Subject: [IGSMAIL-1202] IGS Preliminary (IGP) Orb/clock combination
From: Analysis Coordinator/IGS Analysis Centers
Date: Sat, 3 Feb 1996 19:59:07 PST

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IGS Electronic Mail      Sat Feb  3 19:59:07 PST 1996      Message Number 1202
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Author: Analysis Coordinator/IGS Analysis Centers
Subject: IGS Preliminary (IGP) Orb/clock combination

    
    Dear IGS Colleagues,

    In response to an increasing demand for rapid orbit/clock solutions,
    starting on January 1, 1996, the IGS Analysis Centers (ACs) initiated IGS
    "super" rapid orbit/clock combinations . The AC participation in this pilot
    project is voluntary with submissions within 36h delays (from the last
    observation). The IGS combinations, designated as "IGS Preliminary" (IGP)
    of orbit/clocks and erp, are then produced within 2 hours after the
    submission deadline, i.e. at about 14:00h UT every day, i.e. within a delay
    of about 38h. For the erp, only pole positions are currently combined,
    UT1-UTC from the Bull A prediction is used.  Five ACs (CODE, ESA,
    GFZ, JPL, SIO, EMR) elected to participate and are submitting their
    solutions daily, well within the 36h delay deadlines. The IGP orbit/clock
    and erp combinations are available daily (at about 14:00h UT) from the IGS
    CB and, as a back up, also at the following anonymous ftp site:

    ftp macs.geod.emr.ca
    cd pub/gps/prelim_igs
    files (compressed): igp0WWWD.sp3.Z; igp0WWWD.erp.Z; igp0WWWD.sum.Z, 
    
    where WWW and D denote the GPS week and day (0-6), respectively. Only
    rather limited quality testing and evaluation are performed daily as part
    of the IGP combination. To provide the final quality evaluation, starting
    with GPS week 0837 (Jan 21, 1996), the IGP orbits/clocks are themselves 
    included as another AC (for statistical purposes only) in the IGS Rapid
    combinations which are produced weekly within 11 days from the last
    observation. Based on the first month experience, the AC submissions and
    IGP orbits were well within the above deadlines and the current IGP
    orbits/clocks are approaching the 10 cm/1 ns precision level.
    
    It is our hope that this additional effort of the participating ACs is
    found useful and  worthwhile.

                                Jan Kouba

               

[Mailed From: Jan Kouba <[email-masked]>]