# How are the most sensitive seismometers on Mars protected from the most powerful jackhammer on Mars just a few feet away?

In the image below we are supposed to be looking at the pretty clouds, but all I see is an incredibly sensitive set of seismometers sitting right next to a jackhammer that will slowly drive a metal rod several meters into the planet.

This system of six seismometers, once un-stowed, deployed, and activated on the planet, are extremely sensitive. Is anything done to them to make them less sensitive to the shocks produced during the times that the small robotic jackhammer right next to them is banging away at the planet, either mechanically or electrically?

Spacelfight 101's InSight Instrument Overview says:

SEIS is based on a six-axis hybrid instrument using two different sensor types: three Very Broad Band (VBB) seismic probes reside in a tetrahedron configuration within the vacuum sphere and three Short Period (SP) seismic probes are installed around it. These are supported by various temperature and pressure sensors plus a myriad of electronics, power supplies, feedback boards for the sensors and the MDE deployment system. SEIS has a mass of 11.5 Kilograms and is capable of measuring accelerations down to 10-9 m s-² Hz-½ over frequencies of 0.001 to 10 Hz and 5 x 10-8 m s-² Hz-½ from 0.01 to 100 Hz.

The SEIS sensor head weighs 8.5 Kilograms and is approximately 30 x 30 x 30 centimeters in size, featuring a hook on its upper face to interface with the InSight Instrument Deployment Arm to be lowered to the ground as part of the mission’s two-month commissioning phase.

Each of the VBBs is a leaf-spring inverted pendulum seismometer that employs a precisely defined test mass suspended on a pendulum and placed in motion by external inputs from the ground. Through highly precise Differential Capacitive Sensors (DCS) and electromagnetic feedback from the three VBBs, a three-axis representation of the ground motion can be reconstructed with nanometer precision.

Image source: InSight Sees Drifting Clouds on Mars

• Sensitive does not mean delicate. May 12 '19 at 15:39
• @RoryAlsop Indeed. There's one good answer so far, but it's stalled for lack of any supporting references. If you can add something more, go for it!
– uhoh
May 12 '19 at 15:49
• By "most powerful jackhammer on Mars" are you referring to the HP3? The thing is tiny and uses 2 Watts. Mar 10 at 19:27
• @Schwern is there one that's more powerful? ;-)
– uhoh
Mar 11 at 2:44

It survived launching, entry into the Martian atmosphere and landing. I don't imagine it needs much protection from the someone hitting the ground next to it...

It messes with the readings, but that you know when the hammer was operational.

Interestingly the first 'mars quake' detected was not much gentler than the effects of the hammering. Neither are the effects of wind in terms of measured accelerations. The drilling has so far been the most significant, but not by orders of magnitude. It seems reasonable to assume these are well within safe operation range.

• Nice answer. The grammar of your last sentence is a little awkward and ambiguous. Can you improve it? May 9 '19 at 10:55
• Perhaps a cute answer, but not a "nice answer" yet. Can you address my second sentence "...once un-stowed, deployed, and activated..."? A lot of things happen to the seismometer between landing and deployment, I think a proper answer will require a bit of research. One place to start is the Spaceflight101 link in the question, and further resources can be found in the answer that I've just added a link to as well.
– uhoh
May 9 '19 at 11:25
• @DrSheldon, upon re-reading I am inclined to agree. Edited. I hope its clearer now. May 9 '19 at 13:02
• @ANone can you at least add a supporting link as a source for your statement that "the first 'mars quake' detected was not much gentler than the effects of the hammering"? I think some numbers would be helpful if possible.
– uhoh
May 9 '19 at 14:02
• @uhoh I think your intuition here is wrong. At very least the instrument can withstand Martian gravity which is huge next to the seismic acceleration due to the hammer. If it wasn't they could have done the hammering before deploying the sensor if you believe that makes a significant difference. May 9 '19 at 14:43

tl;dr: $$\text{HP}^3$$ and SEIS compliment each other, SEIS listens to $$\text{HP}^3$$. SEIS adds a digital filter to prevent saturation of its most sensitive instruments.

"The most powerful jackhammer on Mars" is minuscule.

The Heat Flow and Physical Properties Package ($$\text{HP}^3$$) is a "self-hammering nail". The whole assembly weighs 3kg. It uses a 2 Watts to compress a spring and release it against the head. In testing it took over 5 hours to go 5 meters.

Is anything done to them to make them less sensitive to the shocks produced...

SEIS listened to $$\text{HP}^3$$ with special filters in place to avoid overloading its most sensitive instruments.

The SEIS team had this to say in Review of the commissioning phase of the SEIS seismometer on Mars.

During the same period as the calibration operations, the SEIS seismometer also began listening to the vibrations caused by the HP³ mole as it headed down through the Martian sub-soil during sols 92 and 94.

The data collected showed that the SP sensors of the SEIS seismometer, well-suited to high-frequency measurements, record a variety of information—not only on the penetration operations but also on the mole’s internal operation. The signals are so strong when the mole begins hammering that the VBB pendulums saturate.

The objective of the SP sensors is to determine as accurately as possible the arrival time of the signals generated by the complex movements of the mole’s various moving parts whenever it hammers to move forward. A dedicated digital filter will be uploaded to the eBOX electronics unit that controls SEIS to increase the temporal resolution. Depending what the SP sensors hear, the project engineers will know whether the mole is continuing its downward journey (even slowly), if it is just bouncing off something in its path, or if it is completely blocked.

A second digital filter will also be activated to prevent the seismometer’s ultrasensitive VBB sensors from saturating when HP3 uses its hammering mechanism. By analysing the difference in seismic wave propagation depending on the materials encountered, it may be possible to identify the presence of a very hard layer some 30 cm deep.