Angelyn MooreIGS Central Bureau

Jet Propulsion LaboratoryUSA

The IGS Network

Contents

• Stations

• Data Retrieval and Quality Checks

• Summary Information Files

• Network Coordination

Requirements are stated inhttp://igscb.jpl.nasa.gov/network/guide_igs.html

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 domes@lareg.ensg.fr or http://lareg.ensg.ign.fr/ITRF/domesreq.html• [Site] Minimal obstruction to at least 15 degrees elevation• Recommendation: meteorological or weather instruments (especially

precise Barometer)

Equipment at the IGS Stations

Receiver -> modem -> phone line -> modem -> computerReceiver -> computer -> internet -> computerReceiver -> wireless -> computer -> internet -> computerReceiver > VSAT > computer

Operator's choice based on available infrastucture, cost, & benefits

. . . but low latencies are always preferred

Data Retrieval Methods Vary

Sites which meet additional requirements will be attractive to the specialized Working Group and Pilot Project applications.

Ultra-rapid products/Low Earth OrbiterData 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

Application Networks

• 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

Initiation of Operations

• Keep the site log correct and current. Email updates within one day of a major update to the site.• Email the log to igscb@igscb.jpl.nasa.gov or utilize the

automatic submission method described at

http://igscb.jpl.nasa.gov/network/sitelog-submissions.html

• Observe the format. Choose equipment names from the official list at

ftp://igscb.jpl.nasa.gov/station/general/rcvr_ant.tab

Ongoing Site Log duties

• Data quality should be established before transmission toData Center

• Suggest simple monitoring for anomalies:Herb Dragert's "11 fields to monitor"Site ID Sample RateYear Number of observationsJulian day Number of gapsStart Time Number of cycle slipsStop 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 ://www.unavco.ucar.edu/software)

• CDDIS provides such data atftp://cddisa.gsfc.nasa.gov/pub/reports/gpsstatus

but operators should pre-monitor

Ongoing Data Monitoring 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)

Ongoing Data Submission Duties

Following IGSMail #2235:Older IGS receivers such as AOA Rogue and TurboRogue track

4 quantities:C1 = C/A code at L1 frequencyL1(C1) = C/A-based phase at L1 frequencyP2-P1 = cross-correlated pseudorangeL2-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 frequencyL1 (P1) = Y1-codeless-based phase at L1 frequencyP2 = Y2-codeless pseudorange at L2 frequencyL2(P2) = Y2-codeless-based phase at L2 frequency

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.

Transition to Codeless Receivers

• SINEX templateGenerated at CB from current site logsProvides tabulation of station parameters vs. time for

input to analysis

• yyddd.status and check_* files at CDDISSimple teqc reports and latency reports

• igsnetweekly email from CB with each station's Quality,

Quantity, Latency

Quality Quantity Latencyvalid clocks > 250 Avg. # valid clocks Avg. in hrs<100 phase bias resets3D formal location err < 1 cmrms pseudorange residuals <86cmpseudorange meas. > .9*phase meas.

rms phase residuals <13nm

Commonly Used Summaries

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.

Role of Network Coordinator

Angelyn MooreIGS Network Coordinator & Deputy Director, Central BureauJet Propulsion Laboratory4800 Oak Grove Drive, M/S 238-540Pasadena, California 91109 USA

Angelyn.W.Moore@jpl.nasa.gov

Questions?