[IGSMAIL-259] Time
Ruth
Ruth
Mon May 24 09:45:15 PDT 1993
IGS Electronic Mail 24-MAY-1993 09:45:15 Message Number 259
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>From: Ruth Neilan
Subj IGS Newsletter, 93-1
-------------------------
Subject: Time:1:19 PM
OFFICE MEMO IGS Newsletter, 93-1 Date:5/23/93
IGS NEWSLETTER 93-1 MAY 1993
Prof. Gerhard Beutler
Chair, IGS Oversight Committee
Astronomical Institute, University of Bern
Sidlerstrasse 5
CH-3012 Bern Switzerland
FAX: +41-31-65 38 69
Tel.: +41-31-65 85 91
beutler at aiub.unibe.ch
Ruth E. Neilan
Director, Central Bureau of the IGS
JPL / Caltech MS 238-540
4800 Oak Grove Drive
Pasadena, CA 91109 USA
FAX: +1-818-393-6686
Tel.: +1-818-354-8330
ren at logos.jpl.nasa.gov
The 1993 Bern IGS Workshop and the
4th IGS Oversight Committee Meeting
24 - 27 March, 1993 in Bern, Switzerland
----------------------------------------------------------------------
About 90 participants attended the 1993 IGS workshop in Bern. The
workshop was very interesting and stimulating. The 1992 IGS Test
Campaign, Epoch'92, and first results stemming from the IGS Pilot
Service were reviewed and discussed. The high quality standard
reached by the IGS processing centers during the 1992 IGS Test
Campaign and the steady improvements made since are impressive. I
found it most encouraging that the IGS products (orbits and earth
rotation parameters) proved their usefulness for the processing of
Epoch'92 campaigns. The conclusion is simple : The 1992 IGS Test
Campaign in conjunction with Epoch'92 may be considered as the proof
of concept for the routine IGS.
Very fruitful were the discussions between the IERS Directing Board
and the IGS Oversight Committee. It was stated that the relationships
between the two organizations were excellent from the very beginning
of the IGS operations in June 1992; the regular analyses made by the
IERS Rapid Service (Dennis McCarthy) and by the IERS Central Bureau
(Martine Feissel) were and are stimulating for all IGS participants.
According to plans the IGS will be responsible for all GPS
observations in future, the IERS will establish direct contacts with
the IGS processing centers in order to continue the fruitful
collaboration that already exists. The IGS will adopt (as a matter of
fact already has adopted) the IERS standards and will help developing
them if necessary. The IERS will also be responsible for the
terrestrial reference frame used by the IGS.
The IGS Campaign Oversight Committee decided to start writing the IGS
proposal to IAG (International Association of Geodesy) without further
delay. According to our plans the routine IGS should start on January
1st, 1994. It seems that IGS will indeed be established in a very
efficient way. (Remember : IGS was mentioned for the first time in
1989 at the IAG Meeting in Edinburgh)!
In its experimental phase the International GPS Geodynamics Service
was a great and a truly International experiment. It was successful
to an extent nobody has expected. These should also be the
characteristics for the future Service.
Let me thank all of you who attended the IGS meetings in Bern and/or
contributed to the proceedings of the workshop. It was a pleasure to
host this meeting and I already look forward to the next workshop,
probably a combined IERS/IGS workshop hosted by Martine Feissel and
Claude Boucher in Paris.
Au revoir
Bern, 4 April 1993 Gerhard Beutler
Chairman
IGS Oversight Committee
_______________________________________________________________
NETWORK OPERATIONS GROUP REPORT
Ruth Neilan
The Network Operations working group met in Bern and discussed
three key issues that are critical to the improved operations of the IGS:
- Network implementation,
- Network operation,
- Network information: site catalog and information
- Remote location communications
In order to achieve greater cooperation within the Network Working
group, a sub-set of people from key agencies implementing more than
two core stations was established as cognizant and responsible points
of contact for the coordinated operations of the global network.
These people include:
Loic Boloh, CNES
John Dow, ESOC
Bjorn Engen, Statens Kartverk
Pierre Herroux, EMR
Gerry Mader, NOAA
Ruth Neilan, NASA/JPL
Chris Reigber, GFZ
It is also recognized that there are other responsible points of
contact for additional stations who will be included in the network
communications correspondence.
Network Implementation
-------------------------------------------
It was recognized by all that the weak areas of the network are the
Southern Hemisphere, Russia and China. A partial projected inter-
agency implementation plan is listed below and it was agreed that it is
necessary to accelerate the implementation in the areas of poor
coverage.
Network Operation
-------------------------------------------
One of the areas that needs attention is the coordinated operation of the
network, and it is hoped that the establishment of this group can
facilitate communication and jointly develop and agree to procedures
for monitoring and reporting station health, notification of change and
configuration control, problem reporting. This will be important over
the next few years as we learn to deal with the AS environment and
work towards integrating into the system the replacement or upgrade
of existing station hardware, as well as new stations.
Station Information and Documentation
-------------------------------------------
It is evident that there is a lack of a reliable station information for the
different user groups and the analysis centers. This is a problem that
must be dealt with immediately by this group. At the Bern meeting, it
was decided that an electronic form would be generated for detailing
the basic information about the site. This was developed by Zuheir
Altamini, Yehuda Bock, Werner Gurtner, Ulf Lindqwister, and Ruth
Neilan. This form is attached to this newsletter. All station
information should be sent to the Central Bureau and the electronic
forms will be available via the Data Centers. The Central Bureau will
compile the catalog of information, which includes horizon mask, site
map and photographs of the site and this will be distributed to
interested users. An additional set of critical information will be the
list of station coordinates from the IERS, Zuheir Altamini and Claude
Boucher.
Remote Communication
------------------------------------------
One of the reasons for the slower implementation in the Southern
Hemisphere is the lack of adequate communications for timely
retrieval of data in the absence of the Internet. This is also a problem
for station locations projected for Russia and China. One of the next
tasks for the group is to investigate various possibilities and
telecommunication options that may be available through the different
agencies to see if we can arrive at a solution for the remote locations.
The Network group hopes to convene a splinter meeting at the Beijing
review status and progress in these areas.
List of Current Continuously Operating Precision GPS Stations,
June 1993:
SITE AGENCY COUNTRY
1 Alberthead EMR/GSC B.C., Canada
*2 Algonquin EMR/CGS Ont., Canada
*3 Fairbanks NASA/JPL Alaska, USA
4 Fortaleza NOAA Brazil
*5 Goldstone NASA/JPL California, USA
6 Graz ISR Austria
7 Greenbelt NASA/JPL-GSFC Maryland, USA
*8 Hartebeesthoeck CNES South Africa
*9 Herstmonceux RGO East Sussex, U.K.
10 Hobart NOAA Tasmania
11 JPL Mesa NASA/JPL Pasadena, California
*12 Kokee NASA/JPL-GSFC Kuai, Hawaii, USA
*13 Kootwijck DUT Delft, Netherlands
14 Kourou ESA/ESOC French Guiana
*15 Madrid NASA/JPL Spain
16 Maspalomas ESA/ESOC Canary Islands
*17 Matera ISA Italy
*18 McMurdo NASA/JPL Antarctica
*19 Metsahovi FGI Finnland
20 North Liberty NASA/JPL Iowa, USA
*21 Ny Alesund SK Spitzbergen Island, Norway
*22 Onsala OSO Sweden
*23 Penticton EMR/GSC British Colombia, Canada
24 Pie Town NASA/JPL New Mexico, USA
*25 Pinon SIO/JPL California, USA
26 Quincy NASA/JPL California, USA
*27 Richmond NOAA Florida, USA
*28 Santiago NASA/JPL Chile
29 Scripps SIO California, USA
*30 St. John's EMR New Foundland
*31 Tahiti CNES French Polynesia
*32 Taipei AS-IES Taiwan
*33 Tidbinbilla NASA/JPL Australia
*34 Tromso SK Norway
*35 Usuda ISAS Japan
36 Vandenberg SIO/JPL California, USA
37 Westford NOAA Massachussets, USA
*38 Wettzell IfAG Germany
*39 Yarragadee NASA/JPL Australia
*40 Yellowknife EMR Canada
41 Zimmerwald BfL Bern, Switzerland
*IGS Core, oringinal
PLANNED SITE AGENCY COUNTRY DATE
Arequipa NASA/JPL-GSFC Peru 1/94
Bangalore GFZ India
Bar-Giora Survey of Israel Israel
x Bermuda NOAA British
Bogota NASA/JPL Columbia 1/94
Darmstadt ESA/ESOC Germany
Darwin AUSLIG Antarctica 12/93
x Easter Island NASA/JPL-GSFC Chile 4/93
Galapagos Island NASA/JPL Ecuador
Guam/Kwadjalien NASA/JPL U.S Territory 1/94
Kerguelen Island CNES French Territory 10/93
Kiruna ESA/ESOC Sweden
x Kitab GFZ Uzbekistan 7/92
La Platta, GFZ Argentina
Libreville, CNES Gabon, Africa 12/93
McDonald NASA/JPL Texas, USA 6/93
Malindi ESA/ESOC Kenya, Africa 12/93
Novosibirsk GFZ Russia
Perth ESA/ESOC Australia
Petropalovosk GFZ Russia
Seychelles NASA/JPL Island '94
Tiksil ESA/ESOC Russia
Tsukuba GSI Japan 12/93
Villafrance ESA/ESOC Spain
x Station installed, resolving communications problems.
________________________________________________________________
DATA FORMATS
Werner Gurtner
The following topics have been identified and discussed:
RINEX under AS
----------------------------------------
RINEX version 2 does not distinguish between data collected under "normal"
conditions and data collected under Anti-spoofing. Between October 1992
and March 1993 discussions between JPL/NGS/AIUB have been going on in which
way this missing information could be incorporated into the RINEX format:
- One proposal was to define new observation types according to the actual
way different receivers are handling the AS problem (e.g. a "cross-correlation
code delay" type, a "cross-correlation phase" type, a squared L2 phase type,
etc.)
- The second proposal wants to keep the five basic observation types defined
in RINEX (CA,P1,P2,L1,L2), synthesize if necessary these
observation types from the actual observations (e.g. P2=C1+(Y2-Y1))
and flag them using a new flag (bit number 2 in the Loss-of-
Lock Indicators)
It was decided to follow the second proposal. Gurtner will draft a message
to be reviewed by the interested parties and then distribute it through IGSMAIL
and other appropriate channels.
RINEX Header Contents
----------------------------------------
There are still fields in the IGS data RINEX headers that contain non-standar-
dized information, such as:
- Receiver type
- Receiver (firmware) version (Rogues!)
- Antenna type
- Antenna heights
Receiver/Antenna types:
Between October 1992 and March 1993 Ulf Lindqwister compiled a list of
receiver type and antenna type names which has been reviewed several times
by interested parties such as Miranda Chin, Jeff Freymueller, Werner Gurtner.
This list still needs to be further refined --> U. Lindqwister
Receiver firmware version (Rogues):
Ulf Lindqwister promised to define what version numbers should be put
into the corresponding version field
Antenna heights:
Many RINEX files either don't contain an antenna height at all (although
their should be one!) or a height that does not refer to the Antenna Reference
Point.
Actions to be done:
- List of the actual antenna heights according to the specs
- List of the actual antenna types used at the sites
- Operational centers will have to make sure that the correct info
is put into the files
- Generation of character graphics tables for each antenna type
with antenna dimensions
Some of these actions have to be coordinated with similar actions to
create a site description table (site catalogue) suitable for wide
distribution!
Overall responsibility for the proper execution of these actions should
be at the Central Bureau.
Quality Control
----------------------------------------
Operational centers should do some minimum tests such as the size of
the RINEX files prior to transmission in order to prevent empty or nearly
empty files to be sent to the data centers.
___________________________________________________________
COMMUNICATIONS
Werner Gurtner / (Peter Morgan)
Peter Morgan expressed concerns about the IGS-generated data volume, both
mails and file transfers.
On some international nodes up to 5 percent of the Internet traffic may be
IGS data.
Actions:
- IGSREPORTs will be mailed to processing and data centers only (and to
those parties explicitly requesting them)
- IGSREPORTs will be available for public ftp access on several centers,
such as CODE, CDDIS, IfAG, IGN
- The IGSMAIL distribution list will be frequently scanned
- The IGS data flow has to be streamlined to avoid redundant transmission
and to minimize transatlantic or transpacific data traffic. An IGS data flow
chart will be prepared (CDDIS) and distributed. All other traffic generated
by additional bilateral agreements will not be part of IGS.
Actions in Europe have already been initiated to streamline the European
data traffic.
- The hierarchical data structure has to be improved. Not all permanent
stations have to appear on the global data centers.
- Processing centers should download data that is actually processed only
- Concatenation of the daily navigation files into one non-redundant file
on each level. The file called "BRDC" is the only navigation file necessary
on top level.
________________________________________________________________
IGS GLOBAL DATA CENTER REPORT
Carey Noll
The IGS is supported by three global, or network, data centers. These
data centers maintain an on-line archive of GPS tracking data and products.
They serve as the main interface between the data and the analysis centers and
product users.
The three global data centers supporting the IGS are: the Crustal Dynamics
Data Information System (CDDIS) at NASA/GSFC in Greenbelt, Maryland; the
Scripps
Institution of Oceanography (SIO) in La Jolla, California; and the Institut
Geographic National (IGN) in Paris, France. Operational and regional data
centers interface to the GPS receiver, download, RINEX, and compress the data,
and forward these data to a global data center. The three global centers then
equalize their data holdings by accessing and retrieving required data sets
from
each other. All data transmission is near real time; typically, the data
arrives at a global data center within 72 hours of the end of the observation.
The global data centers submit weekly status reports detailing data and
products holdings.
During the 1992 IGS Test Campaign, over 30 global sites participated as
IGS core sites; additional "non-core" sites also submitted data for analysis.
The CDDIS, for example, archived data from over 5400 observations at 60
distinct sites/receivers for a total of 2.6 Gbytes. One day's worth of GPS
data in compressed RINEX format totaled approximately 16 Mbytes. The table
below illustrates the timeliness of the data delivered to the CDDIS during
the 1992 IGS Test Campaign (June 14 through October 31, 1992):
All Prime
All Sites Core Sites Core Sites
---------- ---------- ----------
Arriving within: One day: 46% 49% 48%
Two days: 67% 71% 72%
Three days: 79% 84% 85%
Four days: 85% 90% 91%
One week: 91% 95% 96%
Additional (later than one week): 9% 5% 4%
Number of Sites: 60 44 27
Analysis centers would like to see data arrive at the global data center level
even sooner; thus far, the IGS Pilot Service has delivered 75% of the core data
within 48 hours of the observation.
The global data centers also serve as an archive for products, such as
precise satellite ephemerides, Earth rotation parameters, etc., generated from
IGS data by the analysis centers.
In conclusion, the proposed concepts of the IGS, in particular the
real-time availability of a global set of GPS tracking data, were realized
during the 1992 IGS Test Campaign. The three global data centers successfully
provided the main interface between the IGS data and the user community. The
CDDIS, in particular, learned a great deal from the test campaign. New
archiving procedures, such as automation of data transfers, were developed for
the IGS and are now utilized in other CDDIS activities. The success of the
1992 IGS Test Campaign lives on in the current IGS Pilot Service and will
continue through the operational service.
GLOBAL DATA CENTER CONTACTS:
CDDIS: Carey E. Noll Phone: 301-286-9283
Code 902.2 Fax: 301-286-4943
NASA/GSFC E-mail: noll at cddis.gsfc.nasa.gov
Greenbelt, MD 20771
USA
SIO: Yehuda Bock Phone: 619-534-5292
Scripps Institution of Oceanography Fax: 619-534-5332
IGPP 0225 E-mail: bock at bull.pgga.ca
9500 Gilman Drive
La Jolla, CA
USA
IGN: Loic Daniel Phone: 33-1-4398-8338
Institut Geographic National Fax: 33-1-4398-8488
2, Avenue Pasteur E-mail: daniel at ign.fr
F-94160 Saint-Mande
FRANCE
__________________________________________________________________
ANALYSIS CENTER COORDINATOR REPORT
Clyde Goad
On Wednesday, March 24, the Analysis Center Coordinator presented his
summary of the orbital comparisons for a 36-week period starting from
GPS week 650 along with an example of early plot-based comparisons that
were useful in spotting a few startup problems. A typical three-week
orbit comparison was shown. Maximum and minimum deviations in an rms
sense were given for the extended period. The findings of the study are
given below:
Maximum and Maximum RMS Differences
For a 36-Week Period During and After the
IGS Campaign
Begin Day Week Minimum RMS Day Centers Maximum RMS Day Centers
M-D-Y (m) (m)
02-21-93 685 0.35 4 COD-EMR 1.37 6 ESA-EMR
02-14-93 684 0.23 4 EMR-JPL 1.99 7 EMR-JPL
02-07-93 683 0.23 6 EMR-JPL 0.82 4 ESA-SIO
01-31-93 682 0.21 2 EMR-JPL 1.03 5 COD-ESA
01-24-93 681 0.20 4 EMR-JPL 0.75 6 ESA-SIO
01-17-93 680 0.19 7 EMR-JPL 1.41 1 COD-JPL
01-10-93 679 0.26 5 COD-EMR 1.07 7 COD-ESA
01-03-93 678 0.26 1 EMR-JPL 1.38 3 ESA-JPL
12-27-92 677 0.21 5 EMR-JPL 1.14 3 COD-ESA
12-20-92 676 0.18 7 EMR-JPL 1.01 5 COD-ESA
12-13-92 675 0.24 7 EMR-JPL 1.35 1 ESA-JPL
12-06-92 674 0.27 5 EMR-JPL 1.73 2 COD-ESA
11-29-92 673 0.31 4 EMR-JPL 3.15 5 COD-ESA
11-22-92 672 0.20 3 EMR-JPL 1.48 7 COD-ESA
11-15-92 671 0.19 2 EMR-JPL 1.14 7 COD-ESA
11-08-92 670 0.18 4 EMR-JPL 1.58 2 COD-SIO
11-01-92 669 0.18 7 EMR-JPL 1.34 2 ESA-JPL
10-25-92 668 0.20 5 EMR-JPL 1.57 2 ESA-JPL
10-18-92 667 0.23 3 EMR-JPL 2.95 1 ESA-SIO
10-11-92 666 0.21 3 EMR-JPL 6.37 6 SIO-JPL
10-04-92 665 0.31 5 EMR-JPL 2.47 1 ESA-SIO
09-27-92 664 0.34 4 EMR-JPL 2.31 2 SIO-JPL
09-20-92 663 0.32 4 EMR-JPL 2.71 2 SIO-JPL
09-13-92 662 0.38 5 EMR-JPL 5.83 1 ESA-SIO
09-06-92 661 0.32 2 EMR-JPL 1.72 3 ESA-GFZ
08-30-92 660 0.29 6 UTX-JPL 0.71 7 ESA-JPL
08-23-92 659 0.28 7 EMR-JPL 3.25 2 COD-GFZ
08-16-92 658 0.35 4 GFZ-JPL 4.38 7 COD-SIO
08-09-92 657 0.31 4 COD-JPL 4.76 1 COD-SIO
08-02-92 656 0.34 4 UTX-JPL 4.67 1 UTX-SIO
07-26-92 655 0.32 2 GFZ-JPL 3.32 7 UTX-SIO
07-19-92 654 0.36 1 UTX-JPL 1.69 1 COD-UTX
07-12-92 653 0.37 1 COD-SIO 2.13 3 SIO-GFZ
07-05-92 652 0.39 3 COD-UTX 2.63 6 ESA-GFZ
06-28-92 651 0.45 6 COD-JPL 1.35 1 ESA-GFZ
06-21-92 650 0.68 3 COD-SIO 2.70 1 ESA-UTX
Another item discussed during this presentation was the desire on the
coordinator's part to investigate the possibility of providing precise
satellite clock information in the future. His view was that this was the
one last piece of information left to provide users with a full complement
of products. Currently, to some degree, orbits, station coordinates, and
Earth rotation parameters are available. Discussion from the floor led to
the recommendation that if such information was provided it should not be
included with the current orbital product.
At a subsequent meeting of analysis center representatives, it was decided that
a two-week period of orbits should be redetermined for comparison using a
common set of station coordinates. These coordinates should then be held
fixed among the several centers' determinations if any of these stations's
data were used in the orbit determinations. The chosen stations were as
follows:
ALGONQUIN
FAIRBANKS
GOLDSTONE
HARTEBEESTHOEK
KOKEE PARK
MADRID
SANTIAGO
TIDBINBILLA
TROMSO
WETZELL
YARAGADEE
YELLOWKNIFE
Altamimi and Boucher agreed to provide the set of coordinates for the above
stations. Orbital results were to be deposited into the computer system at
the University of Bern so as not to cause any confusion with the standard
distribution of orbits. The two-week period for the study starts with
GPS week 680 (Jan. 17, 1993)
The above information was presented to the meeting attendees at the Friday
afternoon session (March 26, 1993)
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