GEOSHAFT OBJECTIVES

1
GEOSHAFT Pilot Space Weather Service David J
Rodgers, Karen A. Ford and Keith A Ryden (Space
Department, QinetiQ, Farnborough, Hampshire GU14
0LX, UK) (e-mail djrodgers_at_space.qinetiq.com)

Abstract Internal dielectric charging is one of
the main space weather hazards to spacecraft
electronics. This occurs when electrons at high
energies, typically gt0.5MeV and usually in the
outer radiation belt, penetrate surface
materials and are deposited in underlying
dielectrics. The charging that results leads to
electrostatic discharges which may cause
temporary upsets or permanent damage to
electronic components. In geostationary orbit
electron flux increases of a factor 1000 in a few
hours are not unusual and spacecraft in this
highly populated orbit are at high risk. The
GEOSHAFT prototype space weather service aimed to
provide improved information on the level of this
hazard as an aid to geostationary spacecraft
operators. Products of the service are running
24-hour average of gt2MeV electron fluxes,
modelled charging current and modelled dielectric
electric field. A numerical technique was also
used to provide short term forecasts up to 24
hours ahead. As part of the prototyping activity,
the service was run for a year. During this time,
comments were sought from users and improvements
were made. Users who agreed to take part in this
activity were New Skies NV and Paradigm Ltd. At
the end of the study the device performance was
assessed. The service was found to be reliable,
particularly after the initial period. The
effectiveness of using charging current and gt2MeV
electron flux as an anomaly indicator was
demonstrated. Good correlation was found between
anomalies and the running 24-hour mean of gt2MeV
electron flux and better predictions were
obtained with the calculated current. The
numerical flux predictions were not as successful
as expected and operational problems associated
with of time-tagging the data were suspected.
At the end of the study, the two users
considered that there was a need for a space
weather service addressing satellite anomalies.
However, one user had not experienced problems of
internal charging and so had not found the
service very helpful. The other user did not find
that the service fitted into operational
procedures. Hence neither user derived sufficient
benefit from the service that was produced and
future developments are seen as an essential step
in continuing the service.
INTRODUCTION Spacecraft in the highly populated
geostationary orbit suffer from the effects of
internal charging as a result of space weather.
There is a potential for anticipating anomaly
occurrence from the fact that the internal
charging process is quite slow (typically more
than 1 day). In addition, once a vulnerable
system or component has been identified, there is
the possibility of anticipating future anomalies
by a more physics-based approach, using deposited
current or electric field as hazard indicators.
This is the rationale behind the GEOSHAFT service.
SERVICE EVALUATION Good points Charging current
can be shown to be a better hazard indicator than
fluence. Below, we compare two thresholds in
fluence and current that were set to produced
?80 successful anomaly prediction and ?20 false
alarms respectively for a geostationary
satellite. ?80 successes
?20 false alarms
.

• GEOSHAFT OBJECTIVES
• The Geostationary Spacecraft Hazard and Anomaly
  Forecasting Tool (GEOSHAFT) is a Java based web
  application designed to provide real-time space
  radiation threat information.
• GEOSHAFT aims to provide useful information on
  the level of this hazard as an aid to spacecraft
  operators. It provides users with improved hazard
  indicators for the internal charging process.
• Daily averages of gt2MeV electron flux, every 5
  minutes. This is a general indicator and simply
  packages NOAA data in a more timely way.
• Currents estimated through the shielding around a
  component. This is most useful where the site of
  ESD is known or suspected. However, a default
  typical spacecraft skin thickness may be used as
  a general indicator.
• Maximum electric field estimated in a material.
  This is most useful where both the site of the
  ESD and the material involved are known or
  suspected. However, a typical common default
  material, known to be at risk from this process
  may be used as a general indicator.
• Delivery method
• Hazard levels via web page and alerts by e-mail
• User control of alert levels, shielding and
  material properties
• The service also aims to provide realistic
  forecasts up to 1 day into the future.

• Using the calculated current as a predictor led
  to a reduction in false alarms for the same
  positive success rate and an increase in positive
  success rates for the same false alarm rate.
• Bad points
• In practice, forecast accuracy of gt2MeV daily
  fluence was significantly poorer than that
  achieved during the testing of the prediction
  model on historical data. It is speculated that
  the large number of data gaps in the assessment
  period may be the cause of this but other causes,
  such as non-stationary data and problems with
  data time-stamps may have had an effect.
• Web Statistics
• Monitoring of web hits and origin of users is
  crude due to the actvities of search engines and
  the complex routing of the internet. 76 of hits
  were from the USA. The majority of these are
  believed to be search engines. Around 5 hits per
  day are estimated to be genuine.
• User Feed-back
• New Skies NV and Paradigm Ltd participated in
  the evaluation.
• Cost of anomalies
• Engineering time dealing with space weather
  anomalies
• New Skies - 1½ months of engineer effort per year
  for the 5 spacecraft
• Paradigm - 3 months of engineer effort per year
  for fleet
• Disruption to service
• New Skies - lt 6 or 7 mins not serious, but
  gt10-15 mins a problem
• Documentation for insurance (typically 2/year
  premium)

GEOSHAFT WEB SERVICE The GEOSHAFT web site
(http//geoshaft.space.qinetiq.com/geoshaft/) has
been publicly available during this study with an
additional private area available via
registration. Welcome Page

• BUSINESS PLAN
• For GEOSHAFT a sustainable business plan has to
  be based on an improved service
• Market
• 320 geostationary satellites, 60 systems, 6
  multiple European systems
• System options In-house web service, Hosted
  web service or jointly hosted with related space
  weather services
• Costs
• Funding models
• Subscription 5k/u/yr
• Public service 77k over 3 years
• Comparisons with other similar services
• NOAA SEC, NASAs SpaceWeather.com, IPS in
  Australia, BAS SatRisk and IRF Lund are
  non-subscription, also SPENVIS currently.
• Satellite Users Interference Reduction Group
  15k/u/yr

• PROSPECTIVE IMPROVEMENTS
• Without changes the existing GEOSHAFT service is
  too limited. New requirements are for
• Local time mapping
• Multiple satellites visible at once
• Easier customisation of shielding, no fields
• Automated anomaly comparisons
• Being part of global service makes sense
  financially and practically for users
• New Data sources
• Higher spectral resolution for better internal
  charging calculations feasible
• More GEO monitors would improve predictions and
  local time mapping
• Extension to MEO
• New, sophisticated detectors on GSTB/Galileo
• Galileo itself would be a major new user
• Europe could become the principal provider of
  MEO spacecraft hazard information.
• 1 D.J.Rodgers, K.A.Ryden, G.L.Wrenn,
  P.M.Latham, J. Sørensen and L.Levy, An
  Engineering Tool for the Prediction of Internal
  DielectricCharging, 6th Spacecraft Charging
  Technology Conference, AFRL-VS-TR-20001578, 1
  September 2000
• 2 D.J.Rodgers, S.N.Clucas, C.S.Dyer and
  R.J.K.Smith, Non Linear Prediction of
  Relativistic Electron Flux In the Outer Belt'
  Advances in Space Research, Vol. 31 No. 4

• The service accesses,and processes data from
  NOAAs GOES spacecraft and makes calls to two
  programs
• DICTAT 1 to calculate electric field and
  charging current within a shielded dielectric.
• TSAR 2 to perform prediction using radial basis
  functions.

TSAR forecast performance assessment