A Microseismometer for Penetrometer Deployment

地震学的独特之处在于它能够解析太阳系天体的深层内部结构，从而对它们的当前状态和过去的演化产生强有力的见解。地震学在深入观察地球内部以及后来的月球内部方面的成功，促使在之前的几次任务中，地震仪都被纳入了有效载荷中。然而，自阿波罗计划以来，由于着陆、部署和操作基于常规地震技术的地震仪所需的资源，迄今为止，地震网络的成功运作一直受到阻碍。我们建议为取消的ExoMars地震系统开发一个子系统，一个微机械硅传感器，作为一种潜在的仪器，它应该能够实现穿透仪交付的地震台站和网络。穿透仪将以非常高的速度着陆，将自己埋在我们希望研究的行星或月球的表面以下。这样做的优点是在仪器之间产生良好的机械连接，并且可以很好地保护温度波动和表面上的任何风。与着陆器相比，穿透仪是一种更简单的方法，可以在相同的预算下部署更多的仪器。对于这种仪器来说，最重要的挑战是要具有探测预期的弱地震的灵敏度，同时要非常坚固，以承受预计在穿透仪撞击期间的非常高的冲击水平。微地震仪是基于一组比人类头发还细的硅梁，它提供了一组近乎完美的弹簧，用于探测任何地震。初步的冲击测试表明，这种仪器的一种潜在的技术路线是用升华剂包裹弹簧，在最初的冲击期间保护它们，然后消失以释放弹簧。我们将与传感器和电子设备的替代减震方法同时进行这一研究。微地震仪的硅悬架的制造将与帝国理工大学和牛津大学的测试相结合，牛津大学还将开发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.