# Presentation: 221805

## Exploring the MEO Space Particle Regime

**Gregory Ginet**
**AFRL/VSBX**
**Space Vehicles Directorate**
**Air Force Research Laboratory**

**Briefing to the**
**National Space Weather Program Assessment Team**
**6 Jan 2006**

## Exploring MEOWhy Bother?

- MEO is a desirable orbit regime when trading off number of satellites, global coverage and ground resolution
- MEO comprises a dynamic space radiation and plasma environment
- The MEO space environment is poorly quantified

- Electrons >~ 1 MeV

- Protons >~ 25 MeV

## Exploring MEOCurrent Standard Models (AE8 & AP8)

- For MEO orbit (L=2.2), #years to reach 100 kRad:
- Quiet conditions (NASA AP8, AE8) :  88 yrs
- Active conditions (CRRES active) : 1.1 yrs
- AE8 & AP8 under estimate the dose for 0.23’’ shielding

- Model Dose rates behind 0.23’’ Al
- (>2.5 MeV e ; >135 MeV p)

**L (R****E****)**

**DOSE (Rads/s)**

- HEO dose measurements show that current radiation models (AE8 & AP8) over estimate the dose for thinner shielding

**J. Fennell, SEEWG 2003 **

**Example: Highly Elliptic Orbit (HEO) **

**Example: Medium-Earth Orbit (MEO) **

***Exploring MEO******Current Standard Models (AE8 & AP8)***

## Exploring MEOMEO from LEO? (electrons)

**Dosimeter data   > 1.5 MeV electrons**

**MEO (10000 km, 45 deg)**

**HEO (Molnya)**

**LEO (400 x 1600 km, 69 deg)**

***Exploring MEO******MEO from LEO? (electrons)***

**Qualitative signatures**

## Exploring MEOMEO from LEO? (protons)

**MEO (10000 km, 45 deg)**

**HEO (Molnya)**

**LEO (400 x 1600 km, 69 deg)**

***Exploring MEO******MEO from LEO? (protons)***

**No signatures!**

## Exploring MEODemonstration & Science Experiment (DSX)

**6000-km x 12000-km, 28 deg MEO orbit**

**Space Weather Sensors (SWx)**
- Data for models in critical orbit regime
- Determine near-field antenna environment

**Wave-particle Interactions (WPIx)**
- 50-m tip-to-tip antenna boom
- VLF receiver & transmitter
- Loss cone electron detector & magnetometer

**25-m**

**6-m**

**25-m**

***Exploring MEO******Demonstration & Science Experiment (DSX)***

**SWx and WPIx payloads on DSX will determine MEO wave and particle distributions  –  critical for development of climatology, nowcast and forecast models - rated #2/44 in 2005 DoD SERB**!

**Space Environment Testbed (NASA, AFRL)**
- Measure space environmental effects on materials and electronics
- Determine component system performance

**Low-Energy Imaging Particle Spectrometer (LIPS)**

**High Energy Proton Spectrometer (HEPS)**

**Compact Environmental Anomaly Sensor (CEASE)**

**High-Energy Imaging Particle Spectometer (HIPS)**

**Low Energy Electrostatic Analyzer (LEESA)**

**Physical Sciences, Inc.**

**Amptek, Inc.**

**Designed for stand alone or EELV ESPA options **

## Quiet

**Quiet**

**Active**

**rads(Si)/yr**

**rads(Si)/yr**

**10****5**

**10****4**

**10****3**

**10****5**

**10****2**

**10****1**

**10****6**

**10****4**

**10****3**

**10****2**

**From CRRESRAD model**

**DSX Orbit 1**
**(6000 x 12000 km, 28 deg)**

**DSX Orbit 5**
**(6000 x 12000, 63 deg)**

**X 10**

**X 30-80**

**Quiet**

**Active**

## DSXSWX Sensors

**LEESA**

**LIPS**

**HIPS**

**LEESA**

**LIPS**

**HIPS**

**HEPS**

**LCI**

**CEASE**

**CEASE**

**Sensors**

## Exploring MEOWave-Particle Interactions

- Particles mirroring below
- 100 km are “lost”

- Electromagnetic
- wave

- Pitch-angle

**Electromagnetic waves in the Very Low Frequency (VLF) range (3-30 kHz) scatter and accelerate radiation belt electrons through cyclotron resonance interactions**

***Exploring MEO******Wave-Particle Interactions***

## DSXWPIx Motivation

- Diffusion coefficient along field lines

**An understanding of  VLF wave power distribution & resultant wave-particle interactions is crucial for radiation belt specification & forecasting **

**Wave power in the magnetosphere**

**Diffusion coefficients **
**along field lines**

**Particle lifetime along field lines**
**(approximate 1D solution)**

**Full 3D global, time dependent particle distributions **
***X******i****** =  *****(*****L, E, ************ )***

**Wave-particle resonance condition**

**Diffusion coefficients = sum over resonances**

**Complex dependence on energy, frequency, and pitch angle**

**Distribution of Resonant Wave Vectors**

***DSX******WPIx Motivation***

## DSXWPIx Payload

-  Three search coil magnetometers
-  Two dipole antennas
-  Frequency range: 1 – 50 kHz
- Transmitter:
-  1 – 50 kHz at up to 1 kW
-  50 kHz – 750 kHz at 1W  (local electron density)
-  Loss Cone Detector
-  Pointed into the loss cone, measures 100-500 keV electrons
-  Correlates loss cone filling with natural and/or transmitter generated events
-  DC Vector Magnetometer
-  0-8 Hz three-axis measurement

***DSX******WPIx Payload***

## Exploring MEOSummary

- MEO is a desirable orbit regime but poorly quantified
- DSX science goals:
- Improve understanding of dynamical processes in the slot region
- Develop radiation belt specification and forecast models for the MEO region
- Improve understanding of VLF propagation and wave-particle interactions
- DSX technology goals
- Provide improved climatology models to allow spacecraft manufacturers to optimize designs
- Provide data to DSX SET experiments to help evaluate radiation effects on those systems.
- Validate VLF wave injection models from space and ground based platforms

## Back-up Slides

## Space Weather in MEOA Dynamic Environment

**18 months**

**18 months**

**L shell (Re)**

**1.0**

**7.0**

**L shell (Re)**

**7.0**

**1.0**

**Electrons**

**Protons**

**Solar protons**

**Solar x-rays**

**Solar wind velocity**

**Solar wind magnetic field**

**Geomagnetic Activity Index**

**Geomagnetic storm and proton event**

**Solar cycle**

**Dynamic radiation belts**

***Space Weather in MEO******A Dynamic Environment***

## Model differences depend on energy

**Model differences depend on energy**

## Space Weather in MEODSX Coverage

***Space Weather in MEO******DSX Coverage***

**Pitch-angle resolution enables mapping of distributions above orbit track**

## Wave-Particle InteractionsExperiment Concept of Operation

- Time

- Volts/m

- ~ 1 sec

- ~ 100 msec

**Transmitter Signal**

**Receiver Signal**

- Time

- Volts/m

- ~ 2 sec

- Time

- Volts/m

**Transmitter Signal**

- Time

- Counts/sec

**Loss Cone Particle Detector**

**Stimulated particle precipitation to determine wave-particle interactions**

**VLF sounding to determine far-field properties**

***Wave-Particle Interactions******Experiment Concept of Operation***