AI News, Survey Monitor June/July 2019
Hayabusa2 carries multiple science payloads for remote sensing, sampling, and four small rovers that are investigating the asteroid surface to inform the environmental and geological context of the samples collected.
Carbonaceous asteroids are expected to preserve the most pristine materials in the Solar System, a mixture of minerals, ice, and organic compounds that interact with each other.
Studying it is expected to provide additional knowledge on the origin and evolution of the inner planets and, in particular, the origin of water and organic compounds on Earth,
Compared to the previous Hayabusa mission, the spacecraft features improved ion engines, guidance and navigation technology, antennas, and attitude control systems.
On 21 September 2018, the Hayabusa2 spacecraft ejected the first two rovers, Rover-1A and Rover-1B, from about 55 meters altitude that fell independently to the surface of the asteroid.
The first sample collection was scheduled to start in late October 2018, but the rovers encountered a landscape with large and small boulders but no regolith to sample, so the mission team decided to postpone the sample acquisition to 2019 and evaluated several options.
Hayabusa2 was launched on 3 December 2014, arrived at asteroid Ryugu on 27 June 2018, and remained at a distance of about 20 km to study and map the asteroid.
These engines use microwaves to convert xenon into plasma (ions), which is accelerated by applying a voltage from the solar panels and ejected out the back of the engine.
The spacecraft has four redundant reaction wheels and a chemical reaction control system featuring twelve thrusters for attitude control (orientation) and orbital control at the asteroid.
In order to descend to the asteroid surface for sampling, the spacecraft released one of five target markers in the selected landing zones as artificial landmark with highly reflective outer material that is recognized by a strobe light mounted on the spacecraft.
When the spacecraft is closer to the surface than 30 m during the sampling operation, Laser Range Finders (LRF-S1, LRF-S3) are used to measure the distance and the attitude of spacecraft relative to the terrain. Another
MASCOT carries four instruments: an infrared spectrometer (MicrOmega), a magnetometer (MASMAG), a radiometer (MARA), and a camera (MASCAM) that imaged the small-scale structure, distribution and texture of the regolith.
The original plan was for the spacecraft to collect up to three samples: 1) surface regolith that exhibits traits of hydrous minerals;
The first two surface samples were scheduled to start in late October 2018, but the rovers show a scenery of large and small boulders and no regolith to sample, so the mission team decided to postpone sampling to 2019 and evaluate several options.
When the sampler horn attached to Hayabusa2's underside touched the surface, a projectile (5-gram tantalum bullet) was fired at 300 m/s into the surface.
The sub-surface sample collection required an impactor to excavate a crater to eventually obtain material deeper from the sub-surface, which has not been subjected to space weathering.
to observe and map the precise location of the SCI impact, while the orbiter maneuvered to the far side of the asteroid in order to avoid debris from the impact.
Approximately 40 minutes after separation, when the spacecraft was at a safe distance, the penetrator was fired into the asteroid surface by the detonation of 4.5 kg (9.9 lb) shaped charge of plasticized HMX for acceleration.
The copper impactor was shot to the surface from an altitude of about 500 meters and it excavated a crater of about 10 meters in diameter, exposing pristine material.
The spacecraft collected and stored the samples in separate sealed containers inside the sample-return capsule (SRC), which has a thermal insulation, 40 cm external diameter, 20 cm in height, and a mass of ~16 kg.
The capsule will re-enter the Earth's atmosphere at 12 km/s and it will deploy a radar-reflective parachute at an altitude of about 10 km, and eject its heat-shield, while transmitting a position beacon signal.
When the spacecraft returns and flies past Earth to deliver the sample capsule in December 2020, it is expected to retain 30 kg of xenon propellant, which can be used to extend its service and flyby new targets to explore.
MIT Technology Review
The news: YouTube has disabled 210 channels, writing in a blog post they had “behaved in a coordinated manner while uploading videos related to the ongoing protests in Hong Kong.” The reasoning: YouTube said its action “was consistent with recent observations and actions related to China announced by Facebook and Twitter.” The two companies announced earlier this week that they’d suspended nearly 1,000 accounts thought to be part of a Chinese government operation to spread disinformation about the protests in Hong Kong.
- On 14. april 2021
Science Monitor | 29.06.19
Anchor - Aishwarya Kapoor Rajya Sabha TV | RSTV.
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