1. Jet Propulsion Laboratory
The IGS Network
Angelyn Moore
IGS Central Bureau
Jet Propulsion Laboratory
USA

2. Contents Stations Data Retrieval and Quality Checks
Summary Information Files
Network Coordination

3. Equipment at the IGS Stations
Requirements are stated in
Emphasis is on performance characteristics.
Some key examples:
• [Receiver] Dual-frequency code and phase with AS on or off
• [Receiver] At least 8 channels
• [Receiver] At least 30 second sampling rate
• [Receiver] Observation synchronization +/- 1 ms of true GPS time
• [Monument] First-order geodetic monument with respect to stability,
durability, maintenance, documentation, and access
• [Monument] IERS DOMES number from or
• [Site] Minimal obstruction to at least 15 degrees elevation
• Recommendation: meteorological or weather instruments (especially precise Barometer)

4. Data Retrieval Methods Vary
Receiver -> modem -> phone line -> modem -> computer
Receiver -> computer -> internet -> computer
Receiver -> wireless -> computer -> internet -> computer
Receiver > VSAT > computer
Operator's choice based on available infrastucture, cost, & benefits
. . . but low latencies are always preferred

5. Application Networks
Sites which meet additional requirements will be attractive to the specialized Working Group and Pilot Project applications.
Ultra-rapid products/Low Earth Orbiter
Data submission must be at least hourly; 1 second sampling time
Troposphere Working Group
Meteorological instruments including precise barometer
(recommended for all stations!)
Time Transfer Pilot Project
Suitable receivers, external precise frequency standard (cesium or preferably H maser);
special care in cabling with respect to temperature stability and
reporting of cable changes

6. Initiation of Operations
Clear a 4-character site ID with the Central Bureau
Fill out a site log according to
ftp://igscb.jpl.nasa.gov/station/general/blank.log
Submit site log and sample RINEX to CB
When log is approved and available at CB, begin submitting data to a Data Center and notify the community with an IGSMail

7. Ongoing Site Log duties
Keep the site log correct and current. updates within one day of a major update to the site.
the log to or utilize the automatic submission method described at
Observe the format. Choose equipment names from the official list at ftp://igscb.jpl.nasa.gov/station/general/rcvr_ant.tab

8. Ongoing Data Monitoring Duties
Data quality should be established before transmission to
Data Center
Suggest simple monitoring for anomalies:
Herb Dragert's "11 fields to monitor"
Site ID Sample Rate
Year Number of observations
Julian day Number of gaps
Start Time Number of cycle slips
Stop Time Multipath
*mean ionospheric variations (narrowlane noise normalized by sample rate)
10 of these are available from teqc +qc and do not require ephemerides
(see http ://
CDDIS provides such data at
ftp://cddisa.gsfc.nasa.gov/pub/reports/gpsstatus
but operators should pre-monitor

9. Ongoing Data Submission Duties
Archive raw tracking data
Keep current with RINEX format (defined at ftp://igscb.jpl.nasa.gov/igscb/data/format) and your RlNEX conversion software
Submit daily RINEX to a Data Center by 0200 UT
Information in RINEX header (antenna, DOMES, receiver, height) must be correct and match the site log
Avoid data resubmission but if it is necessary, send an IGSMail
An upcoming request: be ready to switch to an alternate Data Center within 1 business day, in case of major Data Center inavailability
Observe evolving IGS recommendations such as for observables
in RINEX from newer codeless receivers (see next slide)

10. Transition to Codeless Receivers
Following IGSMail #2235:
Older IGS receivers such as AOA Rogue and TurboRogue track
4 quantities:
C1 = C/A code at L1 frequency
L1(C1) = C/A-based phase at L1 frequency
P2-P1 = cross-correlated pseudorange
L2-L1 = phase difference
and report 4 observables:
C1 P2’ = C1 + (P2-P1)
L1(C1) L2’= L1(C1)+(L2-L1)
Codeless receivers, e.g. AOA Benchmark, Ashtech Z-XII track 6 observables:
C1 and L1 (C1)
P1 = Y1-codeless pseudorange at L1 frequency
L1 (P1) = Y1-codeless-based phase at L1 frequency
P2 = Y2-codeless pseudorange at L2 frequency
L2(P2) = Y2-codeless-based phase at L2 frequency

11. Transition to Codeless Receivers
The Problem: Use of the codeless P1 and P2 observables before April 02, 2000 (Wk 1056) or c1 and PZ’ after April 02, 2000 introduces a satellite-dependent bias (~2 ns) in ionosphere-free pseudoranges. Clock products and point positioning become corrupted in an unpredicable way when biased and unbiased (codeless and cross-correlated) measurements are mixed.
Since April 02 (Wk 1056) the P1, P2 observables should be used with all IGS products and operators should be providing them to IGS. See IGS Mail #2744 for more details and how to form P1, P2 when only cross-correlated-styles C1, P2’ are available.

12. Commonly Used Summaries
• SINEX template
Generated at CB from current site logs
Provides tabulation of station parameters vs. time for input to analysis
• yyddd.status and check_* files at CDDIS
Simple teqc reports and latency reports
• igsnet
weekly from CB with each station's Quality, Quantity, Latency
Quality Quantity Latency
valid clocks > 250 Avg. # valid clocks Avg. in hrs
<100 phase bias resets
3D formal location err < 1 cm
rms pseudorange residuals <86cm
pseudorange meas. > .9*phase meas.
rms phase residuals <13nm

17. Role of Network Coordinator
Coordination and liason functions as regards the network as a whole
between station operators, users, data centers, and analysts
? Questions, concerns, suggestions are always welcome!
Examples:
I need to relocate my monument. How can I make the change go smoothly for the analysts?
I am not able to get hourly data quickly enough in Europe.
Why did my station’s quality score decrease?
The SINEX template does not have a phase center for the antenna at station ABCD.

18. Questions? Angelyn Moore IGS Network Coordinator &
Deputy Director, Central Bureau
Jet Propulsion Laboratory
4800 Oak Grove Drive, M/S
Pasadena, California USA