Galileo gets into position
Galileo gets into positionEurope set to launch its rival to the Global Positioning System.
Mark Peplow
This holiday season will see the debut of a serious competitor to America's Global Positioning System (GPS) - the navigational aid used by everyone from car drivers to back-country skiers.
The European Space Agency (ESA) aims to launch the first test satellite in the Galileo network, the European equivalent of GPS, on 28 December. The full constellation of 30 satellites is expected to be operational by 2008.
Although GPS is popular and useful among civilians, they have no guarantee of its working. "GPS is still primarily a military tool," explains Terry Moore, a satellite-navigation expert at Nottingham University, UK. Theoretically, it could be switched off at any time.
Galileo, on the other hand, is designed primarily for civilian use, and promises to stay on in all but the most extreme circumstances. This makes it good in situations where safety is paramount, such as aircraft landings. The governments of ESA member states will be able to buy secure signals for their armed forces and emergency services, adds Dominique Detain, ESA's spokesman for Galileo.
One of Galileo's main benefits will be to provide competition for the GPS, says Moore, forcing both systems to keep their technology up-to-date.
Testing, testing
The test satellite GIOVE-A, built by Surrey Satellite Technology of Guildford, UK, will conduct its scouting mission 23,000 kilometres above the Earth. "This will be the first time ESA has launched a satellite into this orbit," notes Detain. GIOVE-A will measure radiation levels, and ensure that the orbit is suitable for its brethren.
The launch will also stake a claim on the radio frequencies Galileo will use. International Telecommunications Union (ITU) rules state that after submitting a proposal to use a frequency, a satellite must be in orbit and using that part of the spectrum within seven years.
As of 23 December, GIOVE-A's launch had already been delayed for two days due to software problems. But there is still plenty of time left before the December 2006 deadline, says Yvon Henri, head of space services at the ITU in Geneva, Switzerland.
Homing in
Scientists are already looking forward to using the system for more than just navigating in an unfamiliar city.
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More accessible and accurate positioning data will help geologists study plate tectonics, for example. Galileo could be used in conjunction with the 29 GPS satellites, says Philip Moore, a geodesist from Newcastle University, UK. "We'll be able to look at millimetre movements over the time span of a year."
The satellites will also help meteorologists studying the water content of the atmosphere, which is important for weather forecasting. Mapping the disruption of radio waves by water vapour can help meteorologists track weather fronts. Together, the Galileo and GPS networks should provide better forecasting power over a wider area, says Terry Moore.
The system will eventually be a commercial enterprise. But ESA is coordinating launches and monitoring the first test satellites. "We're here to promote research and development in space and harmonize it for our member states," Detain explains.
* UPDATE: The European satellite GIOVE-A launched successfully from the Baikonur Cosmodrome at 05:19 GMT on Wednesday 28 December.
伽利略进入位置
伽利略进入位置欧洲发射全球的定位系统的对手升空。
Mark Peplow
这个假日将会看见美国的全球定位系统（GPS）- 从汽车司机到内地滑雪的人任何人使用的定位导航工具 的重要竞争者的初次登场。
欧洲的空间局 (ESA) 在十二月 28 日 发射了伽利略网络，全球定位测量卫星的欧洲版本,中第一座测试人造卫星。 预期 2008 之前完成30座人造卫星的完整网络。
虽然全球定位测量卫星在平民之中很流行和很有用，但是他们不保证能工作正常。 " 全球定位测量卫星仍然主要地是一个军事的工具,"英国诺丁汉大学的一个人造卫星- 航行专家Terry Moore解释。 理论上，它可以随时被关上。
另一方面伽利略 主要设计为平民使用, 而且允诺保证几乎在最极端的环境中都能用。 这使它成为一些极为重要的情形中的安全保证,例如 飞机着陆。 ESA 成员的政府将会可以 为他们的武装力量和紧急状况服务购买可靠的信号, ESA的 发言人Dominique Detain 附带说伽利略。
伽利略主要益处之一是与全球定位测量卫星竞争, Moore说, 使这两个系统保持他们的技术更新。
测试, 尝试
测试人造卫星 GIOVE-A,由英国 Guildford Surrey 人造卫星技术公司 建造,将在地球上面的23,000个公里 进行它的引导任务。 " 这将会是第一次 ESA 发射一座人造卫星进入这个轨道之内," Detain记录到。 GIOVE- A将会测量放射线水平, 并确定轨道对它的弟兄们是否适当。
这次发射也将会确定伽利略上将使用的无线电电波的要求。 国际的电传视讯联盟 (ITU)在一份使用频率的提议确定之后说, 一座在轨道中的人造卫星一定在七年内使用那个部份的频率。
在十二月 23 日,GIOVE- A已经由于软件问题被延迟长达二天发射。但是在2006年十二月 到截止期限仍然剩下许多时间, Yvon Henri 之前说，空间的无线天线在瑞士日内瓦的ITU 维修。
附带功能
科学家已经在期望使用系统的功能超越仅仅在一座不熟悉的城市中航行。
举例来说比较接近和更准确的定位数据将会帮助地质学者研究板块构造论。 伽利略能够与 29座全球定位测量人造卫星协同工作, 来自英国新堡大学的 一位地理学家Philip Moore说。 " 我们将会可以 察觉在一年的时间里指距上的毫米运动."
人造卫星也将会帮助气象学者研究大气的水状况, 这对天气预测是重要的。 水汽的无线电波的分析图形能帮助气象学者追踪天气发展。伽利略和全球定位测量卫星网络一起提供更大的范围和力量进行更多的预测, Terry Moore说。
系统最终将用于商业企业。 但是 ESA 正在开始协调和监听第一座测试人造卫星。 "我们为我们的成员促进空间的研究和发展，协调," Detain解释。
*更新消息: 欧洲的人造卫星 GIOVE- 一在十二月 28 日星期三在格林威治标准时间 05:19 从 Baikonur 人造宇宙站发射基地成功的发射。
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