哈佛 - 史密森天體物理中心(Harvard-Smithsonian Center for Astrophysics)的Jonathan McDowell在接受英國《衛報》訪問時說,「天宮一號」可能已經失控,這將會令地面人員難以預測其墜落地點和時間,「人們可能在其墜落前的6-7小時前,甚至更短時間才知道。既然不確定落下的時間,就意味根本不知道它會落在什麼地方。」
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Tiangong-1 Space Lab Will Fall to Earth Next Year, China Says
China's first-ever space lab will die a fiery death in Earth's atmosphere toward the end of next year, Chinese officials said.
The 9.4-ton (8.5 metric tons) Tiangong-1 spacecraft is currently intact and orbiting Earth at an altitude of 230 miles (370 kilometers), according to Wu Ping, deputy director of China's Manned Space Engineering office. That's a bit lower than the International Space Station, which usually stays about 250 miles (400 km) above the planet's surface.
Tiangong-1 will likely fall back to Earth in the second half of 2017, and its demise shouldn't cause problems here on the ground, Wu said. [Gallery: Tiangong 1, China's First Space Laboratory]
"Based on our calculation and analysis, most parts of the space lab will burn up during falling," she said during a news conference Wednesday (Sept. 14), according to China's state-run Xinhua news agency.
China is monitoring Tiangong-1 (whose name means "Heavenly Palace" in Mandarin) closely and will issue the appropriate warnings if the space lab threatens to hit a satellite, Wu added. She said that China will release a forecast of Tiangong-1's fall to Earth "if necessary," according to Xinhua.
The update from Wu seems to confirm speculation that China is no longer in control of the 34-foot-long (10.3 meters) Tiangong-1, which launched in September 2011 to test out docking technologies and other skills that China will need to build its planned space station in the early 2020s.
After all, if operators were still controlling the space lab, they could steer it to a guided re-entry over an empty stretch of ocean at a specified time.
Three spacecraft docked with Tiagong-1 during its operational life — Shenzhou-8 in November 2011, Shenzhou-9 in June 2012 and Shenzhou-10 in June 2013. The latter two missions were crewed, each carrying three Chinese "taikonauts" up to the space lab.
Tiangong-1 stopped sending data back to Earth in March 2016, officially ending the space lab's mission. But its successor is now aloft: Tiangong-2 launched atop a Long March 2F rocket on Sept. 15 from the Jiuquan Satellite Launch Center in northwestern China.
Two taikonauts are scheduled to arrive at Tiangong-2 in mid- to late October for a 30-day stay, Chinese officials have said. (The Shenzhou-9 and Shenzhou-10 crews spent eight and 12 days aboard Tiangong-1, respectively.)
China is not part of the multinational consortium, led by the United States and Russia, that operates the 440-ton (400 metric ton) International Space Station. China aims to have its own 60-ton (54 metric tons) space station up and running in Earth orbit by 2022 or so.
Normally, a decommissioned satellite or space station would be retired by forcing it to burn up in the atmosphere. This type of burn is controlled, and most satellite re-entries are scheduled to burn up over the ocean to avoid endangering people. However, it seems that China's space agency is not sure exactly when Tiangong-1 will re-enter the atmosphere, which implies that the station has been damaged somehow and China is no longer able to control it.
哈佛 - 史密森天體物理中心(Harvard-Smithsonian Center for Astrophysics)的Jonathan McDowell在接受英國《衛報》訪問時說,「天宮一號」可能已經失控,這將會令地面人員難以預測其墜落地點和時間,「人們可能在其墜落前的6-7小時前,甚至更短時間才知道。既然不確定落下的時間,就意味根本不知道它會落在什麼地方。」
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China’s Long March 2D places 2 SuperView-1 satellites into wrong orbit
China’s Long March 2D rocket lifted off at 11:23 a.m. China Standard Time (03:23 GMT) on Dec. 28, 2016, from the Taiyuan Satellite Launch Center in Shanxi Province. The booster carried with it two SuperView-1 satellites designed for Earth observation purposes.
While Chinese media reported the launch a success, according to Spaceflight101, orbital data showed the two main payloads did not reach their intended orbit and various flight sequence events did not match up with pre-launch predictions. What orbit the satellites are currently in is not known officially, but a user on Twitter who is tracking a CubeSat which flew piggyback on the flight reported that it was in a 323 by 137 mile (520 by 220 kilometer) orbit.
The mission’s goal was to send the duo of satellites into a Sun-synchronous orbit (SSO) at an altitude of about 310 miles (500 kilometers). From this orbit, they were to acquire high-resolution imagery of the Earth for civilian purposes.
As usual, Chinese media have not revealed the details about pre-launch activities and about the launch itself. Moreover, limited information was available about the mission timeline.
Preparations for the mission entered its final stage with the arrival of both satellites at Taiyuan in November. It was a busy month for the launch center engineers as they conducted initial checkouts and tests of the spacecraft and began the assembly of the Long March 2D launcher.
After liftoff, the rocket began its brief vertical climb before turning south across mainland China, toward the South China Sea. During the initial phase of the flight, the rocket was powered by the main stage’s YF-21C engine delivering 2,962 kilonewtons of thrust. This stage was detached about three minutes after liftoff.
Afterward, the second stage’s YF-24C cluster engine was ignited, marking the start of a seven-minute ride into orbit. This phase should have concluded approximately 10 minutes after liftoff minutes when the spacecraft were deployed into space.
The mission’s passengers, named SuperView-1 01 and SuperView-1 02 (also known as GaoJing-1 01 and GaoJing-1 02), are the first two out of four satellites of the first generation of the SuperView constellation. They are both identical spacecraft, built by the China Academy of Space Technology (CAST). The satellites are based on the CAST3000B platform and are fitted with two deployable solar arrays.
If the off-target orbital insertion can be rectified, the pair of SuperView-1 spacecraft will be operated by the Beijing Space View Technology Co., Ltd. They will provide imagery with 1.64-foot (0.5-meter) panchromatic resolution and 6.56-foot (2-meter) multispectral (blue, green, red, near-infrared) resolution.
The satellites are designed to work in multiple collection modes including long strip, multiple strips collect, multiple-point targets collect, and stereo imaging. They are expected to deliver highly detailed imagery for precise map creation, change detection, and in-depth image analysis.
Both spacecraft feature a data collection capability of two terabytes of storage on board and, if in the proper orbit, are able to obtain images covering 270,300 square miles (700,000 square kilometers) across the globe per day.
“The multiple strips collect mode will realize high-resolution surveying and mapping with large swath width, and the stereo imaging mode will bring large opportunities for DEM (digital elevation model) production,” the SuperView-1 brochure states.
The next two SuperView-1 satellites, namely SuperView-1 03 and SuperView-1 04, are scheduled to be launched into space in mid-2017. They will be deployed into the same intended orbit and will have identical capabilities as the two launched today.
Accordingly, there will be four 1.64-feet resolution SuperView-1 satellites in orbit, phased 90 degrees from each other on the same orbit to collect imagery for clientele across the world, assuming the two launched today can be moved to the correct orbit.
The two-unit CubeSat known as Bayi Kepu Weixing 1 (BY70-1) that piggybacked the mission has a mass of about 4.4 pounds (2 kilograms). This CAST-built tiny satellite is an amateur radio technology demonstrator designed for educational purposes. It will provide telecommand, telemetry, and FM repeater functions.
The Long March 2D is a two-stage rocket developed by the Shanghai Academy of Spaceflight Technology. It is mainly used to launch satellites into low-Earth orbit (LEO). The 135 feet (41.15 meters) tall booster can launch payloads of up to 3.5 metric tons to LEO and has an SSO capability of up to 1.3 metric tons.
The rocket was launched for the first time on Aug. 9, 1992, from the Jiuquan Satellite Launch Center, orbiting the Fanhui Shei Weixing FSW-2-1 recoverable satellite.
Wednesday’s flight was the 244th flight of the Long March rocket series. It was also the ninth orbital launch from the Jiuquan Satellite Launch Center in 2016 and the 21st mission conducted by China this year.
China plans one more orbital launch before year’s end. On Dec. 30, a Long March 3B rocket will lift off from the Xichang Satellite Launch Center, carrying the TJS 2 communications satellite for China National Space Administration.