NASA says taking sample from asteroid harder than expected

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This February 27, 2018 photo from NASA’s OSIRIS-REx spacecraft, obtained March 18, 2019 courtesy of NASA/Goddard/University of Arizona, shows a close up of the asteroid Bennu from a distance of 0.8 miles (1.3 km). (AFP)
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This December 2, 2018 photo from NASA’s OSIRIS-REx spacecraft, obtained March 18, 2019 courtesy of NASA/Goddard/University of Arizona, shows a mosaic image of asteroid Bennu, composed of 12 PolyCam images, from a distance of 12 miles (124 km). (AFP)
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This artist's rendering made available by NASA in July 2016 shows the mapping of the near-Earth asteroid Bennu by the OSIRIS-REx spacecraft. (AP)
Updated 20 March 2019
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NASA says taking sample from asteroid harder than expected

  • The asteroid, which orbits the sun, is 85 million kilometers (52 million miles) from the Earth
  • The samples will be stowed in the probe, which will return to Earth in 2023

WASHINGTON: After two years crossing the solar system, the NASA space probe Osiris-Rex arrived last December near the asteroid Bennu to complete its mission of collecting a sample — but touching the rock will prove much harder than scientists had expected.
The Osiris-Rex team said Tuesday that the surface of the asteroid, which measures 490 meters (1,600 feet) in diameter, was covered in stones and boulders. They had expected it to be smoother and easier for the probe to touch.
“We go back to the drawing board and start thinking again,” Dante Lauretta, the head of the mission, told a press conference. The team’s observations also appeared in the Nature journal on Tuesday.
The probe was designed to head for a flat area with a radius of 25 meters, but the images beamed back since December showed that there is no area that big which is free of boulders.
As a result, the team will have to aim more tightly.
“Now we’re going to try to hit the center of the bullseye,” said project manager Richard Burns.
Since December, the probe has been using its instruments to map Bennu from a close distance, currently three miles.
The asteroid, which orbits the sun, is 85 million kilometers (52 million miles) from the Earth.
The goal is touch the surface with a robotic arm for just five seconds in July 2020, retrieving a sample of between 60 grams and two kilograms (two ounces to 4.4 pounds) of regolith, which means relatively small particles such as gravel or sand, since the machine can only suck up particles measuring less than two centimeters.
The samples will be stowed in the probe, which will return to Earth in 2023.
Bennu is technically known as “rubble-pile asteroid,” that is, it is made up of pieces of debris that had broken off larger celestial bodies and come together under the effect of gravity.
It has more than 200 boulders larger than 10 meters in diameter, and some stretching up to 30 meters, according to researchers writing in Nature Astronomy. It has a number of craters between 10 and over 150 meters in length.
“It is not trivial to deliver a spacecraft with meter scale resolution to the surface of an asteroid in the microgravity environment,” said Lauretta, who nevertheless said he was “confident” that the team would rise to the challenge.
Another surprise Bennu had been withholding was that it emits particles which fall back to the surface like rain. That should not however endanger the probe, the team said.


Greek researchers enlist EU satellite against Aegean sea litter

Greek university students gently deposits a wall-sized PVC frame on the surface before divers moor them at sea at a beach in the island of Lesbos on April 18, 2019. (AFP)
Updated 22 April 2019
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Greek researchers enlist EU satellite against Aegean sea litter

  • “All the targets were carried into the sea, the satellites passed by and we’re ready to fill out the first report”
  • Satellite data is provided free from the European Space Agency (ESA) and hours after the overpass targets should be detected from the Sentinel-2 satellite

LESBOS ISLAND, Greece: Knee-deep in water on a picture-postcard Lesbos island beach, a team of Greek university students gently deposits a wall-sized PVC frame on the surface before divers moor it at sea.
Holding in plastic bags and bottles, four of the 5 meter-by-5-meter (16 foot-by-16-foot) frames are part of an experiment to determine if seaborne litter can be detected with EU satellites and drones.
“This was the first big day,” says project supervisor Konstantinos Topuzelis, an assistant professor at the University of the Aegean department of Marine Sciences, said of the scene from last week.
“All the targets were carried into the sea, the satellites passed by and we’re ready to fill out the first report.”
The results of the experiment — “Satellite Testing and Drone Mapping for Marine Plastics on the Aegean Sea” — by the university’s Marine Remote Sensing Group will be presented at a European Space Agency symposium in Milan in May.
“Marine litter is a global problem that affects all the oceans of the world,” Topouzelis told AFP.
Millions of tons of plastic end up in the oceans, affecting marine wildlife all along the food chain.
“Modern techniques are necessary to detect and quantify marine plastics in seawater,” Topouzelis added, noting that space agencies have already been looking into how drones and satellites can help with the clean-up.
“The main advantage is that we are using existing tools,” which brings down costs and makes it easier to scale up, says Dimitris Papageorgiou, one of the 60 undergraduate and postgraduate students who worked on the experiment.
To prepare, the team gathered some 2,000 plastic bottles and lashed them to the frames. Other targets were crafted with plastic bags, as these are even harder to spot in the water and usually constitute the deadliest threat to Aegean marine life such as dolphins, turtles and seals.
In 2018, a first phase in the experiment was able to detect large targets of around 100 square meters from space.
This year’s experiment uses targets a quarter that size to test the smallest detectable area under various weather conditions.
“It was a crazy idea,” laughs Topouzelis.
“We knew that the European satellite system passes at regular intervals with a spatial resolution of 10 meters.”
In theory, then, the satellites should be able to detect the floating rafts of plastic the team pushed out to sea.
The University of the Aegean is working on the project with Universidad de Cadiz in Spain, CNR-Ismar in Italy and UK environmental consultants Argans Ltd.
Satellite data is provided free from the European Space Agency (ESA) and hours after the overpass targets should be detected from the Sentinel-2 satellite.
The project acts as a calibration and validation exercise on the detection capabilities of the satellites.
But even if relatively small patches of plastic garbage can be spotted from orbiting satellites, the problem of how to remove it from the sea remains.
Last year, a giant floating barrier five years in the making was launched off the coast of San Francisco, as part of a $20-million project to clean up a swirling island of rubbish between California and Hawaii.
But the slow speed of the solar-powered barrier prevents it from holding onto the plastic after it scoops it up.