ICET

Transcription

ICET

ICET Report – SG2 meeting
Taipei, June 21-22, 2010
Jean-Pierre Barriot, Youri Verschelles, Lydie Sichoix
and B. Ducarme (retired, but still very active !)
Where is ICET ?
University of French Polynesia
Tahiti has become a fundamental
geodetic reference since 1997
Tracking satellites with the SLR
OGT GPS system
Other
system :
DORIS
The new OGT tide gauge station in Tubuai
(Australs archipelago)
With SHOM and Protection Civile
Nuku-Hiva (Marquesas) Tide Gauge Station
Tahiti Gphone #59 with Geoscope
broadband seismometers
The PET gravimeter is collocated with GEOSCOPE instruments in Tahiti mountains
Sandwich Isl,
6.6 2009/04/16 14:57:05 -60.215 26.797 10.0 SOUTH SANDWICH
ISLANDS REGION
Gravi in muGal
Gravity filtered between 20 et 100 seconds
Summary of instruments in
French Polynesia:
-- SLR station (ILRS) at OGT
-- 3 permanent GPS colocated with SLR at OGT
-- 1 semi-permanent GPS at Arue
-- 1 DORIS colocated with SLR at OGT
-- 1 gPhone Earth Tides gravimeter at Pamatai
-- 7 tide gauges+GPS stations (all actives 2010):
(2 Tahiti, 1 Huahine (Society), 1 Nuku-Hiva
(Marquesas), 1 Rangiroa (Tuamotu), 1 Tubuaï
(Australs), 1 Mangareva (Gambiers)
Planned: cryogenic gravimeter, VLBI, altimetry
calibration, robotic telescope
ICET activities
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International Centre for Earth Tides (ICET)
http://www.upf.pf/ICET/
Director: Jean-Pierre Barriot (France, French Polynesia)
Overview
The period from mid-2007 to mid-2008 was essentially devoted to
the translation of ICET from Brussels to Papeete. This includes three
main points: web site, the “Bulletin des Marées Terrestres, BIM”,
and GGP data stream validation.
ICET activities: mid-2008/2010
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1/ The web site of ICET has been completely migrated from the Royal Observatory of Belgium to the
University of French Polynesia (www.upf.pf/ICET/).
2/ The new ICET database, presented at the ETS2008 meeting in Vienna, is now on line at
http://maregraph-renater.upf.pf. The database currently hosts all the validated one-minute GGP data
until December 2007 and is able to store any kind of data related to Earth Tides (e.g. tiltmeter or spring
gravimeter data).
3/ A new validation software able to automatically validate GGP data has been developed. The purpose
of this software is to identify and discard jumps and spikes in the raw data on an automated or nearly
automated basis. Based on Wiener-Kolmogorov filtering techniques, it responds to the critics raised
during the ETS2008 meeting in Iena, by re-adding the "noise" to the GGP filtered data. We are currently
testing this software on several GGP raw files. We need beta-testers.
4/ A Python script able to write strictly normalized headers for GGP files is completed. This is another
key to alleviate the burden of validating and storing GGP data.
5/ We developed a new XML format for storing GGP data (see the dedicated poster).
6/ The BIM 144 and 145 are on line on the ICET website. BIM 146 will be on line soon. All together, they
will gather more than 50 papers presented at the ETS2008 meeting.
7/ The new gPhone gravimeter of the ICET center is now in operation in Tahiti-Pamatai. We routinely
monitor all Earthquakes > 6.0 along the Pacific Rim.
8/ ICET is also participating in the deployment in Fench Polynesia of a network of Tide-Gauge / GPS
stations (POGENET, POLynesian GEodetic NETwork), as a contribution to the Global Geodetic Observing
System.
Talk by Youri
Querying the new ICET Earth Tides Database
Schema of the New ICET Earth Tides Database
Main_Information
Series_index
Release_number
File_name
Meaning
Id_relation
Main_relation
Id_relation
Id_unit
Id_calibration
Id_comment
Id_time_sampling
Id_status
Id_operator
Units
Id_unit
Latitude_unit
Longitude_unit
Altitude_unit
Phase_lag_unit
Time_lag_unit
Pressure_unit
Calibration_pressure_unit
Calibration_measure_1_unit
Measure_1_unit
Measure_2_unit
Measure_3_unit
Comments
Id_comment
Comment
Time_sampling
id_time_sampling
Time_sampling
Status
Id_status
Status
Measurements
Series_index
Release_number
Time_of_measurement
Julian_day
Temperature
Atmospheric_pressue
Measure_1
Measure_2
Measure_3
Confidence_index_measurement_1
Calibrations
Id_calibration
Pressure_calibration
Temperature_calibration
Phase_lag
Phase_lag_error
Time_lag
Time_lag_error
Calibration_measure_1
Station_code
Instrument_code
Id_position
Operator
Id_operator
Operator_information
Stations
Station_code
Location
Country_code
Region_code
Instruments
Instrument_code
Instrument_brand
vectorial_type
Id_instrument
Instrument_position
Id_position
Latitude
Latitude_error
Longitude
Longitude_error
Altitude
Altitude_error
Altitude_type
Countries
Country_code
Country_name
Regions
Region_code
Region_name
Instrument_type
Id_instrument
Instrument_name
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gravimeter data).
testing this software on several GGP raw files. See dedicated presentation tomorrow
System.
Gravity
Time
Validation and correction of GGP data at ICET-Tahiti through a generalized collocation
procedure (green: raw data, blue: corrected data)
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gravimeter data).
System.
GGP header Generator (ask for a copy)
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gravimeter data).
System.
New XML
Proposed
format
For GGP data:
header part
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="style.xsl"?>
<data_file xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="schema.xsd">
<header>
<comments>DATA CORRECTED AT ICET (ducarme@oma.be) </comments>
<filename>H1010222_GGP.xml</filename>
<station>
<city>Bad Homburg</city>
<country>Germany </country>
</station>
<instrument>GWR CD030_L</instrument>
<phase_lag unit="sec">
<value>45.</value>
</phase_lag>
<latitude direction="N" unit="deg">
<value>50.2285</value>
</latitude>
<longitude direction="E" unit="deg">
</longitude>
<elevation_msl unit="m" system="orthometric">
</elevation_msl>
<gravity_cal unit="nm...">
<value>-739.5</value>
</gravity_cal>
<pressure_cal unit="hPa/V">
<value>50.3</value>
</pressure_cal>
<author>P. Wolf (peter.wolf@bkg.bund.de)</author>
<header_column_data>
<time_format>yyyymmdd hhmmss</time_format>
<entitled_measure1 unit="V">gravity</entitled_measure1>
<entitled_measure2 unit="V">pressure</entitled_measure2>
</header_column_data>
<data_border>c***********************************************</data_border>
</header>
<tides_data>
New XML
Proposed
format
For GGP data:
data part
<data_blocks>
<eterna>
<code>INSTR</code>
<offset_measure1>1.0000</offset_measure1>
<offset_measure4>0</offset_measure4>
</eterna>
<start_and_drift>
<start_record>77777777</start_record>
<offset_measure1>.000</offset_measure1>
<offset_measure2>.000</offset_measure2>
</start_and_drift>
<dp>
<date>
<y>2001</y>
<m>02</m>
<d>12</d>
<hms>125500</hms>
</date>
<measure1>817.289</measure1>
</dp>
<dp>
<date>
<y>2001</y>
<m>02</m>
<d>12</d>
<hms>125600</hms>
</date>
</dp>
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<dp>
<date>
<y>2001</y>
<m>02</m>
<d>28</d>
<hms>235900</hms>
</date>
</dp>
<end_record>99999999</end_record>
</data_blocks>
</tides_data>
</data_file>
XML GGP data visualization Tool
GGP Data Preprocessing and
Analysis Status
at ICET
B. Ducarme and J.-P. Barriot
GGP Data Preprocessing and Analysis Status
at ICET
B. Ducarme and J.-P. Barriot
The last update of the GGP data had been made before the last Earth Tides symposium in 2008. The new revision
gave the opportunity to process in most of the stations two years of additional data. We welcome the contribution of
Hsinchu (HS) and Pecny (PE), who joined recently GGP. A total of 427 months (n in Table 1) from 14 stations have
been processed since the beginning of 2010. These stations are marked in blue. Perhaps additional data have been
uploaded since our processing as the data base is permanently in evolution. Stations marked in red are late in
uploading their raw data. Four stations operated by the Japanese group (CB, ES, KA, NY) did not upload raw data
since 2007. MA and TC stopped sending data after 2008/06. The instruments marked with a star are no more
operated.
The new data have been analyzed and the results carefully compared with the previous tidal analysis results when
available. The responsibles of the 14 reprocessed stations received a report of our investigations. Global tidal
analyses have been processed. In some stations the end of the data had to be rejected from the global analysis due to
degraded signal to noise ratio (last column of Table 1).The number of days used for the global analysis N and the
standard deviation STD computed with ETERNA (ANALYZE) are given in Table 1. As the stability of the
sensitivity of the superconducting gravimeters is generally better than 0.1%, the STD is a measure of the signal to
noise ratio in the station. For 9 stations among the 14 updated ones the STD is lower than 1nm/s2.
Status of the processed stations
BH: In Bad Homburg the new SG044 is operational for more than 900 days. The STD of this
instrument is one of the lowest among all the GGP stations. The new SG C044 is perfectly
fitting the results of the CD030-L. There is a slight calibration difference, close to 0.1%,
between CD030-L and CD030-H.The phase differences of the different instruments agree
within the associated RMS errors.
CA: Cantley started in 1989. It is the longest series of observations. It suffered from technical
problem and the STD was multiplied by a factor of two during several months in 2006/2007.
This portion of the data was rejected from the global analysis. The change of electronics on
January 22 2008 did not affect the calibration. The amplitude factors agree perfectly. The
new time lag of 16.3s applied since that epoch provides phases which seem a bit too large
compared to previous results. If a precise determination of the true time lag is obtained it will
be possible to normalize the data prior to 2008/01/22 to get homogeneous results.
HS: Hsinchu is a new station which has a large STD. The modelling of the tidal factors using
recent ocean tides models is questionable as it provides ratios obs /mod close to 1.01 in the
diurnal band and close to 0.995 in the semi-diurnal band. The misfit is thus not related to
calibration.
MA: Matsushiro remained a good station and the two last years of data are in perfect agreement with
previous data.
MB: Membach continued to run very well as usual. From It is interesting to note a more or less
continuous drift of sensitivity of the order of 0.03% to 0.04% between 1998 and 2009. This variation
could probably not be detected by calibration. It confirms that the stability of the superconducting
gravimeters is better than 0.1%.
MC : The end of Medicina is a bit noisier than usual. After the change of electronics on 2007/06/12 the
calibration factor was modified as well as the time lag. The new time lag of 11.1s is good as the phase lag
on M2 is not modified. However a large jump of the amplitude factors of the order of 0.4% is appearing,
while the ratio of the new and old calibrations is 1.0043. It is clear that the sensitivity of the voltage
output has not been modified. It is the new calibration value which seems questionable as the results
obtained with the previous calibration were fitting very well the other GGP stations in Europe as shown
in Ducarme et al., 2009.
ME: Metsahovi is also a station which started well before 1997. A comparison of 5 successive
analyses covering each 2 years between 2000 and 2009 has shown no shift of sensitivity at the
level of 0.05%. The registration prior to the GGP period is in agreement with the GGP data
within 0.1%. An adjustment factor of 0.9996 could be introduced for a better fit.
MO: Moxa is an excellent station with very low STD.
PE: Pecny is a new station with exceptionally low STD.. The 900 registration days provide the
same tidal factors as the 6 years of excellent rsults with the modified ASK228 but the RMS
errors on the tidal factors are already lower.
ST: Strasbourg remains an excellent station even if January and December 2009 are
perturbed.
SU: In Sutherland the dual sphere instrument was replaced by SG052 after July 2008. The
RMS error on the unit weight of the new SG C052 is better than the RMS error of the CD
instrument. There was no difference in the tidal factors between CD037-L and CD037-H.
The provisional calibration of the new SG C052 seems to be very slightly too large compared
to both components of CD037, but the series of the new instrument is still too short to draw
firm conclusions.
TC: Only 7 additional months have been processed in Tigo and there is no special remark.
WE: The dual sphere instrument of Wettzell is excellent. After the change of electronics on
April 17, 2007 new calibration values and new time lags have been determined. The
amplitude factors  and the phase differences  of the L and H sensors are now in perfect
agreement. In the previous series there was a difference in the  values between L and H
sensors at the level of 0°05%, while the phase differences were in agreement within the
associated RMS errors.. It should be noticed that the amplitude factors are now increased by
more than 0.1% with respect to the previous values. It confirms the conclusions of Ducarme
et al., 2009 based on the previous results. The authors showed that, after tidal loading
corrections, the c values for O1 and M2 at Wettzell were 0.1% lower than the mean of 15
European stations. To get homogeneous results it should be necessary to apply a
normalisation factor 1.0017 on the previous series of channel L and 1.0012 on channel H.
WU: Wuhan station remains in good shape since its repair at the beginning of 2005. Due to
the failure two years of data have been eliminated from the global analysis i.e. 2003-2004. The
STD is well below 1nm/s2.
Future plans for the Tahiti
Observatory (> 2011):
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Cryogenic gravimeter (2012 ?)
New laser station (2014 +)
VLBI station (2014 +)
All these three colocated at Taravao (TahitiEast)
• + Robotic telescope at Maiao (2011 ?)
• + Altimetry calibration line (2012 ?)
Seismic japanese BBOBS (Jamstec)
(Mirai oceanographic vessel, recovery end2010)
Etablissement d’une miniantenne VLBI à Tahiti-Iti
Observatoire
TIGO
(Conception,
Chile)
A superconducting gravimeter in Tahiti ?
Gravimètre à supraconductivité
de la nouvelle génération
Observation of gravity effects by Prof. Verreault of the
University of Quebec, using a Paraconic pendulum,
hosted at OGT

ICET

Transcription

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