On July 6, 2016, engineers instructed NASA’s Solar Dynamics Observatory, or SDO, to roll 360 degrees on one axis. SDO dutifully performed the seven-hour maneuver, while producing some dizzying data: For this period of time, SDO images – taken every 12 seconds – appeared to show the sun spinning, as if stuck on a pinwheel. This video was taken by SDO’s Atmospheric Imaging Assembly instrument in extreme ultraviolet wavelengths that are typically invisible to our eyes, but was colorized here in gold for easy viewing.
Animation Credits: NASA’s Goddard Space Flight Center/SDO/Joy Ng. This maneuver happens twice a year to help SDO’s Helioseismic and Magnetic Imager, or HMI, instrument take precise measurements of the solar limb, the outer edge of the sun as seen by SDO. Were the sun perfectly spherical, this would be a much simpler task. But the solar surface is dynamic, leading to occasional distortions. This makes it hard for HMI to find the sun’s edge when it’s perfectly still. HMI’s biannual roll lets each part of the camera look at the entire perimeter of the sun, helping it map the sun’s shape much more precisely.
Solar Dynamics Observatory (SDO). Image Credits: NASA/GSFC HMI tracks variations in the solar limb over time to help us understand how the shape of the sun changes with respect to the solar cycle, the sun’s 11-year pattern of solar activity. The more we know about what drives this activity – activity that can include giant eruptions of solar material and radiation that can create hazards for satellites and astronauts – the better we may someday predict its onset.
6 Temmuz 2016 günü NASA'nın SDO uydusu, bir ekseni üzerinde 360 derecelik bir tur attı. Bu tur atma süresi 7 saatlik bir zaman aralığında gerçekleşti. SDO uydusu bu hareketini gerçekleştirdiğinde ise haliyle Güneş de kendi etrafında dönüyormuş gibi göründü. Görüntüleme işlemi, SDO'nun Atmosferik Görüntüleme Montaj enstrümanı ile gözümüzün duyarlı olmadığı dalgaboyu aralığı olan aşırı moröte dalgaboyunda çekilmiştir ve kolay görüş sağlaması açısından renklendirilmesi altın renginde yapılmıştır.
Bu manevra hareketini SDO uydusu yılda 2 kez gerçekleştirmektedir. Manevranın sebebi ise SDO'nun yaptığı hassas ölçümlerin kalibrasyonunu sağlamak içindir. Eğer Güneş farklı dalgaboylarında da mükemmel bir daire şeklinde gözükseydi, bu kalibrasyona gerek kalmayacaktı. Ancak Güneş'in yüzeyi dinamiktir ve sıklıkla dairesellikten bozulmaktadır. Bu da SDO'nun bir enstrümanı olan HMI'ın (Heliosismik Manyetik Görüntüleyici'nin) Güneş'in sınırlarını belirlemesini zorlaştırıyor. Yapılan bu manevra hareketi ise istenen kalibrasyon ayarını sağlamış oluyor.
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SDO does such a somersault twice a year to help its Helioseismic and Magnetic Imager (HMI) instrument take good measurements of the sun’s outer edge.
“Were the sun perfectly spherical, this would be a much simpler task. But the solar surface is dynamic, leading to occasional distortions,” NASA officials wrote. “This makes it hard for HMI to find the sun’s edge when it’s perfectly still. HMI’s biannual roll lets each part of the camera look at the entire perimeter of the sun, helping it map the sun’s shape much more precisely.”
The $800 million SDO mission launched in February 2010 to help scientists better understand what causes variation in solar activity, among other things. The satellite’s observations could aid efforts to predict the eruption of big solar storms, which can damage power grids on Earth and pose dangers to astronauts in space, NASA officials said.
SDO has captured a number of stunning images during its six years in space. Just last week, for example, the satellite snapped a series of photos showing giant, dark “coronal holes” on the sun. In some of these images, the sun appeared to be making a nervous or anxious face, thanks to the fortuitous alignment of various solar features (and the human brain’s tendency to find meaning and patterns in random data).
The SDO has been studying the sun since 2010, and it’s the most advanced telescope ever to do so. The SDO completes this backflip through space twice a year.
The maneuver helps tune up the SDO’s Helioseismic and Magnetic Imager (HMI), an instrument that takes precise measurements of the solar limb (the outer edge of the sun).
Because the surface of the sun is not perfectly spherical, but dynamic and unpredictable, doing this spin and imaging the sun’s perimeter helps re-calibrate the instrument, giving it a better view and allowing it to make more precise maps.
By mapping the solar limb, scientists can understand how the shape of the sun changes with respect to the solar cycle, the sun’s 11-year pattern of solar activity. According to NASA, this allows them to make better predictions about the onset of giant eruptions solar material and radiation that can be a threat to satellites and astronauts.