7 years of ~11 year solar cycle. All of the 7-year STARDUST mission is in the solarmax
years according to the model.
8
10
flare, no shielding
6
10
4
10
2
10
250 mil
36 mil
60 mil
100 mil
0
10
Heavy -Ion Peak Flux (/cm 2/day)
(Omni-Directional)
-2
10
-4
10
-6
10
-8
10
GCR 25 mil
GCR 500 mil
1000 mil
500 mil
-10
10
1 10 100
LET (MeV-cm 2/mg)
JMR 12/10/96
Figure 2.3-6.a Heavy-ion Flux from a 99% Solar Flare at 1 AU and
for Adams’ 90% Worst Case GCR
37