Final Report Testing of Instrumentation for WISSARD
Lake Tahoe, August 20-30, 2012
Lidar bathymetry (US-ACE) + Landsat (provided by Gordon Seitz – CSGS)
Ross D. Powell
& Reed P. Scherer
Department of Geology and Environmental Geosciences Northern Illinois University
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1. Summary This report summarizes outcomes from testing of instrumentation for use in the Antarctic field operations of WISSARD (Whillans Ice Stream Subglacial Access research Drilling). The testing was carried out in Lake Tahoe, CA, in August 2012. Instrumentation that was tested included a suite from Northern Illinois University (including Instrumentation Packages for Sub-Ice Exploration – IPSIEs, a hydraulic percussion corer, a multicorer, and a multipurpose winch and smart cable umbilical), and from University of California at Santa Cruz (including a piston corer and geothermal probe). Testing showed that most instrumentation and equipment is ready for shipping by early October 2012 without further work. Some modifications are underway to make equipment handling easier and more efficient and those should be complete by shipping time. Some instruments require “tweaking” to either enhance their operation for high quality data, or to improve their surface communications; these too will be completed before shipment. 2. Objectives Testing of instrumentation for use in the Antarctic field operations of WISSARD (Whillans Ice Stream Subglacial Access research Drilling) this coming season occurred during August 20-30, 2012 in Lake Tahoe, CA. Instrumentation included a suite from Northern Illinois University (including Instrumentation Packages for Sub-Ice Exploration – IPSIEs, a hydraulic percussion corer, a multicorer, and a multipurpose winch and smart cable umbilical), and from University of California at Santa Cruz (including a piston corer and geothermal probe). The major reason for our testing was to assess and learn how: (i) to modify/improve engineering design to ensure effective communication with, and data streaming from, the scientific instrumentation, (ii) the equipment will meet standards of the WISSARD project in terms of cleanliness and ease of handling and cleaning; and (iii) the equipment will be best loaded/unloaded and transferred for downhole operations in Antarctica. In addition, we wanted to test the winches and smart cable/umbilical, assess instrumentation behavior and sensitivity, including the operation of the Water Distribution System (WaDS) of the IPSIEs, and the instrument communications and data-management systems, and the effectiveness of the percussion coring system. Ultimately our plan was to target some science goals, working in conjunction with the California State Geological Survey and the Tahoe Environmental Research Center. The science goals necessarily were ancillary to instrumentation testing, but were possible once testing was complete and provided all equipment was working well. 3. Background Lake Tahoe is situated in a granite graben near the crest of the Sierra Nevada Mountains on the CA-NV border, at 39oN, 120oW and 1895m amsl (see cover).
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The lake is 33km-long by 18km-wide with a surface area of 500km2 and total volume of 156km3. It has an average depth of 330m and a maximum of 501m. With these characteristics, Tahoe was thought to provide a good testing environment for Antarctica in terms of its depth and water quality. Major participants in the testing and their responsibilities were:
• DOER-Marine – contracted by NIU to design and build most of the equipment to be tested. Prime control of test plan and operations in consultation with NIU.
• Tahoe Marine and Excavating – contracted by DOER to operate the barge platform used for all testing operations.
• Northern Illinois University (NIU) – owner and ultimately operator of much of the instrumentation to be test. Scientists tested the scientific instruments included in the equipment designed by DOER.
• University of California, Santa Cruz – included scientists and engineers to test the instruments designed and built at UCSC. They also provided a ferrying link to and from shore during barge operations.
• California State Geological Survey – included a scientist, Gordon Seitz who was interested in earthquake activity and history of Lake Tahoe. He will write-up scientific results from the testing.
• Tahoe Environmental Research Center – were not involved in testing directly, but provided access to their Tahoe City facility for us to use storage space and wet-lab access when we needed.
• Scripps Institution of Oceanography provided an ROV for observing subsurface behavior of equipment.
4. Daily Operations and Achievements Nine daily field reports were circulated to interested personnel and are available for reading at http://www.niu.edu/geology/news/submersible_testing.shtml. 5. Outcomes Overall, most of our goals for the testing were achieved, even though there were some frustrations with the operating platform and in losing some instrument components. The major outcomes can be grouped into two categories: science instrumentation, and engineering and operations. 5.1 NIU IPSIEs (Instrumentation Packages for Sub-Ice Exploration) These units include a range of sensors that are designed for regular oceanographic and limnological uses. However, they have been redesigned from their common profiling deployment arrangement in a rosette, into a vertical array to fit down an ice borehole. To achieve this and ensure they are all sampling the same water, Tygon tubing connects them with an intake in the Bottom Stage (Fig. 1) and a pump below the Power & Telemetry Stage to draw the water up through each stage.
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The IPSIEs are designed in stages whose instruments can be connected together through the WaDS and electrical whips using flanges (Figs. 2 and 3) to bolt together their outer steel tube casings. All the instruments are mounted in racks that then slide in the protective casings, which also have ports for those that need to be open to the water (e.g., Aquadopp) or those to which we need access.
Figure 2: Steel flange used to bolt IPSIE stages together.
Figure 1: Engineering schematic layout of the POP (Physical Oceanography Package) and the WIPSIE (Water chemistry Instrument Package for Sub-Ice Exploration) of the IPSIE sensors: 1- Contros nutrient stage (HydroC - CO2, CH4), 2- Envirotech nutrient stage (PO4, SiO4, NH4, NO3), 3- Envirotech water-bag sampler stage, 4- Bottom stage (down- and side-looking cameras with LED lights, Wetlab fluorometer and optical-backscatter (FLNTU), Contros electromagnetic current meter, Tritech altimeter), 5- WaDS pump stage, 6- lifting power and telemetry stage, 7- Physical properties stage (Seabird CTD and dissolve oxygen sensor, LISST Deep particle-size analyzer, Wetlab CStar transmissometer, Nortek Aquadopp Doppler current meter).
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We are planning to use two configurations of stages and instrumentation in Antarctica for WISSARD. One configuration is the Physical Oceanographic Package (POP) and the other is Water chemistry Instrument Package for Sub-Ice Exploration (WIPSIE) (Fig.4). All instruments within each configuration are listed in Figure 1 caption and are shown in additional figures set in their racks. IPSIEs are deployed on a strengthened fiber-optic umbilical or “smart cable” and winch (Fig. 5), the cable being directly terminated to the top Power & Telemetry Stage (Fig. 6). The other end of the fiber-optic cable is connected directly to the topside data system that, processes, plots, and archives all of the instrument data in real-time. Algorithms are built-in to the custom-designed data processing software to synchronize the data from each instrument in time and depth by using the known flow rate through the WaDS. These two stages are deployed each time with the IPSIE. The other stage that is always attached in IPSIEs is the Bottom Stage (Fig. 7). That stage is important because it houses a Tritech altimeter to provide real-time distance above bottom. The Bottom Stage also contains side-looking and downward-looking cameras to help visually with any issues in the borehole and as we descend through the water column and stop just above the sediment floor. In addition, to these two critical components the other instruments in this stage are the Wetlab fluorometer and optical-backscatter (FLNTU) and Contros electromagnetic current meter that can determine velocity directly at the base of IPSIE.
Figure 3: The WaDS system showing the Tygon tubing on the left, water flowing from the outflow at the end of the tubing in the left center, and the pump on the right. The pump itself is located at the top of the IPSIE units to draw the water upward from the bottom to enable all instruments to sample the “same water” and also to lower the chance of cavitation by drawing water up rather than pushing it.
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Figu
re 4
: B
otto
m c
ente
r – IP
SIE
sta
ges
lyin
g on
the
deck
with
con
nect
ing
WaD
S h
oses
and
el
ectri
cal w
hips
ext
endi
ng o
ut th
roug
h th
eir f
lang
es. I
PS
IEs
are
then
hoi
sted
ver
tical
ly fr
om th
e ho
rizon
tal b
y on
e en
d an
d th
en c
an b
e de
ploy
ed v
ertic
ally
.
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Figu
re 5
: Win
ch w
ith le
vel w
ind
and
HP
U b
ox s
pool
ed w
ith th
e sm
art c
able
or a
rmor
ed u
mbi
lical
with
st
reng
then
ing
stee
l wire
s ar
ound
fibe
r-op
tics
fiber
s an
d po
wer
wire
s al
l cas
ed in
non
-pol
lutin
g an
d cl
eana
ble
jack
et.
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Figu
re 6
: Mot
or a
nd e
lect
roni
cs s
tage
with
“tel
emet
ry b
rain
” tha
t is
enla
rged
at t
he b
otto
m le
ft. T
he in
tern
al u
nits
of
this
sta
ge a
re b
eing
slip
ped
into
the
casi
ng a
nd it
is th
en h
oist
ed v
ertic
ally
to b
e co
nnec
ted
to th
e W
aDS
sta
ge w
ith
elec
troni
cs a
nd h
ydra
ulic
hos
es th
at a
re th
en p
rimed
bef
ore
final
set
-up.
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The EnviroTech water bag sampler can collect six samples on one deployment (Fig. 8) and is a stage in itself. It can be deployed with both the POP and WIPSIE configurations.
The POP configuration focuses on physical measurements of the water column (Fig. 9). Instruments that complete this configuration in addition to the Water
Figure 7: The bottom stage that includes cameras, altimeter, fluorometer and
optical-backscatter (FLNTU) and electromagnetic current meter.
Figure 8: The EnviroTech water bag sampler with 48 ports for 1L sample bags. Due to space we will be able
to collect six samples per deployment in bags that are housed within protective plastic sheet (left image) in the rack.
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Sampler and the Bottom Stages, include a Seabird CTD and dissolve oxygen sensor, a Wetlabs CStar transmissometer, a Sequoia Scientific’s LISST Deep particle-size analyzer and a Nortek Aquadopp Doppler current meter (Fig. 10).
The WISPIE configuration (Fig. 9) includes chemical instrumentation for measuring nutrients in the water column. It includes two stages: the Contros Nutrient Stage that has HydroC sensors for CO2 and CH4, and an EnviroTech Nutrient Stage with sensors for determining PO4, SiO4, NH4 and NO3. In-line filters at the limits of sand, silt and clay are mounted before water enters these nutrient sensors and can be used to quantify transmission (CStar) and backscatter sensors (FLNTU) and to verify particle size estimates of the LISST Deep (Fig. 11). 5.1.1 Engineering outcomes Both the Power and Telemetry Stage performed well in our testing, as did the WaDS pump stage, although the latter needs modification to fully integrate the CTD and size analyzer (see 5.1.2).
Figure 9: Engineering schematic layout of the POP (Physical Oceanography Package) and the WIPSIE (Water chemistry Instrument Package for Sub-Ice Exploration) of the IPSIE sensors: 1- Contros nutrient stage (HydroC - CO2, CH4), 2- Envirotech nutrient stage (PO4, SiO4, NH4, NO3), 3- Envirotech water-bag sampler stage, 4- Bottom stage (down- and side-looking cameras with LED lights, Wetlab fluorometer and optical-backscatter (FLNTU), Contros electromagnetic current meter, Tritech altimeter), 5- WaDS pump stage, 6- lifting power and telemetry stage, 7- Physical properties stage (Seabird CTD and dissolve oxygen sensor, LISST Deep particle-size analyzer, Wetlab CStar transmissometer, Nortek Aquadopp Doppler current meter).
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Fitting the EnviroTech water sampler and its sample bags, WaDS tubing and wiring whips within its rack and into the casing was very tight, and so some modifications are being made by DOER to make that process easier in the field, including new wiring and connectors and tubing. There was also an issue of some water leakage into the unit and that is being addressed at DOER too.
Figu
re 1
0: T
he P
OP
Sta
ge w
ith a
Sea
bird
CTD
and
dis
solv
e ox
ygen
sen
sor,
a W
etla
bs C
Sta
r tra
nsm
isso
met
er,
a S
equo
ia S
cien
tific
’s L
ISS
T D
eep
parti
cle-
size
ana
lyze
r and
a N
orte
k A
quad
opp
Dop
pler
cur
rent
met
er
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5.1.2 Science outcomes All of the instruments in the Bottom Stage worked well in their communications with the surface and in data generation (Fig. 12). Communications with the EnviroTech water sampler are good at the surface, but there were issues once submerged. These issues are being worked on at DOER now so it can be commanded to collect samples (up to 1L) where needed in the water column.
Figure 11: WIPSIE configuration that includes two stages: the Contros Nutrient Stage that has HydroC sensors for CO2 and CH4 (center image), and an EnviroTech Nutrient Stage with sensors for determining PO4, SiO4, NH4 and NO3 (outside two images).
Figure 12: Topside computer command center with display and archiving of all instrument data in real-time.
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Each of the sensors in the POP configuration performed well with surface communications and in generating appropriate data (Fig. 13). However, two units require modification in the POP configuration to integrate them completely into the WaDS – the Seabird CTD/DO and the LISST Deep, and DOER is currently carrying out these modifications.
Fi
gure
12:
Des
cent
pro
files
of d
iffer
ent v
aria
bles
mea
sure
d by
the
IPS
IE in
stru
men
ts in
Lak
e Ta
hoe.
The
se d
ata
show
that
the
inst
rum
enta
tion
was
wor
king
app
ropr
iate
ly w
ith o
ne m
ajor
issu
e th
at is
bei
ng m
odifi
ed. T
he C
TD/D
O d
ata
wer
e ob
tain
ed w
ith
the
inst
rum
ents
out
side
of t
he W
aDS
sys
tem
and
thus
wer
e af
fect
ed b
y a
dela
y tim
e fo
r wat
er m
ixin
g in
to th
e ca
sing
dur
ing
desc
ent.
The
stra
nge
“kic
ks” i
n T,
O a
nd tu
rbid
ity (~
30m
dep
th in
top
prof
ile a
nd ~
50m
dep
th in
bot
tom
pro
file)
are
due
to
turb
ulen
t mix
ing
and
bubb
le c
reat
ion
in th
e w
ater
as
the
barg
e w
as b
eing
mov
ed (n
oted
on
our e
vent
log
reco
rds
and
seen
on
the
vide
o fro
m th
e do
wnw
ard-
look
ing
cam
era)
. Kic
ks in
the
plot
s at
the
botto
m s
how
whe
re IP
SIE
cam
e cl
ose
to th
e la
ke fl
oor.
Thes
e da
ta a
re c
ompa
rabl
e to
thos
e co
llect
ed o
ver m
any
year
s by
the
TER
C g
roup
.
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The Contros sensors in the WIPSIE configuration are communicating well and providing data, but the EnviroTech units have had communications issues that have been a combination of the units themselves and the telemetry system of the IPSIEs. DOER is in the process of trouble shooting this problem. Like the water sampler, these EnviroTech units are a tight squeeze in the casings and we are modifying the WaDS hosing, whips and chemistry bags within the racks for easier handling in the field. Two descent profiles of different variables measured by the IPSIE instruments in Lake Tahoe are shown in Figure 13. These data show that the instrumentation was working appropriately with one major issue mentioned just above, that is, the CTD/DO data were obtained with the instruments outside of the WaDS system and thus were affected by a delay time for water mixing into the casing during descent. The strange “kicks” in T, O and turbidity (~30m depth in top profile and ~50m depth in bottom profile in Fig. 13) are due to turbulent mixing and bubble creation in the water as the barge was being moved (noted on our event log records and seen on the video from the downward-looking camera). Kicks in the plots at the bottom show where IPSIE came close to the lake floor and caused slight disturbance. These data are comparable to those collected over many years by the TERC. 5.2 NIU Percussion Corer The percussion corer (Fig. 14) is designed to be lowered to the lake or sea floor on the smart cable of the multipurpose winch, and then to hammer a core barrel up to 5m-long into stiff over-consolidated sediment such as subglacial till. As the corer is deployed, a 2000lb mass is released within its casing by unbolting an
Figure 14: DOER engineering CAD of the NIU Percussion Corer
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extension section from inside the casing (Figs 15 and 16; refer to pink section in Fig. 14). Once deployed on the sediment surface, the hydraulic motor is commanded to drive a piston that raises the mass to its maximum height within its casing, and then is tripped to be released in a free-fall, to then strike a plate on the top of the core barrel. This process is automatically repeated every 20-30 seconds until commanded to stop.
Figure 15. Upper stages of the percussion corer including the power and hydraulic motor stage and the telemetry stage. Below these is the drop-weight stage (the weight can be seen through the holes at the bottom of the stage in image on the left.
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Figu
re 1
6: U
nbol
ting
the
exte
nsio
n se
ctio
n to
rele
ase
the
drop
-wei
ght b
efor
e de
ploy
ing
the
perc
ussi
on c
orer
. On
the
right
, the
cor
er is
at i
ts fu
ll ex
tent
with
the
5m c
ore
barr
el b
eing
the
low
est s
tage
.
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A linear position sensor is used to measure the penetration distance with each strike. Coring is stopped when there is either a lack of further penetration or the 5m-barrel is fully buried in the bottom sediment. To avoid large pullout strains beyond the capacity of the cable, which is 10,000lb, the hydraulic system is designed to help extract the core barrel. The hydraulics can be commanded to force pressurized-water down between the core liner and core barrel; the water exiting via jets through holes in the core cutter head (Fig. 17). The water is then forced up the outside of the core barrel to decrease friction between it and the sediment.
Also for added safety if the hydraulic flushing process fails to extract the barrel, weak-link bolts that fail in tension will break away at the top of the barrel so that the rest of the corer assembly can be recovered and only the barrel is lost. 5.2.1 Engineering outcomes Initially there were issues with having enough hydraulic pressure to drive the drop-weight vertically at its designed speed. Adjustments to the hydraulic system were made and then the weight behaved as expected. DOER is making
Figure 17: Specifics of the core barrel of the percussion corer. Clockwise the images are: water jet holes at the base of the drop-weight stage that attaches to the top of the core barrel; top flange of the core barrel with water jet holes; linking the base of the drop-weight stage to the core barrel (two images); core cutting head; looking up the core cutting head at the core catcher; the core liner exposed without the core barrel attached to the core cutter with custom sealing ring with water jet holes.
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modifications to the hydraulic system design to permanently accommodate the adjustments made for efficient operation of the drop-weight. The other main issue was that the weak-link tension bolts were shown to fail in shear in addition to the tension for which they were designed. On one of its deployments, the core barrel penetrated the lake floor sediment, but when it was resting at a ~15o angle, the weak bolts failed under the strain and sheared off, releasing the core barrel. All of this was observed with the ROV and DOER is redesigning the bolts to accommodate more shear force. The bolts are being slightly modified so they are stronger in shear, but will still fail under high tension. The hydraulic water flushing system worked as expected. 5.2.2 Science outcomes We selected sites on the bottom of Lake Tahoe that have highly consolidated sediment that we consider to be till from the last glacial maximum underlying a thin cover of very gravel-rich (granules to boulders) biogenic mud (Fig. 18). This type of setting could well be what we will need to be sampling in Antarctica. The corer performed as designed except for the initial slowness of the hammering process as described above. Only short cores were recovered due to the slow hammering process until the bolts sheared and we lost the core barrel. Even though the cores were short, the corer showed that it is easily capable of penetrating these types of sediment.
Figure 18: ROV images of the percussion corer penetrating coarse sediment on the lake floor. Upper middle image shows the drop-weight stage at the top of the core barrel. Top right image is the base of a stiff till sample within the core cutter.
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5.3 Uwitec Multicorer The multicorer is a lightly modified off-the-shelf system designed by the Swiss Uwitech Company (Fig. 19) that is well-tried in many lakes around the world. It is designed to take three replicate cores at the one time after self-triggering on striking the bottom sediment during descent. It recovers undisturbed top-most sediment, the sediment-water interface and the bottom water in contact with the sediment in each of the tree core liners. Thus it is also an effective bottom water sampler. It also comes with a custom sediment slicer with which you can extrude sediment in discrete intervals for sequential sampling through the top-most lake floor sediment.
5.3.1 Engineering Outcomes There were no engineering/design issues with the Uwitech corer. 5.3.2 Science Outcomes The Uwitech corer provided the upper-most lake floor sediment, the undisturbed sediment-water interface, and the bottom lake water and performed very well, as per its specifications (Fig. 19).
Figure 19: Uwitech multicorer that takes three replicate cores at once preserving the top-most sediment, the sediment-water interface and the water column. Two bottom right images show a sample being recovered.
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5.4 Top-side Data Management and Instrument Communications Initially there were issues in communicating with several instruments via the telemetry system in the IPSIEs and then through the 3km of fiber optics in the smart cable. Modifications of the customized software quickly improved communications, although there still appears to be some issues with the EnviroTech instruments that are currently being worked on. We are now in a situation where all of the instruments are under direct command from the surface through the customized software, which has been modified from each of the packages that come with the instruments. In this way, each instrument can be commanded from an integrated interface running on a single workstation. Likewise data streaming up to the surface are also being collected in a customized software package and being displayed real-time through that package and simultaneously being stored as raw ASCII data files (Figs. 12 and 13), including back-ups. This includes video streams from the cameras. Where appropriate, we will also recover any binary data, logged in each instrument’s original proprietary format. 5.5 University of California Santa Cruz Instrumentation UCSC instrumentation to be tested included a piston corer with its own winch and cable that is modeled on the previous CalTech corer (Fig. 20), and a geothermal probe modeled on those used by IODP.
Figure 20: Preparing and deploying the UCSC piston corer. Bottom right image is from the ROV of the protruding bent core barrel with its lower section being stuff in stiff till.
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The piston corer was deployed and appeared to work appropriately; however, it was not recovered and remains on the floor of Lake Tahoe. As it was deployed and struck bottom, the barge platform started drifting in the wind and waves. The movement placed a strain on the cable because, as we found later, the core barrel was embedded and stuck in the stiff till sediment sampled during percussion coring. The piston core winch was not strong enough to extract the core barrel, especially with the angle on the cable due to barge drift. The cable was cut and a buoy placed on the surface to mark its location. The ROV was then deployed from the barge and the corer was found and seen to be stuck, with a bent core barrel, in the sediment (Fig. 20). The ROV with manipulator arm made several attempts to recover the corer, but unfortunately they all failed. Due to a significant amount of operational time being lost to problems of anchoring and stabilizing the barge for operations in wind and waves, there was no time during the Tahoe testing to deploy and test the geothermal probe. Ian Griffith of DOER offered to assist the testing of the probe at their facility, which was completed on September 17 and is described in a separate report by Ken Mankoff. 5.6 Additional Engineering & Operations Other components to be used in Antarctica beyond the direct instrumentation were also operationally assessed in their performances. 5.6.1 Hydraulic motor and Telemetry Stages Both the Power and Telemetry Stages performed well in our testing after some adjustments were made in the hydraulics and in the Ethernet cans used in communications between the surface and the instruments. Due to some leakages, pressures in the hydraulic system were adjusted in the field to improve operations of the whole hydraulic system. DOER is making modifications to the hydraulic system design to permanently accommodate the adjustments made for efficient operation. Minor adjustments were made in the field to the “telemetry brain” and it worked well afterward; no more adjustments are required. 5.6.2 Casings, Flanges, Racks, WaDS, Whips/wiring Casing and flanges showed appropriate structural integrity and strength to stand up to handling required in the field. More access holes will be cut in the casings for easier access to the instruments and for cleaning. Bolting of the flanges in the field may be a slow part of the operation. Fitting of the racks, with WaDS tubing and instrument telemetry whips, was an issue and are being modified before shipping for easier use in the field. Whips and tubing will be fitted and customized for each stage so once in, can be joined through the flanges to the next stage. More room will be made by relocating them within the problem racks so as not to
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get hung up on the casing. The WaDS system also needs modification to fully integrate the CTD and size analyzer (see 5.1.2). 5.6.3 Smart winch and umbilical operation and handling The smart winch worked well. Its gearing and computer control is being adjusted so it can descend at faster rates to increase the speed of penetration of the geothermal probe as it enters the sea floor. There was a minor issue with the level wind that will also be adjusted before shipping. The smart cable behaved well and met expectations. It needs to be re-terminated to the Power Stage after a stressful bending at the connection during the learning process of how best to handle the equipment. 5.6.4 Load transfer The load transfer stanchion constructed at the side of the barge worked well in operations Fig. 21). It is a helpful template for design of the load transfer cage to be used at the moon-pool above the ice borehole. 6. Conclusions This testing in Lake Tahoe of instruments and equipment for the WISSARD project in Antarctica has shown that the bulk of them are ready to ship to Antarctica. Some issues with the instruments and equipment were highlighted during the testing process and NIU, DOER and UCSC are currently dealing with these in order to meet the shipping deadline of early October and to be further tested near McMurdo Station.
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Figu
re 2
1: L
oad
trans
fer p
roce
dure
from
the
cran
e to
the
smar
t cab
le a
nd w
inch
, an
d th
en o
ver a
she
ave
and
load
-tran
sfer
sta
nchi
on o
n th
e si
de o
f the
bar
ge.
