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松鼠的空天随笔

 
 
 

日志

 
 

UARS再入  

2011-09-23 17:14:48|  分类: BMDS |  标签: |举报 |字号 订阅

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美国高层大气研究卫星(UARS)即将再入大气层,预定时间是在美国东部时间9月23日下午,也就是说北京时间24日凌晨。不过具体时间很不确定,高层大气受地磁活动和太阳活动影响很大,10日和18日太阳活动引发两个小的地磁暴,大气密度增加不少,因此NASA的预定再入陨落时间就提前了不少。
UARS即将再入 - squirrel - 松鼠的空天随笔
UARS的轨道下降历史,2005年退役废弃,做了一次降轨操作降低近地点(Perigee)
 
 
NASA在9月12日的update1还说9月最后一个星期:
As of Sept. 12, 2011, the orbit of UARS was 145 mi by 165 mi (235 km by 265 km). Re-entry is expected during the last week of September.

随后15的update2就说24日了:
As of Sept. 15, 2011, the orbit of UARS was 143 mi by 158 mi (230 km by 255 km). Re-entry is expected Sept. 24, plus or minus a day.

17日的update3进一步提前到23日:
As of Sept. 16, 2011, the orbit of UARS was 140 mi by 155 mi (225 km by 250 km). Re-entry is expected Sept. 23, plus or minus a day. The re-entry of UARS is advancing because of a sharp increase in solar activity since the beginning of this week.
不过到update3,都是+/-1天的误差,也就是说update3表示22日或是24日再入都是在误差范围内。update3明确说太阳活动导致UARS再入时间提前。

19日的update4的时间预定仍然是23日,正负1天:
As of Sept. 18, 2011, the orbit of UARS was 133 mi by 149 mi (215 km by 240 km). Re-entry is expected Sept. 23, plus or minus a day.

20日的update5:
As of Sept. 19, 2011, the orbit of UARS was 130 mi by 143 mi (210 km by 230 km). Re-entry is expected Sept. 23, plus or minus a day.

21日的2个update6:
2011年9月21日 4:00:
As of Sept. 20, 2011, the orbit of UARS was 127 mi by 140 mi (205 km by 225 km). Re-entry is expected Sept. 23, plus or minus a day. It is still too early to predict the time and location of re-entry. Predictions will become more refined over the next two days.
2011年9月21日 20:03,提到此时预测再入时间和范围仍然太早:
As of Sept. 20, 2011, the orbit of UARS was 120 mi by 130 mi (195 km by 210 km). Re-entry is expected Sept. 23, United States time. The time reference does not mean that the satellite is expected to re-enter over the United States. It is simply a time reference. Although it is still too early to predict the time and location of re-entry, predictions of the time period are becoming more refined.

22日的update7:
2011年9月22日 6:35
As of 1:30 p.m. EDT Sept. 21, 2011, the orbit of UARS was 120 mi by 130 mi (190 km by 205 km). Re-entry is expected sometime during the afternoon of Sept. 23, Eastern Daylight Time. The satellite will not be passing over North America during that time period. It is still too early to predict the time and location of re-entry with any more certainty, but predictions will become more refined in the next 24 to 48 hours.

22日的update8:
2011年9月22日 19:44
As of 7 a.m. EDT Sept. 22, 2011, the orbit of UARS was 115 mi by 120 mi (185 km by 195 km). Re-entry is expected sometime during the afternoon of Sept. 23, Eastern Daylight Time. The satellite will not be passing over North America during that time period. It is still too early to predict the time and location of re-entry with any more certainty, but predictions will become more refined in the next 24 to 36 hours.

23日的update9:
2011年9月23日 10:01
As of 9:30 p.m. EDT Sept. 22, 2011, the orbit of UARS was 110 mi by 115 mi (175 km by 185 km). Re-entry is possible sometime during the afternoon or early evening of Sept. 23, Eastern Daylight Time. The satellite will not be passing  over North America during that time period. It is still too early to predict the time and location of re-entry with any more certainty, but predictions will become more refined in the next 24 hours.

UARS的电池板和姿控的动量轮还是可用的,可以调整姿态改变高层大气阻力,这个避开北美的再入区很可能是精密计算的结果,当年天空实验室(Skylab)就进行了这样的操作。但话说回来,NASA再神勇也只能做到这一步,毕竟2005年降低轨道已经耗尽了推进剂。姿态控制改变高层大气的阻力从而改变再入区其实很不靠谱,Skylab碎片最后落入印度洋和澳大利亚荒凉的西南部,如果落区控制真的很有效,更好的位置是再入到无人烟的南太平洋海域,哪怕全落到南印度洋也很好,只可惜这对人类目前的技术能力,无控制再入不可能那么精确的。

据称NASA将在再入前公布12小时、6小时和2小时连续发布公告,但即使是T-2 hours的公告,仍然是具体再入时间仍然是plus or minus 25 minutes,这意味着即使到这时落区仍然是卫星轨迹上24000千米(+/-12000km)的一条范围.
Normal procedure is for TIP (Tracking and Impact Prediction) messages to be prepared and released to the public (via the Space-Track.org website) at the following intervals:
T – 4 days, T – 3 days, T – 2 days, T – 1 day, T – 12 hours, T – 6 hours, and T – 2 hours
TIP messages provide the best estimates of reentry time and location but have large uncertainties.  Even at T – 2 hours, the uncertainty of reentry time is on average +/- 25 minutes for nearly circular orbits.  This equates to +/- 12,000 km on the Earth.

所谓可能砸到莫斯科,按照现在的TLE星历数据看,还真在25分钟误差之内UARS即将再入 - squirrel - 松鼠的空天随笔到时候具体怎么样,天知道。
附注刚刚查到的UARS最新的5个TLE星历数据:
1 21701U 91063B   11265.82991118  .03313120  11450-4  45803-3 0  6240
2 21701 056.9390 268.5519 0007918 016.4206 343.7810 16.34380841108974
1 21701U 91063B   11265.95218509  .03652113  11479-4  45372-3 0  6251
2 21701 056.9386 267.9457 0007840 008.7158 351.4275 16.35383759108992
1 21701U 91063B   11266.07439795  .03876143  11501-4  43566-3 0  6268
2 21701 056.9364 267.3394 0006639 013.1080 347.0384 16.36334468109011
1 21701U 91063B   11266.13547510  .03593875  11504-4  38862-3 0  6275
2 21701 056.9373 267.0416 0005916 017.3592 342.7453 16.36702003109028
1 21701U 91063B   11266.31859715  .04606671  11556-4  39986-3 0  6284
2 21701 056.9426 266.1345 0005381 013.7946 346.4549 16.38632826109054

ps,北京也在这个+/-25分钟的范围内,真热闹啊。莫斯科反导说不定要值夜班了,中南海和克里姆林宫的灯啊,彻夜长明。可惜A-135的SH11/51T6已经退役了,靠底层拦截的SH08/53T6实在不太可靠。虽然监视系统肯定要值夜班,不过作为军事爱好者,还是想知道五寨基地或是东方基地会不会架起来XX-1反卫星导弹待命。

不过话说回来,所谓反导待命都是玩笑话。每年人类航天活动发射的LEO轨道发射多的是,比如每次向国际空间站运人运货、这次天宫一号和2个月后神舟八号的发射,还有其他一些LEO轨道的发射。LEO发射火箭最后一级都是入轨的,随后会无控再入大气层烧毁,这些东西大多数可是一点不比这个5.6吨的UARS轻。比如日本的H-IIB火箭、美国的Falcon9火箭、俄罗斯的Soyuz火箭,上面级都是大东西。不过美俄这群人不去炒作也就没人关注而已。有心思担心被UARS砸到头上,不如想想怎么晴天不被雷劈靠谱些。

严肃的说,作为具有悠久历史、诞生了杞人忧天成语的古老民族,虽然不担心真被UARS碎片砸到,不过看看会落下来什么东西还是必要的:
UARS即将再入 - squirrel - 松鼠的空天随笔
UARS的碎片再入,红框内是可能落到地面的部件。落区长度大约800千米

23日的update10,改变了姿态,降低了下降速度:
As of 10:30 a.m. EDT on Sept. 23, 2011, the orbit of UARS was 100 miles by 105 miles (160 km by 170 km). Re-entry is expected late Friday, Sept. 23, or early Saturday, Sept. 24, Eastern Daylight Time. Solar activity is no longer the major factor in the satellite’s rate of descent. The satellite’s orientation or configuration apparently has changed, and that is now slowing its descent. There is a low probability any debris that survives re-entry will land in the United States, but the possibility cannot be discounted because of this changing rate of descent. It is still too early to predict the time and location of re-entry with any certainty, but predictions will become more refined in the next 12 to 18 hours.
很奇怪美国人到底想把UARS坠落到哪里,不过现在预言确切的再入时间和落区地点仍然为时过早

24日(北京时间)的update11:
As of 7 p.m. EDT on Sept. 23, 2011, the orbit of UARS was 90 miles by 95 miles (145 km by 150 km). Re-entry is expected between 11 p.m. Friday, Sept. 23, and 3 a.m., Sept. 24, Eastern Daylight Time (3 a.m. to 7 a.m. GMT). During that time period, the satellite will be passing over Canada, Africa and Australia, as well as vast areas of the Pacific, Atlantic and Indian oceans. The risk to public safety is very remote.
哈哈,坠落时间推迟了,美国东部时间晚上11点到24日凌晨3点,北京时间24日就是24日上午11点到下午3点了,这应该和update10提到的改变姿态有关。可能的坠落时间里会经过加南大、非洲和澳大利亚,以及太平洋大西洋和印度演的广阔海域。不过确切地点和时间还是未知,不过危险性还是可以肯定的说,不大的。被砸到的几率比被天打雷劈高不了多少

美国战略司令部的消息是GMT4点50分(12:50 a.m. EDT),不过正负4个小时,Orz!
U.S. Strategic Command's latest projection shows re-entry occurring around 12:50 a.m. EDT (0450 GMT). But the margin of error is plus or minus four hours

Update 12,再入时间还是一个粗略值,北京时间11点45到12点45:
As of 10:30 p.m. EDT on Sept. 23, 2011, the orbit of UARS was 85 miles by 90 miles (135 km by 140 km). Re-entry is expected between 11:45 p.m. Friday, Sept. 23, and 12:45 a.m., Sept. 24, Eastern Daylight Time (3:45 a.m. to 4:45 a.m. GMT).  During that time period, the satellite will be passing over Canada and Africa, as well as vast areas of the Pacific, Atlantic and Indian oceans. The risk to public safety is very remote.

update13,正在确认再入时间和地点,到时候会有具体通知:
As of 10:30 p.m. EDT on Sept. 23, 2011, the orbit of UARS was 85 miles by 90 miles (135 km by 140 km). Re-entry was expected between 11:45 p.m. Friday, Sept. 23, and 12:45 a.m., Sept. 24, Eastern Daylight Time (3:45 a.m. to 4:45 a.m. GMT). During that time period, the satellite was passing over Canada and Africa, as well as vast areas of the Pacific, Atlantic and Indian oceans. The risk to public safety was very remote. NASA is working to confirm the re-entry location and time and will provide an update shortly.

spaceflightnow的status:
0458 GMT (12:58 a.m. EDT)
NASA says the agency is working to confirm the re-entry location and time. It will provide an update shortly.
0434 GMT (12:34 a.m. EDT)
"It's possible that UARS is down by now," NASA just said. "We're waiting for confirmation from U.S. Strategic Command."
NASA在等战略司令部的确认

根据twitter上的消息:
Confirmed debris falling over okotoks, Alberta. Canada
莫非真的鸟飞返故乡么,最后还是落在北美了,不过是加拿大
不过NASA官方还是很谨慎:
NASA
We're still waiting for #UARS Done! confirmation. If debris fell on land (and that's still a BIG if), Canada is most likely area.


Update14:
Sat, 24 Sep 2011 07:16:50 GMT
NASA’s decommissioned Upper Atmosphere Research Satellite fell back to Earth between 11:23 p.m. EDT Friday, Sept. 23 and 1:09 a.m. EDT Sept. 24. The satellite was passing eastward over Canada and Africa as well as vast portions of the Pacific, Atlantic and Indian oceans during that period. The precise re-entry time and location are not yet known with certainty.

Update15,最后nasa还是一问三不知,嘎嘎:
Sat, 24 Sep 2011 07:46:42 GMT
NASA’s decommissioned Upper Atmosphere Research Satellite fell back to Earth between 11:23 p.m. EDT Friday, Sept. 23 and 1:09 a.m. EDT Sept. 24. The Joint Space Operations Center at Vandenberg Air Force Base in California said the satellite penetrated the atmosphere over the Pacific Ocean. The precise re-entry time and location are not yet known with certainty.


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