Emily Lakdawalla

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  spot in the center. So Curiosity moves the arm while brushing to sweep out the center,

  creating an oval spot. The entire brushed area is contained within a 60-millimeter circle.

  Figure 5.16 shows two different kinds of brushed spots. The size of the brushed spot depends upon how close the brush gets to the surface. Originally, Curiosity brushed at a

  height of 1 centimeter, which produced a brushed spot about 46 millimeters in diameter.

  Concern that the bristles could wrap around the center post following the discovery of the

  bent bristles led them to use a higher standoff of 1.5 centimeters thereafter, which

  5.6 Organic Check Material 211

  Table 5.2. Summary of dust removal tool (brush) to sol 1806. List courtesy Ken Edgett.

  Bradbury Group

  Pahrump Hills

  North of the dunes

  Among the dunes South of the dunes

  150 Ekwir

  722 Bonanza

  975 Albert

  1358 Oudam

  1681 Duck Brook

  169 Wernecke

  King

  998 Ronan

  1366 Auberes

  Bridge

  291 Cumberland 755 Maturango

  999 Wallace

  1380 Koes

  1695 Mason Point

  612 Windjana

  758 Moenkopi

  1057 Buckskin

  1416 Chibia

  1702 Fern Spring

  767 Morrison

  1092 Ledger

  1418 Marimba

  1710 White Ledge

  805 Pelona

  1105 Winnipeg

  1436 Conda

  1715 Timber Point

  806 Ricardo

  1109 Cody

  1444 Ganda

  1736 Winter Harbor

  808 Rosamond

  1114 Big Sky

  1474 Jwaneng

  1744 Mingo

  809 Mojave

  1119 Big Sky 2

  1477 Catumbela 1806 Robinson Rock

  813 Punchbowl 1130 Greenhorn

  1484 Serowe

  814 Afton

  1157 Augusta

  1491 Sebina

  Canyon

  1166 Swartkloofberg 1511 Penobscot

  815 Topanga

  1245 Kudis

  1523 Sutton

  819 Mescal

  1251 Kuiseb

  Island

  824 Puente

  1259 Gorob

  1531 Precipice

  828 Pickhandle

  1266 Stockdale

  1586 Belle Lake

  830 Goldstone

  1273 Schwarzrand

  844 Santa Ana

  1275 Mirabib

  853 Tecoya

  1279 Khomas

  880 Mojave 2

  1287 Sesriem

  905 Telegraph

  Canyon

  Peak

  1293 Brukkaros

  936 Hyrum

  1300 Bero

  1318 Lubango

  1330 Okoruso

  1341 Kwakwas

  1348 Meob

  1355 Inamagando

  produces a brushed spot about 40 millimeters in diameter. Either way, the cleared area is

  slightly wider than the field of view of APXS, so even with positioning uncertainty,

  APXS’s field of view will be entirely in the brushed area.

  When the brush interacts with very soft rocks, the wire bristles may scratch the surface.

  If the rock is extremely soft, wires near the center can get hung up on a protuberance and

  actually drill into the rock (see Figure 5.17 for an example).

  5.6 ORGANIC CHECK MATERIAL

  A palette on the front center of the rover contains 5 cylinder-shaped bricks of hermetically sealed organic check material provided by the SAM team (Figure 5.18).19 It is intended to check the cleanliness of the whole SAM sample processing pathway, to ensure that any

  19 Conrad et al (2012)

  212 SA/SPaH: Sample Acquisition, Processing, and Handling

  Figure 5.16. Moenkopi (left), brushed on sol 758, was a raised feature. Maturango (right), brushed sol 755, was a flat spot, and the brush was moved during brushing. The Confidence Hills drill site is in the background. Drill holes are 16 mm across; brushed spots are at least 45 mm across. Left Mastcam image 0758MH0001900010204611C00. NASA/JPL-Caltech/MSSS.

  organic materials detected by SAM in Martian material really do come from Mars and are

  not Earthly contamination left behind on the external parts of the sample processing chain: the drill, CHIMRA, and sample inlets. The five bricks are identical. They are composed of

  a ceramic that has been doped with a minute amount of fluorinated hydrocarbon chemical

  that can be detected by SAM. Each brick is covered with a foil seal. It can be drilled and

  sampled just like a rock, and the sample dropped into SAM. Drilling it breaks the seal, so

  each brick can be used only once. Figure 5.19 shows how the rover would position the drill on one of the bricks for sampling.

  The organic check material has not yet been used. (For more information, see 9.5.1.12.) The

  team tested the process of positioning the drill to sample the organic check material on sols 34

  and 1076, taking images with MAHLI to document turret positioning (Figure 5.19). They also performed imaging of the organic check material with the MAHLI cover closed on sol 1416.

  5.7 Sample Playground 213

  Figure 5.17. Scratches and drilling near the center of a brushed spot at Pelona, at the Pahrump Hills site, sol 805. MAHLI images 0805MH0001900010300492C00 and

  0805MH0003070010300514C00. NASA/JPL-Caltech/MSSS.

  5.7 SAMPLE PLAYGROUND

  Immediately in front of the mast is a suite of tools intended to allow the rover to study the properties of drilled or scooped sample. This “sample playground” was a late addition to

  the rover design, added after the experience of the Phoenix mission, which had a difficult

  time handling clumpy Martian materials (see section 1.5.11). 20 The sample science team looked at how their mature design might be vulnerable to clumpy soil, and developed a set

  of tools to help them investigate sampled material before committing to delivering it to

  CheMin and SAM.

  The sample playground comprises the science observation tray, engineering tray,

  CheMin surrogate funnel and soil capture plate, dust removal tool scratching post, and two

  portion pokers (Figure 5.20). Sols in which science cameras were used to image parts of the sample playground are listed in Table 5.3, but the playground is also often captured in Mastcam and Navcam views of the work volume, and in MAHLI self-portraits.

  The science observation tray, also known as the “O-tray”, is a circular titanium plate 75

  millimeters wide. The rover can drop portions of drilled or scooped sample onto it for

  20 Anderson et al (2012)

  214 SA/SPaH: Sample Acquisition, Processing, and Handling

  Figure 5.18. The organic check material mounting plate bolted to the front center of the rover contains five foil-capped cylinder-shaped bricks of ceramic material. Between the five bricks are smaller drill positioning pads, places for the drill contact stabilizers to press during drilling. Below the mounting plate is one of the two spare drill bit boxes and the four front Hazcams. Mosaic of four MAHLI self-portrait frames taken on sol 1065.

  NASA/JPL-Caltech/MSSS.

  investigation with APXS, MAHLI, and mast-mounted cameras. It was intended to provide

  a surface of known composition on which to perform APXS observations of sampled

  material. Unfortunately, vibration from CHIMRA, necessary for portion delivery, appears

  to transfer through the rover arm to the body and cause delivered portions to “walk” off of the sample tray (see Figure 5.20 for an example). This behavior, which is much worse on Mars than it was in the Earth test
bed, has prevented much use of the observation tray for

  science. The APXS team has developed a different method of measuring the composition

  of drilled materials by studying the composition of pre- and post-sieve dump piles. The

  APXS team has also occasionally taken advantage of the vibration-induced cleaning of the

  observation tray to perform measurements of the composition of airfall dust.

  5.7 Sample Playground 215

  Figure 5.19. A test of the drill’s positioning on one of the organic check material bricks. From this point of view, you can see the tubular inlet and outlet ports that allowed the SAM team to dope the ceramic bricks with a fluorinated compound after they were sealed in their can-shaped housings. Navcam image NLB_493020688RAD LF0490814NCAM00467M1, sol

  1076. NASA/JPL-Caltech.

  216 SA/SPaH: Sample Acquisition, Processing, and Handling

  Figure 5.20. Parts of the sample playground seen from above by Mastcam and from the right side by MAHLI. In the top image, two portions have been dropped to the center of the observation tray. CHIMRA vibration transferred through the arm to the rover body has caused the first portion to “walk” off the tray during delivery of the second portion. Delivery of both portions has also shifted some of the accumulated dust off of the tray. Mastcam image

  ML0005780000102730E01 and MAHLI image 0544MH0003460000201460C00. NASA/

  JPL-Caltech/MSSS/Emily Lakdawalla.

  5.8 SAM and CheMin Inlets and Wind Guards 217

  Table 5.3. Sols with

  Mastcam

  MAHLI

  targeted imaging of

  the sample playground

  70

  37

  (mostly of the observation

  76

  73

  tray).

  77

  93

  78

  95

  79

  177

  81

  544

  95

  571

  284

  572

  289

  The rest of the sample playground elements have not been used on Mars. The engineer-

  ing tray, located closer to the rover body than the observation tray, has a checkerboard

  pattern made of 0.25-inch (6.35-millimeter) squares. It was intended for use in estimating

  the volume of portions dropped to SAM and CheMin. To the left is the CheMin surrogate

  funnel and soil capture plate. If there are concerns about soil clumping and potentially

  clogging the CheMin inlet funnel, the drop can be tested with the surrogate funnel. On the

  right side of the engineering tray, a palette of screw heads provides a place to clean off the DRT in the event that Martian material clings to its brushes. Finally, two portion pokers,

  one pointing vertically and one horizontally, provide Curiosity with the capability to poke out the CHIMRA portion hole if it should become clogged with material. However, the

  inverted funnel shape of the CHIMRA portion hole makes it very unlikely that material

  could pass all the way through CHIMRA and then clog the portion hole; the portion pokers

  have not been used and hopefully never will be.

  5.8 SAM AND CHEMIN INLETS AND WIND GUARDS

  The final elements in the sample delivery chain are the motorized sample inlets on the top

  of the rover deck. Three flaps (two for SAM’s inner and outer carousel rings, and one for

  CheMin) open and close to allow CHIMRA to deliver portions. Mastcam shoots photos of

  the inlets before and after each delivery in order to check whether wind blew the sample

  away from the inlet and deposited it on the deck nearby. The rover also uses MAHLI to

  image the fine mesh grate over the open CheMin sample inlet from time to time, often at

  night, when the MAHLI LEDs can be used as flashlights to evenly illuminate the interior.

  The goal of this imaging is to check for clogging by excessively large particles. All these imaging activities are summarized in Table 5.4.

  An amusing side effect of the repeated imaging of the sample inlets is that it has been

  possible to track the motions of bits of gravel on the rover deck over the course of the

  landed mission (Figure 5.21). This gravel was tossed onto the deck during landing and has rattled around the top surface ever since, occasionally drawing squiggly lines in accumulated deck dust.

  The difficult experiences of sample delivery in the Phoenix mission caused engineers

  to be concerned about wind blowing Curiosity’s tiny sample portions away. To mitigate

  against this possibility, they added spring-loaded collars around the sample inlets, and a

  corresponding plate over the CHIMRA portion hole. In the event that wind dispersal of

  218 SA/SPaH: Sample Acquisition, Processing, and Handling

  Table 5.4. Imaging of the CheMin and SAM inlet ports by Mastcam and MAHLI to sol 1800.

  CheMin inlet (Mastcam)

  CheMin inlet (MAHLI)

  SAM inlets (Mastcam)

  SAM inlet (MAHLI)

  14

  36

  14

  93

  51

  74

  90

  96

  71

  81

  93

  282

  94

  94

  96

  195

  195

  114

  282

  282

  116

  623

  411

  117

  765

  558

  196

  884

  564

  224

  922

  666

  227

  1061

  774

  281

  1121

  895

  286

  1139

  1028

  290

  1226

  1064

  353

  1323

  1091

  367

  1334

  1123

  381, 382

  1362

  1136

  413, 415

  1375

  1142

  463, 464

  1425

  1184

  624

  1466

  1259

  653

  1496

  1287

  694

  1324

  773

  1337

  887, 888

  1348

  891

  1364

  892

  1375

  928

  1402

  954

  1427

  1075

  1438

  1129

  1459

  1147

  1466

  1178

  1470

  1224

  1477

  1230

  1484

  1231

  1489

  1233

  1496

  1382

  1409

  1443

  1456

  1651

  5.8 SAM and CheMin Inlets and Wind Guards 219

  Figure 5.21. CheMin inlet and wind guard as seen from Mastcam. Pebbles that have been on the deck since landing leave tracks as the rover’s motion vibrates them across the deck. NASA/

  JPL-Caltech/MSSS/Emily Lakdawalla.

  sample is found to be a problem, the engineers can deliver sample with the portion plate

  pressed against a wind guard. This capability has not been used. Mastcam videos of por-

  tion delivery recorded on sols 64, 78, 284, and 289 showed the portions dropping straight

  down for a distance longer than the few centimeters separating the portion hole and sample

  inlets. The mission has also taken advantage of REMS wind
data to select times of day for

  sample delivery when winds are expected to be minimal.

  220 SA/SPaH: Sample Acquisition, Processing, and Handling

  5.9 REFERENCES

  Anderson R et al (2012) Collecting samples in Gale crater, Mars: an overview of the Mars

  Science Laboratory Sample Acquisition, Sample Processing and Handling System.

  Space Sci Rev 170:57–75, DOI: 10.1007/s11214-012-9898-9

  Billing R and Fleischner R (2011) Mars Science Laboratory robotic arm. Paper presented

  to the 14th European Space Mechanisms and Tribology Symposium, 30 Sep 2011,

  Constance, Germany

  Conrad P et al (2012) The Mars Science Laboratory organic check material. Space Sci Rev

  170:479–501, DOI: 10.1007/s11214-012-9893-1

  Grotzinger J et al (2014) A habitable fluvio-lacustrine environment at Yellowknife Bay,

  Gale Crater, Mars. Science 343, DOI: 10.1126/science.1242777

  Kuhn S (2013) Curiosity’s scoop campaign, a summary. http://www.planetary.org/blogs/

  guest-blogs/curiositys-scoop-campaign-kuhn.html Article dated 8 Jan 2013, accessed 6 May 2016

  JPL (2014) Lesson Learned: Recognize that Mechanism Wear Products May Affect

  Science Results. http://llis.nasa.gov/lesson/10801. Article dated 8 Jun 2014, accessed 14 Oct 2015

  Kim W et al (2013) Mars Science Laboratory CHIMRA/IC/DRT flight software for sam-

  ple acquisition and processing. Paper presented to the 8th International Conference on

  System of Systems Engineering, 2–6 Jun 2013, Maui, Hawaii, USA

  Lakdawalla E (2017) Curiosity update, sols 1548–1599: Serious drill brake problem

  as Curiosity drives through Murray red beds. http://www.planetary.org/blogs/emily-

  lakdawalla/2017/02031109-curiosity-update-sols-1548-1599.html Article dated 3 Feb 2017, accessed 9 Feb 2017

  Limonadi D (2012a) Sampling Mars, part 1: The hardware. http://www.planetary.org/

  blogs/guest-blogs/20120816-limonadi-sampling-mars-1-tools.html Article dated 16

  Aug 2012, accessed 26 Feb 2016

  Limonadi D (2012b) Sampling Mars, part 3: Key challenges in drilling for samples. http://

  www.planetary.org/blogs/guest-blogs/20120821-limonadi-sampling-mars-3-drilling-

  challenges.html Article dated 21 Aug 2012, accessed 6 May 2016

  Manning R and Simon W (2014) Mars Rover Curiosity: An Inside Account from

  Curiosity’s Chief Engineer. Smithsonian Books, Washington DC

  Novak K et al (2008) Mars Science Laboratory rover actuator thermal design. Presentation

  to the Spacecraft Thermal Control Workshop, 11–13 Mar 2008, El Segundo, California,

  USA, DOI: 10.2514/6.2010-6196

 

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