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irect freight train service linking E China, Duisburg launched

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irect freight train service linking E China, Duisburg launched

Повідомлення liyifeng12345 » 14 березня 2019, 08:36

LOS ANGELES Rush Kalen Ballage Jersey , Sept. 14 (Xinhua) -- On Friday morning, the U.S. National Aeronautics and Space Administration (NASA)'s Cassini spacecraft will dive into Saturn's atmosphere and disintegrate.


"Look up tonight & see Saturn in the sky. Tomorrow, our spacecraft will be part of the planet it studied for so long," Cassini's team said on Twitter Thursday night.


The probe was running low on fuel, and the 13-year tour of the Saturn system mission must end. The spacecraft will make a deliberate plunge into Saturn's atmosphere to avoid the small possibility of it crashing into a potentially habitable moon, in particular Enceladus.


The long-lived spacecraft's fateful dive was the final beat in the mission's Grand Finale, which began in late April Rush Durham Smythe Jersey , through the gap between Saturn and its rings. No spacecraft has ever ventured so close to the planet before.


On its final orbit, Cassini will plunge into Saturn's atmosphere at tens of thousands of miles per hour, sending back new and unique science to the very end. After losing contact with Earth, the spacecraft will burn up like a meteor, becoming part of the planet itself.


"The spacecraft is transmitting the last data from its recorders," Cassini team tweeted on Thursday afternoon.


The spacecraft is in the process of emptying its onboard solid-state recorder of all science data, including the final images taken by its imaging cameras Rush Jerome Baker Jersey , prior to reconfiguring for a near-real-time data relay during the final plunge. The communications link with the spacecraft is continuous from now through the end of mission.


Because of Earth's rotation, this 11-hour downlink begins with the NASA Deep Space Network (or DSN) antenna station in California, which then hands off receiving to a station in Canberra, Australia. From this point the spacecraft holds this orientation, its antenna pointed toward Earth, for the remaining several hours of the mission.


According to the mission's final calculations, after beginning its descent into Saturn's upper atmosphere Rush Jordan Phillips Jersey , the spacecraft is expected to lose radio contact with Earth at 4:55 a.m. PDT (1155 GMT) on Friday.


Cassini will enter Saturn's atmosphere at an altitude of about 1,915 km above the planet's estimated cloud tops, where the air pressure is 1-bar, equivalent to sea level on Earth. During its dive into the atmosphere, the spacecraft's speed will be approximately 113,000 km per hour.


According to NASA, when the probe first begins to encounter Saturn's atmosphere Rush DeVante Parker Jersey , Cassini's attitude control thrusters will begin firing in short bursts to work against the thin gas and keep Cassini's saucer-shaped high-gain antenna pointed at Earth to relay the mission's precious final data.


As the atmosphere thickens, the thrusters will be forced to ramp up their activity, going from 10 percent of their capacity to 100 percent in the span of about a minute. Once they are firing at full capacity, the thrusters can do no more to keep Cassini stably pointed, and the spacecraft will begin to tumble.


Cassini is set to make groundbreaking scientific observations of Saturn. Before contact is lost, eight of Cassini's 12 scientific instruments will be operating. All of the mission's magnetosphere and plasma science instruments, plus the spacecraft's radio science system Rush Xavien Howard Jersey , and its infrared and ultraviolet spectrometers will collect data during the final plunge.


In particular, the spacecraft's Ion and Neutral Mass Spectrometer (INMS) will be directly sampling the atmosphere's composition, which cannot be done from orbit. It will potentially offer insights into the giant planet's formation and evolution.


When the antenna points just a few fractions of a degree away from Earth, communications will be severed permanently. The predicted altitude for loss of signal is about 1,500 kilometers above Saturn's cloud tops. From that point, the spacecraft will begin to burn up like a meteor.


Within about 30 seconds following loss of signal, the spacecraft will begin to come apart; within a couple of minutes Rush Laremy Tunsil Jersey , all remnants of the spacecraft are expected to be completely consumed in Saturn's atmosphere.


"The spacecraft's final signal will be like an echo. It will radiate across the solar system for nearly an hour and a half after Cassini itself has gone," Earl Maize, Cassini project manager at NASA's Jet Propulsion Laboratory, said in a statement.


Due to the travel time for radio signals from Saturn, which changes as both Earth and the ringed planet travel around the Sun, events currently take place there 83 minutes before they are observed on Earth. This means that, although the spacecraft will begin to tumble and go out of communication at 3:31 a.m. PDT (1031 GMT) at Saturn Rush Cordrea Tankersley Jersey , the signal from that event will not be received at Earth until 83 minutes later.


"Even though we'll know that, at Saturn, Cassini has already met its fate, its mission isn't truly over for us on Earth as long as we're still receiving its signal," Maize said.


On Thursday, other Cassini instruments will make detailed, high-resolution observations of Saturn's auroras Rush Raekwon McMillan Jersey , temperature, and the vortices at the planet's poles.


Cassini's imaging camera will take a last look at the Saturn system on the day before the plunge and will be off during this final descent.


Launched in 1997, the 3.26 billion U.S. dollar Cassini-Huygens mission has been touring the Saturn system since arriving there in 2004. The Huygens lander separated from Cassini and plopped down on the surface of Saturn's moon Titan shortly after the arrival. The Cassini probe was scheduled to study the Saturn system until 2008, but the mission was given two extensions that stretched its lifetime into 2017. During its journey, Cassini has made numerous dramatic discoveries.


1st direct freight train service linking E China, Duisburg launched


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