Lunar Super Low-Frequency Atomic Seismometer

We propose to develop a super low-frequency atomic seismometer for lunar landers and network applications. The seismometer instrument employs using atomic test masses as the inertial reference frame and atom interferometry for displacement measurements. The baseline technology has been investigated and demonstrated as a quantum gravity gradiometer for earth gravity measurements and an orbiter atomic drag-free reference instrument for planetary gravity measurements. Due to its reliance on the atomic system, the measurement system can be more stable over longer time period than its mechanical counter parts. Therefore, the atomic seismometer will provide unprecedented seismic sensitivity at frequency ranges from Hz down to µHz. Seismology has been a key technique for understanding a planet and its interior. Seismic measurements have extensively provided unique and valuable information about the interior structure and dynamics of the Earth. Indeed, almost all first lander mission of a planet carried seismometers, including on the moon. The need and benefit of broadband planetary seismometers with low-frequency sensitivity are exemplified by the VBB instrument on the InSight mission. The potential for the atomic seismometer to achieve extremely high sensitivity and low noise at very low frequencies (sub-µHz) is vital for science on the moon, which is very quiet in comparison with Earth or even the activity levels predicted for Mars. In particular, the low-frequency sensitivity of the instrument enables science beyond that achieved with the instruments from the Apollo missions, including long-period surface waves and normal modes at frequencies down to sub-mHz range and tide measurements in the sub-µHz range. The atomic seismometer instrument is based on the principle of quantum matter-wave interferometry. It utilizes the interference of atom waves, with atoms laser cooled to microKelvin temperatures without cryogenics. One major difference of the atomic seismometer from traditional mechanical ones is the use of totally free-fall test masses without any spring mechanism or measurement back-action. This allows for high acceleration sensitivity and extreme measurement stability without the need for on-board calibrations. Through NASA ROSES programs, we have demonstrated a transportable atomic gravity gradiometer and subsequently miniaturized it into a shoebox-sized accelerometer sensor system. The objective of the DALI effort is to develop and mature an integrated instrument system of atomic seismometer specifically for moon deployment, perform full characterizations and evaluations, and make it ready to be infused into for a lunar lander mission. More »