The SEIS instrument rests on the march instrument. Image: NASA / JPL-Caltech The US government may be in partial shutdown…
The SEIS instrument rests on the march instrument. Image: NASA / JPL-Caltech
The US government may be in partial shutdown mode, but operations to configure instruments critical to NASA’s InSight mission on Mars are right on schedule and things are swimming as it does latest mission update confirms.
Our latest update from the InSight mission came on December 20 following the probe’s successful implementation of the SEIS instrument, or Seismic Experiment for Interior Structure, on the Mars surface. The configuration of this hexagonal unit is still ongoing, but an update from the SEIS team shows that things continue as planned. In recent weeks, mission techniques have leveled the seismometer, manipulated the cable connecting the inSight to the device, and – most importantly, three of the instrument’s six internal seismic sensors, while confirming the functionality.
When SEIS is running, it will search for seismic vibrations, which gives an insight into the Red Plan’s internal activity. The hexagonal unit is passively resting on the Martian surface, and a tether connects it to the InSight lander. SEIS should be able to detect the smallest vibrations, including those caused by Marsquakes or dumps by a meteorite impact. When these important tasks are sent back to earth, scientists will gain a better understanding of the material that first formed the stony planets of the solar system, and perhaps learn about floating water or plumes of active volcanoes beneath the Mars surface.
Leveling of SEIS was done on December 27, 2018. GIF: NASA / JPL-Caltech
Soon after InSight’s robotic arm placed SEIS on the surface, the mission engineers learned that the unit was resting on a slope angled at 2.5 degrees. At full expectation, SEIS is equipped with three configurable legs, each of which can be ordered remotely to orient the unit along both horizontal and vertical planes. An operation to level the instrument on December 27 was a success.
SEIS is now completely level with the martian surface, but it is too high. The next step, called “leveling low”, will see the unit move as close to the Martian surface as possible for optimal data acquisition results. Currently, the seismometer’s legs are in the midpoint, so the mission engineers have room to work with. When it is as low as it can go, the unit becomes horizontal again.
Mission engineers could also review sensors inside the device. SEIS is equipped with six internal seismic sensors, three of which are broadband called VVB, or Very Broad Band and three are short-term sensors. As Emily Lakdawalla wrote in an article for The Planetary Society, the three VBBs were successfully centered and they seem to work:
The VBBs are pendants mounted on rotational twists that are as close to frictionless as possible. When the ground moves, it also moves the pendants. But the movements they are trying to discover are extremely small, so small that they have any hope of discovery, the VBBs must function in a vacuum and perfect level.
The VBBs were the main headache for InSight’s development efforts. The failure of vacuum chamber development is what led to InSight’s costly launch delay, but the VBBs were difficult pieces of hardware even before that problem. “It was a difficult way to get to where we had these broadband sensors to the point where they worked, and we could trust them,” [project scientist Bruce Banerdt]. “I always had this concern because we were going to Mars and they wouldn’t work.”
Mission technicians ordered the VBBs to center their commuters on December 31, but they did not receive confirmation of the results until January 2 news that was “greeted by applause”, according to the SEIS team. The fragile VBBs survived atmospheric entry and landing on Mars, and they gather good data.
Finally, the mission techniques must have made cable wiring.
Temperature fluctuations on Mars deform the tether, as shown here. GIF: NASA / JPL-Caltech
The seal that connects SEIS with InSight expands and contracts dramatically due to significant temperature fluctuations during March’s night cycle. It is of course not good for a cable that shuffles around on the surface, and is also connected to a seismometer. This can interfere with data collection by introducing unwanted sounds. The team has literally spent weeks trying to figure out the best orientation for the cable to isolate it as much as possible from SEIS, which they do by trying to create a lot of carelessness.
InSight can lift and lower the seal to GIF: NASA / JPL-Caltech
A decent configuration was achieved the first week of January, but the cable management process is still incomplete. The commission engineers must ensure that the seal is firmly attached to the surface. For this purpose, a scoop is used at the end of InSight’s robot arm to align a weighted block or a tensioning mass to prevent wind from blowing the seal around.
So much to do! In addition to carrying out more cable management work, the commission engineers will place the dome-like wind and the heat shield over SEIS to protect it from the elements. The assignment is currently underway and scientific data collection should begin in February.
Mission technicians still need to install the heat probe instrument, but we will get it on time.
[The Planetary Society, SEIS]