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	South Atlantic Anomaly - Wikipedia, the free encyclopedia
		The SAA is produced by a "dip" in the Earth's magnetic field at that location, caused by the fact that the center of Earth's magnetic field is offset from its geographic center by 450 kilometers (280 miles).
		The South Atlantic Anomaly is of great significance to satellites and other spacecraft that orbit at several hundred kilometers altitude and at orbital inclinations between 35° and 60°; these orbits take satellites through the Anomaly periodically, exposing them to several minutes of strong radiation each time.
		The drift rate of the SAA is very close to the rotation differential between the Earth's core and its surface, estimated to be between 0.3 and 0.5 degrees per year.
	en.wikipedia.org /wiki/South_Atlantic_Anomaly (392 words)

	The South Atlantic Anomaly (Henry Spencer)
		In that area, known as the South Atlantic Anomaly, the Van Allen belts come down low enough that radiation intensity in low Earth orbit is noticeably greater there.
		This is troublesome both to astronauts and to sensitive electronics; for example, it's common for astronomy missions to suspend operations during passage through the SAA because the radiation causes unacceptably high noise levels in their sensors.
		The SAA is an area where the inner belt is unusually close to Earth's surface, close enough that LEO satellites see significantly elevated radiation levels there.
	yarchive.net /space/science/south_atlantic_anomaly.html (626 words)

	South Atlantic
		In the South Atlantic these transform faults are typically spaced some 50-100 km apart, reflect relative plate motion directions of the newly formed crust and occur at offsets of the normal faulted median rift valley that marks the axis of the ridge.
		For South America (east of the Andes), as noted above, the plate motion is consistently to the NW with an Euler pole located at approximately 25.4°S and 126.4°W. For South America west of the Andes the motions to the NE are consistent with the subduction of the Nazca plate beneath the Andes.
		Inspection of the satellite gravity for the South Atlantic indicates that deformation of the oceanic crust appears to be quite common and may be the controlling factor in the development of the Walvis Ridge and Rio Grande Rise aseismic ridges.
	www.mantleplumes.org /SAtlantic.html (3636 words)

	What is the South Atlantic Anomaly? (via CobWeb/3.1 planetlab2.tamu.edu) (Site not responding. Last check: 2007-11-06)
		Above South America, about 200 - 300 kilometers off the coast of Brazil, and extending over much of South America, the nearby portion of the Van Allen Belt forms what is called the South Atlantic Anomaly.
		Astronauts are also affected by this region which is said to be the cause of peculiar 'shooting stars' seen in the visual field of astronauts.
		The data were collected by the South Atlantic Anomaly Detector (SAAD) aboard the ROSAT spacecraft.
	www.astronomycafe.net.cob-web.org:8888 /qadir/q525.html (290 words)

	South Atlantic Anomaly (SAA) (Site not responding. Last check: 2007-11-06)
		It requires higher shielding for the crew, particularly during spacewalks (EVAs), and is also of concern in the design of photovoltaic cells which are degraded faster by higher particle fluxes.
		A special case of trapped protons; the high proton fluxes result in a greater number of single event upsets (SEU's) and contribute to a large portion to total dose radiation.
		South Atlantic Anomaly Detector (SAAD) aboard the ROSAT spacecraft.
	www.ll.mit.edu /ST/sbv/saa.html (193 words)

	Astron. Astrophys. 343, 899-903 (1999) (Site not responding. Last check: 2007-11-06)
		This region is called the South Atlantic Anomaly and its boundary at an altitude of 500 km ranges from -90 and +40 degrees in geographic longitude and from -50 and 0 degrees in latitude.
		To map the influence of the SAA on the data we calculated the subsatellite position of the HST in geographic coordinates and indicated any positions for which the FGS count rate exceeded a given threshold (Fig.
		As it was not possible to model reliably the boundary to the SAA we had to remove all "bad" data obtained within a heuristically determined trapezoidal shaped area (Fig.
	aa.springer.de /papers/9343003/2300899/sc2.htm (1013 words)

	Volcanic & Air Quality SO2 Service (Site not responding. Last check: 2007-11-06)
		This region is named the South Atlantic Anomaly (SAA) and it covers a part of South America and the southern Atlantic Ocean: it lies roughly between latitudes 5 and 40 degrees South, and between longitudes 0 and 80 degrees West -- the precise strength, shape and size of the SAA varies with the seasons.
		This reduction of the signal-to-noise also affects the retrieval of SO2 slant columns: in the SAA region the variation in slant column values is much higher than elsewhere.
		The image is taken from the ROSAT page on the South Atlantic Anomaly.
	www.oma.be /BIRA-IASB/Molecules/SO2archive/info/?kind=saa (453 words)

	Chandra :: Resources :: Q&A: X-Ray Astronomy
		The South Atlantic Anomaly (SAA), is the name for an area that exhibits a local minimum in the magnetic field.
		The centre of the South Atlantic Anomaly is located at approximately latitude -30 and longitude -45.
		The increased radiation level in the SAA is characterized by an increased level of high energetic protons.
	chandra.harvard.edu /resources/faq/x-ray/x-ray-7.html?set=cxcpub (189 words)

	South Atlantic Anomaly (SAA) (Site not responding. Last check: 2007-11-06)
		Q.: I Need to complete a log of HST observations including the durations the telescope was in the south atlantic anomaly.
		A.: SAA 05 is the operation contour for NICMOS.
		This will print all the SAA passages to the screen, with the daynumber (and fraction of a day) of entry and exit, and the total time the spacecraft was inside contour 5 in minutes (last column).
	www.stsci.edu:8083 /hst/nicmos/faqs/SAA.faq (375 words)

	BIOMEDICAL RESULTS FROM SKYLAB - Visual Light Flash Observations on Skylab 4 (Sec.2,Ch.14)
		Because the trajectory periodically passed through the South Atlantic Anomaly, another study objective was the investigation of possible visual flashes during passage through this region.
		It is apparent that the flash rate in the South Atlantic Anomaly coincides remarkably well with the increased radiation levels detected by the Van Allen Belt Dosimeter.
		A greater particle flux in the trajectory through the South Atlantic Anomaly during the second observation period probably explains the increased number of flashes observed at that time, but there were also more flashes observed outside the anomaly during this second period where the cosmic particle environment should have been comparable.
	lsda.jsc.nasa.gov /books/skylab/Ch14.htm (1590 words)

	Earth’s Magnetic Pole or “Dipole”, Van Allen Belts, and Dangerous Radiation - Part II (Site not responding. Last check: 2007-11-06)
		At the north magnetic pole, the field is stronger, effectively keeping the inner proton belt farther away; at the south magnetic pole, the field is weaker, allowing the proton belt to come closer to the planet's surface.
		If the flashes increased when Mir entered the South Atlantic Anomaly, then protons would be revealed as the likely cause; if not, then heavy ions (which appear in equal amounts inside and outside the proton belt) would be indicated.
		The frequency of the flashes increased in the Anomaly, but only slightly, suggesting that protons alone are not responsible, but neither are heavy ions.
	www.red-ice.net /news/2005/10oct/poleshift2.html (1513 words)

	MODIS Website
		The anomaly occurred as Terra was passing over the South Atlantic Anomaly.
		The South Atlantic Anomaly is a dip, or weakening, in the Earth's magnetic field off the coast of Brazil that allows cosmic rays and charged particles to reach far down into the atmosphere.
		At the time of the anomaly, the external power supply feed current to MODIS (the processing of this telemetry point occurs external to the MODIS processor) dropped from ~1.5 Amps to 0.07 Amps suggesting that all MODIS components, with the exception of the power supply, powered down at that time.
	modis.gsfc.nasa.gov /news/individual.php?news_id=100031 (350 words)

	:: NASA Quest > Archives :: (Site not responding. Last check: 2007-11-06)
		I've chosen longitude 203 as the highest priority because there is an interesting bright spot in the south polar regions and because there are some differences between the visible and UV images.
		This is an area over the South Atlantic Ocean off the coast of South America where the Van Allen Radiation Belts dip closer to the atmosphere due to the shape of the magnetic field of the Earth.
		For any object in the sky, there is roughly 6-7 hours each day where you cannot observe the object because you are in the SAA when the object is not blocked by the earth.
	quest.arc.nasa.gov /hst/fjournals/buie-1.html (1324 words)

	The South Atlantic Anomaly
		The boundaries of the SAA vary with altitude above the Earth.
		At an altitude of 500 km, the SAA ranges between -90 and +40 in geographic longitude and -50 to 0 in geographic latitude.
		In this region, the extent of the SAA increases with increasing altitude.
	imagine.gsfc.nasa.gov /docs/ask_astro/answers/961004.html (220 words)

	Messages from Space - Trapped Radiation and the South Atlantic Anomaly: Geomagnetic Shielding
		The reason for this particular region of high concentrations of particles is complex - due to the tilt and offset of the magnetic dipole with respect to the geographic axis.
		This results in significant populations of particles located in a relatively close trapped radiation belt being brought down to low altitudes in an area over the South Atlantic ocean centred just to the East of Brazil.
		The SAA region is relatively stable and gives rise to significant proton fluxes for low altitude spacecraft.
	www.ph.surrey.ac.uk /satellites/main/tutorial2_3.html (249 words)

	Background level and variations in the GRBM and AC ratemeters (Site not responding. Last check: 2007-11-06)
		Since the satellite is in a low-earth, almost equatorial orbit it crosses the South Atlantic Geomagnetic Anomaly (SAGA) once per orbit, at a latitude that varies during the day from about +4 to -4 because of the Earth rotation.
		The data gaps are due to the satellite passage close to the South Atlantic Anomaly and therefore identify the single orbits.
		The pre-SAGA anomaly is huge in the previous orbit and evident in the orbit of GRB970228 itself.
	www.tesre.bo.cnr.it /~amati/tesi/node52.html (824 words)

	Satellite observations of electric fields in the South Atlantic anomaly region during the July 2000 magnetic storm
		Adjacent to the region of density dropout was a region of density enhancement with irregularities.
		The obtained results suggest that ionospheric density variation in the SAA region during intense magnetic disturbances might play an important role in the low-latitude ionosphere electrodynamics.
		Citation: Lin, C., and H. Yeh (2005), Satellite observations of electric fields in the South Atlantic anomaly region during the July 2000 magnetic storm, J.
	www.agu.org /pubs/crossref/2005/2003JA010215.shtml (513 words)

	Solar Protons
		In the Southern Hemisphere display there is a geographic region over South America and the South Atlantic where the sensor count rates are normally high and are plotted yellow.
		This region is the southern extension of the South Atlantic Anomaly where the energetic particle intensities are normally large and does not indicate the presence of solar protons.
		In addition to the enhanced intensities associated with the South Atlantic Anomaly, there are regions of enhanced sensor responses (appearing as swathes of yellow and red) that appear within regions closer to the poles in both the northern and southern hemisphere.
	www.sec.noaa.gov /tiger/SolarProtons.html (716 words)

	Closure of the UK Ionosondes at Chilton and Port Stanley
		It is the key dataset in the South American sector of the world.
		It is close to the South Atlantic Anomaly in the geomagnetic field, a region where energetic particles from the radiation belts are more likely to be deposited into the upper atmosphere.
		Unusual features, which are seen in Stanley data, may be related to its proximity to the South Atlantic Anomaly.
	www.southgatearc.org /news/march2006/uk_ionosondes.htm (1277 words)

	ESA - Observing the Earth - Focus on our magnetic planet
		Mission controllers cross their fingers whenever the Sun is stormy and their spacecraft have to fly over the South Atlantic.
		The South Atlantic Anomaly, as the experts call it, is one pressing reason why they are intensifying their exploration of the Earth’s magnetism.
		These satellites show that the danger zone for satellites over Brazil and the South Atlantic is growing wider towards the southern Indian Ocean.
	www.esa.int /esaEO/SEMV6K71Y3E_index_0.html (1244 words)

	Scientific Challenges of Magnetic Field Dynamics
		Intriguingly, this decay rate is characteristic of magnetic reversals, which paleomagnetic observations have shown occur on average, though with great variability, about once every half million years.
		Geographically, the recent dipole decay is largely due to changes in the field beneath the South Atlantic Ocean.
		This pattern is connected to the growth of the South Atlantic Magnetic Anomaly, an area in which the field at the Earth's surface is now about 35% weaker than would be expected.
	solidearth.jpl.nasa.gov /PAGES/mag02.html (320 words)

	9. Energetic particle radiation
		The so-called south Atlantic anomaly is the inner edge of the inner radiation belt encountered in low altitude orbits.
		The south Atlantic anomaly (see Section 9.2.1.1) produces an "island" of radiation and provides the only significant radiation encountered on low Earth orbits with altitudes below about 800km and inclinations below about 40°.
		The slow movement of the south Atlantic anomaly as a result of shifts in the geomagnetic field has been clearly observed and agrees with expectation.
	www.spenvis.oma.be /spenvis/ecss/ecss09/ecss09.html (7282 words)

	ATSR-1 Anomaly Log (Site not responding. Last check: 2007-11-06)
		Phase changed from 100.1 deg to 97.87 22 Jan 94 During investigation of an RA anomaly ATSR was switched down to STBY between:- 022:16:24:13 UTC and 022:21:16:52 UTC.
		The present belief is that this was an SEU as ERS-1 was in the South Atlantic Anomaly region at this time.
		The 12um was therefore commanded at approx 11:10 UTC to a fixed gain of 38 and offset of 0.46v for the rest of the reactivation.
	www.atsr.rl.ac.uk /satellite/logs/anomaly/archive/ers-1/index.shtml (4985 words)

	Quickie Questions - Extraordinary Earth - Gravity/Magnetism
		Yes, magnetic anomalies are dectable and have been detected by satellite.
		This area is referred to as the South Atlantic Anomaly (SAA).
		Anyhow, you'd think there would be a corresponding anomaly (area of intense radiation) in the Northern hemisphere...but because of the offset of the magnetic axis with respect to the rotational axis, there is no symmetry involved.
	www.windows.ucar.edu /tour/link=/kids_space/qearth_grav.html (1405 words)

	Artemis Project: Option for Staging in Geosynchronous Transfer Orbit
		We can go up to orbits as high as 360 nautical miles (depending on solar activity and other vagaries of Nature) and still stay out of the radiation zone, but any higher than that puts us into an environment which is inimical to life.
		This is a spot over the South Atlantic Ocean where the radiation belts tend to dip down as low as 100 nautical miles.
		The SAA accounts for the majority of radiation experienced by astronauts on the Space Shuttle.
	www.asi.org /adb/04/01/01/01/gto-staging.html (830 words)

	MISR status 02-Feb-2000
		The cameras, still operating with the cover closed, have detected the South Atlantic Anomaly.
		Many of these charged particles come from the Sun, and the South Atlantic Anomaly (SAA) and the Van Allen Radiation Belts are locations where variations in the Earth's magnetic field cause these particles to become "trapped".
		In addition to being the source of the occasional Terra High Gain Antenna resets, we have found a definitive correlation between passage through the South Atlantic Anomaly and the frequency of random "hits", or fleeting bright points, in the MISR "dark" images.
	www-misr.jpl.nasa.gov /news/2000/news020200.html (612 words)

	ESA - Living Planet Programme - Swarm - Focus on our magnetic planet
		Spacecraft faults are more common over the South Atlantic during times of high solar activity.
		This 'South Atlantic Anomaly' is illustrated here with a chart showing memory upsets to the veteran UoSAT-2 spacecraft.
		Scientists and satellite operators try to shield instruments and computers against the penetrating particles and limit the use of these types of systems while drifting through the South Atlantic Anomaly.
	www.esa.int /esaLP/SEMV6K71Y3E_LPswarm_1.html (270 words)

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