A Microseismometer for Penetrometer Deployment

地震学在解决太阳系天体深层内部结构方面具有独特的能力，可以对它们的当前状态和过去的演变产生强有力的见解。地震学在探测地球内部以及后来的月球内部方面取得的成功促使在以前的几次飞行任务的有效载荷中包括地震仪。然而，自阿波罗以来，基于传统地震技术的地震仪的着陆、部署和操作所需的资源迄今为止阻碍了地震网络的成功运作。我们建议开发一个子系统的取消ExoMars地震系统，微加工硅传感器，作为一个潜在的工具，应该能够提供地震仪地震台站和网络。一个重力仪会以非常高的速度降落，把自己埋在我们想要研究的行星或月球的表面之下。这具有在仪器之间产生良好的机械连接的优点，并且可以很好地保护表面免受温度波动和任何风的影响。与着陆器相比，一个多普勒仪是一种更简单的方法来部署这样一个仪器，允许更多的仪器部署在相同的预算。这种仪器面临的最大挑战是具有检测预期弱地震的灵敏度，同时非常坚固，以承受在地震仪冲击期间预期的非常高的震动水平。微震仪是基于一组比人的头发丝还细的硅梁，它提供了一组近乎完美的弹簧来检测任何地震。初步的撞击测试表明，这种仪器的一个潜在技术路线是用升华剂包装弹簧，在最初的撞击过程中保护它们，但后来消失以释放弹簧。我们将在传感器和电子设备的替代减震方法的同时追求这一点。微震仪硅悬浮体的制造将与帝国理工学院和牛津大学的测试相结合，牛津大学还开发了接收地震信号所需的电子设备。

Seismology is unique in its ability to resolve the deep internal structure of the bodies in the solar system, producing powerful insights into both their current state and past evolution. The success of seismology in looking deep into the interior of the Earth, and later the Moon, has motivated the inclusion of seismometers in the payload on several previous missions. However, since Apollo the resources required to land, deploy and operate seismometers based on conventional seismic technology have so far prevented the successful operation of a seismic network. We propose to develop a subsystem of the cancelled ExoMars seismic system, a micromachined silicon sensor, as a potential instrument which should enable penetrometer-delivered seismic stations and networks. A penetrometer would land at very high velocity, burying itself below the surface of the planet or moon we wish to study. This has the advantage of producing an excellent mechanical connection between to the instrument and good protection from temperature swings and any wind on the surface. Compared to a lander, a penetrometer is a much simpler way of getting such an instrument deployed allowing many more instruments to be deployed for the same budget. The overiding challenge for such an instrument is to have the sensitivity to detect the weak quakes expected while being extremely robust to withstand the very high shock levels expected during the impact of the penetrometer. The microseismometer is based on a set of silicon beams thinner than a human hair that provide a set of near perfect springs for detection of any quakes. Preliminary impact testing has suggested one potential technology route for such an instrument based on packing the springs with a sublimant, protecting them during the initial impact but later disappearing to free up the springs. We will pursue this in parallel with alternative shock-mitigation approaches for both the sensor and electronics. Fabrication of the silicon suspension of the microseismometer will be combined with testing at Imperial and Oxford, with Oxford also developing the electronics needed to pick up the seismic signal.