The Mars SEIS Experiment : Development Status

The objective of the Mars SEIS experiment is the determination of the deep internal structure of Mars. In particular, geophysical parameters of first importance, such as the state (liquid/solid) and size of the core, as far as structure of the mantle and shape of discontinuities will be determined by the experience. The experiment integrates a Very Broad Band (2 axis) seismometer, a (3 axis) short period seismometer and environmental sensors for pressure, infrasounds and temperature. The sensors measure signals in an ultra-broad band, from the tidal frequencies (0.05 mHz) up to the short period frequencies (50 Hz). Long term VBB bias will be actively decorrelated from temperature and pressure variations, allowing the sensor to operate in a thermal environment with daily variations of about 40°K Infrasounds, which might be associated to dust devils and atmospheric discharge, will be also monitored. The overall mass of the SEIS experiment is 2.3 kg, including all sensors, data control processors and depployment devices. Acquisition will be performed by a series of 24 bits A/D converters, while the thermal and drift control will be performed by a feedback generated by a 24 bits D/A converter. A breadboard of the VBB axis is been delivered by industry in July 2004 and will be calibrated at IPGP facilities. A breadboard of the electronics has already been delivered and supports currently the development of the software first iteration. A functional breadboard of sphere (15 cm diameter) containing 2 VBB axis, environmental sensors and electronics will be delivered at the beginning of 2005. IPGP has the overall responsibility of the experiment and is responsible for the VBB sensor and environmental sensors. ETHZ is responsible for the electronics of the experiment and JPL for the Short Period sensors. The SEIS is one of the core instruments of the former Netlander mission, which objective is to deploy a network of 4 stations on Mars for one Martian year of operation. This design allows also an implementation under the form of a "geophysical package" to be dropped on Mars by other Martian missions.