Agulhamagnetica - AGULHA MAGNÉTICA
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Magnetic compass adjustaments.
Adjustment of the compass is the arranging of magnetic and soft iron correctors about the binnacle so that their effects are equal and opposite to the effects of the magnetic material in the ship, thus reducing the deviations and eliminating the sectors of sluggishness and unsteadiness.
Celestial Mechanics Around the Solar System During December 2019
The dance of planets, moons and spacecraft around the solar system creates a host of rare alignments in late December 2019. Here’s what’s coming up.
Dec. 21: Winter solstice in the Northern Hemisphere
Dec. 21 is the 2019 winter solstice for the Northern Hemisphere. A solstice marks the point at which Earth’s tilt is at the greatest angle to the plane of its orbit, also the point where half of the planet is receiving the longest stretch of daylight and the other the least. There are two solstices a year, in June and December: the summer and winter solstices, respectively, in the Northern Hemisphere.
The winter solstice is the longest night of the year, when that hemisphere of Earth is tilted farthest from the Sun and receives the fewest hours of sunlight in a given year. Starting Dec. 21, the days will get progressively longer until the June solstice for those in the Northern Hemisphere, and vice versa for the Southern Hemisphere.
Dec. 26: Annular solar eclipse visible in Asia
On Dec. 26, an annular solar eclipse will be visible in parts of Asia. During an annular eclipse, the Moon’s apparent size is too small to completely cover the face of the Sun, creating a “ring of fire” around the Moon’s edge during the eclipse.
Credit: Dale Cruikshank
Solar eclipses happen when the Moon lines up just right with the Sun and Earth. Though the Moon orbits Earth about once a month, the tilt in its orbit means that it’s relatively rare for the Moon to pass right in line between the Sun and Earth — and those are the conditions that create an eclipse. Depending on the alignment, the Moon can create a partial, total or annular solar eclipse.
On Dec. 26, the Moon will be near perigee, the point in its orbit when it’s farthest from Earth. That means its apparent size from Earth is just a bit smaller — and that difference means that it won’t completely cover the Sun during the Dec. 26 eclipse. Instead, a ring of the bright solar surface will be visible around the Moon during the point of greatest eclipse. This is called an annular eclipse.
It is never safe to look directly at an annular solar eclipse, because part of the Sun is always visible. If you’re in the path of the annular eclipse, be sure to use solar viewing glasses (not sunglasses) or another safe viewing method to watch the eclipse.
Dec. 26: Parker Solar Probe flies by Venus
After the eclipse, more than 100 million miles away from Earth, Parker Solar Probe will pull off a celestial maneuver of its own. On Dec. 26, the spacecraft will perform the second Venus gravity assist of the mission to tighten its orbit around the Sun.
During the seven gravity assists throughout the mission, Parker Solar Probe takes advantage of Venus’s gravity to slow down just the right amount at just the right time. Losing some of its energy allows the spacecraft to be drawn closer by the Sun’s gravity: It will fly by the Sun’s surface at just 11.6 million miles during its next solar flyby on Jan. 29, 2020. During this flyby, Parker Solar Probe will break its own record for closest-ever spacecraft to the Sun and will gather new data to build on the science already being shared from the mission.
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Extreme Science: Launching Sounding Rockets from The Arctic
This winter, our scientists and engineers traveled to the world’s northernmost civilian town to launch rockets equipped with cutting-edge scientific instruments.
This is the beginning of a 14-month-long campaign to study a particular region of Earth’s magnetic field — which means launching near the poles. What’s it like to launch a science rocket in these extreme conditions?
Our planet is protected by a natural magnetic field that deflects most of the particles that flow out from the Sun — the solar wind — away from our atmosphere. But near the north and south poles, two oddities in Earth’s magnetic field funnel these solar particles directly into our atmosphere. These regions are the polar cusps, and it turns out they’re the ideal spot for studying how our atmosphere interacts with space.
The scientists of the Grand Challenge Initiative — Cusp are using sounding rockets to do their research. Sounding rockets are suborbital rockets that launch to a few hundred miles in altitude, spending a few minutes in space before falling back to Earth. That means sounding rockets can carry sensitive instruments above our atmosphere to study the Sun, other stars and even distant galaxies.
They also fly directly through some of the most interesting regions of Earth’s atmosphere, and that’s what scientists are taking advantage of for their Grand Challenge experiments.
One of the ideal rocket ranges for cusp science is in Ny-Ålesund, Svalbard, off the coast of Norway and within the Arctic circle. Because of its far northward position, each morning Svalbard passes directly under Earth’s magnetic cusp.
But launching in this extreme, remote environment puts another set of challenges on the mission teams. These launches need to happen during the winter, when Svalbard experiences 24/7 darkness because of Earth’s axial tilt. The launch teams can go months without seeing the Sun.
Like for all rocket launches, the science teams have to wait for the right weather conditions to launch. Because they’re studying upper atmospheric processes, some of these teams also have to wait for other science conditions, like active auroras. Auroras are created when charged particles collide with Earth’s atmosphere — often triggered by solar storms or changes in the solar wind — and they’re related to many of the upper-atmospheric processes that scientists want to study near the magnetic cusp.
But even before launch, the extreme conditions make launching rockets a tricky business — it’s so cold that the rockets must be encased in styrofoam before launch to protect them from the low temperatures and potential precipitation.
When all is finally ready, an alarm sounds throughout the town of Ny-Ålesund to alert residents to the impending launch. And then it’s up, up and away! This photo shows the launch of the twin VISIONS-2 sounding rockets on Dec. 7, 2018 from Ny-Ålesund.
These rockets are designed to break up during flight — so after launch comes clean-up. The launch teams track where debris lands so that they can retrieve the pieces later.
The next launch of the Grand Challenge Initiative is AZURE, launching from Andøya Space Center in Norway in March 2019.
For even more about what it’s like to launch science rockets in extreme conditions, check out one scientist’s notes from the field: https://go.nasa.gov/2QzyjR4
For updates on the Grand Challenge Initiative and other sounding rocket flights, visit nasa.gov/soundingrockets or follow along with NASA Wallops and NASA heliophysics on Twitter and Facebook.
@NASA_Wallops | NASA’s Wallops Flight Facility | @NASASun | NASA Sun Science
Beautiful views of the Transit of Mercury across the sun. HAPPENING NOW.
#plastimo #compass
See the aurora and the magnetic field.
