[IGS-DCWG-6] Data Center Requirements Documentation

[Carey Noll]

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IGS-DCWG Mail      24 Feb 13:55:04 PST 2003      Message Number 6
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Author:  Carey Noll/CDDIS

Dear Colleagues,

    Please forgive the long delay in getting in touch with the IGS Data
Center Working Group.  I have been quite late in getting activity going.
Included below in this email is an IGS data center requirements document
written a couple of years ago.  Data center requirements were discussed
briefly at the IGS governing board meeting in December and I realized we
never "formalized" the requirements.  I would ask that you review this
document and provide any feedback in the next couple of weeks.  I envision
adding this document to the IGS website as a reference for future data
center inquiries.

     As you may know, there will be several IGS working group meetings in
Nice during the EGS/AGU joint assembly.  Right now, they are planned for
Saturday, April 5.  I would like to find out how many people will be in
Nice and could make a meeting of the data center WG.  Perhaps if we have
alot of people coming to the EGS who had not planned to be there on
Saturday we could meet briefly during the week sometime.  Let me know!

Best regards,
Carey.

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Ms. Carey Noll  Manager, Crustal Dynamics Data Information System (CDDIS)
                                           Secretary, ILRS Central Bureau
Code 920.1                                 E-mail:  Carey.E.Noll at nasa.gov
NASA GSFC                                           Voice: (301) 614-6542
Greenbelt, MD 20771                                   Fax: (301) 614-5970
USA                  WWW:  http://cddisa.gsfc.nasa.gov/cddis_welcome.html
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IGS Data Centers Requirements
Carey Noll/CDDIS

IGS data centers fall into three categories: Operational, 
Regional, and Global Data Centers. 

The Operational Centers are in direct contact with the 
tracking sites.  Their tasks include data validation and 
monitoring, suitable data reformatting into a uniform format 
(RINEX), compression of data files, maintenance of a local 
archive of the tracking data in its original receiver and 
reformatted format, and the electronic transmission of data 
to a Regional or Global Data Center.  The Operational Center 
must download data from the receivers located at IGS stations 
on a timely basis (either hourly or daily), without 
interruption.  Operational Centers typically do not allow 
users direct access to their data holdings.

The Regional Data Centers reduce traffic on electronic 
networks by archiving data from sites in a limited geographic 
region (e.g., Europe, Australia, etc.) or agency network 
(e.g., JPL).  They collect reformatted tracking data from 
several Operational Centers, maintain a local archive of the 
data received, provide on-line access to these data to the 
user community of the region, and transmit data from a subset 
of their sites (minimally IGS global stations) to the Global 
Data Centers. 

The Global Data Centers are the main interfaces to the 
Analysis Centers and the user community in general.  They 
receive/retrieve, archive, and provide online access to 
tracking data provided by the Operational/Regional Data 
Centers.  At a minimum, Global Data Centers archive data from 
IGS sites identified as global stations.  The Global Data 
Centers also archive and provide online access to IGS 
products generated by the IGS Analysis and Associate Analysis 
Centers.  Finally, the IGS Global Data Centers backup and 
secure their holdings of IGS data and products, exchanging 
data between other data centers in order to ensure 
equalization of data holdings. 

Data centers at all levels should perform routine quality 
control on incoming data in order to detect bad or corrupt 
data prior to making these data available to the user 
community. 

The online archive of GPS data available through the IGS 
Global Data Centers should include:

o Daily files of GPS data (minimum all IGS global 
stations) at a 30-second sampling rate (minimum of one 
year online); includes daily files of GLONASS data in 
support of the IGS GLONASS Pilot Project (IGLOS-PP) as 
GPS/GLONASS stations are made official IGS sites
o Hourly files of GPS data at a 30-second sampling rate 
(minimum of three days online)

All data should be available in RINEX format, both Hatanka 
and Z compressed.  Data archive should also include broadcast 
ephemeris, meteorological, and other auxiliary files 
identified by the IGS as an analysis center requirement.

The online archive of IGS products available through the IGS 
Global Data Centers should include:

o Weekly solutions of classic IGS products from the IGS 
Analysis Centers
o Combined weekly solution from the IGS Analysis Center 
Coordinator
o Daily rapid and sub-daily ultra-rapid solutions from the 
IGS Analysis Center Coordinator
o Combined station coordinates and velocities from IGS 
Reference Frame Coordinator
o Associate Analysis Center products as they are approved 
by the IGS Governing Board as Pilot Projects or Working 
Groups, including:
  o Regional and Global Network Analysis Center 
  solutions in SINEX format from the Pilot Project 
  for the Densification of the ITRF
  o Zenith path delay files from the Troposphere 
  Working Group
  o Ionosphere parameters from the Ionosphere Working 
  Group