Solar storms and communications problems
A pair of scorching explosions on the Sun’s surface is sparking the biggest radiation and geomagnetic storm the Earth has experienced in five years, space weather experts said Wednesday (7 March 2012).
The full brunt of the storm hit Earth early Thursday (US time) and last through Friday. These storms potentially disrupting power grids, GPS systems, satellites, and forcing airplanes to change their routes around the polar regions.
New information by the Hermanus Magnetic Observatory suggests more solar flares can be expected in the coming days and months.
Intelsat provided the following explanation on the impact of solar storms on satellite communications.
Every once in a great while, a report surfaces about a communications satellite which has been partially or completed disabled as the result of a sudden knockout blow delivered by the sun. The first thing to keep in mind is that these things do happen. The second thing to keep in mind is that they happen very rarely.
Out of the hundreds of satellites successfully launched over the past 5 decades, only a mere handful have succumbed to any form of so-called “solar weather” which satellites are designed and built to withstand.
The study of solar weather is ongoing, and, operators are constantly monitoring the sun’s activities and improving their ability to respond to the impact of solar events.
Satellite operators focus on four elements of solar weather that can affect satellite communications: solar wind, coronal holes, coronal mass ejections (CME’s) and solar flares.
The solar wind is constant but varies in intensity, while the other three solar phenomena come and go. The goal in terms of space infrastructure has been to identify and effectively counter the sun’s link to so-called single-event upsets (SEUs) which happen whenever the performance of one or more spacecraft components abruptly changes without warning.
SEU’s are not apt to be caused by the solar wind itself which is relatively low in energy and seldom penetrates the outer layers or protective skin of a spacecraft. Instead, solar flares, CME’s and coronal holes—their powerful reach often extends beyond the orbit of Mars—can be disruptive.
When solar storms erupt, they can bombard a satellite with highly – charged particles and increase the amount of charging on a spacecraft’s surfaces. When CMEs occur in the Sun’s corona or outer atmosphere, for example, a huge amount of plasma and magnetic energy is emitted.
The huge and quite visible explosions on the sun are known as solar flares – the most extreme form of solar storms. They discharge large amounts of radiation and a highly charged cloud of protons in particular. X-ray observations provide an important early warning for astronauts in orbit, while slower – moving CMEs often trail behind subject to the sun’s magnetic field.
CME’s follow a curving path as they leave the sun. Because of this, the CME may not actually impact satellites at all. When a CME impacts the earth, the earth’s magnetic field compresses on one side and stretches out on the other. This can result in dazzling auroral displays over the poles, for example. Fortunately, most CMEs last only 3 days or less.
Thankfully, the sun is fairly predictable in this regard, and sunspot activity takes place in 11-year cycles with the maximum or most intense stage lasting about 2 years, and the least intense stage lasting about 5 years.
Since 2006, we have experienced the least active period of major solar weather events in recent history. In other words, the sun has been very quiet lately.
Coping with electrostatic discharges from the sun that can potentially disrupt satellite services are part of the everyday reality of the satellite world. Losing solar power is not a serious concern whereas losing total control and command of a satellite as the result of solar weather is the most severe effect.
Solar panels on satellites are the most affected components, and normal erosion rates for solar panels are usually 0.3% to 1% per year.
A solar storm can reduce solar panel performance by 3% to 5% in a day, but since this phenomenon is well understood, spacecraft manufacturers increase the tolerances by design, and attach larger than needed solar panels to satellite in order to allow for losses during the anticipated solar storms.
The body of a communications satellite, which contains vital control and communication components, is specially adapted using special materials as well as active and passive measures so as to be highly resilient. A so-called “Faraday Cage” protects the satellite’s internal equipment from external electrical charges. High – energy particles discharged by the sun rapidly lose strength as they pass through the multiple layers of a spacecraft’s body or bus as well. There, they encounter a series of specially designed circuit dividers, individual compartments, and other unique structural elements that act as barriers.
The disruptive nature of solar weather impacts far more than satellite operations, and adversely affects terrestrial power and communications grids.
For these and other reasons, a considerable amount of manpower and money has been devoted to monitoring the sun’s activity, and more research into solar phenomena in general is planned in the future. Among other things, one benefit has been a steady improvement in our ability to rapidly detect and track these solar events using powerful observation and detection systems both on the ground and in space.
NASA, the U.S. National Oceanic and Atmospheric Administration and the U.S. Department of Defense oversee much of this activity. For example, besides NASA’s twin Solar Terrestrial Relations Observatory (STEREO) spacecraft, the Air Force Research Laboratory launched the Communication/Navigation Outage Forecasting System (C/NOFS) satellite several years ago to forecast the presence of ionospheric irregularities caused by the sun that adversely impact communication and navigation systems. Space and ground-based measurements have been taken to help determine how the plasma irregularities affect the propagation of electro-magnetic waves, among other things.
Satellites depend upon the sun, and satellite operators have steadily developed tools and techniques which allow them to ensure the operational integrity of all satellites in the face of all forms of solar weather. That weather changes over time, while satellite performance and design gets better and better. Thanks to proper planning, design and execution, the survival rate of satellites is quite remarkable.
Satellite
Tobias Nassif, Intelsat’s Vice President, Satellite Operations & Engineering, talks about solar weather and the company’s ongoing efforts to build a better spacecraft.
What are some of the potential dangers of solar weather on satellites?
The environment in space can be very harsh, especially during certain peaks in the 11- year sunspot cycle or during solar flares that emit electromagnetic radiation at high frequencies and the electrons, protons and ions they sometimes sends through space. That type of space weather can have some severe consequences on satellites and aircraft, as well as terrestrial systems such as the power grid.
So what steps does Intelsat take to prepare its satellites for that environment?
We have always designed our satellites to handle the possibility of severe solar weather and the harsh space environment. They are engineered with those criteria in mind. As an industry, we work in close cooperation to share knowledge about the space environment and its weather patterns, incorporating what is learned as part of an ongoing effort to build better spacecraft.
How does the current solar cycle compare to past events?
According to the latest NASA reports, Solar Cycle 24 will peak in 2013 with a below-average number of sunspot activity.
The Naval Research Laboratory issued a press release citing solar storm activity as the likely cause of the Galaxy 15 anomaly? Were they correct? On what did they base that conclusion?
As far as we know, there is no hard evidence that solar storm activity was the cause of the G-15 anomaly. It is certainly one of the possible causes, but there is nothing conclusive. Since the Naval Research Laboratory did not have access to any of our post-anomaly data, we do not know the evidence they used to reach their conclusion.
What is the process normally used to investigate an anomaly?
We rely on a scientific process using fault tree analysis. That process has been refined through the years to look at all possible causes, both what is likely and unlikely. We essentially test for both to follow through on every branch of the fault tree. It takes more time but we want to get it right. All too often, expediency leads to the easy and wrong conclusion.
So how did the May 2010 story about the solar storm knocking out G-15 get its start?
A trade magazine wrote an article about the possibility of solar weather as the root cause of the G-15 anomaly shortly after the event occurred. It was based on pure speculation, but it sounded plausible and made for good headlines.
Has this incident changed the way we prepare our satellites for space?
This is an evolving science. If our investigations reveal something we can do differently, we will certainly do it. However, these are state-of-the-art spacecraft built to withstand the space environment, and they have by and large served the industry well through the years. They have a very high rate of mission success.
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