Meteoroid captured skimming Earth's atmosphere over Europe
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The planet’s atmosphere is a lot less uniform than most would assume and that can spell trouble for spacecraft operators. One region of the atmosphere that has proven to be a nuisance for satellites is the so-called polar cusp some 250 miles above the North Pole. Every day at noon local time, when the Sun is at its highest point, a funnel-shaped gap opens up in the Earth’s magnetic field.
For the most part, the field protects our planet from the charged particles streaming towards us from the Sun.
But according to NASA, this funnel-shaped gap allows solar winds from the Sun to interact directly with the planet’s atmosphere and that can have some bizarre effects on radio and GPS signals in the region.
Even more bizarrely, scientists have observed that spacecraft passing through the polar cusp appear to slow down – and they are now trying to figure out why.
Towards this goal, NASA will launch the Cusp Region Experiment-2 (CREX-2) mission, which will involve firing a sounding rocket into the sky from Norway.
Mark Conder, CREX-2 principal investigator and physicist at the University of Alaska Fairbanks, said: “At around 250 miles above Earth, spacecraft feel more drag, sort of like they’ve hit a speed bump.”
Spacecraft passing through the polar cusp slow down because the air there is considerably denser than at any other point in Earth orbit.
But scientists have so far been unable to figure out why or how this happens.
The CREX-2 mission was originally pencilled in to blast off in 2019 but remained grounded until now.
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The space weather conditions at the time were not right and the Covid pandemic threw another spanner in the works.
But the Sun is more active now and with Covid restrictions loosening around the world, NASA’s scientists are hopeful the mission will launch on December 1 from Andenes, Norway.
The atmosphere’s density drops with altitude but remains fairly consistent horizontally.
But this is not the case in the polar cusp where the air is about one-and-a-half times denser than the surrounding air at the same altitude.
The CREX-2 mission will investigate what process is supporting this additional mass.
The scientists will investigate a number of potential scenarios and “try and sort out which one is doing the work”.
Professor Conde said: “You can’t just increase the mass in a region by a factor of 1.5 and do nothing else, or the sky will fall.”
One theory proposes that electric and magnetic effects in the ionosphere – 30 to 600 miles up – support the denser air.
The CREX-2 rocket will launch into the sky and eject 20 soda can-sized canisters, each armed with a small rocket motor.
The canisters will release vapour tracers that will produce colourful, glowing clouds in a “three-dimensional grid in the sky”.
Scientists will then monitor how air moves through these clouds to better understand what is going on up there.
Professor Conde said: “We’re threading a needle. We get about an hour or two each day when conditions are suitable to do the experiment.”
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