- 3615 - SOLAR STORMS - we are loosing satellites? There is a lot of complex physics that we still don't fully understand going on in the upper layers of the atmosphere where it interacts with the solar wind. This interaction causes an upwelling of the atmosphere. That means that the denser air shifts upwards to higher altitudes.
--------------------- 3615 - SOLAR STORMS - we are loosing satellites?
- On February 4, 2022, SpaceX launched 49 satellites as part of Elon Musk's Starlink internet project, most of which burned up in the atmosphere days later. The cause of this more than $50 million failure was a geomagnetic storm caused by the sun.
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- “Geomagnetic storms” occur when space weather hits and interacts with Earth. “Space weather” is caused by fluctuations within the sun that blast electrons, protons and other particles into space.
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- When “space weather’ reaches Earth, it triggers many complicated processes that can cause a lot of trouble for anything in orbit. The sun is always releasing a steady amount of charged particles into space. This is called the “solar wind“.
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- Solar wind also carries with it the solar magnetic field. Sometimes, localized fluctuations on the sun will hurl unusually strong bursts of particles in a particular direction. If Earth happens to be in the path of the enhanced solar wind generated by one of these events and gets hit, we get a “geomagnetic storm“.
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- The two most common causes of geomagnetic storms are “coronal mass ejections” are explosions of plasma from the surface of the sun and solar wind that escapes through coronal holes, which are spots of low density in the sun's outer atmosphere.
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- The speed at which the ejected plasma or solar wind arrives at Earth is an important factor. The faster the speed, the stronger the geomagnetic storm. Normally, solar wind travels at roughly 900,000 mph. But strong solar events can release winds up to five times as fast, 4,900,000 mph.
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- The strongest geomagnetic storm on record was caused by a coronal mass ejection in September 1859. When the mass of particles hit Earth, they caused electrical surges in telegraph lines that shocked operators and, in some extreme cases, actually set telegraph instruments on fire. Research suggests that if a geomagnetic storm of this magnitude hit Earth today, it would cause roughly $2 trillion in damage.
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- The Earth's magnetic field acts as a shield that absorbs most solar wind. Emissions from the sun, including the solar wind, would be incredibly dangerous to any life form unlucky enough to be directly exposed to them. Thankfully, Earth's magnetic field does a lot to protect humanity.
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- The first thing solar wind hits as it approaches Earth is the magnetosphere. This region surrounding the Earth's atmosphere is filled with plasma made of electrons and ions. It's dominated by the planet's strong magnetic field. When solar wind hits the magnetosphere, it transfers mass, energy and momentum into this layer.
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- The magnetosphere can absorb most of the energy from the everyday level of solar wind. But during strong storms, it can get overloaded and transfer excess energy to the upper layers of Earth's atmosphere near the poles. This redirection of energy to the poles is what results in fantastic aurora events, northern lights, but it also causes changes in the upper atmosphere that can harm space assets.
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- The different layers of Earth's atmosphere are all affected by solar storms differently.
There a few different ways geomagnetic storms threaten orbiting satellites that serve people on the ground daily. When the atmosphere absorbs energy from magnetic storms, it heats up and expands upward. This expansion significantly increases the density of the thermosphere, the layer of the atmosphere that extends from about 50 miles to roughly 600 miles above the surface of Earth. Higher density means more drag, which can be a problem for satellites.
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- This situation is exactly what led to the demise of the the SpaceX Starlink satellites in February, 2022. Starlink satellites are dropped off by Falcon 9 rockets into a low-altitude orbit, typically somewhere between 60 and 120 miles above Earth's surface. The satellites then use onboard engines to slowly overcome the force of drag and raise themselves to their final altitude of approximately 350 miles.
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- The latest batch of Starlink satellites encountered this geomagnetic storm while still in very low-Earth orbit. Their engines could not overcome the significantly increased drag, and the satellites began slowly falling toward Earth and eventually burned up in the atmosphere.
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- Drag is just one hazard that space weather poses to space-based assets. The significant increase in high-energy electrons within the magnetosphere during strong geomagnetic storms means more electrons will penetrate the shielding on a spacecraft and accumulate within its electronics. This buildup of electrons can discharge in what is basically a small lightning strike and damage electronics.
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- Penetrating radiation or charged particles in the magnetosphere, even during mild geomagnetic storms, can also alter the output signal from electronic devices. This phenomenon can cause errors in any part of a spacecraft's electronics system, and if the error occurs in something critical, the entire satellite can fail.
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- Geomagnetic storms can disrupt the ability of satellites to communicate with Earth using radio waves. Many communications technologies, like GPS, for example, rely on radio waves. The atmosphere always distorts radio waves by some amount, so engineers correct for this distortion when building communication systems.
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- But, during geomagnetic storms, changes in the ionosphere, the charged equivalent of the thermosphere that spans roughly the same altitude range, will change how radio waves travel through it. The calibrations in place for a quiet atmosphere become wrong during geomagnetic storms.
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- This makes it difficult to lock onto GPS signals and can throw off the positioning by a few meters. For many industries, aviation, maritime, robotics, transportation, farming, military and others, GPS positioning errors of a few meters are simply not tenable. Autonomous driving systems will require accurate positioning as well.
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- Some of the risks can be minimized by shielding electronics from radiation, or developing materials that are more resistant to radiation. But there is only so much shielding that can be done in the face of a powerful geomagnetic storm.
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- The ability to accurately forecast storms would make it possible to preemptively safeguard satellites and other assets to a certain extent by shutting down sensitive electronics or reorienting the satellites to be better protected.
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- But while the modeling and forecasting of geomagnetic storms has significantly improved over the past few years, the projections are often wrong. The National Oceanic and Atmospheric Administration had warned that, following a coronal mass ejection, a geomagnetic storm was "likely" to occur the day before or the day of the February Starlink launch. The mission went ahead anyway.
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- In late 2021, operators of the European Space Agency's (ESA) “Swarm constellation” noticed something worrying: The satellites, which measure the magnetic field around Earth, started sinking toward the atmosphere at an unusually fast rate, up to 10 times faster than before.
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- The change coincided with the onset of the new solar cycle, and experts think it might be the beginning of some difficult years for spacecraft orbiting our planet. In the last five, six years, the satellites were sinking about 1.5 miles a year, But, since December, 2021, they have been virtually diving. The sink rate between December and April has been 12 miles per year.
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- Satellites orbiting close to Earth always face the drag of the residual atmosphere, which gradually slows the spacecraft and eventually makes them fall back to the planet. They usually don't survive this re-entry and burn up in the atmosphere. This atmospheric drag forces the International Space Station's controllers to perform regular "reboost" maneuvers to maintain the station's orbit of 250 miles above Earth.
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- This drag also helps clean up the near-Earth environment from space junk. Scientists know that the intensity of this drag depends on solar activity, the amount of solar wind spewed by the sun, which varies depending on the 11-year solar cycle.
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- The last cycle, which officially ended in December 2019, was rather sleepy, with a below-average number of monthly sunspots and a prolonged minimum of barely any activity. But since last fall, the star has been waking up, spewing more and more solar wind and generating sunspots, solar flares and coronal mass ejections at a growing rate.
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- The Swarm constellation, launched in 2013, consists of three satellites, two of which orbit Earth at an altitude of 270 miles, about 20 miles above the International Space Station. The third Swarm satellite circles the planet somewhat higher about 320 miles above ground. The two lower-orbiting spacecraft were hit more by the sun's acting out than the higher satellite was.
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- The situation with the lower two got so precarious that by May, operators had to start raising the satellites' altitude using onboard propulsion to save them. In February, SpaceX lost 40 brand-new Starlink satellites that were hit by a solar storm just after launch.
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- The sun unleashed a major X1.1 class solar flare from an active sunspot cluster on its eastern limb on April 17, 2022. In such storms, satellites suddenly drop to lower altitudes. The lower the orbit of the satellites when the solar storm hits, the higher the risk of the spacecraft not being able to recover, leaving operators helplessly watching as the craft fall to their demise in the atmosphere.
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- Starlink satellites have operational orbits of 340 miles , which is above the most at risk region. However, after launch, Falcon 9 rockets deposit the satellite batches very low, only about 217 miles above Earth. SpaceX then raises the satellites' orbits using onboard propulsion units.
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- SpaceX says that approach has advantages, as any satellite that experiences technical problems after launch would quickly fall back to Earth and not turn into space debris. However, the increasing and unpredictable behavior of the sun makes those satellites vulnerable to mishaps.
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- By coincidence (or beginner's luck), the onset of the new space revolution came during that sleepy solar cycle. These new operators are now facing their first solar maximum. The sun's activity in the past year turned out to be much more intense than solar weather forecasters predicted, with more sunspots, more coronal mass ejections and more solar wind hitting our planet.
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- The “solar cycle 25” that we are entering now is currently increasing very steeply. While the harsh solar activity is bad news for satellite operators, who will see the lifetimes of their missions shortened. Even satellites with onboard propulsion will run out of fuel much faster because of the need for frequent altitude boosts, the situation will have some welcome purifying effects on the space around Earth.
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- In addition to becoming populated with hundreds of new satellites over the past decade, this region of space is cluttered with a worrying amount of space debris, old satellites, spent rocket stages and collision fragments.
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- The omnipresent junk hurtling around the planet threatens the safety of satellite services, forcing operators to conduct frequent avoidance maneuvers. The positive effect can already be observed, as fragments produced by the November, 2021, Russian anti-satellite missile test are now coming down much faster than before.
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- A greater flux of debris means the need for even more frequent fuel-burning avoidance maneuvers and a temporarily increased risk of collisions, which could potentially generate more dangerous fragments.
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- SpaceX is currently raising the orbit of the two low-orbiting Swarm satellites by 28 miles . The satellites might require even more adjustments later this year, 2022. If they still have fuel to get through another solar cycle.
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June 30, 2022 SOLAR STORMS - we are loosing satellites? 3615
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