Message-Id: <200508101715.j7AHFdR03587@cnes.fr>
From: Tavernier Gilles <gilles.tavernier@cnes.fr>
To: "'ids.analysis.forum@cls.fr'" <ids.analysis.forum@cls.fr>
Subject: RE : [ids.analysis.forum] temporary DORIS stations
Date: Wed, 10 Aug 2005 19:15:30 +0200
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Dear colleagues,

My feeling is that, in order to take a station into account for geodetic work, we need measurements:
- as continuous as possible
- for a minimum duration
- from several satellites

Although very interesting as a major IERS co-location site, the DORIS WETB station only provided scarce data for several reasons:

- it was switched off several days a week to avoid interferences when operating VLBI

- transmissions started on May 20 2003 and the station worked until January 2004 (beacon failure)

- in order to avoid jamming with nearby European DORIS stations, it was operated with so-called "shifted frequencies". Only two satellites are able to perform measurements on such a station: ENVISAT and Jason-1 (and we know that this satellite doesn't contribute much to geodetic work, due to the "SAA" effect). This situation should improve by the end of the year with the launch of CRYOSAT and an update of the DORIS/SPOT-5 flight sofware: 4 satellites will then be able to perform measurements on "shifted frequencies" stations.

As Herve was able to supply POD teams with accurate stations coordinates (see DORISMail N°243), it might have been possible to use the WETB station for ENVISAT and Jason-1 POD. As a matter of fact, WETB measurements were too scarce and not accurate enough because of frequent switch-off.

Hervé gave information on other IDS proposals (GAVB and BELB).

On a general point of view, we could try, Hervé and I, to give you more information on the status of new or specific stations.

Anyway, don't hesitate to use the Analysis Forum for such discussions.

Best regards,

Gilles

Gilles TAVERNIER           
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