Participation in the CONSERT instrument on Rosetta in order to inform the science team of up-to- date cometary nucleus models.

罗塞塔任务是欧洲航天局的基石任务之一，它的主要目标是将一艘宇宙飞船插入彗星核的轨道，并在彗星表面放置一个着陆器。轨道飞行器和着陆器都将携带几个独立的仪器。其中一种仪器，在轨道器和着陆器上都有组件，是彗星核无线电波传输探测实验（CONSERT）。CONSERT实验的主要科学目的是确定原子核深处的结构和组成。它将通过从轨道飞行器发射无线电波来实现这一目标，无线电波将穿过彗核，被“菲莱”号探测器接收。在接收到初始波后，着陆器将发射第二波，第二波将再次穿过核心并被轨道飞行器接收。从测量的传输时间和功率损耗，可以推断出内部的组成（折射率）以及内部反射的次数。这将被重复很多次。该任务的设计假设目标是46P/Wirtanen彗星。发射的延迟意味着飞往46P/Wirtanen彗星的窗口已经失去，必须选择一个新的目标，67P/Churyumov-Gerasimenko彗星。对于许多仪器来说，这只是一个微小的变化，但对于CONSERT来说，由于67P/Churyumov-Gerasimenko彗星比46P/Wirtanen彗星更大，所以它的意义更为重大。所选频率的无线电波（现在无法改变）是否能穿透67P/丘留莫夫-格拉西门科彗星彗核的较长弦（也相当长），这是非常不重要的，尽管这只有在彗核内部有更好的模型可用时才能准确确定。不管波是否会穿透所有的和弦，对于CONSERT的仪器来说，把着陆器放在一些较短的和弦的末端附近是有益的。然而，这引起了关于尘埃环境的问题，因为这样的着陆需要最深的穿透任何周围的尘埃。因此，CONSERT团队需要在遇到67P/Churyumov-Gerasimenko彗星之前尽可能详细地了解彗星的核心，以最大限度地提高仪器的科学性。这既是为了确定沿较长的和弦传播是否可能，也是为了估计在较短的和弦末端着陆的危险。此外，为了从实测数据中获得地层的组成和结构，需要一定的反演方法和建模。这反过来也需要最好的彗核模型。这既可以从对67P/Churyumov-Gerasimenko的直接观测中得到，当观测几何形状有利时，也可以从对类似轨道上类似大小的彗星的研究中得到。有关彗星喷射尘埃的信息可以从对流星流的研究中获得。作为一个整体，CONSERT团队还不够专业，无法进行这种建模。自上世纪90年代中期首次被选中以来，这位提案人一直是CONSERT的联合研究员，而levser - regourd教授是Co-I中仅有的两位有能力做这件事的彗星/流星科学家。这一提议将使CONSERT团队尽可能地了解彗星核。没有为完成上述任务所需的实际研究寻求资金，只有为允许提议者参加与CONSERT相关的研讨会和会议而寻求旅费，以便CONSERT团队充分了解事态发展和影响。

The Rosetta mission is one of the cornerstone missions of the European Space Agency, it principal aim being to insert a spacecraft in orbit about a cometary nucleus and to place a lander on the surface. Both the orbiter and the lander would carry several independent instruments. One of the instruments, with components on both the orbiter and the lander is The COmet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT). The main scientific aim of the CONSERT experiment is to determine the structure and composition of the deep interior of the nucleus. It will do this by transmitting a radio wave from the orbiter which will pass through the nucleus and be received by the lande (Philae). On receiving the initial wave, the lander will transmit a second wave that will again pass through the nucleus and be received by the orbiter. From the measured time of transmission and the power loss, deductions can be made about the composition (refractive index) of the interior as well as the number of internal reflections. This will be repeated many times. The mission was designed on the assumption that the target was comet 46P/Wirtanen. Delay in the launch meant that the window for a flight to comet 46P/Wirtanen was lost and a new target, comet 67P/Churyumov-Gerasimenko, had to be selected. For many of the instruments, this was a minor change, but for CONSERT, as 67P/Churyumov-Gerasimenko is a larger comet than 46P/Wirtanen, it was rather more significant. It is very marginal as to whether or not the radio waves at the selected frequency (which can not now be changed) can penetrate all the way through the longer chords of the nucleus of comet 67P/Churyumov-Gerasimenko (which is also quite elongated), though this can only be accurately determined when better models of the interior of the nucleus are available.Whether or not waves will penetrate along all chords, for the CONSERT instruments, having the lander placed near the ends of some of the shorter chords would be beneficial. However, this raises problems regarding the dust environment, since such a landing requires the deepest penetration through any surrounding dust. Hence the CONSERT team require the most detailed knowledge possible regarding the nucleus of comet 67P/Churyumov-Gerasimenko before encounter in order to maximize the scientific from the instrument. This is required in order both to determine whether transmission along the longer chords is likely to be possible and to estimate the danger from landing near the end of one of the shorter chords. Also, in order to obtain the composition and structure from the measured data, some inversion methodology and modeling is required. This also in turn requires the best possible models of a comet nucleus. This can be obtained both from direct observations of 67P/Churyumov-Gerasimenko when the observing geometry is favourable and also from the study of comets of a similar size on similar orbits. Information regarding dust ejected from comets can be obtained from the study of meteor streams. The CONSERT team as a whole is not expert enough to carry out this modeling. The proposer, who has been a Co-Investigator on CONSERT since it was first selected in the mid 90's and Professor Levasser-Regourd are only two cometary/meteor scientists amongst the Co-I's capable of doing this. This proposal will allow the CONSERT team to be as well-informed as is possible regarding cometary nuclei. Funding is not being sought to carry out the actual research that is necessary to fulfill the above task, only travel costs to allow the proposer to attend CONSERT related workshops and meetings so that the CONSERT team is kept full aware of developments and implications.