Subject: Re: [ids.analysis.forum] Re: ILRS observation of shift in EOPs (fwd)
From: Laurent soudarin <[email-masked]>
To: [email-masked]
Date: Thu, 27 Jan 2005 12:59:05 +0100

Dear colleagues

here are some preliminary results for the EOP series around Dec. 26.

Some data after the Sumatra earthquake are now available (until Dec. 27 for 
Envisat, 28 for Spot2, 29 for Spot4, 30 for Spot5).
For each satellite, I processed the data over an arc starting on Dec 22. 
until  the last day of available data.
The combined solution (fixed network) for the daily pole values is shown on 
the figure below.
Blue dots with bars are the DORIS solution, the red ones are the a priori 
eopc04 series.
Time is in CNES julian days (20079 = Dec.22; 20083 = Dec.26; 20086 = Dec. 30)

The discontinuity in ypole seems to be similar to the one obtained with SLR.

More precise results after the Dec. 27 should be obtained when new data for 
Envisat, Spot2 and Spot4 will be available.

Best regards

Laurent Soudarin
LEGOS/CLS analysis center

9878395.jpg

At 08:43 21/01/2005 +0100, you wrote:
>Dear colleagues
>
>You'll find hereafter a mail from the new Chairman of the IERS Directing
>Board, Chopo Ma, to the Analysis Coordinators of the IDS, IGS and IVS, and
>other IERS members concerning a claim from ILRS that they see a 4-5 cm
>move of the Earth's pole of inertia at the date of the Sumatra earthquake. 
>I encourage you to participate in its assessment, as proposed by C. Ma.
>While a move this size may be difficult to assess with the Doris data, we
>have here an excellent opportunity to test the current Doris capability
>concerning polar motion.
>
>Best regards.
>Martine Feissel-Vernier
>IDS Analysis Coordinator
>---------- Forwarded message ----------
>Date: Wed, 19 Jan 2005 17:18:26 -0500
>From: Chopo Ma <[email-masked]>
>To: Ron Noomen <[email-masked]>, C Ma <[email-masked]>
>Cc: Gerd Gendt <[email-masked]>, A Nothnagel <[email-masked]>,
>    M Feissel <[email-masked]>, [email-masked],
>    [email-masked], [email-masked],
>    [email-masked]
>Subject: Re: ILRS observation of shift in EOPs
>
>Dear Ron,
>
>The ~1.5 mas jump in ypole in the ILRS combined EOP series shown in Figure 
>1 of the attachment is certainly interesting.  A combination from all 
>space geodesy techniques or a detailed comparison would enhance the 
>reliability of the result, and this could be coordinated by the IERS or by 
>the technique analysis coordinators.  However, it is most important that 
>the analysis results be properly interpreted, and I wonder if the 
>comparison with USNO finals.daily is the best way to see a break.  It 
>might be useful to directly compare the SLR, GPS and VLBI EOP series for 
>the time interval around Dec. 26 and investigate the significance of any 
>discontinuity internal to each series.  With respect to a geophysical 
>estimate, Ben Chao and Richard Gross have a short article in the 4 Jan 
>2005 issue of EOS.
>
>I will contact the other services to ask their assessment of their data.
>
>Yours,
>
>Chopo
>
>At 06:34 PM 1/19/2005 +0100, Ron Noomen wrote:
>
>>dear dr. Ma, dear Chopo,
>>
>>As we all know, the enormous earthquake off the coast of Sumatra on 
>>December 26
>>last year generated a devastating tsunami with tragic consequences. Whilst
>>feeling powerless to have mitigated the effects of this event, it is 
>>incumbent
>>on the scientific community to make and report observations that may lead to
>>greater understanding of such events.
>>
>>As you know, the ILRS has in place a rapid weekly station coordinate and 
>>Earth
>>orientation computation program, which provides to the community a combined
>>solution from our official and backup combination centres. From this 
>>operational
>>series we have observed a significant shift in one of the Earth Orientation
>>Parameters, in particular the y-component. These results must be reported 
>>to the
>>community at large, of course. But we think it would strengthen the 
>>solution and
>>be more appropriate if we were to derive a common result and statement by the
>>overall geodetic community, through an inter-technique combination, involving
>>IGS, IVS and ILRS. In this case, for obvious reasons, we feel this effort 
>>should
>>be coordinated by the IERS.
>>
>>I attach a report of our SLR-based findings, as they are visible in our 
>>official
>>combination product, which may form the basis of a joint-services paper. 
>>I would
>>like to request you, the chairman of the IERS, to investigate and 
>>stimulate the
>>possibility to derive a multi-technique combination observation of the 
>>effect of
>>the earthquake on geophysical parameters, in this case polar motion and 
>>perhaps
>>LOD/UT1.
>>
>>It would be very nice if the findings could be complemented by an 
>>interpretation
>>by one of our IERS colleagues involved in geophysics/global fluids, like 
>>Richard
>>Gross. On the other hand, we feel that the publication of this observational
>>evidence should not suffer from a fully-detailed geophysical analysis (which
>>could very well take quite some time before the final result is out).
>>
>>We consider that the IERS should coordinate a rapid, joint services 
>>publication
>>in a journal, such as Nature.
>>
>>We hope you will give this proposal a serious and timely consideration.
>>
>>Kind regards,
>>
>>Ron Noomen
>>ILRS Analysis Coordinator
>>
>