Subject: [SCIGN-0142] JPL Rapid Orbits
From: JPL GPS Analysis Team
Date: 16 Jan 1996 16:54:07

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SCIGN Electronic Mail    Tue Jan 16 16:54:07 PST 1996      Message Number 0142
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Author: JPL GPS Analysis Team
Subject: JPL Rapid Orbits

Rapid precise GPS orbit and clock solutions are now available from JPL
in sp3 format (see below for access details) within about 20 hours of
the close of the UTC day.  These rapid orbits typically agree with the
final JPL IGS orbit to about 20 cm rms.  Earth orientation is 
adjusted in these solutions and reported to the IGS, IERS, and USNO.

These solutions are used to compute rapid solutions from over 100 sites
daily, including all SCIGN sites in Southern California. These rapid
positions typically agree with our final positions at the sub-cm
level.  Publicly available Rinex data from new sites will be processed
as the sites become operational. Results are available upon request
for sites of interest. 

A 3-day predicted orbit is also available in the sp3 format.  Because of
the rapid turn-around, this means that a real-time orbit, based on
extrapolations of between 20 and 44 hours, is available, with an accuracy
significantly better than the broadcast orbits. We find that 24 hour
predicted orbits are typically 50-80 cm, and 48 hour predictions
gernerally 1-2 meters.

The final JPL IGS orbit and Earth orientation are now computed with a
4 day lag (access details below).  All sites are also processed using this
final orbit, with ambiguities resolved for regional networks.

Access details
______________

Connect to sideshow.jpl.nasa.gov (128.149.70.41) with anonymous ftp.
Then

  cd pub/gipsy_products/RapidService/orbits

The usual sp3 filename convention is used. For example, the file

   jpl08354.sp3.Z

contains precise orbits and clocks for day 4 (Thursday) of GPS week 835,
that is, Jan 11, 1996.  Also, the file

   jpl08354_pred.sp3.Z

contains orbit predictions for Jan 12, 1996, 00:00 through Jan 14, 1996,
23:45.

Final orbits:
Connect to sideshow.jpl.nasa.gov (128.149.70.41) with anonymous ftp.

Then

   cd pub/jpligsac/WWWW

   where WWWW is the 4 digit GPS week, e.g. 0834

The usual sp3 filename convention is used. For example, the file

   jpl08344.sp3.Z 
   
contains precise orbits and clocks for day 4 (Thursday) of GPS week 834,
that is, Jan 4, 1996.  Also, for those interested, other files are available:

   jpl08344.yaw.Z contains estimated yaw rates for the eclipsing spacecraft
   jpl08347.erp.Z contains the estimated Earth orientation parameters
--
Michael M. Watkins  Satellite Geodesy and Geodynamics Group
NASA/Caltech Jet Propulsion Laboratory  Mail Stop 238-600
Pasadena, CA 91109-8099  (818)354-7514, Fax (818)393-4965
Internet: [email-masked]

[Mailed From: Michael M. Watkins <[email-masked]>]