CGMS-41 NOAA-WP-15
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Prepared by NOAA
Agenda Item: II/11
Discussed in WGII
REPORT ON GROUND AND SPACE-BASED SPACE WEATHER OBSERVING
SYSTEMS
In response to CGMS action/recommendation …
Ground and space-based observations are at the heart of space weather
forecasting and specification. These observations extend from the Sun to
interplanetary space, to the magnetosphere, ionosphere and upper atmosphere,
and are used to support a growing and diverse user community. Space weather
observations are used as situational awareness, as input to drive models that can
provide spatial and temporal forecasts, in assimilative models, to validate model
performance, and for research that may ultimately lead to improved space weather
applications. NOAA supports both ground and space-based observations that
provide continuous measurements of the vast space environment. These
observations, such as from the NOAA GOES and POES satellites are discussed.
Also critical for supporting space weather operations are data from NASA, NSF,
the USAF, the USGS, and international partners. New observations and new
priorities, guided by new challenges and customer needs, are also discussed This
paper describes many of the space weather observing systems in use, and
planned for, at the NOAA Space Weather Prediction Center and how these
observations support space weather services.
CGMS-41 NOAA-WP-15
v1, 24 May 2013
REPORT ON GROUND AND SPACE-BASED SPACE WEATHER OBSERVING
SYSTEMS
1
INTRODUCTION
Ground and space-based observations are at the heart of space weather forecasting
and specification. These observations extend from the Sun to interplanetary space,
to the magnetosphere, ionosphere and upper atmosphere, and are used to support a
growing and diverse user community. Space weather observations are used as
situational awareness, as input to drive models that can provide spatial and temporal
forecasts, in assimilative models, to validate model performance, and for research
that may ultimately lead to improved space weather applications. NOAA supports
both ground and space-based observations that provide continuous measurements
of the vast space environment. Also critical for supporting space weather operations
are data from NASA, NSF, the USAF, the USGS, and international partners. This
paper describes many of the space weather observing systems in use, and planned
for, at the NOAA Space Weather Prediction Center and how these observations
support space weather services.
2
GROUND-BASED OBSERVING SYSTEMS
2.1 Ground-Based Magnetometer Observing Network
NOAA’s Space Weather Prediction Center (SWPC) collaborates with agencies
around the world to monitor geomagnetic activity in real-time at global locations. The
result of this cooperative arrangement is the production of a real-time estimate of the
Planetary Kp-index (see Figure 1). The Kp index is the physical measure of
geomagnetic activity used for determining the NOAA Space Weather Scale for global
geomagnetic activity, also known as the G-scale. The following observatories are
fully operational at this time: Boulder, Colorado; Chambon la Foret, France;
Fredericksburg, Virginia; Fresno, California; Hartland, UK; Newport, Washington;
Sitka, Alaska. The availability of these data is only possible through the efforts of the
following collaborating agencies: the U.S. Geological Survey, the British Geological
Survey, and the Institut de Physique du Globe de Paris. In addition, development and
negotiations are in progress to add the following stations: Jeju, Korea (Korean Space
Weather Center), Canberra, Australia (Geoscience Australia); Ottawa and Meanook,
Canada (Natural Resources Canada); Niemegk and Wingst, Germany (German
Research Centre for Geosciences - GFZ).
2.2 Ground-Based Solar and Radio Observations
SWPC depends upon a number of organizations to provide ground-based solar
optical and radio data used by forecasters to develop a variety of products. The
USAF works in partnership with SWPC and provides ground-based solar optical and
radio data from a worldwide network of Solar Electro-Optical Network (SEON)
observatories. SEON optical and radio data are employed by SWPC forecasters to
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develop a variety of daily products including probabilistic X-ray/proton flare forecasts,
Solar Region Summaries, Forecast Discussions and Solar Synoptic Analyses. In
addition, SWPC forecasters use SEON data as input to the Proton Prediction System
and various space weather alerts. SWPC forecasters use optical data from the NSF
supported National Solar Observatory/Global Oscillation Network Group
(NSO/GONG) to produce the daily Solar Synoptic Analysis and as input to the WSA-
Figure 1: The estimated Planetary Kp index from May 16 through 18, 2013. Kp =5
(shown by the red bars) is the physical measure that indicates a G1 or minor
geomagnetic storm is in progress.
Enlil Solar Wind Model, which is used to predict coronal mass ejections (CMEs) and
coronal hole high-speed stream arrival times. The Dominion Radio Astrophysical
Observatory, located in Penticton, British Columbia, Canada, provides 10.7 cm solar
radio flux measurements used by SWPC forecasters to develop daily 7-day 10.7 cm
solar radio flux forecasts.
2.3 Ground-Based Global Satellite Navigation System (GNSS)
Ground-based, dual frequency, receivers of Global Satellite Navigation System
(GNSS) signals can provide estimates of the total electron content along the line of
sight. Networks of receivers combined with data assimilation techniques can
optimally map the total electron content (TEC) over well-observed regions. As shown
in Figure 2, SWPC currently provides TEC maps over the CONUS every 15 minutes
in near real time and will shortly release an extended version covering North America
(NA-TEC), including the CONUS, Canada, Alaska, Hawaii, and Mexico. In addition to
the vertical TEC, the product includes estimates of the uncertainty, departures of the
current map from a 10-day mean at the same UT, and maps of the slant-TEC
estimates to all the GNSS satellites in view from each location. The vertical TEC
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products can be used to indicate situational awareness of ionospheric activity; the
slant-path maps can be used to estimate signal delay on each satellite to receiver
path to improve positioning and navigation accuracy.
Figure 2: A 15-min snapshot of vertical total electron content (TEC) on 22 May 2013
from GNSS data and an assimilative ionospheric model.
The current products use a real-time data stream from NOAA’s National Geodetic
Survey (NGS) Continuously Operating Reference Stations (CORS), GPS/MET, realtime International GNSS Service (IGS) (RTIGS), and the Wide Area Augmentation
System (WAAS). The data stream will shortly migrate over to the Networked
Transport of RTCM via Internet Protocol (NTRIP) broadcast format, to enable TEC
maps to be extended to other geographic regions, and eventually to provide global
coverage. The global coverage will require additional information from the
Constellation Observing System for Meteorology, Ionosphere, and Climate
(COSMIC-II) satellite constellation radio occultation data to augment the groundbased networks over regions not so well observed, particularly over the oceans.
COSMIC-I and II are joint US-Taiwan ventures. The six-satellite COSMIC-I
constellation was launched in April 2006. COSMIC-II will include six low and six high
inclination satellites. A 2015 launch is scheduled for the first six of the twelve
satellites.
Another source of ground-based ionospheric data is real-time ground-based
ionosonde measurements that are used at SWPC for model validation and
verification. The data are also made available to other space weather service
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providers. Presently there are more than 25 globally distributed ionosonde stations
available at SWPC in real-time.
3
SPACE-BASED OBSERVING SYSTEMS
3.1 NOAA’s Polar Operational Environmental Satellite (POES)
The POES/MetOp satellites, in polar orbit, carry instruments for monitoring variations
of the Earth’s low-altitude space particle radiation environment that is hazardous to
satellites and human space missions. The SEM-2 instrument suite measures protons
and electrons from 50 eV up to 250 MeV. The data from these instruments provide a
global specification of the radiation threat and are currently used in a variety of realtime products and alerts. For low-Earth orbit, satellite operators use the POES
radiation belt indices to understand when satellites are threatened.
Recent updates and improvements in space particle radiation monitoring include the
launch of the MetOp-B satellite that carries the NOAA Space Environment Monitor
(SEM-2) as part of a joint NOAA-EUMETSAT project. Since the recent launch, there
are now 6 SEM-2 suites in low-Earth orbit providing more complete global coverage
of the radiation environment and reduced data latency. With this new launch, the
NOAA SEM-2 data ingest and processing system was upgraded to remove
dependency on legacy systems and ensure continuity into the future. The new
system provides improvements such as real-time data access for external users,
more accurate measurements in physically meaningful units for easy ingest into
higher-level products, and expanded energy coverage due to better calibration
analysis.
The POES satellites also carry the Solar Backscatter Ultraviolet Radiometer (SBUV)
that is used for Earth ozone measurements. Fortunate for space weather and space
climate applications, the instrument also measures the solar UV flux that is used to
construct the Mg II index, a proxy for solar chromospheric activity. These
measurements are one of the longest records (spanning about 35 years) of solar
variability. The index is used in modelling the stratosphere, thermosphere, and
ionosphere, as well as in climate models.
3.2 NOAA’s Geostationary Operational Environmental Satellite (GOES)
The GOES satellites have hosted space weather instruments since the program was
initiated in the mid-1970’s. These instruments measure solar X-rays; solar,
magnetospheric and galactic energetic particles; and Earth’s time-varying magnetic
field at geosynchronous orbit. These observations have been continued on the
current series of GOES satellites and are planned for the future GOES-R series. In
addition, solar X-ray imaging (beginning with GOES-12), lower energy particle
measurements, and solar extreme ultraviolet observations were added to more
recent satellites. For GOES-R, energetic particles with even lower energies will be
monitored, as well as very energetic heavy ions. Also on the GOES-R series there
will be changes in the solar X-ray imaging wavelengths toward the ultraviolet, as well
as changes in the way EUV and XRS measurements are made. Each of these
instruments contributes critical data needed to support SWPC’s mission “to deliver
space weather products and services that meet the evolving needs of the nation.”
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3.2.1 GOES Energetic Particle Measurements
The GOES satellites carry instruments for monitoring variations of the near-Earth
space particle radiation environment that is hazardous to satellites and human space
missions. The current GOES-13,-14, and -15 series of satellites has several
improvements over the previous series for measuring energetic particles. Current
measurements include: the Magnetospheric Proton Detector (MAGPD) and
Magnetospheric Electron Detector (MAGED) that measures protons and electrons in 5
energy bands and 9 look directions from 30-600 keV for electrons and from 80-800 keV
for protons. The Energetic Proton, Electron, and Alpha Detectors (EPEAD) is the same
as on GOES 8-12, but there are two look directions East and West with electrons at
energies of 0.8, 2, and 4 MeV and protons 2.5-433 MeV. The High Energy Proton and
Alpha Detector (HEPAD) is the same as on GOES 8-12 measuring protons from 330 to
greater than 700 MeV. With some differences, the GOES-R series will make similar
measurements, but also include: Magnetospheric Particle Sensor - Low Energy Range
(MPS-low) that measures electrons and ions from 30eV to 30 keV in 15 bands and 12
look directions and the Energetic Heavy Ion Sensor (EHIS) that measures 10-200
MeV/nucleon ions in 5 mass groups and 1 look direction.
The data from these instruments provide a global specification of the radiation threat
and are currently used in a variety of real-time products and alerts. The GOES
particle data are the primary input to the Space Environmental Anomalies Expert
System Real Time (SEAESRT) that shows the likelihood of a satellite anomaly
occurring at geosynchronous orbit. The forecasters at the NOAA Space Weather
Prediction Center issue warnings and alerts when GOES particle flux levels reach
critical thresholds.
As described above, the future GOES-R satellite series will provide extended
measurement capabilities as requested by users. The instruments will cover the full
range of particles that can adversely affect satellites, adding measurements to what
was previously available, of the lower energies that cause electrostatic discharges
and energetic heavy ions that can cause single event upsets of electronic
components. The new data will be ingested into algorithms under development that
will provide more quantitative actionable information. These will include such things
as integrated proton event fluences compared to typical satellite design thresholds
and particle densities and temperatures used as input to surface charging models.
3.2.2 GOES X-Ray Sensor (XRS) and Extreme Ultraviolet Sensor EUVS
The GOES solar X-Ray Sensor (XRS) observes the solar x-ray irradiance in two
wavelength bands (0.05-0.4 nm and 0.1-0.8 nm) at a cadence of 3-seconds. The
solar x-ray emissions are highly variable, changing by several orders of magnitude
over only a few minutes during solar flares. This detector provides the primary
standard for determining the timing and magnitude of solar x-ray flares. On the
GOES-R series, an upgraded instrument will have a flare location capability. These
observations also provide the first warning of other possible space weather events
such as solar radiations storms or geomagnetic storms that are driven by solar
eruptions. Solar x-rays also impact the ionosphere and can affect or even block
high-frequency (HF) radio transmissions. For this reason, the XRS observations
drive the solar radio blackout NOAA scale.
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The GOES solar Extreme Ultraviolet Sensor (EUVS) observes the Sun in five
wavelength bands between 5 and 121 nm at a cadence of 10 seconds. The solar
EUV emissions are highly variable changing by factors of 10 over time scales from
minutes to years. The solar EUV flux at Earth is absorbed in the upper atmosphere
thus heating the thermosphere and ionizing it to create the ionosphere. The large
changes in the solar EUV irradiance result directly in similar magnitude changes in
the temperature of the thermosphere and the density of the ionosphere. The GOES
EUVS observations provide accurate measurements of the solar energy flux into the
upper atmosphere and are used in specification and forecast models of the
Ionosphere/Thermosphere system.
3.2.3 GOES Magnetometer (MAG)
The GOES Magnetometer (MAG) measures Earth’s magnetic field, and its dynamic
variations, in geosynchronous orbit. On the current satellite series, GOES-13, -14,
and -15, there are two magnetometers mounted on an 8.5 m boom to avoid
spacecraft interference. The magnetic field is sampled twice per second with about 1
nT accuracy and 0.03 nT resolution. The magnetometer data are used by space
weather forecasters and customers for a wide variety of purposes including:
magnetopause crossings that can affect some satellite operations, interpreting GOES
energetic particle data, assessing the level of geomagnetic activity, supporting
decisions on scientific rocket launches, and in the future these data will be critical for
the validation of large-scale scientific and operational numerical models of solarterrestrial space weather conditions. Magnetometers with similar features are under
development for the future GOES-R satellite series.
3.2.4 GOES Solar X-ray Imager (SXI) and Solar Ultraviolet Imager (SUVI)
The GOES Solar X-Ray Imager (SXI) monitors the Sun’s outer atmosphere, or
corona, for features and phenomena that result in space weather effects at Earth
(see Figure 3). This portion of the Sun’s atmosphere radiates in the extreme
ultraviolet and X-ray spectral regions because of its very hot temperatures of 1-2
million Kelvins. The instrument flies on the GOES 13, 14 and 15 satellites and
provides images that are formed into movies for forecaster assessment. The GOESR series of spacecraft replaces the SXI with an improved similar instrument, the
Solar Ultraviolet Imager (SUVI). By imaging in the extreme ultraviolet it will allow
improvements in spatial resolution and retrieval of physical parameters of the corona.
The solar features SXI monitors (and SUVI will monitor) includes coronal holes long-lived, large areas of open magnetic field in the solar atmosphere - that are the
sources of high-speed solar wind that can drive recurring geomagnetic storms. The
largest geomagnetic storms occur when a coronal mass ejection (CME) from the Sun
throws into the interplanetary medium billions of tons of plasma which envelops
Earth's magnetic field. Solar radiation storms originate either in direct association
with solar flares or with shocks associated with CMEs. Radio blackouts occur in
direct response to the enhanced X-ray radiation from solar flares. Increased satellite
drag is associated with longer-term increases in solar EUV flux. These solar drivers
lead to the specific high-level observational goals for NOAA imaging observations of
the Sun:
 Locate coronal holes for forecasts of recurring geomagnetic activity
 Locate flares for forecasts of solar energetic particle events
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Assess active region complexity for flare forecasts
Monitor active regions beyond the east limb for solar activity (F 10.7) forecasts,
and
Determine occurrence of coronal mass ejections
Figure 3: Solar X-ray image from GOES-13 showing solar active regions (bright) and
coronal holes that are sources of high-speed solar wind (dark).
3.3
Space Assets From Other Agencies Supporting NOAA’s Space Weather
Operations
The NASA Advanced Composition Explorer (ACE) satellite has been used by the
Space Weather Prediction Center since 1998 to provide highly accurate warnings of
geomagnetic storms. From its location, 1.5 million kilometers sunward of Earth, ACE
observations provide crucial information about the magnetic field embedded within
interplanetary coronal mass ejections (CMEs) allowing for warnings to customers
with lead times before striking Earth of 15-60 minutes. The ACE data also provide
valuable information about the background solar wind, including high-speed winds
that also cause geomagnetic storms. The ACE satellite also provides particle data
that provides longer lead-time information about approaching CMEs and particle data
that complements the GOES particle measurements of Solar Radiation Storms. The
Space Weather Prediction Center manages the Real Time Solar Wind (RTSW)
global network of ground stations to ensure continuous real-time receipt of ACE data.
The NASA/ESA Solar and Heliospheric Observatory (SOHO) was launched in 1995
and today is still used to provide solar coronagraph images at a cadence sufficient to
observe the onset of Coronal Mass Ejections. Observing CMEs from the time they
leave the Sun gives from 1 to 4 days lead time for geomagnetic storm watches. The
SOHO coronagraph images are also used to generate the inputs for the WSA-Enlil
solar wind model used to predict the arrival time at Earth of CMEs. The WSA-Enlil
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model also uses solar magnetograms from NSF supported National Solar
Observatory/Global Oscillation Network Group (NSO/GONG).
Another satellite, NASA’s Solar Terrestrial Relations Observatory (STEREO) has
been used since 2006 at SWPC to enhance forecasting. STEREO is a pair of
satellites offering the first ever, stereo view of the Sun and solar atmosphere. The
main impacts have been improved lead-time and quantitative assessment of the
background solar wind and coronagraph observations of CMEs to derive improved
inputs to the WSA-Enlil solar wind model. Also available from STEREO in real-time
are ultraviolet solar images, heliosphere images of the entire space between the Sun
and the Earth, radio burst data, and energetic particles. SWPC manages the
STEREO beacon global network of ground stations to ensure near-continuous realtime receipt of STEREO data.
The NASA Solar Dynamics Observatory (SDO) was launched in 2010 and has been
used by SWPC to obtain unprecedented views of solar active regions, the sources of
solar flares and of the strongest CMEs. SDO provides the highest spatial resolution
full-disk solar images ever taken, providing views in extreme ultraviolet and of the
solar magnetic field. It also has an extreme ultraviolet sensor that can be used to
provide a backup to the GOES XRS during eclipse season or other outages, and
solar magnetograms that are used by space weather forecasters.
NASA has also provided space weather beacons on other research satellites that
can contribute to space weather applications. One such satellite mission, the Van
Allen Probes, was recently launched in August 2012. The mission consists of two
satellites that fly in formation. The satellites are in a near-equatorial elliptical orbit that
comes close to Earth at perigee and nearly out to geosynchronous orbit at apogee.
The satellites will provide the best measurements ever of Earth’s radiation belts in
order to understand the acceleration, transport and loss of the particles. Efforts are
underway to incorporate the real-time measurements from the Van Allen Probes into
an assimilative model that will provide “maps” of the radiation belts that can be
evaluated by forecasters for their ability to provide new information to operators of
satellites flying in Earth’s radiation belt region.
3.4
NOAA Planned Space Assets for Space Weather Operations
NOAA is planning to add the Deep Space Climate Observatory (DSCOVR) to its
space-borne fleet in late 2014 (see Figure 4). DSCOVR will orbit the L1 Lagrange
point 1.5 million kilometers sunward of Earth. DSCOVR is a multi-agency effort with
NASA providing the satellite, the AF providing the launch, and NOAA providing for
the refurbishment of the satellite and instruments and developing the ground-data
collection (with national and international partners) and processing. DSCOVR will be
used to replace the aging NASA ACE satellite that has been in used since 1998.
DSCOVR has two primary space weather sensors, a solar wind plasma detector and
a solar wind magnetic field detector.
Together, these instruments will provide the continuity of the most important
measurements from ACE. DSCOVR will provide 15-60 minutes of lead-time for the
strongest geomagnetic storms caused by coronal mass ejections. DSCOVR will also
provide data on the background solar wind, features of which can also drive
geomagnetic storms. The data from DSCOVR will allow SWPC to issue highly
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accurate warnings to customers. DSCOVR data will be available continuously in
near-real time using the same Real Time Solar Wind global network of stations as
developed for ACE to receive the data.
Figure 4: The Deep Space Climate Observatory (DSCOVR) will be used to provide
advanced warning of solar wind conditions from the L1 Lagrange point 1.5 million
kilometers sunward of Earth.
3.5
Space-based Assets Planned with NOAA Participation
In order to increase the lead time for geomagnetic storm warnings from 15-60
minutes provided by observations from the L1 Lagrange point, a satellite needs to be
located further upstream and closer to the Sun. The Sunjammer mission is a NASA
technology demonstration mission to do just that. NOAA is partnering with L’Garde
on the Sunjammer mission to take a satellite twice as close to the Sun as L1 using
solar sail technology. The primary technology being demonstrated will be the
successful navigation of the satellite using a solar sail. A secondary objective is
being met with a contribution from the United Kingdom Space Agency of solar wind
plasma (University College London, Mullard Space Science Laboratory) and
magnetic field sensors (Imperial College) for this mission. Sunjammer will be used to
show if it is possible to make these critical space weather measurements in the
presence of a solar sail. This could pave the way for NOAA to provide highly
accurate geomagnetic storm warnings with increased lead time.
Also, as discussed in Section 2.3, global coverage of the ionosphere will be
enhanced by radio occultation data from the Constellation Observing System for
Meteorology, Ionosphere, and Climate (COSMIC-II) satellite constellation. These
data will augment the ground-based networks over regions not so well observed,
particularly over the oceans. COSMIC-II is a joint US-Taiwan venture. COSMIC-II will
include six low and six high inclination satellites. A 2015 launch is scheduled for the
first six of the twelve satellites.
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Yet another satellite, with NOAA participation is the Global-scale Observations of the
Limb and Disk (GOLD) mission of opportunity that was recently selected by the
NASA Explorers program. GOLD is an ultraviolet imaging spectrograph that will be
flown on a geostationary satellite to measure temperatures and composition in the
daytime thermosphere. GOLD will provide simultaneous measurements of two critical
state variables - neutral temperatures and composition (O/N2 ratio) - in the Earth’s
lower thermosphere, information that is essential to advancing our physical
understanding of the coupling between the space environment and the Earth’s
atmosphere and to developing an understanding of the Sun’s effects on Earth. In
addition, GOLD will provide peak electron density on the night side and will be able to
see scintillation producing structure in the low-latitude ionosphere. GOLD’s capability
to provide real-time data, and knowledge gained from the observations, can also
advance space weather specification and forecasting capabilities. GOLD will be used
at SWPC in a real-time data assimilation scheme to specify and forecast the
thermosphere and ionosphere.
4
CONCLUSIONS
This paper has described the various ground and space-based observing systems
used for space weather forecasting and specification. These systems support a
multitude of diverse space weather customers, both on the ground and in space, that
are affected by conditions in the space environment. The paper highlights the
importance of NOAA observations, and national and international partnerships for
providing a broad range of measurements needed to monitor the vast space
environment. New observations and priorities, guided by new challenges and
customer needs, are also discussed.
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