Integrity – Service – Excellence

Headquarters U.S. Air Force

Satellite Anomaly Assessment

Lt Col Kelly Doser AF Director of Weather

AF/A3O-W 23 April 2012

Joseph Mazur

Paul O’Brien Aerospace Corporation

1

Surface degradation from radiation

Solar array arc

discharge

Electromagnetic pulse from vehicle discharge

(on surface, behind thin shielding, or deep inside)

Single event effects in microelectronics

Spacecraft components become radioactive

False stars in star tracker CCDs

1101 0101

Solar array power

decrease due to

radiation damage

Before After

Before

During exposure to

multi-MeV protons

Electronics degrade due

to total radiation dose

Induced

Voltage

Time

Major Space Environment Hazards

1

10

100

1000

0

50

100

RBSP

SA

MP

EX

LIC

A

Charg

ing E

vents

L ~ Equatorial Radial Distance (RE)

HEO

GPS

CR

RE

S M

EP

-SE

U A

nom

alie

s

0

CR

RE

S V

TC

W A

nom

alie

s

Inner

Belt

Slot

Outer Belt

5

10

15

1 2 3 4 5 6 7 8

SEEs

Internal

Charging

Surface

Charging

(Dose behind 82.5 mils Al)

Plasma

Sheet

Magnetic Latitude in LEO (deg) 0 45 55 60 63 66 68 69

GEO

Surface charging and resulting ESD

• spacecraft or surface potential elevated

• 2000-0800 local time in the plasma sheet

• regions of intense field-aligned currents

• observed, but not explained, at very low L

Locations of Operational

Space Environment Hazards

Internal charging and resulting electrostatic discharges (ESD)

• broad range of L values

• corresponding to the outer belt

• where penetrating electron fluxes are high

Single Event Effects (SEEs)

• inner (proton) belt and higher L shells with solar particle event

• quiet-times from galactic cosmic rays

HEO

GEO

For orbits such as HEO, solar energetic particles are important sources of heavy ions that can cause single event effects

For awareness in HEO, the timing of the GEO environment is good information but not sufficient for anomaly diagnosis

However, the trapped electrons and protons in the Van Allen belts dominate the total dose hazard

Space is Not One Place: January

2012 SEP Events

Anomalies Attributed to the Space

Environment

5

Two anomaly studies attributed to space environment:

• Koons et al. Aerospace Report No.TR-99(1670)-1

• Unpublished (2009)

Databases differ

• coverage in time/space vehicles

• most frequent attributions (SEE or ESD)

However, two conclusions clear:

• Anomalies occur at all times

• Vehicle charging and single-event effects are the most frequently cited causes

Environment Hazards Versus Solar Cycle

6

Solar cycle

SEE

environment

(from solar

particle events)

Proxy for

surface

charging

Internal

charging

environment at

GEO

SEE from solar energetic particles is the only hazard whose probability strongly depends on solar cycle

Vehicle charging (and single events from the inner van Allen belt & galactic cosmic rays) can occur at any time

Hazard Visualization

Very different impact regions

Solar Proton Event in Progress

Anomaly at

L < 2

History of

GCR SEE?

Investigate SEE

Anomaly at

L >3

YES YES

YES

NO NO

NO

NO

START

Alt < 2000 km

YES

NO

Investigate SEE SEE Unlikely

Anomaly at

L < 3

NO

POES

P35MEV Slot

Index > 0

YES YES

POES

P35MEV Slot

Index > 0

In ESAA In SAA

YES YES

YES

NO NO

NO

YES

NO

Single Event Effects Flow Chart

Surface Charging:

• Kp, AE

• Field-Aligned Current intensity (LEO)

• Electron temperature

SEE:

• 20-50 MeV proton flux

• (heavy ions would be nice, too)

Internal Charging:

• 0.3-2 MeV electron flux

Total Dose:

• 1-20 MeV proton flux

Initial Global Specification Targets

I n t e g r i t y - S e r v i c e - E x c e l l e n c e

Headquarters U.S. Air Force

10

Questions?

Operations

Research &

Development

Acquisition

Customers

Rising Sun Over Pyramid (painting) – Paul Greco, 2009