level 2 ocean salinity l2os v610 & ott post-processor
DESCRIPTION
Level 2 Ocean Salinity L2OS v610 & OTT post-processor. 5 July 2013. ARGANS & SMOS L2OS ESL. L2OS v610 status. Significant changes from v600 OTT post-processor OTT running average tracking L1 drift, updated daily in DPGS & reprocessing no more compareTBs! TEC from Stokes 3 - PowerPoint PPT PresentationTRANSCRIPT
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SMOS L2 Ocean Salinity
www.argans.co.uk
Level 2 Ocean Salinity
L2OS v610 & OTT post-processor
5 July 2013
ARGANS & SMOS L2OS ESL
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SMOS L2 Ocean Salinity
www.argans.co.uk
Significant changes from v600
• OTT post-processor• OTT running average tracking L1 drift, updated daily in DPGS & reprocessing
• no more compareTBs!
• TEC from Stokes 3• impact on high TEC descending orbits; ignore L1c IRI TEC
• Multi-threading• > 2 x speed increase
• Simplified slim-line UDP; extended DAP• remove unnecessary flags & fields, make it easy for users to extract good quality data
L2OS v610 status
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SMOS L2 Ocean Salinity
www.argans.co.uk
Real-time salinity retrieval requires near real-time OTT to track short term drift: while processing L1c,
L2OS v610 extracts deltaTBs for South Pacific region and writes them to AUX_DTBXY_. The OTT post-
processor runs once per day, reads AUX_DTBXY_ and a set of current deltaTBs (from AUX_DTBCUR),
writes a new set of OTTs, and updates AUX_DTBCUR. The L2OS processor always uses the latest set of
OTT.
deltaTBs(DTBXY_)
current deltaTBs
(DTBCUR)
OTT post-
processor
OTTsL2OS
processorL1c
L2OSUDP & DAP
OTT post-processor
By-products:
• daily drift statistics available in AUX_DTBCUR.HDR for analysis & monitoring
• other (non-OTT) regions may be specified (in AUX_CNFOSF) for monitoring (output in DTBXY_)
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SMOS L2 Ocean Salinity
www.argans.co.uk
• L2OS v610for each region in AUX_CNFOSF
apply region snapshot filter // use snapshot if enough measurements & all within region
if OTT region
apply OTT snapshot filter // ignore if TBs out-of-range, RFI, L1c error
apply OTT grid point filter // not ocean, hi/lo WS, ice
if count(snapshots) > Min_Snapshots & count(gridpoints) > Min_Grid_Points
if OTT region apply OTT measurement filter // ignore sun_point, rfi_tails
deltaTB[region] = use forward model to compute deltaTBs & statistics
write deltaTB & statistics to AUX_DTBXY_
• OTT post-processormerge all AUX_DTBXY_ from previous day with current AUX_DTBCUR
discard old sets of deltaTBs (last-in/last-out)
compute & write new OTT using current set of deltaTBs
write current set of deltaTBs & statistics to new AUX_DTBCUR
OTT post-processor overview
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SMOS L2 Ocean Salinity
www.argans.co.uk
for each selected measurement
map xi,eta onto x,y grid
count[x,y] += 1
sumDeltaTB[x,y] += TBsmos – Tbmodel
sumDeltaRA[x,y] += (TBsmos – Tbmodel) / ra
sumDeltaRA2[x,y] += ((TBsmos – Tbmodel) / ra)2
flags[x,y] |= selected L1c & L2OS flags
for x = 0 to 128
for y = 0 to 128
n = count[x,y]
write n
mean_deltaTB[x,y] = sumDeltaTB[x,y] / n
write mean_deltaTB[x,y]
stdra[x,y] = sqrt(((n * sumDeltaRA2[x,y] – sumDeltaRA[x,y]2) / (n * (n – 1)))
write stdra[x,y]
write flags[x,y]
AUX_DTBXYcount[x,y]deltaTB[x,y]stdra[x,y]flags[x,y]
Statistics for fov, affov, eaffov, & filtered by flags
Flags for off-line analysis:
OTT post-processor: L2OS v610 algorithm
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SMOS L2 Ocean Salinity
www.argans.co.uk
deltaTB referencemax_orbits (nominally 10)
quality thresholds (RFI, L1c errors)
ott_strategy (mean/gaussian)
ott_validity_start (first/mean/last)
List of regionsName, IDtype (OTT/REG)orbit dir (A/D/?)lat/longsnapshot thresholdsgrid point thresholds
AUX_CNFOSF <OTTPP> section
Source of geophysical reference parameters for computing deltaTBs:
0 = climatology, L1c TEC & ECMWF priors
1 = model 1 retrieved parameters
And new filters:
OTT_SNAPSHOT_FILTER
OTT_REGION_FILTER
OTT_STATS_FILTER
New OTT post-processor section in AUX_CNFOSF
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SMOS L2 Ocean Salinity
www.argans.co.uk
n x regions:IDsnapshot start/stop timessnapshot start/stop ID
for 3 modelsfor 8 polarisations
4 x statisticscount[x,y]deltaTB[x,y]stdra[x,y]flags[x,y]
AUX_DTBXY_ datablock
Statistics for FOV, AFFOV, EAFFOV, & filtered by flags[x,y]: mean, median, min, max, std.
OTT post-processor components: AUX_DTBXY_
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SMOS L2 Ocean Salinity
www.argans.co.uk
read all deltaTB orbits from AUX_DTBCUR // ignore
ottA/D
for each AUX_DTBXY_
if region = South Pacific OTT region & good quality
read deltaTB for this orbit
// keep n ascending & n descending deltaTBs...
trim deltaTB // discard oldest first
ottA = average(deltaTB, ascending)
ottD = average(deltaTB, descending)
for model = 1 to 3
write ottA(model) & ottD(model) to AUX_OTT1/2/3
deltaTB += ottA
deltaTB += ottD
write deltaTB to new AUX_DTBCUR // including ottA/D
Options:
number of deltaTB orbits (nominally 10+10)
mean or weighted mean (nominally mean)
filter DTBXY by quality
OTT post-processor: OSCOTT algorithm
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SMOS L2 Ocean Salinity
www.argans.co.uk
Header contains quality information for each region:
Grid point quality informationtotal grid points in region, number of grid points used after filteringnumber of grid points:
too near to land/coast; rain/ice contaminationmissing ECMWF data; low WS (<3m/s), high WS (>7m/s)
Measurement quality informationtotal measurements in region; number of measurements used after filteringnumber of measurements flagged:
as sun point, sun tails, with sun/moon/galactic glintcontaminated by RFI (by L1 or L2), L1c error flags
Quality information is from forward model 1 only:
used by OSCOTT to select ‘good’ sets of deltaTBs.
OTT post-processor components: AUX_DTBXY_
Snapshot quality informationtotal snapshots in region, number of snapshots used after filteringnumber of XX/YY/XXY/YYX snapshotsnumber of snapshots with each of 4 L1c error flags setnumber of snapshots with TB out-of-range, high std/std_Stokes3/4
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SMOS L2 Ocean Salinity
www.argans.co.uk
Header contains quality information for each region:
Grid point quality informationtotal grid points in region, number of grid points used after filteringnumber of grid points:
too near to land/coast; rain/ice contaminationmissing ECMWF data; low WS (<3m/s), high WS (>7m/s)
Measurement quality informationtotal measurements in region; number of measurements used after filteringnumber of measurements flagged:
as sun point, sun tails, with sun/moon/galactic glintcontaminated by RFI (by L1 or L2), L1c error flags
Quality information is from forward model 1 only:
used by OSCOTT to select ‘good’ sets of deltaTBs.
OTT post-processor components: AUX_DTBXY_
Snapshot quality informationtotal snapshots in region, number of snapshots used after filteringnumber of XX/YY/XXY/YYX snapshotsnumber of snapshots with each of 4 L1c error flags setnumber of snapshots with TB out-of-range, high std/std_Stokes3/4
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SMOS L2 Ocean Salinity
www.argans.co.uk
AUX_DTBXY_ datablock
m x AUX_DTBXY + extra sets:set type (L1c, OTT...)region IDorbit direction (A/D)orbit polarisation (D/F)snapshot start/stop timessnapshot start/stop IDL1c filename
AUX_DTBCUR datablock
OSCOTT
m x AUX_DTBXYn x regions:
IDsnapshot start/stop timessnapshot start/stop ID
for 3 modelsfor 8 polarisations
4 x statisticscount[x,y]deltaTB[x,y]stdra[x,y]flags[x,y]
for 3 modelsfor 8 polarisations
4 x statisticscount[x,y]deltaTB[x,y]stdra[x,y]flags[x,y]
OTT post-processor components: AUX_DTBCUR
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SMOS L2 Ocean Salinity
www.argans.co.uk
OTT post-processor components: AUX_DTBCUR
Header contains quality information statistics for ascending & descending OTTs generated by
the last OTT post-processor run:
Ascending OTT quality informationcount of orbits used to make OTTsnapshot start/stop timesfor 3 polarisations
for 8 polarisations4 x statistics (same format as AUX_DTBXY_ statistics(count, mean, median, std for fov, affov, eaffov, & filtered)
Descending OTT quality information(same fields as above)
List of L1c datasets
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SMOS L2 Ocean Salinity
www.argans.co.uk
OTT post-processor components: AUX_DTBCUR
Header contains quality information statistics for ascending & descending OTTs generated by
the last OTT post-processor run:
Ascending OTT quality informationcount of orbits used to make OTTsnapshot start/stop timesfor 3 polarisations
for 8 polarisations4 x statistics (same format as AUX_DTBXY_ statistics(count, mean, median, std for fov, affov, eaffov, & filtered)
Descending OTT quality information(same fields as above)
List of L1c datasets
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SMOS L2 Ocean Salinity
www.argans.co.uk
OTT post-processor preliminary results
AUX_DTBXY_ x 10
AUX_OTT1F_
deltaTB, XX pol, ascending
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SMOS L2 Ocean Salinity
www.argans.co.uk
OTT post-processor preliminary results
AUX_DTBXY_ x 10
AUX_OTT1F_
Median = 0.58 K
Histograms of deltaTB in XX FOV, ascending orbits, AUX_DTBCUR 20110501
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SMOS L2 Ocean Salinity
www.argans.co.uk
OTT post-processor preliminary results
AUX_DTBXY_ x 10
AUX_OTT1F_
std/ra, XX pol, ascending
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SMOS L2 Ocean Salinity
www.argans.co.uk
OTT post-processor preliminary results
AUX_DTBXY_ x 10
AUX_OTT1F_
Histograms of std/ra in XX FOV, ascending orbits, AUX_DTBCUR 20110501
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SMOS L2 Ocean Salinity
www.argans.co.uk
OTT post-processor preliminary results
Comparing OTT from DPGS with OTTPP: re-sampled grid
DPGS OTT (20110504) OSCOTT (20110501) delta = OSCOTT – DPGS
Differences along border-belt-suspenders & tails
XX
YY
XX
YY
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SMOS L2 Ocean Salinity
www.argans.co.uk
• Which statistics should be used to select/reject DTBXY deltaTB data?• Current implementation has thresholds for maximum % measurements contaminated
by L1 RFI, L2 RFI, or with L1c error flags set
OTT post-processor issues: good AUX_DTBXY
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SMOS L2 Ocean Salinity
www.argans.co.uk
• What is the optimal running average window?• Averaging many sets of deltaTBs gives better quality OTTs but with a slower response to
rapid TB drift
OTT post-processor issues: averaging window
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SMOS L2 Ocean Salinity
www.argans.co.uk
OTT post-processor issues: priors or retrievals?
std(priors) std(model 1 retrievals)
deltaTB(priors-model1)
deltaTBs are computed as the difference
between forward model TBs and L1c TBs
Should we run the forward model using
priors (SSS from climatology, SST/WS
from ECMWF, TEC from L1c or A3TEC)?
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SMOS L2 Ocean Salinity
www.argans.co.uk
OTT post-processor issues: xi/eta grid sampling
-1.0 xi 1.0
1.0
eta
-1.0
-0.7 xi 0.7
0.4
eta
-0.7
v600 v610
v600: 129x129 (xi ±1.0, eta ±1.0): sampling interval 0.016
v610: 129x129 (xi ±0.7, eta -0.7 to 0.4): sampling interval 0.011 in xi, 0.008 in eta
What grid sampling interval is best for OTTs?
Grid point density varies within snapshot – highest at leading edge of AFFOV
Typical total 5600 grid points, >100 along leading edge (±0.25 xi): ~0.005 sampling?
Blackman pixels ~0.04 diameter: with pixel overlap 1.4, sampling interval 0.028
Small sampling interval leads to higher noise in OTTs.
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SMOS L2 Ocean Salinity
www.argans.co.uk
OTT post-processor issues: merge OTTs?
long integration time short integration time delta
OTTs are similar – should they be merged?
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SMOS L2 Ocean Salinity
www.argans.co.uk
OTT post-processor issues: merge OTTs?
long integration time short integration time
OTTs are similar – should they be merged to reduce noise
(especially for short integration time)?
![Page 25: Level 2 Ocean Salinity L2OS v610 & OTT post-processor](https://reader036.vdocument.in/reader036/viewer/2022062518/56814573550346895db24281/html5/thumbnails/25.jpg)
SMOS L2 Ocean Salinity
www.argans.co.uk
OTT post-processor issues: merge OTTs?
XXY YYX delta
OTTs are similar – should they be merged?
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SMOS L2 Ocean Salinity
www.argans.co.uk
L1PP v600 20110505T040402
tecu
tecu
latitude
latitude
L1cTEC & A3TEC
Cross-verification between Matlab breadboard & v610: delta = breadboard-v610
TEC from Stokes 3: descending orbit, high TEC
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SMOS L2 Ocean Salinity
www.argans.co.uk
L1PP v600 20110505T040402
tecu
latitude
L1cTEC & A3TEC
TEC from Stokes 3: descending orbit, high TEC
Tuning:
decreased sigma prior, increased gaussian smoothing, added outlier filtering, TEC height changed from 450 to 400 km
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SMOS L2 Ocean Salinity
www.argans.co.uk
L1PP v600 20110505T040402
tecu
latitude
L1cTEC & A3TEC
TEC from Stokes 3: descending orbit, high TEC
L2OS retrieved TEC follows A3TEC better than L1c TEC
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SMOS L2 Ocean Salinity
www.argans.co.uk
L1OP v601 20110505T040448
tecu
latitude
L1cTEC & A3TEC
TEC from Stokes 3: descending orbit, high TEC
L1OP v601 using consolidated VTEC
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SMOS L2 Ocean Salinity
www.argans.co.uk
Ascending orbit with low TEC – noisy A3 TEC retrieval, but good match with L1c
L1PP v600 20100802T153815
tecu
L1cTEC & A3TEC
TEC from Stokes 3: ascending orbit
latitude
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SMOS L2 Ocean Salinity
www.argans.co.uk
L1cTEC & A3TEC
TEC from Stokes 3: ascending orbit
L1PP v600 20100802T153815
tecu
latitude
Tuning:
decreased sigma prior, increased gaussian smoothing, added outlier filtering, TEC height changed from 450 to 400 km
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SMOS L2 Ocean Salinity
www.argans.co.uk
L1cTEC & A3TEC
TEC from Stokes 3: ascending orbit
L1PP v600 20100802T153815
tecu
latitude
L2OS retrieved TEC follows A3TEC better than L1c TEC?
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SMOS L2 Ocean Salinity
www.argans.co.uk
L1cTEC & A3TEC
TEC from Stokes 3: ascending orbit
L1OP v601 20100802T153855
tecu
L1OP v601 using consolidated VTEC
latitude
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SMOS L2 Ocean Salinity
www.argans.co.uk
Faraday rotation depends on TEC altitude (not only on TEC amplitude).
Tomography using Stokes 3:first analysis shows mean altitude of electronic layer is about 390 kmelectron density not located at same altitude along the orbittomography depends on TEC prior
TEC from Stokes 3: altitude of TEC
Estimated
Prior
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SMOS L2 Ocean Salinity
www.argans.co.uk
Changing TEC altitude in v610 from 450 to 400km
TEC from Stokes 3: altitude of TEC
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SMOS L2 Ocean Salinity
www.argans.co.uk
Motivation
• run OTT post-processor per-day during reprocessing (same as DPGS)• average L2OS run time in DPGS/reprocessing is 2.5 – 3 hours (TBC)
• x3 speed-up with 4 threads would match SM performance (Antonio de la Fuente)
• 15% faster CPU clock in reprocessing platform
• L2OS maximum run time per half-orbit is ~370 minutes (Pacific Ocean)(on 5 year old original specification server)
• L2OS v610 uses OpenMP to multi-thread time-consuming loops• Pacific Ocean test orbit results (includes 25 minutes I/O) :
3 threads: 160 minutes (5.3G) – 2.3 x speed-up
4 threads: 144 minutes (5.1G) – 2.6 x speed-up
• average run-time (20110416) with 4 threads 124 minutes (max 166, min 77)
Multi-threading L2OS
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SMOS L2 Ocean Salinity
www.argans.co.uk
Motivation
• UDP includes too many flags & fields – confusing• make it easy for users to extract good quality data from UDP
• move unnecessary UDP flags & fields to DAP
• UDP is for oceanographers, not for analysis
• make the DAP easier to use• variable length grid point records in v600 makes reading DAP grid point data very slow
• restructure DAP into a block of all grid point data (fixed size records), followed by a block of all measurement data (variable size records)
• users/ESL can read just the grid point data & ignore measurements (measurement data can still be read slowly if needed)
Summary
• new UDP only contains geophysical outputs from L2OS processor
• simplified UDP quality index & quality flags for each model
• no compatibility with existing UDP/DAP readers• requires new versions of SDV, GMT, Beam toolbox & bespoke tools
Simplified UDP & extended DAP
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SMOS L2 Ocean Salinity
www.argans.co.uk
Improving the UDP
n x grid points:
Grid point dataID, latitude, longitude, footprint, time x_swath, distance to coast
Science flags (4)near landsuspect rain, ice (Acard), RFI
Geophysical retrievals (2 x 7)
SSS1, SSS2, SSS3, AcardWS, SST, TEC,
sigmas on all retrieved parameters
Product confidencequality index for SSS1/2/3/Acard
Product confidence flags (4 x 3)
High/medium/low for SSS1/2/3/Acard
RFI probabilitycounters for DGGRFI
v600 (176 flags & 57 fields) v610 (16 flags & 29 fields)
n x grid points:
Grid point dataID, latitude, longitude, footprint, time
Science flags (4 x 30)land/sea/coast, rainice (4 flags: climatology, ECMWF, TBs,
Acard)high/low wind/SSS/SST, sea state
Geophysical priorsWS & SST from ECMWF
Geophysical retrievalsSSS1/2/3/Acard & sigmas
TB42.5 (8)modelled BTs & sigmas at surface & antenna
Control flags (4 x 28)range, sigma, chi, chi2, sun/moon/gal glintmax iterations, low/min #measurements,too many outliers, convergence limit, poor retrieval, poor geophysical, RFI suspect, RFI prone
Product confidence (34)
chi, chi2, #iterations, quality for SSS1/2/3/Acardvalid, border, affov, tails, sun/moon/gal glint, iceRFI probability counters for DGGRFIx_swath
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SMOS L2 Ocean Salinity
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Fg_high_quality
High quality flag is set if Fg_ctrl_poor_retrieval = 0 & Fg_ctrl_poor_geophysical = 0 & Dg_af_fov > 130 (grid points with lots of measurements in the AFFOV). Users filtering with this flag will get the best quality, suitable for cal-val.
Fg_medium_quality
Medium quality flag is set if Fg_ctrl_poor_retrieval = 0 & Fg_ctrl_poor_geophysical = 0. Users filtering with this flag will get all the high quality retrievals, plus those with Dg_af_fov <= 130. This set is suitable for oceanography, , since we know there were no retrieval or geophysical problems.
Fg_low_quality
Low quality flag is set if Fg_ctrl_poor_retrieval = 0. Users filtering with this flag will get all the high & medium quality retrievals, plus those without any retrieval problems (but there may be geophysical problems). This is the lowest quality we would recommend to users: these retrievals have passed the chi2P/max iterations/convergence tests, so may be ok.
Proposed UDP v610 quality flags (per model)
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n x grid points:
ID, lat/longpriors & sigmas (4 x 14)
posts & sigmas (4 x 14)
oor flags (4 x 27)
fields (8)
m x measurements:
flags (4 x 30)
fieldsdeltaTB (x4)
TBgal (x2)
n x grid points:
ID, lat/longpriors & sigmas (12)
posts & sigmas (24)
science flags (4 x 30) control flags (4 x 28)
oor flags (4 x 27)
fields (45)
n x grid points:
IDm x measurements:
snapshot IDxi, etaflags (4 x 30)
fieldsdeltaTB (x4)
TBgal (x2)
Fixed block size grid pointsVariable
block size grid points
Variable block size
measurements
Improving DAP readabilityv600 v610
Extra fields & flags from
v600 UDP
v600 priors, posts & sigmas (112 fields) allow for 7 parameters per model – only 5+4+3+2 parameters retrieved: 50% unused.
For a large DAP (eg South Pacific) with typically 150k grid points & 120 measurements/grid point:
v600 = 360M (70M grid points + 290M measurements)
v610 = 400M (50M grid points + 350M measurements)
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L1OP v601 & L2OS v610
32 ascending & 25 descending L1OP v601 orbits processed using L2OS v610, deltaTBs extracted from AUX_DTBXY_
Orbits don’t intersect OTT region, so deltaTB statistics extracted for South Pacific test region 122 (30S to 0, 160W to 120W)
Some correlation, but:climatology for 122OTT shifted (late)
v601 reduces long term drift?
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L1OP v601 & L2OS v610: RFI test orbit 20100709T034234
L1OP v504 REPR L1OP v601Fm_L1c_RFI set mostly by Fm_RFI_XX & Fm_RFI_YY
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SMOS L2 Ocean Salinity
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L1OP v601 & L2OS v610: RFI test orbit 20100709T034234
L1OP v504 REPR L1OP v601(using L2OS v600 L1OP v504 REPR OTTs)
For RFI (& other) tests we need to ensure OTTs match L1c...
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L1OP v504 & v601: RFI test orbit 20100802T153855
L1OP v504 REPR L1OP v601Region ID 126 - Equatorial Ocean ±10: small islands?
>1K delta in mean/median
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L1OP v504 & v601: RFI test orbit 20100802T153855
L1OP v504 REPR L1OP v601 delta = v504 – v601
v601 has larger spatial bias than v504 – why?
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SMOS L2 Ocean Salinity
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L1OP v504 & v601: RFI test orbit 20110128T125103
L1OP v504 REPR L1OP v601Region ID 126 - Equatorial Ocean ±10: RFI @ 5N
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SMOS L2 Ocean Salinity
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L1OP v504 & v601: RFI test orbit 20110128T125103
L1OP v504 REPR L1OP v601 delta = v504 – v601
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SMOS L2 Ocean Salinity
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L1OP v504 & v601: RFI test orbit 20110128T125103
L1OP v504 REPR L1OP v601Improved Stokes 3 & 4
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Verification scheduled August/September
• requires at least 1 month reprocessed L1c to verify (May 2011)• OTT post-processor – run at ARGANS
• TEC from Stokes 3 – run on G-POD?
• multi-threading
Remaining work before delivery
• Simplified slim-line UDP; extended DAPneed specification of weighted distance-to-coast (TBC)
• New galactic map LUTs?
Schedule• delivery mid-September, FAT early October?
L2OS v610 status summary