InSight Replace, sols 25-42: Seismometer sensors working!

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InSight Replace, sols 25-42: Seismometer sensors working!

Emily LakdawallaJanuary 9, 2019

Tough setup and cable administration on Mars

Within the weeks since my last update, InSight has methodically labored by way of many of the lengthy listing of actions required to arrange its delicate seismometer experiment, SEIS. Engineers have leveled the seismometer and labored on cable administration. Most importantly for the science mission, they’ve balanced the Very Broad Band sensors — three of SEIS’ 6 seismic sensors — and confirmed that they’re producing good knowledge. This can be a enormous milestone and an enormous aid for the science group, undertaking scientist Bruce Banerdt informed me.

(Due to Bruce for an informative cellphone name yesterday, and to the seismometer group for posting this detailed and informative article about recent work on SEIS placement.)

Over the subsequent couple of weeks, they may full cable administration work and place the wind and thermal defend over the instrument. The mission remains to be on observe to be gathering good-quality science knowledge by February. Within the meantime, the science group is already writing up outcomes; they’re submitting greater than 50 abstracts to the Lunar and Planetary Science Conference, to be held in March. (Most of those will concern setting and climate measurements, however some might be placeholders for future seismometer outcomes.)

NASA / JPL-Caltech / Paul Hammond

Load Shunt Meeting opening on InSight (annotated)

Animation of two photographs collected on sols 38 and 41.

Right here’s a play-by-play of the current InSight exercise, since they positioned the SEIS instrument on the bottom on sol 22.

According to the SEIS team, the primary knowledge from the short-period sensors seemed extraordinarily good and never very noisy, even with the grapple nonetheless hooked up, on sol 24. Putting it on the bottom had dramatically dropped the noise stage being detected by the short-period sensors.

On sol 25, the grapple let go of SEIS, leaving all of it by itself on the floor. “It was one thing we’ve been dreaming about. It really seemed kinda lonely on the market all by itself,” Bruce informed me. “I’m wanting ahead to getting HPthree [the heat probe instrument] on the market and making Mars look slightly extra populated.”

However that’s getting forward of ourselves. There’s a shocking quantity of labor concerned in inserting an exquisitely delicate seismometer on one other planet. Step one after placement was to stage the instrument, which the SEIS group did on sol 30, canceling out the slight, 2.5-degree slope of the workspace.

NASA / JPL-Caltech

SEIS leveling (sol 30)

InSight’s SEIS instrument has three legs that may be independently lengthened and shortened to stage it out. The bottom slopes barely, so on sol 30 (27 December 2018) the instrument was efficiently commanded to compensate for the bottom tilt.

With the instrument stage, they might “recenter the VBBs.” What’s that, and why is it essential? “VBB” stands for “Very Broad Band” sensors within the seismometer. The seismometer has three VBB sensors along with the three short-period sensors. The VBBs are pendulums mounted on pivots which are as almost frictionless as potential. When the bottom strikes, it units the pendulums in movement as effectively. However the motions they’re looking for to detect are extremely small, so small that to have any hope of detection, the VBBs need to function in a vacuum and completely stage.

The VBBs have been the most important headache for the InSight growth effort. The failure of the vacuum chamber growth is what led to InSight’s pricey launch delay, however the VBBs have been tough bits of hardware even earlier than that drawback. “It was a tough street to get to the place we had these wideband sensors to the purpose the place they have been working, and we might belief them,” Bruce stated. I all the time had this fear at the back of my thoughts that we might get to Mars they usually wouldn’t work.”

To make them work on Mars, the group has to command the VBBs to heart their pendulums, permitting them to swing freely with floor movement. 

IPGP / David Ducros

VBB Recentering

Animation displaying the “recentering” operation of the InSight seismometer’s Very Broad Band (VBB) seismic pendulums. Recentering is a calibration exercise that fine-tunes the instrument’s sensitivity to gradual seismic waves. There are three VBB sensors within the SEIS instrument.

The command executed on 31 December (sol 34), however the group didn’t obtain the ensuing knowledge till early within the morning of two January, Bruce informed me. “We lastly obtained vibrational knowledge again from all three of the VBBs. To see that knowledge coming again, and evaluation confirmed it was performing identical to we anticipated and hoped, that’s once I went house and determined to rejoice.” The SEIS group stated:

L’arrivée des premières données au cours du sol suivant (sol 36, 2 janvier 2019) à 8h21 a été accueillie par des salves nourries d’applaudissements, l’équipe s’étant réunie pour l’event devant l’écran principal de la salle d’opérations de SEIS au Jet Propulsion Laboratory

With some assist from Google translate:

On New 12 months’s Day, in the midst of sol 35, the balancing motor of the three VBB pendulums was activated on Mars, to put the shifting a part of the sensor in its central equilibrium place. The arrival of the primary knowledge on the subsequent sol (sol 36, 2 January 2019) at eight:21 was greeted by bursts of applause, the group having gathered for the event in entrance of the principle display screen of the SEIS working room on the Jet Propulsion Laboratory.

Having confirmed that the sensors are working correctly, the group decentered them, parking them for the subsequent steps in organising the experiment. SEIS is linked to the spacecraft with a ribbonlike tether. With Mars’ broadly various temperatures, that tether can transfer lots in a single day:

NASA / JPL-Caltech

InSight SEIS tether strikes with altering temperature

Temperatures on Mars differ broadly between day and evening, inflicting spacecraft supplies to increase and contract barely. Consequently, the InSight SEIS tether moved in a single day between sols 37 and 38. These two pictures have been taken within the afternoon, close to the most well liked a part of the day (at 13:24 and 14:09 native time, respectively). The load shunt meeting positioned near the SEIS instrument is designed to isolate SEIS from this thermoelastic deformation of the tether.

Such giant motions of the tether could be transmitted to the SEIS sensors, swamping them with spacecraft-generated noise. So the group is spending weeks to do cable administration, isolating the instrument as a lot as potential from motions of the tether. Step one was to dump the remainder of the tether on the bottom, which they did on sol 37.

NASA / JPL-Caltech

InSight tether storage field opening

As soon as the seismometer was positioned in its ultimate location on the bottom, engineers commanded InSight to open up the storage field that held the remainder of the tether, permitting the remaining size to fall to the bottom. The tether will increase and contract with the temperature adjustments of each Martian day and evening, so it is essential that there be loads of slack within the line to accommodate these adjustments.

So now the lander isn’t tugging on the tether in any respect. However nonetheless, thermal enlargement and contraction of the tether can tug on SEIS. So the subsequent step was to open up the load shunt meeting, a component on SEIS that I defined in my earlier submit. Opening the load shunt meeting concerned firing a “frangibolt,” which is a bolt that gives a everlasting attachment till you apply present to it, which causes it to interrupt. As you can see at 2:10 in this demo video, opening a frangibolt is a good jolt to your hardware, and jolts are enemies of seismometers. “That was really a regarding operation — we might examined it, but it surely’s one of many sharpest blows the SEIS will get over its lifetime, so we have been involved watching it, however that went off with no hitch. We recentered the VBBs, and located they have been working positive.”

The animation under reveals the earlier than and after situation of the firing of the frangibolt on the load shunt meeting.

NASA / JPL-Caltech

InSight SEIS Load Shunt Meeting opening

Animated sequence of photographs obtained by the InSight arm digicam displaying the opening of the Load Shunt Meeting (LSA) on the SEIS instrument on sol 40 (6 January 2019). The LSA gives mechanical separation between the tether and the seismometer to isolate the seismometer from disturbances attributable to the lander as a lot as potential.

The subsequent step was is “leveling low.” The SEIS group had leveled their instrument, however to make its coupling to Mars as tight as potential, they need the instrument as near Mars as potential. The three leveling legs have been all near the midpoints of their ranges of movement. They are going to command SEIS to decrease itself on all three legs, bringing it as near the bottom as potential, after which re-level it.

The load shunt meeting is now open, however the outer bit remains to be leaning on SEIS, so it may possibly nonetheless impart motions from the tether to SEIS. The group might want to pull on the tether slightly bit as a way to open up the load shunt meeting extra. The group has been practising within the testbed to open up the load shunt meeting by tugging on part of the tether utilizing the news on the robotic arm.

NASA / JPL-Caltech / IPGP / Philippe Labrot

InSight tether pinning mass adjustment take a look at

To ensure the InSight seismometer is totally mechanically remoted from any noise from the lander, the InSight group plans to tug barely on the tether to tug open the cable bend on the load shunt meeting (on the left facet of this photograph). They plan to make use of the news on the tip of the arm to tug on a grapple level on the tether’s “pinning mass,” a weighted block supposed to forestall the tether from shifting within the Martian wind. This photograph reveals the news poised over the pinning mass within the Earth-based testbed.

They need to watch out, as a result of they wish to open up the load shunt meeting sufficient for it to isolate SEIS from tether enlargement and contraction, however not a lot that it interferes with placement of the wind and thermal defend excessive of SEIS. The fascinating quantity of opening is between a number of millimeters and a few centimeters, Bruce informed me. Tugging on it’s a lot simpler than attempting to shove it closed once more. So they may simply tug slightly bit (probably as early as Friday), and will must run the operation one or two occasions extra to have it positioned simply completely.

As soon as they’ve completed all this cable administration, they may take a number of sols to gather a set of seismic knowledge with out the wind and thermal defend, however solely throughout the daytime, as a result of the instrument might be too chilly at evening. Then, and solely then, will they have the ability to place the defend over SEIS, and its setup might be full. The way in which the timeline seemed yesterday, which may occur round sol 54 (20 January), but it surely may very well be delayed for any variety of causes. Persistence is a advantage with InSight!

Within the meantime, take pleasure in my response to the design of the skirt on the wind and thermal defend.


20190109_LSA_Release_animation_f840 InSight Replace, sols 25-42: Seismometer sensors working!

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