Creating an Eclipse

Europe’s Proba-3 mission will create an ‘artificial eclipse’ to the study sun’s corona

An illustration of two satellites in space, separated by a relatively short distance. In the back, there is the sun.

An illustration of the pair of satellites that’ll create an artificial eclipse. (Image credit: ESA)

While the world eagerly awaits the total solar eclipse in April, scientists are already planning observations for the next — except this will be an “artificial” one. Here’s what that means.

Proba-3, a mission led by the European Space Agency (ESA), has been in the making for at least 14 years. It’s due to finally launch this September, and is designed to better detect tiny, faint features in the sun’s extremely dim outer atmosphere called the corona.

To accomplish that goal, the mission will launch two small satellites together which will separate once in space and fly in tandem in an orbit around Earth. Much like the moon passes in front of the sun during a solar eclipse, the two satellites — an occulter and a specialized instrument called a coronagraph — will mimic a natural solar eclipse by lining up 144 meters (472 feet) apart, such that the former blocks out the sun’s glaring disk for the latter.

“This will be achieved autonomously, without relying on guidance from the ground,” according to a previous ESA statement.

While the pair of satellites will take 19.5 hours to circle Earth once, they will maintain their formation for just six hours in each orbit to reduce fuel costs, said ESA. Such a configuration, reportedly the first of its kind, will bring the corona into view. This solar feature is so faint that it’s visible only during natural solar eclipses, which don’t last very long and aren’t very common.

“We won’t see quite as close to the solar limb as during a terrestrial eclipse,” Russell Howard, an astrophysicist at the John Hopkins University Applied Physics Lab who was not involved with the Proba-3 mission, said in the statement. “But having such images for hours on end compared to the five to 10 minutes duration of an eclipse event will be spectacular.”

Coronagraphs normally include an occulter, so they come capable of blocking out the sun’s bright disk themselves. But they also experience data-damaging diffraction, a consequence of light spilling around their edges and sometimes overshining very faint signals.

“The best way to reduce diffraction is to increase the distance between the occulter and the coronagraph, which is precisely what Proba-3 is going to do,” Proba-3’s project manager Damien Galano said in a statement earlier this week.

Europe temporarily lacks independent access to space after it retired its Ariane 5 rocket and is yet to debut its successor, Ariane 6. It also delayed the return to flight date of another rocket, Vega C, to late 2024. Not to fear, the Proba-3 mission will lift off from India instead, from the country’s spaceport in Sriharikota.

from:    https://www.space.com/proba-3-europe-artificial-eclipse-launch-satellites-india-sun

“A Pothole in Space”

NASA Keeping Tabs on the Growing Rip in Earth’s Magnetic Field

“Although the South Atlantic Anomaly arises from processes inside Earth, it has effects that reach far beyond Earth’s surface. The region can be hazardous for low-Earth orbit satellites that travel through it. If a satellite is hit by a high-energy proton, it can short-circuit and cause an event called single event upset or SEU. This can cause the satellite’s function to glitch temporarily or can cause permanent damage if a key component is hit. In order to avoid losing instruments or an entire satellite, operators commonly shut down non-essential components as they pass through the SAA.”

The European Space Agency (ESA) weighed in earlier this year about the South Atlantic Anomaly (SAA) – the mysterious dent in Earth’s magnetic field over the South Atlantic that is being weakened to the point of splitting apart by the planet’s molten metal outer core churning around and shifting old tectonic plates on top of each other so that they block the outer core from forming the magnetic field. Now NASA decided it’s time to reveal its concern about the SAA and how it’s affected NASA’s moneymakers – satellites.

In a press release accompanying an explanatory video (watch it here), NASA scientists explain how the SAA is like “a pothole in space,” jarring satellites every time they pass over it, causing electronic glitches, short circuits and other physical damage. And no, they can’t just fly around it because the SAA is far too big and a detour would make the area of missed communications even larger.

“In addition to measuring the SAA’s magnetic field strength, NASA scientists have also studied the particle radiation in the region with the Solar, Anomalous, and Magnetospheric Particle Explorer, or SAMPEX – the first of NASA’s Small Explorer missions, launched in 1992 and providing observations until 2012.”

Even though the rip keeps getting bigger, NASA appears less concerned about what’s directly underneath it on the surface, so it seems to imply that the increased solar radiation is nothing to worry about … yet. It can still affect ships and planes passing through, but the worst part is that the anomaly is “slowly but steadily drifting in a northwesterly direction.” You don’t need Google maps (although you might want to use them while you still can) to figure out that ‘northwest’ is the direction of South and North America. However, the press release still refers to the South Atlantic Anomaly as a “dent” and focuses primarily on “Modeling a safer future for satellites” – where NASA and SpaceX make their money.

Cynical? Yes. The SAA is obviously more than a “pothole in space” to be getting this kind of attention.

from:    https://mysteriousuniverse.org/2020/08/nasa-keeping-tabs-on-the-growing-rip-in-earths-magnetic-field/