Satellite locations
GOES satellites are stationed at specific
longitudes along the equator.
File Naming
D075YYMM.TXT
D -> Data version:
'G' GOES X-ray, Mag., Electrons & Uncorrected Proton Channels
'Z' GOES X-ray, Mag., Electrons & Corrected Proton Channels
'I' GOES X-ray, Mag., Electrons & Corrected Integral Protons
'H' GOES X-ray, Mag., Electrons & HEPAD
'A' GOES X-ray, Mag., Electrons & Uncorrected Alpha-Particles
07 -> GOES-7, etc.
5 -> 5-minute averages, 1 -> 1-minute averages
YY -> year
MM -> month
Data Channels
X-Rays
XL 1 - 8 Å X-rays
XS 0.5 - 4 Å X-rays
Magnetic Field
HP Parallel to satellite spin axis
HE Earthward
HN Normal to HP and HE, points West for GOES 1-4, East for GOES
5+
Htot Magnitude of total magnetic field vector
Energetic Particles from SMS-1 -> GOES7
Electrons
E1 > 2 MeV (Electrons/cm2 sec sr)
Protons
Corrected and uncorrected
P1 .6 - 4.2 MeV (Protons/cm2 sec sr MeV)
P2 4.2 - 8.7 MeV (Protons/cm2 sec sr MeV)
P3 8.7 - 14.5 MeV (Protons/cm2 sec sr MeV)
P4 15.0 - 44.0 MeV (Protons/cm2 sec sr MeV)
P5 39.0 - 82.0 MeV (Protons/cm2 sec sr MeV)
P6 84.0 - 200 MeV (Protons/cm2 sec sr MeV)
P7 110.0 - 500.0 MeV (Protons/cm2 sec sr MeV)
'I' designates Integrated protons, corrected
I1 > 1 MeV (Protons/cm2 sec sr)
I2 > 5 MeV (Protons/cm2 sec sr)
I3 > 10 MeV (Protons/cm2 sec sr)
I4 > 30 MeV (Protons/cm2 sec sr)
I5 > 50 MeV (Protons/cm2 sec sr)
I6 > 60 MeV (Protons/cm2 sec sr)
I7 > 100 MeV (Protons/cm2 sec sr)
Alpha Particles
'A' designates Alpha-particles, not corrected
A1 3.8 - 9.9 MeV (Alpha-particles/cm2 sec sr MeV)
A2 9.9 - 21.3 MeV (Alpha-particles/cm2 sec sr MeV)
A3 21.3 - 61. MeV (Alpha-particles/cm2 sec sr MeV)
A4 60.0 - 180 MeV (Alpha-particles/cm2 sec sr MeV)
A5 160.0 - 260 MeV (Alpha-particles/cm2 sec sr MeV)
A6 330.0 - 500 MeV (Alpha-particles/cm2 sec sr MeV)
HEPAD
P8 370 - 480 MeV (Protons/cm2 sec sr MeV)
p9 480 - 640 MeV (Protons/cm2 sec sr MeV)
P10 640 - 850 MeV (Protons/cm2 sec sr MeV)
P11 > 850 MeV (Protons/cm2 sec sr)
A7 630 - 850 MeV (Alpha-particles/cm2 sec sr MeV)
A8 > 850 MeV (Alpha-particles/cm2 sec sr)
Energetic Particles from GOES-8 -> GOES-12
Electrons
E0 > 0.6 MeV (Electrons/cm2 sec sr)
E1 > 2.0 MeV (Electrons/cm2 sec sr)
E2 > 4.0 MeV (Electrons/cm2 sec sr)
Protons
P1 <= 0.8 to 4 (Protons/cm2 sec sr MeV)
P2 4 to 9 (Protons/cm2 sec sr MeV)
P3 9 to 15 (Protons/cm2 sec sr MeV)
P4 15 to 40 (Protons/cm2 sec sr MeV)
P5 40 to 80 (Protons/cm2 sec sr MeV)
P6 80 to 165 (Protons/cm2 sec sr MeV)
P7 165 to 500 (Protons/cm2 sec sr MeV)
P8 350 to 420 HEPAD (Protons/cm2 sec sr MeV)
P9 420 to 510 HEPAD (Protons/cm2 sec sr MeV)
P10 510 to 700 HEPAD (Protons/cm2 sec sr MeV)
P11 > 700 HEPAD (Protons/cm2 sec sr)
'I' designates Integrated protons, corrected
I1 > 1 MeV (Protons/cm2 sec sr)
I2 > 5 MeV (Protons/cm2 sec sr)
I3 > 10 MeV (Protons/cm2 sec sr)
I4 > 30 MeV (Protons/cm2 sec sr)
I5 > 50 MeV (Protons/cm2 sec sr)
I6 > 60 MeV (Protons/cm2 sec sr)
I7 > 100 MeV (Protons/cm2 sec sr)
Alpha Particles
A1 4 to 10 (Alpha-particles/cm2 sec sr MeV)
A2 10 to 21 (Alpha-particles/cm2 sec sr MeV)
A3 21 to 60 (Alpha-particles/cm2 sec sr MeV)
A4 60 to 150 (Alpha-particles/cm2 sec sr MeV)
A5 150 to 250 (Alpha-particles/cm2 sec sr MeV)
A6 300 to 500(Alpha-particles/cm2 sec sr MeV)
A7 2560 to 3400 HEPAD (Alpha-particles/cm2 sec sr MeV)
A8 >3400 HEPAD (Alpha-particles/cm2 sec sr)
Data Cautions
The volume of these data makes it impossible to issue a guarantee
as to the quality of each data point. A quality pass has been
made though each file to identify values that make wild excursions
from the norm, and instances of such have been looked at on
a case by case basis and compared with concurrent data from
other satellites. Data identified as bad have been replaced
with the bad data flag. Users should be suspicious of 'spikes'
in the data and attempt to correlate them with other sources
before assuming that they represent the space environment.
The time of these observations has not been corrected for the
down-link and preprocessing delays. The Space Environment Center
estimates that delay to be 5-6 seconds.
X-ray Data Quality
The X-ray sensors may experience significant bremsstrahlung
contamination. This contamination is caused by energetic particles
in the outer radiation belts and depends on satellite local
time, time of year, and the local particle pitch- angle distribution.
The X-ray sensors are also sensitive to background contamination
due to energetic electrons that either deposit their energy
directly in the telescope or strike the external structure and
produce bremsstrahlung X- rays inside the ion chamber. Comparison
of X-ray measurements from two concurrently operating GOES satellites
reveals a systematic difference signal that shows both diurnal
and seasonal variations. These variations are most noticeable
when solar activity is low to moderate. Beginning with the GOES-8
detector the dynamic range of the instrument was shifted upwards
to allow the highest flux events to be recorded. As a consequence
of this, the lowest flux recordings are clipped.
Ion Data Quality
Users of GOES particle data should be aware that significant
secondary responses may exist in the particle data, i.e. responses
from other particles and energies and from directions outside
the nominal detector entrance aperture. A description of the
algorithm that partially corrects for these effects is described
below.
Electron Data Quality
The Electron detector responds significantly to protons above
32 MeV; therefore, electron data are contaminated when a proton
event is in progress. Beginning with GOES-8 the electron data
have had a preliminary correction applied, however, even these
data are not to be considered research quality at this time.
The GOES-5 electron channel is noisy from 1986 onwards and
readings are a possible factor of 2 high. One component of the
GOES-6 particle detector system has had radiation damage since
1986 that reduced its counting efficiency progressively. At
present the E1 and P4 channels derived from this component record
at only a few percent of their proper rates. In 1991 the telescope
component of the GOES-7 energetic particle detector system experienced
episodes of malfunction (noise). The first period began at 0330
UT, October 18, 1991 and extended to November 5, 1991. The detector
was commanded off for 12 hours. At turn-on the detector appeared
to have recovered, but failed again on November 11, with a rerecovery
on November 12 after a second turn-off of three hours. The detector
has since operated normally. The noise periods may be identified
by unusually high rates being shown by the P1 channel and the
derived > 1 MeV integral channel. Currently, the GOES-7 Energetic
Particle Sensor is left turned off for 4 hours after eclipse
to minimize bad data.
More on GOES-8 through GOES-10 Electrons from Terry Onsager:
1. The GOES 11 satellite is in storage mode and spinning. The
electron fluxes vary with the spin of the spacecraft, and therefore
the flux levels can easily be misinterpreted. It is safest not
to use these data.
2. There are questions with the geometric factor used for processing
the 0.6 MeV electron channel (GOES-8 thru GOES-12). The relative
variations of the 0.6 MeV electrons are useful for scientific
studies, but spectral indices inferred from the 0.6 MeV and
2.0 MeV channels may not be accurate.
3. The minimum value allowed in our processing is 1.33E-01.
Our processing takes the accumulated electron counts in a short
interval, converts to counts/second, and then subtracts off
an estimated contamination from protons. When the electron count
level is near the background level, the correction we do for
proton contamination can take the count rate below zero. To
avoid this we impose a floor on the count rate. I forget what
this floor is, but when it's converted to flux, you get 1.33E-01.
4. You should not trust any data where the flux is below about
10 (cm2 s sr)^-1. Once you get near the background level of
the instrument, the effect of the proton correction can be significant,
even when the proton levels are near their background.
Onsager, T. G., A. A. Chan, Y. Fei, S. R. Elkington, J. C.
Green, and H. J. Singer, The radial gradient of relativistic
electrons at geosynchronous orbit, J. Geophys. Res., 109, A05221,
doi:10.1029/2003JA010368, 2004.
Onsager, T. G., G. Rostoker, H.-J. Kim, G. D. Reeves, T. Obara,
H. J. Singer, and C. Smithtro, Radiation belt electron flux
dropouts: Local time, radial, and particle-energy dependence,
J. Geophys. Res., 107(A11), 1382, doi:10.1029/2001JA000187,
2002.
Onsager, T. G., R. Grubb, J. Kunches, L. Matheson, D. Speich,
R. Zwickl, and H. Sauer, Operational uses of the GOES energetic
particle detectors, SPIE Conference Proceedings, Vol. 2812,
p. 281-290, GOES-8 and Beyond, Edward R. Washwell, ed., 1996.
Magnetometer Data Quality
The GOES-5 magnetometer HP component had an artificial offset
from January 2, 1986 to March 13, 1986. The data are left as
is. The GOES-6 magnetometer experienced irregularities in the
magnetometer on September 9, 1991. The transverse component,
which is deconvoluted into the HE and HN components (orthogonal
to spin axis), began to yield bad values due most likely to
an error in locating Earth's limb. The problem persists to this
time. Although the possibility exists that a proper deconvolution
may be arrived at, the data for these values have been replaced
with the bad data flag and will not be plotted.
In summary, the HE and HN components of the GOES-6 magnetometer
have been filled with the bad data flag from September 9, 1991
onwards. The HP component is left intact. The GOES-7 magnetometer
experienced instrument failure of its transverse component in
May 1993. Only the HP component is available from May 1993 onwards.
The HN and HE components are filled with the bad data flag.
The absolute accuracy of HP (spin axis component) on all GOES
can be uncertain because of difficulties in calibration.
Data Gaps
GOES-6 1-minute data from June 5, 1988 to August 14, 1988 are
missing particle and magnetometer components. GOES-6 5-minute
data from June 5, 1988 to July 31, 1988 are missing particle
and magnetometer components.
Due to the failure of the P6 and P7 channels on GOES-12, the
"Z" and "I" files will not be generated.
GOES Energetic Particle Correction Algorithm
R. D. Zwickl
NOAA Space Environment Center
In January 1990, an upgraded algorithm for calculating the
energetic-particle differential and integral proton flux from
measurements made by the energetic particle monitors onboard
the GOES-6 and -7 satellites became operational in NOAA's Space
Environment Center (SEC). The following is a brief description
of the rationale for the new algorithm and its basic features.
Why Did We Need a New Algorithm?
The energetic particle monitors are simple solid-state sensors,
designed to handle large count rates without overwhelming the
electronics. Since their launch these instruments have met their
design goals and have never saturated, even during the largest
events. However, because they were required to measure high
rates, the detectors were built with passive shielding (no anti-
coincidence). This has allowed particles to pass through the
shielding from any direction and be counted as though they had
entered through the front collimator.
During solar energetic-particle events the low-energy passbands
would detect particles at exactly the same time as the high-energy
passbands did, even though it was impossible for the lower-energy
particles to be present at such early times. During quiet times,
cosmic rays and their secondary particles produce a very high
background in the GOES sensors, in contrast to their effect
on more advanced sensors that use active shielding (>100
times the "nominal" background).
The initial algorithm, used until January 1990, did not take
either of those effects into account. (NGDC has since applied
the correction algorithm to the earlier data from 1986 to 1990.)
The Upgraded Algorithm
The count rate as measured by any one of the seven energetic
particle proton channels on GOES-6 or -7 (identical systems)
can be given by
CMeas = CTrue + S + BG
where CMeas is the actual measured count rate, CTrue is the
true count rate, S is the count rate generated by particles
entering through secondary energy passbands (i.e., those particles
not passing through the collimator), and BG is the background
count rate (produced primarily by cosmic rays). Simply stated,
the new algorithm solves for CTrue as follows:
CTrue = CMeas - S - BG
The first step in the algorithm is to determine the background
count rate for each of the seven channels. Since the background
varies with time, a filter technique is used to find a new minimum
value within the previous 10 days or use the previous value.
This background value is then subtracted from CMeas. It is then
assumed that the energy spectrum of the energetic particles,
from one energy channel to the next, can be represented by a
simple power law in energy ( ), and that the secondary energy
passbands that were determined during calibration are responsible
for all of the secondary count rate. The resulting set of equations
can then be solved, starting with the highest energy channel
and working toward lower energies. All seven energy channels
must contain data or no values are calculated.
Finally, each set of 5-minute-averaged values is calculated
independently of every other set of values. This allows the
corrected values to be calculated continuously in an operational
environment.
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