GOES Particle Intracalibration ToolkitWilliam Rowland

NOAA/NESDIS/STAR, GMURobert Weigel, PhD

George Mason University Changyong Cao, PhDNOAA/NESDIS/STAR

GOES MAGED Sensor

GOES NOP SEM Instruments

Coordinate System

EPS HEPAD Handbook

MAGED

• Solid State Detector, collimator, and electronics

• Determines energy of electrons based on energy deposited.

• Energy range in table below.

GOES-NOP Data book

GOES MAGED

EPS HEPAD Handbook

GOES MAGED Energy Captured

EPS HEPAD Handbook

State of GOES Calibration

Pre-launch

• Initial factors determined during ground calibration.– No standards between beamlines– Full energy/flux range may not be calibrated– Only one telescope generally characterized

On-orbit

• In-flight Calibration– Should track electronics degradation– Not useful in some channels of current generation– Currently not performed even for useful channels

• During Post-Launch testing comparisons are sometimes performed– Between telescopes on a single GOES satellite– Between GOES satellites

On-orbit (continued)

• After Post-launch testing– Generally no resources have been devoted to

following changes in cal factors due to different rates of degradation

– Neither SWPC nor NSOF has the resources necessary

Objectives for Future GOES Calibration

STAR’s Role

• Stewards of L1b Data Quality– Analyze and trend performance of instruments– Recommend adjustments to calibration factors as necessary– Participate in anomaly resolution as necessary

• Limited manpower necessitates development of tools– GOES Particle Intercalibration Toolkit

• Permit intracalibration of telescopes aboard the same satellite.• Permit intercalibration of satellites.• Make the data obtained publicly available, so that others involved

in the process (like NSOF) and the user community can track performance as desired.

Why use Pitch Angle to identify intracalibration data?

• Phase space consists of 3 position vectors, 3 velocity vectors, a scalar number density.

• Phase space coordinates express this in terms of 3 adiabatic invariants (μ, K, L*), 3 phases, and a scalar.

• For intracalibration– Position is the same for all telescopes on a satellite.– K and L* depend on the magnetic field. All

telescopes are in the same magnetic field.

Chen et. al, 2005

• First Adiabatic invariant defines

• Where

• B1=B2, vTot1~VTot2

, m1 = m2

• Therefore, if α1=α2 then μ1= μ2

• In this case all adiabatic invariants are the same for the particles measured by the two telescopes.

• These data may be useful for calibration.

Selection Criteria for Data

• Calculate representative pitch angles using– Magnetic Field measurements– Knowledge of the orientation of the particle

sensors

• Currently spacecraft reference frame is utilized– Any common frame works

• Pitch Angle “match” is defined as the angles matching to within 1 degree.– Particle sensor orientation knowledge is no better.

• This may be overly restrictive– Less stringent requirements yielded visually similar

results, at least to several degrees

• Additional constraints– Magnetic field vector direction changing quickly• Necessary for the First Adiabatic Invariant to be

meaningful• Used a limit of 1 degree per integration cycle for the

current plots• Parameter is included in metadata

– User can view different results if desired

• Additional constraints or possible confounds which are being considered– Dst values

• Did not appear to make a large difference– Rate of change in count rates

• Have not examined the current data set to see if an impact is noticeable.

– Local time• Have not examined data set for impact• This may have more of an impact at lower energies (S/C

charging)

Toolkit Results

Toolkit Results Statistics

Statistics for data from beginning of May 2010 to end of July 2010

Toolkit Development Status

Current tasks

• Quantify impact of additional effects– Dst, changes in count rate, local time, etc…

• Obtain further peer review• Automate code– Currently can manually order it to retrieve and

analyze a month’s worth of data• Make results available to SWPC– STAR does not have a mandate to calibrate GOES-

NOP

Software issues

• File sizes are getting too large. Need to either– Optimize code– Change platforms– Bundle datasets into 3 month sets

Future Work

• Code must be adapted to work for GOES-R.– Should be fairly easy

• Same technique could be used for satellite intercalibration– Probably will use a magnetic field model such as

Tsyganenko– Limitations of field models make things more difficult– Satellite needs to have magnetometers, particle

instruments measuring the same energy ranges, and similar Fields of View

References• Chen et al., Multisatellite determination of the relativistic electron phase

space density at geosynchronous orbit: Methodology and results during geomagnetically quiet times, JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, 2005

• M. Wüest et al., Calibration of Particle Instruments in Space Physics, ISSI Scientific Report 007, 2007

• Boeing, GOES-N Series Data Book, Rev. D, Feb. 2010• GOES-N Vol 3 Rev A, EPS HEPAD Handbook, Assurance Technology

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