本帖最后由 voyagerbb 于 2010-5-17 19:03 编辑
这也是维基上的一个词条,还没有见到中文版,所以试着翻译了一下,有些地方不是对字对句的.
Pioneer anomaly
先驱者号异常
The Pioneer anomaly or Pioneer effect is the observed deviation from predicted trajectories and velocities of various unmanned spacecraft visiting the outer solar system, most notably Pioneer 10 and Pioneer 11.
先驱者号异常或称先驱者号效应,是指观测到的几个访问外太阳系的无人探测器轨道与速度跟人们的预计之间存在差异,尤以先驱者10号和先驱者11号最为明显.
Both Pioneer spacecraft are escaping from the solar system, and are slowing down under the influence of the Sun's gravity. Upon very close examination, however, they are slowing down slightly more than expected. The effect can be modeled as a slight additional acceleration towards the Sun.
两个先驱者号探测器正在逃离太阳系,且在太阳引力的作用下逐渐减速. 然而,经过非常仔细的检查,它们的减速比预期的要多一些.这个效应可描述为一个微弱的指向太阳方向的加速度.
The anomaly has no universally accepted explanation. The explanation may be mundane, such as measurement error, thrust from gas leakage or uneven radiation of heat. However, it is also possible that current physical theory does not correctly explain the behaviour of the craft relative to the sun.
对这个异常现象尚没有能够为大家所普遍接受的解释,原因可能很平常,比如测量误差啊,来自泄露气体或者不均匀热辐射的反冲啊之类的.但是也还有一种可能是,目前的物理理论尚无法正确地解释远离太阳的探测器的行为.
Contents
目录
1 Initial indications
初始迹象
2 Other indications
其它征兆
3 Proposed explanations
现有解释
◦ 3.1 Observational errors
观测误差
◦ 3.2 Recording errors
记录误差
◦ 3.3 The deceleration model
减速模型
◦ 3.4 New physics
新物理
▪ 3.4.1 Clock acceleration
时钟加速
▪ 3.4.2 Definition of gravity modified
修改引力定义
▪ 3.4.3 Definition of inertia modified
修改惯性定义
4 Further research avenues
进一步的研究途径
5 Meetings and conferences about the anomaly
关于此异常的研讨会
6 See also
另见
7 Notes
注
8 Primary references
原始文献
9 References
参考文献
10 Further reading
进一步阅读
11 External links
外部链接
Initial indications
初始迹象
Pioneer 10 and 11 were sent on missions to Jupiter and Jupiter/Saturn respectively. Relatively simple, the spacecraft were spin-stabilised in order to keep their main antennas pointed towards Earth using gyroscopic forces. Although the spacecraft included thrusters, these were left unused after their primary encounters, leaving them on a long "cruise" phase through the outer solar system. During this period, both spacecraft were repeatedly contacted to obtain various measurements on their physical environment, providing valuable information long after their initial missions were complete.
先驱者10号和先驱者11号分别被发往木星和木星/土星执行任务.它们通过自转保持平衡以使其主天线通过回转力指向地球. 探测器本身带有的推进器在它们第一次相会之后就不再使用,自那以后它们就进入了一个穿越外太阳系的漫长巡弋.在此期间,探测器不断跟地球保持联系以对其周围的物理环境进行大量的测量,在其开始的任务完成之后的很长时间内,它们提供了非常有价值的信息.
Since the spacecraft were flying without additional stabilization thrusts during their "cruise", it is possible to characterize the density of the solar medium by its effect on the spacecraft's motion. In the outer solar system this effect would be easily calculable, based on ground-based measurements of the deep space environment. However, when these effects were taken into account, along with all other known effects, the calculated position of the Pioneers did not agree with measurements based on timing the return of the radio signals being sent back from the spacecraft. These consistently showed that both spacecraft were closer to the inner solar system than they should be, by thousands of kilometres - small compared to their distance from the Sun, but still statistically significant. This apparent discrepancy grew over time as the measurements were repeated, suggesting that whatever was causing the anomaly was still acting on the spacecraft.
探测器在其巡弋期间没有持续的推力,而太阳系的介质会对其运动产生效应,这种效用有可能用来标示这些介质的密度.通过在地面上对深空环境的测量,外太阳系中的这个效应很容易被计算出来.然而,当这个效应跟其它已知的效应一起被考虑的时候,人们计算出的先驱者号的位置跟由探测器本身发出的无线电信号测量出的位置并不一致(译注:估计就是计算无线电波从发出到接收之间传播的距离,探测器上有个钟,跟地面上的钟校对过).这表明探测器比预期的要更靠近内太阳系些,大概近了数千公里,虽然跟其离太阳的距离相比非常小,但在统计学的意义上来看依然非常显著.随着时间的推移和测量的继续,这个不一致越来越大,表明造成这个异常的因素仍在发挥作用.
As the anomaly was growing, it appeared that the spacecraft were moving more slowly than expected. Direct measurements of the spacecraft's speed using the Doppler effect demonstrated the same thing: the Pioneers were slowing down more than expected.
这个异常一直在增长,表明探测器的运动比预期的要慢.直接通过多普勒效应(Doppler effect)来测量其速度也得到了同样的结论: 先驱者号比预期的要慢.
When all known forces acting on the spacecraft are taken into consideration, a very small but unexplained force remains. It appears to cause a constant sunward acceleration of (8.74 ± 1.33) × 10−10 m/s2 for both spacecraft. If the positions of the spacecraft are predicted one year in advance based on measured velocity and known forces (mostly gravity), they are actually found to be some 400 km closer to the sun at the end of the year. The magnitude of the Pioneer effect is numerically quite close to the product of the speed of light and the Hubble constant, but the significance of this, if any, is unknown. Gravitationally bound objects such as the solar system, or even the galaxy, do not partake of the expansion of the universe — this is known both from theory[1] and by direct measurement.[2]
考虑到所有已知的作用在探测器上的力,人们发现还有一个非常小的力无法解释.这个力对所有的探测器都产生了一个恒定的指向太阳的加速度,大小为: (8.74 ± 1.33) × 10−10 米/秒2.
如果根据测到的速度和所有已知的力(最重要的是引力)先提前计算出探测器一年后的位置,并在一年后去观测,人们会发现其离太阳的距离比计算的要近400公里.先驱者号效应在数值上非常接近光速跟哈勃常数的乘积,但是这个结果是不是真有重要的意义,人们依然不清楚.不过理论和观测都表明,宇宙的膨胀对引力束缚系统,如太阳系甚至星系,是没什么影响的.
Other indications
其它征兆
The Pioneers were uniquely suited to discover the effect because they have been flying for long periods of time without additional course corrections. Most deep-space probes launched after the Pioneers either stopped at one of the planets, or alternately used thrusting throughout their mission.
先驱者号是仅有的适合发现这一效应的探测器,因为它们一直在进行长时间的无轨道修正的飞行.先驱者号后面发射的大多数深空探测器要么就停在了某一行星处,要么就是在任务过程中一直在使用推进器.
The Voyagers flew a mission profile similar to the Pioneers, but were not spin stabilized. Instead, they required frequent firings of their thrusters for attitude control to stay aligned with Earth. Spacecraft like the Voyagers acquire small and unpredictable changes in speed as a side effect of the frequent attitude control firings. This 'noise' makes it impractical to measure small accelerations such as the Pioneer effect.
旅行者号探测器的任务历程跟先驱者号类似,但没有通过自转来维持稳定,而是通过推进器的频繁点火来进行姿态控制,从而保持与地球的联系.类似旅行者号这样的探测器的速度会有小的且不可预料的变化,这是频繁点火进行姿态控制的副产品.这些”噪音”使得测量诸如先驱者号效应那样的小的加速度变的不现实.
Newer spacecraft have used spin stabilization for some or all of their mission, including both the Galileo and Ulysses. These spacecraft indicate a similar effect, although for various reasons (such as their relative proximity to the Sun) firm conclusions cannot be drawn from these sources.
更新的空间探测器,包括伽利略号和尤利西斯号,则在其部分或全部任务中使用了自转保持稳定.这些探测器也表现出了类似的效应,不过由于各种原因(如它们离太阳相对来说要近些)尚不能从中得出确切的结论.
The Cassini mission has reaction wheels as well as thrusters for attitude control, and during cruise could rely for long periods on the reaction wheels alone, thus enabling precision measurements. However, it also had radioisotope thermoelectric generators (RTGs) mounted close to the spacecraft body, radiating kilowatts of heat in hard-to-predict directions. The measured value of unmodelled acceleration for Cassini is (26.7 ± 1.1) × 10−10 m/s2, roughly three times as large as the Pioneer acceleration. Unfortunately, the measured value is the sum of the uncertain thermal effects and the possible anomaly. Therefore the Cassini measurements neither conclusively confirm nor refute the existence of the anomaly.[3]
卡西尼探测器使用反作用轮(reaction wheel)和推进器进行姿态控制,并且在长时间巡弋期间仅使用反作用轮,这使得进行精确的测量成为可能.然而,这个探测器携带的放射性同位素热电发生机 (radioisotope thermoelectric generators, RTGs)非常靠近探测器本身,在各个难以预料的方向上都有可能辐射出上千瓦的热量.卡西尼号的额外加速度是 (26.7 ± 1.1) × 10−10 米/秒2 , 大致为先驱者号加速度的3倍.不幸的是这个测量结果实际上是各种不确定的热效应和可能的异常效应之和. 因此对于这种加速度的异常,卡西尼号的测量既不能证真也不能证伪.
Proposed explanations
现有解释
There have been a number of proposed explanations for acceleration towards the sun have been pursued. These are defined as the following: observational errors, an unaccounted for real deceleration, and explanations that would essentially be New Physics.
针对这个指向太阳方向的加速度,人们已经提出了一些解释,这些解释可以这样归类:观测误差,还没有被考虑到的真正的减速,一种本质上的新物理.
Observational errors
观测误差
The possibility of observational errors, which include measurement and computational errors, has been advanced as the reason for Pioneer anomaly interpretation of data. This would be the cause of approximation and statistical errors.
有人提出测量误差和计算误差来解释先驱者异常.
Further analysis has determined that significant errors are not likely because seven independent analyses have shown the effect as of March 2010.[4]
进一步的分析表明不大可能存在大的误差,因为至2010年3月(译注:此处疑为2007 年)七个独立的分析都给出了这个效应.
Recording errors
记录误差
The effect is so small that it could be a statistical anomaly caused by differences in the way data were collected over the lifetime of the probes. Numerous changes were made over this period, including changes in the receiving instruments, reception sites, data recording systems and recording formats.
在整个探测器的一生中,人们使用不同的方式收集数据,而先驱者号效应非常小,因此它可能实际上是由这种不同的收集数据的方式而导致的统计异常.在先驱者号的工作期间,人们更改了很多东西,包括接收仪器,接受站,数据记录系统及格式.
The Planetary Society announced on 1 June 2006 that 30 years of Pioneer data had been saved. It announced on 28 March 2007 that analysis of the data was underway. On March 19, 2008, it announced that one source of acceleration, uneven thermal radiation, had been found to explain some of the deviation, but not all.[5][6][7]
美国行星协会(the Planetary Society)于2006年6月1日宣布已经保存了先驱者号工作30年的数据,并于2007年3月28日宣布正在对这些数据进行分析.2008年3月 19日,该协会宣布发现一种新的加速源,非均匀的热辐射,可用来解释一部分的异常,但不是全部都能解释.
The deceleration model
减速模型
It has been viewed as possible that a real deceleration is not accounted for in the current model for several reasons.
人们认为,可能确实有一个真实存在的减速度没有为当前的模型所考虑到,原因如下:
First, it is possible that deceleration is caused by gravitational forces from unidentified sources such as the Kuiper belt or dark matter. However, this acceleration does not show up in the orbits of the outer planets, so any generic gravitational answer would need to violate the equivalence principle (see modified inertia below). Likewise, the anomaly does not appear in the orbits of Neptune's moons, challenging the possibility that the Pioneer anomaly may be an unconventional gravitational phenomenon based on range from the Sun.[8][9]
首先,也许这个减速度是由尚未识别的源的引力引起的,如柯伊伯带或者暗物质.然而,其它的外行星轨道并没有展示出这种加速度来,所以如果用普遍的引力来作答的话,就必然会破坏等效原理(equivalence principle,参见下面的修改惯性部分).同样, 海王星卫星的轨道也没有这种异常,这使得那些认为先驱者号异常可能是由一种跟到太阳距离有关的引力现象引起的理论受到挑战.
Second, the cause could be drag from the interplanetary medium, including dust, solar wind and cosmic rays. However, the measured densities are too small to cause the effect.
其次,减速可能来自于行星际介质(interplanetary medium)的拖曳,包括尘埃,太阳风及宇宙线.然而,人们测量到的这些物质密度都很低,不足以引起这个效应.
Third, gas leaks, including helium from the spacecrafts' radioisotope thermoelectric generators (RTGs) has been viewed as possible causes.
第三,气体泄露,包括探测器的放射性同位素热电发生机(RTGs) 泄露的氦也被视为一种可能的原因.
Fourth, a real deceleration not accounted for in the current model could result from radiation pressure of sunlight, the spacecraft's radio transmissions, or asymmetrical thermal radiation of the heat from the spacecraft. Possibilities include the asymmetrical radiation of heat from the RTGs (See Radioisotope rocket) or the spacecraft electronics. Additionally, even if the RTGs themselves radiate symmetrically, some of their radiation will reflect from the back of the spacecraft’s dish-like main antenna, causing a recoil like sunlight striking a solar sail.
第四,有一种确实存在的减速度没有被当前的模型考虑到,这个减速度可以来自于太阳光,探测器的无线电传输或者非对称的热辐射的辐射压.可能包括RTGs(参见放射性同位素火箭,Radioisotope rocket)或者探测器本身的电子设备的非对称辐射.
However, the radiation pressure of sunlight is too small at this distance, and points into the wrong direction. The same applies to the spacecraft's radio emissions. The asymmetrical radiation of heat remains a prime suspect, as presented at the second ISSI meeting in Berne, Feb 2007. A presentation at the APS April 2008 meeting suggests that differential heating may account for as much of 1/3 rd of the observed acceleration.[10]
然而在这样远的距离上,太阳光的压强太小了,而且方向也不对,探测器本身的无线电传输也是如此. 2007年2月在伯尔尼举行的第二届ISSI会议上,人们仍然认为非对称的热辐射是最主要的嫌疑.2008年4月的APS会议上,一个报告指出这种热辐射的方向差异可能产生观测到的1/3强的加速度.
Finally, a real deceleration not accounted for in the current model could be from electromagnetic forces due to an electric charge on the spacecraft.
最后,还有一种可能来自电磁力的减速度没有被当前的模型所考虑到,这种电磁力来自于探测器本身所带有的电荷.
New physics
新物理
Because the "Pioneer anomaly" does not show up as an effect on the planets, Anderson et al speculated that this would be interesting if this was new physics. Later, with the doppler shifted signal confirmed, the team again speculated that one explanation may lie with new physics, if not some unknown systemic explanation.[11]
由于”先驱者号异常”并没有在行星上得到体现, Anderson 等人猜测,如果这是一种新的物理原理的话那将会非常有趣. 稍后,多普勒红移的信号得以证实,这个团队再次猜想新的物理原理可能是一种解释,如果这个异常不是由未知的系统误差造成的话.
Hence, new physics would take into consideration at least one of three possibilities: clock acceleration, a modification of the law of gravity, or modified inertia.
因此,新的物理原理可能至少是这三种可能性之一:时钟加速,修改引力定律或者修改惯性.
Clock acceleration
时钟加速
Clock acceleration is an alternate explanation to anomalous acceleration of the spacecraft towards the Sun. This theory takes notice of an expanding universe, which creates an increasing background 'gravitational potential'. The increased gravitational potential then accelerates cosmological time. It is proposed that this particular effect causes the observed deviation from predicted trajectories and velocities of Pioneer 10 and Pioneer 11.[11]
时钟加速是空间探测器向太阳方向反常加速的一个可能的解释.这一理论从膨胀的宇宙中得到启发,膨胀的宇宙产生了一个增长的背景”引力势”. 这一增长的引力势加速了宇宙时标.于是人们提出这个特殊的效应导致了观测到的先驱者10号跟11号的轨迹和速度跟理论预期之间的差异.
From their data, Anderson's team deduced a steady frequency drift of 1.5 Hz over 8 years. This could be mapped on to a clock acceleration theory, which means all clocks would be changing in relation to a constant acceleration. In other words, that there would be a nonuniformity of time. Moreover, for such a distortion related to time, Anderson's team reviewed several models in which time distortion as a phenomenon is considered. They arrived at the "clock acceleration" model after completion of the review. Although the best model adds a quadratic term to defined International Atomic Time, the team encountered problems with this theory. This then led to non-uniform time in relation to a constant acceleration, as the most likely theory.[note 1]. [11]
据他们的数据, Anderson的团队导出了一个稳定的频率漂移:每8年1.5赫兹.这个结论可以被映射到时钟加速理论上,意味着所有的时钟都会有变化,这种变化跟一个常值加速度有关.换句话说,时间会有不均匀性.更进一步,对于这样一个跟时间有关的畸变,Anderson的团队总结了几个模型,在这些模型中时间畸变作为一种现象被考虑到.在这个总结完成之后”时钟加速”模型就诞生了. 尽管最好的模型在国际原子时(International Atomic Time)上添加了一个二阶项,这个理论还是遇到了一些问题.从这里面最合适的理论来看,这一解释导致了跟恒定加速度有关的非均匀的时间.(译注:说实在这一段我看得一头雾水).
Definition of gravity modified
修改引力定义
The theory MOND (Modified Newtonian Dynamics) proposes that the force of gravity deviates from the traditional Newtonian value to a very different force law at very low accelerations on the order of 10−11 m/s2.[12] Given the low accelerations placed on the spacecraft while in the outer solar system, MOND may be in effect, modifying the normal gravitational equations.
修改牛顿动力学理论(Modified Newtonian Dynamics, MOND)提出,在加速度低至 10−11 米/秒2 的量级的情况下,引力会偏离传统的牛顿定律给出的值.空间探测器所处的外太阳系加速度非常低,MOND理论的效应将会得以体现,从而改变通常的引力方程.
Definition of inertia modified
修改惯性定义
MOND can also be interpreted as a modification of inertia, perhaps due to an interaction with vacuum energy and such a trajectory-dependent theory could account for the different accelerations apparently acting on the orbiting planets and the Pioneer craft on their escape trajectories.[13] More recently, a model for modified inertia using Unruh radiation and a Hubble-scale Casimir effect has been proposed to explain the Pioneer anomaly,[14] and a possible test for evidence of modified inertia on Earth has been proposed.[15] It has also been suggested that a modification of inertia can explain the flyby anomaly.[16]
MOND理论也可以被理解为修改了惯性,也许是由于跟真空能(vacuum energy)之间有相互作用的原因,这一理论依赖于物体轨迹,可以解释处于绕太阳轨道上运行的行星跟处于逃逸轨迹上的先驱者号所受到的加速度的差异. 不久之前,有人提出了一个使用盎鲁辐射(Unruh radiation)和哈勃尺度上的卡西米尔效应(Casimir effect)的修改惯性的模型来解释先驱者号异常,还有人提出了一个可能的实验,用以在地球上检验修改惯性理论.修改惯性理论还可以解释飞越异常 (flyby anomaly).
Further research avenues
进一步的研究途径
It is possible, but not proven, that this anomaly is linked to the flyby anomaly.[17] Although the circumstances are very different (planet flyby vs. deep space cruise), the overall effect is similar - a small but unexplained velocity change is observed on top of a much larger conventional gravitational acceleration.
这一异常现象可能是跟飞越异常 (flyby anomaly)是有关联的,虽然未经证实.尽管二者的环境十分不同(飞跃行星跟深空巡航相比),整体效应却类似---在通常的引力加速度之外人们观测到了一个无法解释的小的速度变化.
The Pioneer spacecraft are no longer providing new data, (the last contact having been on 23 January 2003)[18] and Galileo was deliberately burned up in Jupiter's atmosphere at the end of its mission. So far, attempts to use data from current missions such as Cassini have not yielded any conclusive results. There are several remaining options for further research:
先驱者号探测器已不再提供新的数据(最后一次联络是在2003年的1月23日)而伽利略号则已在其结束任务之后烧毁在了木星的大气层之内.到目前为止,对现有探测器,如卡西尼号的数据的分析还没有给出任何结论性的结果.对进一步的研究来说, 有如下的一些选择:
Further analysis of the retrieved Pioneer data.
进一步分析已经得到的先驱者号的数据
The New Horizons spacecraft to Pluto is spin-stabilised for much of its cruise, and there is a possibility that it can be used to investigate the anomaly. New Horizons may have the same problem that precluded good data from the Cassini mission - its RTG is mounted close to the spacecraft body, so thermal radiation from it, bouncing off the spacecraft, may produce a systematic thrust of a not-easily predicted magnitude, several times as large as the Pioneer effect. Nevertheless efforts are underway to study the non-gravimetric accelerations on the spacecraft, in the hopes of having them well modeled for the long cruise to Pluto after the Jupiter fly-by that occurred in February 2007. In particular, despite any large systematic bias from the RTG, the 'onset' of the anomaly at or near the orbit of Saturn might be observed.[19]
新地平线号探测器在其去往冥王星的途中,很多时间都在使用自转来维持稳定,因此可能被用来研究这一异常效应.新地平线号跟产生很好的数据的卡西尼号探测器面临同样的问题---它的RTG也是跟探测器本身很靠近,从探测器上反射回来的热辐射可能会产生一个系统性的冲力,比先驱者号的要大好几倍,而且强度很难预测.尽管这样,人们还是在努力研究探测器上的非重力的加速度.新地平线号在2007年2月飞越木星之后就进入通往冥王星的漫长巡航,人们期望在这期间它受到的非重力加速度可以被模型很好地描述.特别期望在忽略掉RTG 造成的系统误差之后,在土星轨道或接近土星轨道处开始显现的异常现象会被观测到.
A dedicated mission has also been proposed.[20] Such a mission would probably need to surpass 200AU from the Sun in a hyperbolic escape orbit.
有人提出了做一个专用探测器的方案.这样的一个探测器可能需要沿双曲逃逸轨道在距太阳 200天文单位处越过.
Observations of asteroids around 20AU may provide insights if the anomaly's cause is gravitational.[21][22]
观测约20天文单位处的小行星可能会提供更深入的了解,如果这以异常是由引力产生的话.
In November 2009, ESA's Rosetta spacecraft measured its velocity during flyby to within a few millimeters per second in an effort to explain the flyby anomaly.[23] However, no anomaly was found on this most recent flyby.[24]
[/color=Blue]2009年11月,欧洲空间局(ESA)的罗塞塔号探测器在飞越时以几毫米每秒的精度测量了其速度,以致力于解释飞越异常.然而在这最近的一次飞越中人们没有发现任何异常.
Meetings and conferences about the anomaly
关于这个异常的会议与研讨会
A meeting was held at the University of Bremen in 2004 to discuss the Pioneer anomaly.[25]
不来梅大学于2004年举办了一个会议来讨论先驱者号异常.
The Pioneer Explorer Collaboration was formed to study the Pioneer Anomaly and has hosted three meetings (2005, 2007, and 2008) at International Space Science Institute in Berne, Switzerland to discuss the anomaly, and discuss possible means for resolving the source.[26]
先驱者号探测器协作会(Pioneer Explorer Collaboration)建立的目的就是为了研究先驱者号异常现象,并已于2005年,2007年和2008年在瑞士伯尔尼的国际空间科学研究所 (International Space Science Institute)分别主办了3次会议,以讨论这一异常及可能的分辨源的方法.
(下略...)
维基上的英文原文地址:
http://en.wikipedia.org/wiki/Pioneer_anomaly |
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