Emily Lakdawalla
Page 34
landing the team planned to use MAHLI during traverses to take single pre- or post-drive
images to document the changing landscape. MAHLI takes these images from its stowed
position, so they can be captured on sols when available resources restrict use of the arm.
When stowed, the camera looks over the rover’s left shoulder (measured about 110° to the
left of the rover’s forward direction), and images are rotated about 150° counterclockwise
from horizontal. MAHLI performed its first infinity-focus test on sol 274, just before leaving Yellowknife Bay. The experiments determined the best-focus motor position for land-
scape imaging (a motor count of 12552), and throughout the drive to Mount Sharp MAHLI
took a single photo at this motor count after most drives. An example of a MAHLI land-
scape image is shown in Figure 7.17. The last such routine landscape image was on sol 1112, but the team continues to occasionally request such photos when they’re expected to
show a subject of scientific or engineering interest.
268 Curiosity’s Science Cameras
Figure 7.16. MAHLI images of target “Mojave” taken at night on sol 809 under
LED illumination at three different working distances, after the target had been
brushed. Images 0809MH0004440010300853C00, 0809MH0004450010300857C00, and
0809MH0004460010300905C00. NASA/JPL-Caltech/MSSS/Emily Lakdawalla.
7.4 MAHLI: Mars Hand Lens Imager 269
Table 7.9. Sols and names of MAHLI mosaics as of sol 1648.
Bradbury Group
Pahrump Hills
North of the Dunes
South of the Dunes
66 Rocknest Scoop 1
802 Garlock
974 Bigfork
1407 Robotic arm workspace
Trough
805 Pelona
998 Ronen
1407 Boulder with targets
67 Rocknest Scoop 2
805 Ricardo
1028 Big_Arm
named Tumba and Funda
Trough
808 Rosamond
1031 Dog's eye of
1409 Funda
84 Self Portrait
809 Mojave
Missoula Area
1418 Marimba
85 Self Portrait (stereo) 810 Potatoe
1032 Clark
1457 Quela
154 Persillion
813 Punchbowl
1057 Buckskin
1463 Self Portrait
158 Tindir
814 Anaverde
1065 Rover
1463 Ombomboli
168 JK/YKB Drill
814 Afton_Canyon
Undercarriage
1474 Utuseb
Candidate Site
815 Topanga
inspection
1474 Jwaneng
177 Self Portrait
819 Mescal
1092 Lebo
1482 Cassongue
230 John Kllein Hole
824 Puente
1105 Sacajawea
1491 Sebina
and Cuttings
828 Chinle Oblique
1105 Winnipeg
1504 Thrumcap
270 McGrath
868 Self Portrait
1114 Big_Sky
1504 Wonderland
283 Cumberland Drill
869 Mojave Chunk
1126 Self Portrait
1514 Southwest_Harbor
Site
882 Self Portrait
1157 Augusta
1518 Folly_Island
291 Narrows_3
Extension
1166 Swakop
1523 Seawall
292 Narrows_3
905 Telegraph_Peak
1182 track_wall
1531 Precipice
303 Point Lake
930 Coalville
1182 Weissrand
1552 The_Anvil
322 Ailik_RP
935 APXS vein material
1202 Greenhorn Sieved 1566 Old_Soaker Workspace
324 Fleming
raster
Sample
1566 Old_Soaker
387 Ruker
937 Back of Coalville
1228 Gobabeb Scoop 1 1566 Bar_Island
398 vein_mosaic
938 APXS vein material
1228 Self-portrait
1570 Valley_Cove ( and
400 vein_mosaic
raster extension
1241 Self Portrait
Gilley_Field)
400 conglomerate
946 Kern_Peak
Supplemental frames
1581 Smalls_Falls
mosaic_left
946 Vein Material
1254 Kuiseb
1589 Cape_Elizabeth
400 conglomerate
T-shaped
1275 Palmhorst
1591 Munsungun
mosaic_right
948 Vein Material Stereo
1275 Palmwag
1593 Misery
442 Cooperstown
mosaic
1277 Sperrgebiet
1611 Patch_Mountain
487 Cumberland Dump
1277 Klein_Aub
1614 Chain_Lakes
Pile
1278 Sperrgebiet
1614 Spider_Lake
550 Bungle Bungle
1279 Khomas
1634 Canada_Falls
583 Square_Top
1325 Lianshulu
1668 Morancy_Stream
584 Square_Top
1327 Lubango
1675 Lookout_Point
Dogseye
post-sieve discard pile
1679 Maple_Spring
585
1330 Okoruso
1702 Fern_Spring
right of Square_Top
1338 Self Portrait
1714 Prays_Brook
585 Square_Top
1341 Kwakwas
1715 Old_Mill_Brook
585 Rock face right of
1341 Okoruso Site
1727 Jones_Marsh
Square_Top
1344 Impalila
1734 Pecks_Point
591 Tickalara Trough
1351 Dog's eye of
1749 Ile_Damour
605 Lagrange
Nauaspoort
1788 Dumplings_Island
612 Windjana
1371 Berg_Aukas
1811 Mount_Ephraim
613 Self Portrait
1380 Koes
1865 Barberton
615 Windjana
627 Windjana Drill
Hole Cuttings
629 Stephen
722 BonanzaKing2
722 BonanzaKing1
726 BonanzaKing2
270 Curiosity’s Science Cameras
Figure 7.17. A MAHLI stowed-position landscape image from sol 952, in “Artist’s Drive”
beyond Pahrump Hills. Image 0952MH0003250050304147E01. NASA/JPL-Caltech/MSSS.
7.4.3.4 MAHLI engineering support images
MAHLI is regularly used to examine hardware on the rover, in particular the rover’s
wheels, because the mast-mounted cameras can only see the right side wheels partially
and the left side wheels not at all. MAHLI documented the first visible puncture in a rover
wheel on sol 411, and has monitored wheel condition since then (see section 4.6.4).
MAHLI also monitors dust accumulation on the REMS ultraviolet sensor and has been
used as a diagnostic tool for the condition of the REMS wind booms, dust accumulation
on the ChemCam and ChemCam windows, and interior of the CheMin inlet.
7.4 MAHLI: Mars Hand Lens Imager 271
7.4.3.5 MAHLI self-portraits
Self-portraits are a special rover self-examination product. They are mosaics of more than
50 MAHLI images, taken with the arm held out and in front of th
e rover. A MAHLI self-
portrait has become part of the standard set of documentation activities performed at sam-
ple sites, though the mission forgoes the self-portrait if pressed for time.
The rover usually holds MAHLI about 2 meters above the bottoms of the rover wheels
(that is, at “eye level”) for self-portraits. To capture the images for the mosaic, the arm rotates the camera in such a way as to keep MAHLI fixed in one location with only its
optical axis pivoting. MAHLI takes images for the upper half of the mosaic first, then
repositions the arm to keep it from blocking the camera’s view and takes the photos for the lower half. Rover planners time the mosaic carefully to keep not only the arm but also its
cast shadows out of view as much as possible, because the moving arm shadows make
assembly of the mosaic difficult.
At the Buckskin drill site on sol 1065, the rover planners implemented a special posi-
tion for the self-portrait, with MAHLI held in nearly the same position as it is for wheel
imaging. The low perspective gives the impression of the rover looming over the observer.
Figure 7.18 shows some of the MAHLI frames used to create the Buckskin self-portrait, which also graces the cover of this book.
Table 3.3 documents all sampling activities, including self-portraits at sample sites. At John Klein, Windjana, Confidence Hills, and Quela, the MAHLI team took a full self-portrait on one sol, before drilling, and then supplemented the self-portrait with extra
frames taken on subsequent sols to document the change at the site after sampling activi-
ties were complete. Two self-portraits have included imaging of the mast head in more
than one position. At Windjana, MAHLI imaged the head both facing the camera and
looking down at the drill site. At Okoruso, MAHLI imaged the head both facing the cam-
era and facing away, looking at Mount Sharp.
7.4.4 Anomalies and precautions
Through sol 1800, MAHLI has had no hardware issues apart from the dusting of the origi-
nally transparent lens cover during the rover’s descent to the surface. However, on one
occasion, a MAHLI problem caused a robotic arm fault, and on another, a MAHLI issue
required a 2-week recovery including 8 sols in which the dust cover was open.
The first of these anomalies occurred on sol 615. MAHLI was imaging the recently
drilled Windjana mini-drill hole when the camera head faulted, causing the arm to be
unable to move while the rover awaited analysis and further instruction from Earth.
During the 2-sol wait, MAHLI was held just 5 centimeters above the fresh drill cut-
tings, with its cover open. The fault had to do with real-time MAHLI image compres-
sion producing unexpectedly large image files. MAHLI was returned to normal
operation on sol 627.
The second anomaly occurred on Sol 1619. In this case, the MAHLI cover failed to
open completely. As in the previous fault, the arm didn’t move, pending further instruc-
tion from the ground. The dust cover stayed open for 8 sols. Inspection using the
Mastcams, Navcams, and Hazcams, followed by careful testing of the dust cover on
272 Curiosity’s Science Cameras
Figure 7.18. Top: A subset of the MAHLI frames used to produce the mosaic printed on the cover of this book, taken at Buckskin on sol 1065. Bottom: View of the turret taken from the left front Hazcam during the Buckskin self-portrait sequence. A small local low in topography allowed the rover planners to create this unusual low-angle view. MAHLI is located on the upper right side of the turret in this view. NASA/JPL-Caltech/MSSS/Emily Lakdawalla.
subsequent sols, showed normal operation. Investigation revealed that while MAHLI was
operating within its allowable temperature range, the fault occurred at a temperature
lower than MAHLI had ever been commanded to operate before. Flight rules were modi-
fied to require MAHLI operation at higher temperatures, with the low-temperature limit
set at –20°C. 19
On sols 764, 774, and 1575, the arm has faulted during MAHLI imaging, leaving the
MAHLI cover open for a few sols during recovery. To avoid long periods of the MAHLI
19 Ashwin Vasavada, interview dated March 10, 2017, and Ken Edgett, email dated April 10, 2017
7.5 References 273
cover being left open as a result of an arm fault, MAHLI now requires the cover to be
closed for all imaging performed within a few sols before holiday or conjunction peri-
ods. That leaves enough time for recovery and cover close before a command
moratorium.
Toward the end of September 2016, as Curiosity cleared the Murray buttes and re-
entered the Bagnold dune field and its sand transport corridor, repeat imaging of sandy
spots showed dramatic wind-induced sand motion. Blowing sand presents little hazard to
MAHLI (sand grains are too heavy to stick to the window), but finer materials like drill
tailings could be a concern. If blowing sand grains strike dust or drill cuttings on the
ground, the fine material can be lofted into the wind and then stick electrostatically to
MAHLI’s sapphire window. Between the Sebina, Precipice, and Ogunquit Beach sample
sites in late 2016 and early 2017, the MAHLI team performed all close-up imaging with
the cover closed. And as a precaution while driving across windy sand transport corridors,
the MAHLI team modified their operations procedures to open the dust cover with the
camera aimed down, so that any sand particles that do strike the front of MAHLI’s optics
will (hopefully) bounce or roll off.
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8
Curiosity’s Environmental Sensing Instruments
8.1 INTRODUCTION
Environmental sensing instruments include the Rover Environmental Monitoring Suite
(REMS), a package of several meteorological instruments, and the Radiation Assessment
Detector (RAD), which measures the radiation dose at the surface. Dynamic Albedo of
Neutrons (DAN) straddles the boundary between remote and environmental sensing; in
passive mode it detects ambient neutrons, and in active mode it can also bombard the sur-
face with neutrons to explore for subsurface water and light elements.
The environmental instruments operate mostly in the background, quietly taking data