A New View of August's Total Solar Eclipse

NASA's Total and Spectral solar Irradiance Sensor, or TSIS-1, is a mission to measure the sun's energy input to Earth. Various satellites have captured a continuous record of this solar energy input since 1978. TSIS-1 sensors advance previous measurements, enabling scientists to study the sun's natural influence on Earth's ozone layer, atmospheric circulation, clouds, and ecosystems. These observations are essential for a scientific understanding of the effects of solar variability on the Earth system. NASA Goddard Space Flight Center manages the project. The University of Colorado's Laboratory for Atmospheric and Space Physics (LASP) built both instruments and provides mission operations. The International Space Station carries TSIS-1. TSIS-1 makes two key measurements: total solar irradiance, or TSI, the sun's total energy input into Earth, and solar spectral irradiance (SSI), the distribution of the sun's energy input across ultraviolet, visible, and infrared wavelengths of light. TSI measurements are needed to quantify the solar variations in the total amount of energy input to the Earth. SSI measurements are also vital because different wavelengths of light are absorbed by different parts of the atmosphere. NASA's Total and Spectral solar Irradiance Sensor, or TSIS-1, will measure the total amount of solar energy input to Earth as well as the distribution of The Sun's energy input across a wide range of wavelengths. In this animation we see how various wavelengths of light are partially reflected into space at different places in the column of atmosphere above the ground. The sensors of TSIS-1, the Total Irradiance Monitor (TIM) and the Spectral Irradiance Monitor (SIM), are significantly improved versions of sensors included on NASA’s Solar Radiation and Climate Experiment (SORCE) mission launched in 2003. Both sensors are more accurate and more precise than their predecessors. Earth's energy budget is a metaphor for the delicate equilibrium between energy received from the Sun versus energy radiated back out in to space. Research into precise details of Earth's energy budget is vital for understanding how the planet's climate may be changing, as well as variabilities in solar energy output. NASA’s (The Clouds and the Earth's Radiant Energy System) CERES and NASA's Total and Spectral solar Irradiance Sensor (TSIS-1), missions play key roles in our continued understanding of Earth’s Energy Budget.NASA’s TSIS helps scientists keep a close watch on the sun’s energy input to Earth. Various satellites have captured a continuous record of this solar energy input since 1978. TSIS-1 sensors advance previous measurements, enabling scientists to study the sun's natural influence on Earth's ozone layer, atmospheric circulation, clouds, and ecosystems. These observations are essential for a scientific understanding of the effects of solar variability on the Earth system. TSIS-1 makes two key measurements: total solar irradiance, or TSI, the sun's total energy input into Earth, and solar spectral irradiance (SSI), the distribution of the sun's energy input across ultraviolet, visible, and infrared wavelengths of light. TSI measurements are needed to quantify the solar variations in the total amount of energy input to the Earth. SSI measurements are also vital because different wavelengths of light are absorbed by different parts of the atmosphere.For more than 20 years, NASA Langley's CERES (System) instruments have measured the solar energy reflected by Earth, the heat the planet emits, and the role of clouds in that process. The final CERES Flight Model, CERES FM6 launched aboard NOAA’s JPSS-1 in Fall 2017. CERES FM6 contributes to an already extensive CERES dataset that helps scientists validate models that calculate the effect of clouds on planetary heating and cooling. The same data can also be helpful for improving near-term, seasonal forecasts influenced by weather events such as El Niño and La Niña. El Niño and La Niña are weather patterns that develop when ocean temperatures fluctuate between warm and cool phases in the Equatorial Pacific Ocean. Built by Northrop Grumman and managed by Langley, CERES FM6 joins five other CERES instruments orbiting the planet on three other satellites.NASA Goddard Space Flight Center manages the TSIS-1 project. The University of Colorado's Laboratory for Atmospheric and Space Physics (LASP) built both instruments and provides mission operations. The International Space Station carries TSIS-1.Earth's energy budget is a metaphor for the delicate equilibrium between energy received from the Sun versus energy radiated back out in to space. Research into precise details of Earth's energy budget is vital for understanding how the planet's climate may be changing, as well as variabilities in solar energy output. NASA’s (The Clouds and the Earth's Radiant Energy System) CERES and NASA's Total and Spectral solar Irradiance Sensor (TSIS-1), missions play key roles in our continued understanding of Earth’s Energy Budget.NASA’s TSIS helps scientists keep a close watch on the sun’s energy input to Earth. Various satellites have captured a continuous record of this solar energy input since 1978. TSIS-1 sensors advance previous measurements, enabling scientists to study the sun's natural influence on Earth's ozone layer, atmospheric circulation, clouds, and ecosystems. These observations are essential for a scientific understanding of the effects of solar variability on the Earth system. TSIS-1 makes two key measurements: total solar irradiance, or TSI, the sun's total energy input into Earth, and solar spectral irradiance (SSI), the distribution of the sun's energy input across ultraviolet, visible, and infrared wavelengths of light. TSI measurements are needed to quantify the solar variations in the total amount of energy input to the Earth. SSI measurements are also vital because different wavelengths of light are absorbed by different parts of the atmosphere.For more than 20 years, NASA Langley's CERES (System) instruments have measured the solar energy reflected by Earth, the heat the planet emits, and the role of clouds in that process. The final CERES Flight Model, CERES FM6 launched aboard NOAA’s JPSS-1 in Fall 2017. CERES FM6 contributes to an already extensive CERES dataset that helps scientists validate models that calculate the effect of clouds on planetary heating and cooling. The same data can also be helpful for improving near-term, seasonal forecasts influenced by weather events such as El Niño and La Niña. El Niño and La Niña are weather patterns that develop when ocean temperatures fluctuate between warm and cool phases in the Equatorial Pacific Ocean. Built by Northrop Grumman and managed by Langley, CERES FM6 joins five other CERES instruments orbiting the planet on three other satellites.NASA Goddard Space Flight Center manages the TSIS-1 project. The University of Colorado's Laboratory for Atmospheric and Space Physics (LASP) built both instruments and provides mission operations. The International Space Station carries TSIS-1. Related pages

A view of the Moon's shadow during the August 21, 2017 eclipse from both the night and day sides of the Earth. This visualization combines the views from several previous visualizations (#4390, #4321, and #4314) to create a continuous camera flight from the night side of the Earth to the day side, showing the relationship of the Earth, Moon, and Sun during the August 21, 2017 eclipse. It shows the direction of the Moon's motion and the Earth's rotation, the complete path of the umbra from the moment it touches down on the Earth until the moment it departs, and the true scale of the Earth-Moon system. For More InformationSee [eclipse2017.nasa.gov](eclipse2017.nasa.gov) Related pages

The August 21, 2017 total solar eclipse as seen from a satellite in orbit around L1, a point about 1.5 million kilometers from Earth in the direction of the Sun. A number of satellites will be watching the August 21, 2017 total solar eclipse from space. One of them, the Deep Space Climate Observatory (DSCOVR) will see the eclipse from its orbit around L1, the Lagrange point located about 1.5 million kilometers from Earth along the Earth-Sun line. From this vantage point, DSCOVR's EPIC camera continuously images the full sunlit disk of the Earth.This animation simulates the view that EPIC will have of the 2017 eclipse. The shadow size and opacity are based on the eclipse obscuration, the fraction of the Sun's disk covered by the Moon. The bright spot near the equator is the reflection of the Sun on the water. The red streak shows the path of totality, the locations on the Earth where observers will see the Sun completely covered by the Moon.EPIC will see both the Moon's shadow and the Sun's reflection because DSCOVR's orbit takes it several degrees off both the Sun-Earth line and the Sun-Moon line. For the same reason, the Moon will not be in the frame. The animation places the virtual camera in a plausible position for DSCOVR. The actual position of the spacecraft at the time of the eclipse will be affected by adjustments to its orbit that may be made in the coming months.EPIC has already captured the total solar eclipse of March, 2016. Related pages

A view of the United States during the total solar eclipse of August 21, 2017, showing the umbra (black oval), penumbra (concentric shaded ovals), and path of totality (red) through or very near several major cities. A view of the United States during the total solar eclipse of August 21, 2017, showing the umbra (black oval), penumbra (concentric shaded ovals), and path of totality (red). This version omits the city and state names and the statistics display. A view of the United States during the total solar eclipse of August 21, 2017, showing the umbra (black oval), penumbra (concentric shaded ovals), and path of totality (red). This version includes images of the Sun showing its appearance in a number of locations, each oriented to the local horizon. On Monday, August 21, 2017, the Moon will pass in front of the Sun, casting its shadow across all of North America. This will be the first total solar eclipse visible in the contiguous United States in 38 years.The Moon's shadow can be divided into areas called the umbra and the penumbra. Within the penumbra, the Sun is only partially blocked, and observers experience a partial eclipse. The much smaller umbra lies at the very center of the shadow cone, and anyone there sees the Moon entirely cover the Sun in a total solar eclipse.In the animation, the umbra is the small black oval. The red streak behind this oval is the path of totality. Anyone within this path will see a total eclipse when the umbra passes over them. The much larger shaded bullseye pattern represents the penumbra. Steps in the shading denote different percentages of Sun coverage (eclipse magnitude), at levels of 90%, 75%, 50% and 25%. The yellow and orange contours map the path of the penumbra. The outermost yellow contour is the edge of the penumbra path. Outside this limit, no part of the Sun is covered by the Moon.The numbers in the lower left corner give the latitude and longitude of the center of the umbra as it moves eastward, along with the altitude of the Sun above the horizon at that point. Also shown is the duration of totality: for anyone standing at the center point, this is how long the total solar eclipse will last. Note that the duration varies from just 2 minutes on the West Coast to 2 minutes 40 seconds east of the Mississippi River.About AccuracyYou might think that calculating the circumstances of an eclipse would be, if not easy, then at least precise. If you do the math correctly, you’d expect to get exactly the same answers as everyone else. But the universe is more subtle than that. The Earth is neither smooth nor perfectly spherical, nor does it rotate at a perfectly constant, predictable speed. The Moon isn’t smooth, either, which means that the shadow it casts isn’t a simple circle. And our knowledge of the size of the Sun is uncertain by a factor of about 0.2%, enough to affect the duration of totality by several seconds.Everyone who performs these calculations will make certain choices to simplify the math or to precisely define an imperfectly known number. The choices often depend on the goals and the computing resources of the calculator, and as you'd expect, the results will differ slightly. You can get quite good results with a relatively simple approach, but it sometimes takes an enormous effort to get only slightly better answers.The following table lists some of the constants and data used for this animation.Earth radius6378.137 kmEarth flattening1 / 298.257 (the WGS 84 ellipsoid)Moon radius1737.4 km (k = 0.2723993)Sun radius696,000 km (959.634 arcsec at 1 AU)EphemerisDE 421Earth orientationearth_070425_370426_predict.bpc (ΔT corrected)Delta UTC68.184 seconds (TT – TAI + 36 leap seconds)A number of sources explain Bessel’s method of solar eclipse calculation, including chapter 9 of Astronomy on the Personal Computer by Oliver Montenbruck and Thomas Pflager and the eclipses chapter of The Explanatory Supplement to the Astronomical Almanac. The method was adapted to the routines available in NAIF's SPICE software library.The value for the radius of the Moon is slightly larger than the one used by Fred Espenak and slightly smaller than the one used by the Astronomical Almanac. The Sun radius is the one used most often, but see figure 1 in M. Emilio et al., Measuring the Solar Radius from Space during the 2003 and 2006 Mercury Transits for a sense of the uncertainty in this number.Both the elevations of locations on the Earth and the irregular limb of the Moon were ignored. The resulting small errors mostly affect the totality duration calculation, but they tend to cancel out—elevations above sea level slightly lengthen totality, while valleys along the lunar limb slightly shorten it. The effect on the rendered images is negligible (smaller than a pixel).Another minor complication that's ignored here is the difference between the Moon's center of mass (the position reported in the ephemeris) and its center of figure (the center of the disk as seen from Earth). These two centers don't exactly coincide because the Moon's mass isn't distributed evenly, but the difference is quite small, about 0.5 kilometers. Related pages