# Presentation: 767780

## The Aerospace Space Weather InitiativeMaking the Case for Space Weather Sensors on All Spacecraft

**Harry Koons (Delivered by Paul O’Brien)**
**Space Science Applications Laboratory**

## The Problems

**Situational Awareness**
**Need to increase awareness of space operators to space environmental hazards when they are present**
**Spacecraft Anomalies**
**Operators do not have the experience needed to assess space weather reports in near real time to determine if space weather might be responsible for an observed anomaly**
**Design and Test Specifications**
**Make our satellites as immune from environmentally induced anomalies as possible**
**Improve specifications to deal with all hazards**
**Enforce specifications**

## Space Weather Instrumented Sentinel System

**SWISS/GEO**
**24-Spacecraft GEO Constellation **
**SWISS/HEO**
**6-Spacecraft Constellation in three equatorial orbits**
**Same Sensors as GEO**
**Apogee near GEO**
**Supports MEO and HEO orbits**
**SWISS/Client****	**
**Weather Sensors on Client Spacecraft**
**Augment small-sat constellations with local measurements for reliability**
**Essential for Space Situational Awareness**
**Sensors**
**Surface Charging Monitor**
**Internal Charging Monitor**
**Dosimeters **
**ESD Monitor**

**SWISS-GEO**

## Surface Charging Measurements Near GEOon a Well-Instrumented Spacecraft

**Spacecraft frame potential measured by an electrostatic analyzer.**
**Kapton potential measured by a differential surface-potential monitor**
**The frame did not charge at the beginning of the event because some of the frame was still in sunlight.**
**The discharges shown did not occur on the Kapton sample.**
**The discharges correlate with the charging event**
**Discharges do not correlate with the maxima in either potential measurement. **

## Problem: Correlation Distance for Surface Charging is Very Short

**Problem: Correlation Distance for Surface Charging is Very Short**

- Conclude that surface-charging sensor must be on client vehicle!

**Sensor****	****Client****	****Client****	********LT****	****	****Warnings****	****Correct****	****False****	****Failures****	****	****	****	****Events****	**** hrs****	****	****  (Red)****	****	****	****	****Alarms****	****to Detect**
**801****	****	****806 ****	****	****5559****	****0.60****	****	****  4313****	****	****1120****	****3193****	****4439**
**801****	****	****803****	****	****3056****	****0.67****	****	****  4313****	****	****513****	****	****3800****	****2543**
**801****	****	****805****	****	****4804****	****1.60****	****	****  4313****	****	****746****	****	****3567****	****4058**

## Problems Dealing with Situational Awarenessfor Surface Discharges

**Problem 1: Correlation distance for surface charging is very short.**
**Less than one hour in local time in geosynchronous orbit**
**Problem 2: Surface potential measurements are sensor type and location dependent**
**Sensors that measure the spacecraft potential with respect to the plasma do not respond at the same time as sensors that measure differential potentials on the spacecraft**
**Sensors in darkness respond differently from sensors in sunlight**
**Problem 3: Charging is a necessary but not a sufficient condition for an ESD event.**
**How do you know a discharge occurred?**

## Problem: Flux Dropouts Can Invalidate Normally Reliable Use of Fluxes fromRemote Energetic Electron Sensors

**Problem: Flux Dropouts Can Invalidate Normally Reliable Use of Fluxes from****Remote Energetic Electron Sensors**

**The client was at 4 AM local time**
**Vehicle 084 with a plasma analyzer and energetic electron sensors was located nearby**
**The preponderance of the evidence showed that the environment for internal charging was very high**
**However, the client was in a flux dropout in which internal charging levels had been very low for over an hour**
**The plasma analyzer on 084 showed the frame was charged to over one kilovolt negative**
**The hazard at the client was surface charging not internal charging  **

- Conclude that internal-charging sensors must be on client vehicle!

## Space Environment and Effects Sensors areRequired on Every Spacecraft(SWISS Client Payload)

**Required**
**Surface Charging Monitor**
**Internal Charging Monitor**
**ESD Monitor**
**Dosimeters**
**Optional**
**Electrostatic Analyzer**
**Magnetic Spectrometer**

## SWISS Client Measurements

## Conclusions

**It is very important for the long-term to have well-calibrated, continuous, data sets to gather the statistics needed to establish awareness and confidence levels**
**Can be accomplished to some extent with operational sensors + occasional full science-quality missions like CRRES**
**Surface charging sensors are required on client vehicles**
**Nearby measurements are not reliable because of the short correlation distance.**
**Simple internal charging sensors are required on client vehicles to determine if the vehicle is in a flux dropout**
**Discharge monitors are required on client vehicles**
**A measurement of charging alone cannot determine if an anomaly was caused by ESD.**
**Becomes more important as the incidence of ESD events decrease because there is less statistical evidence linking the environment to an anomaly.**
**Forecasting and predictions are of limited value for client awareness and anomaly diagnosis because even severe environments can be highly variable on relatively small spatial scales **