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[美国发射] 美GPS导航系统最新进展:3家公司展开GPS IIIB竞标

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jingyan66 发表于 2009-5-11 15:19 | 显示全部楼层 |阅读模式

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本帖最后由 cmj9808 于 2016-5-6 15:42 编辑

美众院听证会:GPS星座已老而无用,新卫星尚未准备好

  

2009-05-11


    [据美国defensesystems网站近日报道]5月7日,美国太空联合功能组成司令部(JFCC SPACE)司令对众议院小组称,美国国防部的天基全球定位系统(GPS)是美国国家安全不可或缺的一部分,对美国全球军事作战的成功起到至关重要的作用。

    但是,太空联合功能组成司令部目前正在维持老化的系统,而新一代的卫星还在准备中。与其它军用卫星星座一样,GPS星座中有的卫星已超过设计寿命,只有部分能力还在运行;有的只剩单个关键部件尚未失灵。

    目前,首颗下一代卫星将于2009年11月发射,和原计划比,已经推迟了3年;政府问责署(GAO)称,正在开发阶段的后续卫星的进度安排过于乐观。空军是否能按时获得新卫星尚难确定。如果不能,某些军事作战与民用用户最早在明年就会受到影响。

    由于担心可能失去GPS服务或降低其服务,众议院监督及政府改革委员会的国家安全和外交事务小组委员会针对GPS遇到的困难举办听证会。2009年3月,空军发射了第七颗当代GPS卫星Block IIR-M,2007年空军还以新的地面站替换了一个22年的控制站,新地面站将支持下一代卫星GPS IIF。首颗IIF卫星预计于2009年11月发射,后续卫星将在未来3~5年发射。按计划,IIIA卫星的初步设计评审将在未来数周内完成,2014年发射首颗IIIA卫星。支持这些卫星的控制系统、接收器及其他系统也在研发中。

    不过GAO对这项进度表不报乐观态度,认为如果计划延期启动,新的承包商将面临过去太空采办遇到的问题和挑战。尤其是GPS采办的领导问题,太空项目缺少单一授权机构,频繁更换项目经理,都阻碍了需求的制定、投资的稳定性及资源分配。GAO还注意到卫星研制及采办不能与地面控制及支持设备的采办同步进行,以及未能与民间股东充分合作。

    国防部表示认识到了集权监管GPS演进的重要性,并将促进民间机构对国防部采办程序的理解,加强民事机构的参与。GAO认为,提高管理与合作很关键。如果空军不能按时研发GPS IIIA卫星,2010年,老卫星开始失灵,整个星座的卫星数可能会降低到所需的数量之下。这种能力缝隙将对所有GPS用户造成巨大影响,尽管空军和其他机构有若干措施想要将这些影响最小化。
shaolin1254 发表于 2009-5-11 18:37 | 显示全部楼层
汗。。。。这是朝元老院喊话要钱吧。。。。。。。
zhangwee 发表于 2009-5-11 19:24 | 显示全部楼层
本帖最后由 zhangwee 于 2009-5-13 14:51 编辑

IIIA的计划也要拖很久了。。。
cmj9808 发表于 2009-5-11 20:56 | 显示全部楼层
GPS2F的平台是什么?601?601HP?
 楼主| jingyan66 发表于 2009-5-17 09:51 | 显示全部楼层

GPS定位精度将从2010年起逐年降低

2009-05-15    驱动之家[原创]

根据加拿大自然资源部相关团队的测算,由于维护问题,我们目前的全球卫星定位系统GPS将从2010年起开始逐年降低精度。

根据今年四月公布的报告显示,下一个GPS卫星将在2009年11月发射升空,这已经比之前预定的发射日期晚了3年。目前及时的维修和更换太空中的卫星至关重要,因为现在轨道中运行的卫星有些已经使用了20年。如果维护没有跟上,那么全球卫星定位系统GPS的精度将逐年下降。

根据测算,目前在轨道中的24颗GPS卫星,在2010年前能为用户提供95%的定位精度。到2011年和2012年,定位精度将降低至80%,如果不及时放出下一代GPS III卫星,那么GPS的定位精度将在2017年降低至10%。
shaolin1254 发表于 2009-5-17 11:48 | 显示全部楼层
降低民码精度,保证军码么-----------------这下国际合作定位的露馅了吧。。。。。。。没自己的东西永远要受制于人呀
cmj9808 发表于 2009-5-17 12:31 | 显示全部楼层
定位精度下降是由什么造成的?整星失灵导致覆盖率降低还是星上部分载荷失灵造成的?
cmj9808 发表于 2009-5-17 12:47 | 显示全部楼层
本帖最后由 cmj9808 于 2009-5-17 12:49 编辑

维基截止08年底的数据,当时在役的31颗GPS中有13颗IIA型全部过了使用寿命(最早的是90年发射的 ),12颗IIR中最早的三颗过了使用寿命,也就是说现有的GPS星座中的半数正在超期服役。
Nighthawk 发表于 2009-5-17 16:08 | 显示全部楼层
超期服役精度肯定有影响,原子钟的精度会有漂移的吧,无线电的东西也会漂移吧。我不太懂信号的东西。
shaolin1254 发表于 2009-5-17 17:10 | 显示全部楼层
gps卫星超期服役,星上的设备肯定对定位精度有影响,但美军保军码,降民码的做法,对于要搞全球定位卫星的国家肯定有所触动。不知欧空局的伽利略在这个情况下能扯完没
cmj9808 发表于 2009-5-17 18:55 | 显示全部楼层
gps卫星超期服役,星上的设备肯定对定位精度有影响,但美军保军码,降民码的做法,对于要搞全球定位卫星的国家肯定有所触动。不知欧空局的伽利略在这个情况下能扯完没
shaolin1254 发表于 2009-5-17 17:10

如果星载设备老化导致民用精度降低,为何对军码的精度不产生影响?
shaolin1254 发表于 2009-5-17 23:23 | 显示全部楼层
这个结果是俺的猜测,因为gps保美军军用是其根本所在。增加要点地区组网密度(比如中东,东亚),应该能保证军码的精度
 楼主| jingyan66 发表于 2009-5-22 23:10 | 显示全部楼层

美空军驳斥了此前一些对GPS导航系统的担心

GPS satellites not 'falling out of the sky': Air Force


WASHINGTON, May 20 (AFP) May 21, 2009

You can put those maps away. The US Air Force has shot down fears that the space-based Global Positioning System (GPS) is going to crash.

A possible disruption in GPS service, relied upon by the US military as well as millions of drivers around the world as a navigation device, was raised in a recent report by the Government Accountability Office (GAO).

The GAO, the investigative arm of the US Congress, expressed concern that GPS could be interrupted because of delays in modernizing and deploying the constellation of Air Force satellites which provides the service.

"It is uncertain whether the Air Force will be able to acquire new satellites in time to maintain current GPS service without interruption," the GAO report said.

"If not, some military operations and some civilian users could be adversely affected," it warned.

There are currently 31 active GPS satellites orbiting 12,600 miles (20,200 kilometers) above the Earth and at least 24 operational satellites are needed to provide optimal accuracy in calculating a user's position.

The United States plans to invest over 5.8 billion dollars in GPS space- and ground-based systems through 2013 but the GAO expressed concern that "over the next several years many of the older satellites in the constellation will reach the end of their operational life faster than they will be replenished."

The GAO said that if the Air Force, which plans to launch a new satellite in August and another in early 2010, did not meet its schedule, GPS service could be affected as early as next year.

"Such a gap in capability could have wide-ranging impacts on all GPS users, though there are measures the Air Force and others can take to plan for and minimize these impacts," it said.

The GAO report prompted the Air Force Space Command to reassure the public on Wednesday that the system is not in danger of failing.

In keeping with its high-tech mission, Colonel Dave Buckman, a spokesman for Air Force Space Command, which is based at Peterson Air Force Base in Colorado, took to micro-blogging service Twitter to allay any fears.

"No, GPS will not go down," Buckman said in a Twitter message. "GPS isn't falling out of the sky."

Buckman did echo the GAO's concerns of a "potential risk associated with a degradation in GPS performance" but said "we have plans to mitigate risk and prevent a gap in coverage."

"We have 30+ satellites on orbit now. We'll launch another in Aug 09, and again early 10. Going below 24 won't happen," he said.

GPS has a myriad of uses besides just helping drivers get from Point A to Point B with real-time personal navigation devices affixed to the dashboard of their cars.

Most smartphones today come equipped with GPS, allowing a user to map his precise location at any moment, and it is widely used by the maritime and aviation industries, mass transit systems, communications networks and even electrical power grids.

Besides civilian applications, the US military uses encrypted GPS signals for troop movements, logistics, communications and search and rescue.

It also uses GPS to direct "smart" bombs and missiles and the GAO report warned that decreased performance could have an impact on military strikes.

"The accuracy of precision-guided munitions that rely upon GPS to strike their targets could decrease," the GAO said. "The risks of collateral damage could also increase."
 楼主| jingyan66 发表于 2009-5-27 11:40 | 显示全部楼层

最近媒体对GPS系统未来运行能力的质疑源自GAO的一篇报告

The GAO, the media, and GPS


by Taylor Dinerman
Tuesday, May 26, 2009


If one were to go by last week’s headlines the GPS system will collapse sometime next year. Thanks to a poorly phrased Government Accountability Office (GAO) report, and the ability of the national media to makes mountains out of molehills, we are in for a long, noisy unenlightening debate.

The relationship between the GAO and the mainstream media has never been adequately studied. In the 1980s a series of mildly negative GAO reports about the hardware involved in the Reagan military build-up were transformed by the media into an apocalyptic narrative that led much of the public to expect that high-tech US forces would collapse the first time they were faced with an enemy armed with “simple, robust” weapons. People who relied on the nation’s principal newspapers, magazines, and TV news shows for their knowledge of US military capabilities were shocked when, in 1991, the US thoroughly and completely defeated a “battle hardened” Iraqi army equipped with exactly the kinds of weapons the military reformers who had strongly influenced both the GAO and the media of that era advocated.

Like today’s GPS, the weapons being procured in the 1980s had some flaws, but they were fairly minor. They were the normal ones faced by any complicated piece of technology in the early stages of development and deployment. That today’s GPS program is behind schedule and faces a number of challenges should surprise no one. No one should expect any government project to be immune from what Heinlein called Cheops’s Law (after the pharaoh who built the Great Pyramid of Giza), which states “Nothing ever gets built on time or within budget.” This is no reason not to complain, but it does put things in perspective.

Congressman John Tierney (D-MA), who chaired the hearing where the report was discussed, ordered the Air Force representative, General Neil McCasland to avoid any “happy talk”. As a Massachusetts politician he knows all about cost overruns, construction delays, shoddy workmanship, and other problems thanks to Boston’s “Big Dig”. Compared to that fiasco, nothing that Air Force Space Command has done or not done in recent decades, not even the Space Based Infrared Satellites (SBIRS), comes close.

The expected three-year delay in the GPS IIF satellite program is fairly typical of the procurement problems faced by most Defense Department programs. In her statement to Congress, Christina Chaplain of the GAO, who led the GPS study, said that “In fact DoD continues to face cost-overruns in the billions of dollars, schedule delays adding up to years, and performance shortfalls stemming from programs that began in the 1990s and after that were poorly structured, managed and overseen.” She neglected to mention that in 1993 the civilian procurement expert cadre that had been painfully built up in the 1980s, in part as a response to the GAO and media critiques, was wiped out when the Secretary of Defense at the time, Les Aspin, fired most of them.

In any case General McCasland said that he is confident that the first GPS IIF will launch in the first half of fiscal year 2010, which gives the Air Force a pretty big window. This program has, like so many others, been restructured and given a new layer of management. This may do some good and insure that the quality control needed for success is there, but nothing is guaranteed. What is almost certain, however, is that the GPS constellation is going to remain operational and will provide positioning, navigation, and timing (PNT) services to all the users. The only question is, with how much precision and availability?

What the GAO found was that “some military operations and some civilian users could be adversely affected.” That’s hardly the “collapse” that some media outlets described. In fact, the core of the report indicates that there is an 80% chance that the system will not have the full complement of 24 operational satellites at some point between 2010 and 2014. Yet as long as Air Force Space Command maintains more than 30 operational satellites—and even has four non-operational on-orbit spares—the possibility of a real system degradation, excluding the unlikely scenario where the system is attacked, is pretty low.

The GAO concentrates on the procurement problems—that is, after all, its main function—but it does not take into account the remarkable record that the GPS system operators have earned over the years. When needed they have been able to tweak the system to radically improve overall performance. The men and women who run the constellation have the skills and the experience to keep the system running, even if a few of the satellites fail on orbit or if the replacement units are again delayed.

The biggest problem is not with the GPS system itself but with the way the Air Force has treated its space responsibilities, and here the GAO recommendation tends to be both too timid and too radical at the same time. “We recommend that the Secretary of Defense appoint a single authority to oversee the development of the GPS system, including space, ground control and user equipment assets, to ensure that the program is well executed and resourced and that potential disruptions are minimized.” This is the usual Washington solution: name a czar, no doubt with a full staff of “under-czarlings”.

If the GAO wanted to be truly visionary they would have recommended that the Administration and Congress establish a United States Space Force with its own chain of command and its own budget. To expect the Air Force, as it is currently organized, to be enthusiastic about its space responsibilities is to accept the impossible. The US Navy is never very happy when it has to divert its ships from their maritime role, especially when it involves taking their aircraft off of Nimitz-class carriers and replacing them with US Army helicopters. Why should the top leaders in the Defense Department expect the Air Force to act differently? Are Air Force generals any less subject to human nature than Navy admirals?

Keeping GPS the most reliable, accurate, and comprehensive PNT system in the world is a vital national interest. The Air Force has, with a few exceptions, done an adequate, but hardly stellar job. The media hysteria over the GAO report was to be expected, and the harm done to the USAF’s reputation is largely, but not wholly, undeserved. The mainstream media, though, has earned more black marks against itself for exaggeration, bias, ignorance, and credulity. The Air Force (or in the future the Space Force) will fix what needs to be fixed and will carry on.
cmj9808 发表于 2009-5-27 12:47 | 显示全部楼层
GAO的任务只是提交一份第三方报告,为政府项目的评估提供一个客观视角。
问题出在媒体的解读上,几乎所有大众媒体在转述GAO的报告时都不同程度的夸大了问题的严重性,他们所不知道也不关心的是GAO已经连续三年提出过这个问题,且半数GPS星座超期服役的状况至少已持续两年之久。
因此像space review这种专业媒体是非常必要的。
shaolin1254 发表于 2009-5-27 18:42 | 显示全部楼层
gps这类全球导航卫星从组网成功后,每年不都应该发射几颗新星用来替换早期发射超过寿命的么,整个项目应该像个长流水似的,只要还在用就源源不断呀。这次报告不会是为了像元老院要钱在被媒体夸大了问题吧
 楼主| jingyan66 发表于 2009-6-5 16:10 | 显示全部楼层

洛·马公司GPS III团队按计划成功完成初始设计评审阶段

2009-05-22

  [据美通社2009年5月21日报道]  洛·马团队正在开发美国空军的下一代全球定位系统(GPS)卫星——GPS III卫星,现在已经成功完成了初始设计评审(PDR)阶段,这是该项目一个重要的里程碑,之后洛·马团队将开始进入关键设计评审(CDR)阶段。
  
  在过去6个月,洛·马、ITT以及通用动力公司一起完成了航天器段的综合PDR。来自美国空军和民间社团的大约150名代表出席了在洛·马公司举行的为期4天的航天器PDR。PDR的完成表明设计满足了作战人员与民用的需求,并将GPS III项目推进到关键设计评审阶段。
  
  GPS III将改进定位、导航和授时服务,并提供先进的抗干扰能力,获得较高的系统安全性、准确性和可靠性。洛·马团队是依据2008年5月签署的30亿美元的开发与生产合同来开展工作的,最多将建造12颗GPS IIIA 卫星,首次发射计划在2014年进行。

  下一代GPS IIIA卫星与目前的GPS卫星相比将得到显著的改善,包括将拥有一个新的国际民用信号(L1C)和增强全球军队用户军码的抗干扰能力。
  
      通过精确的定位和授时信息,GPS星座为军队提供关键的态势感知和精确武器制导,并对广泛的民用应用提供支持。位于施里弗空军基地的美国空军太空司令部的第二太空作战中队(2SOPS)负责管理和运行GPS星座。
 楼主| jingyan66 发表于 2009-6-17 09:26 | 显示全部楼层

洛·马公司GPS III进入关键设计评审阶段

2009-06-16

  [据美国洛克希德·马丁公司网站2009年6月15日报道]  洛克希德·马丁公司研发美国空军全球定位系统(GPS)III计划的团队已按计划进入关键设计评审(CDR)阶段,这是一个在生产下一代卫星系统之前的重要阶段。

  2010年,洛·马公司太空系统部与工业合作伙伴ITT和通用动力公司将对GPS III卫星子系统、装配和组件进行70次独立关键设计评审。2010年秋对太空载具进行关键设计评审,此阶段将验证GPS III的设计细节,以确保其满足作战人员和民用的需求。此后评审阶段结束。

  GPS III将改进定位、导航和授时服务,并提供抗干扰能力,以得到更出色的系统安全、精确度和可信度。下一代GPS IIIA卫星将具备比目前GPS卫星更为优良的重要改进,包括一个新国际民用信号(L1C)和为军事用户提供覆盖全球的增强型M-编码抗干扰能力。

  通过精确定位和授时信息,GPS星座将为军方提供关键的态势感知和精确武器制导服务,并支持广泛领域的民用、科学和商业用途。其中包括空中交通管制、ATM银行,以及互联网。美国空军太空司令部的第二太空作战中队(2SOPS)负责为军民双方用户管理和运营GPS星座。
 楼主| jingyan66 发表于 2009-6-19 08:32 | 显示全部楼层

美国卫星轨道发生变化 GPS无法正常接受信号

2009/6/18/17:15   来源:GPS报

据了解,从6月14日上午约9点左右开始,已确认的三星方案的GPS导航仪基本上收不到卫星信号,有些只能收到一些虚的卫星信号。掌微方案的机型以及远峰机型也相继出现该情况,采用这些方案的GPS导航仪也受到影响。

据悉,该情况可能由于美国卫星出现故障引起。由于美国GPS卫星系统更新出现故障,卫星轨道运行发生了一些变化,因此计算方法就随之也发生了改变,此次卫星轨道的变化造成了全球所有定位系统都出现了问题,GPS无法正常接受信号,这对于用户使用频率较高的GPS导航仪而言,影响最为严重。据了解,不同芯片的GPS导航仪所反映出来的现象有一定不同。很多GPS厂商通过升级软件,解决了GPS导航仪无法定位的现象,更新软件后可恢复正常。据悉,6月20日中午12点,GPS定位系统有望自动恢复。

【相关阅读】

GPS定位是利用一组卫星的伪距、星历、卫星发射时间等观测量来是的,同时还必须知道用户钟差。因此,通俗一点说如果你除了要知道经纬度还想知道高度的话,那么,必须对收到4颗卫星才能准确定位。

GPS存在三部分的误差:

第一部分是所有GPS接收机都有的,如卫星钟误差,星历误差、电离层误差、对流层误差等;、

第二部分是传播延迟误差;

第三部分是所有GPS接收机固有的误差,例如通道延迟、多径效应、内部噪声等;

第一部分误差利用差分技术可以完全消除;,

第二部分误差大部分也可以消除,主要取决于基准接收机和用户接收机的距离。

第三部分误差无法消除,具体原因

如下:

1、电离层和对流层的影响

电离层的电子性质不稳定,会对无线信号造成很大的影响。

对流层充满了水汽,影响电波的传送速度

2、多路径干扰

GPS信号在接收机附近的障碍物多次所产生的影响,比如附近的高楼大厦、高山等,有时信号甚至被完全遮挡。

3、信号的接收角度

如果被捕捉到的几个卫星之间所形成的角度较大时,接收的效果较理想,反之则效果教差。

4、接收环境的影响

如是内、地下、水中等地方,电波干扰也影响精度。

5、人为干扰

美国为了国际安全利益的需要,1992年开始实行了所谓的SA政策,对定位的精度做了人为的限制和干扰,

在SA开启的时候精度降低为150-100米左右。
 楼主| jingyan66 发表于 2009-6-20 20:02 | 显示全部楼层

美空军又站出来力挺GPS

JUNE 19, 2009, 5:01 P.M. ET

Air Force Reports Confidence in GPS Satellites


By ANDY PASZTOR

The GPS fleet of military and civilian navigational satellites has resolved a recent technical problem and has "the greatest capability ever," according to the Air Force.

In a press conference with reporters Friday, Air Force Col. Dave Madden, the program manager for the Global Positioning System, said three months of studies and ground simulations has resolved a previously reported technical problem with the most recent satellite placed into orbit. Col. Madden said the problem -- which reduced the accuracy of some signals -- has "no significance" to military users of the system, and isn't expected to affect later satellite models.

But in still another apparent schedule slip for a new generation of GPS satellites being assembled by Boeing Co., Col. Madden said the first launch of those satellites could come as late as February 2010. The launch, which would update what is already considered the premier satellite-navigation system, initially was slated for this summer and then late fall.

Describing the condition of the current GPS satellite fleet as robust, Col. Madden said some satellites are lasting up to 16 years in orbit and that is expected "to keep the constellation healthy" and provide substantial backup capacity for roughly the next decade.

The latest Air Force comments are the strongest response yet to a recent critical Government Accountability Office report that raised a red flag about GPS reliability and accuracy through the middle of the next decade.

"I'm concerned about the tone" of the GAO report, the GPS program chief said. The Air Force has "continuously met service commitments" to GPS users since the inception of the system and "we have extremely high confidence" in maintaining that service, Col Madden said.

Despite the high-profile technical problems that have cropped up on the latest addition to the GPS fleet since March, Col. Madden told the media teleconference that the overall accuracy of the GPS fleet recently has shown "the best performance ever." Many locations on the ground identified by GPS signals have been accurate within about two feet.
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