IVS Observing Program

Session Descriptions: 2011

This section has brief descriptions of each type of session coordinated by IVS. Refer to the master files for the details of each session such as start times, participating stations, correlator, and current status.



IVS-R1 and IVS-R4:

The purpose of of the IVS-R1 and IVS-R4 sessions is to provide twice weekly EOP results on a timely basis. These sessions provide continuity with the previous NEOS and CORE series.

The "1" and "4" indicate that the sessions are on Mondays and Thursdays, respectively. Widely separate sessions during the week gives approximately even spacing between these two sessions for monitoring periodic terms in tides and nutation.

The "R" stands for rapid turnaround because the stations, correlators, and analysts have a commitment to make the time delay from the end of recording to results as short as possible. The time delay goal is a maximum of 15 days. Participating stations are requested to ship disks or e-transfer the data to the correlator as rapidly as possible. Disks from the Monday session should arrive no later than Friday, disks from the Thursday session (ending late on Friday) should be shipped as early on Monday as possible to arrive no later than Thursday.

Each network for the R1 and R4 sessions has 8 stations. There is a core network for each day plus one or two other stations. The R1 and R4 sessions will be recorded with a data rate of 256 Mbit/s.

The networks and correlators are:

Session Day Networks Correlator
R1 Monday Cycle through these networks:
R4 Thursday Cycle through these networks:

The purpose of the IVS-T2 sessions is to monitor the TRF via bi-monthly sessions. All geodetic stations participate in at least two T2 sessions each year. These sessions replaced the IRIS-S sessions observed in previous years until 2002.

The hour-long 1-baseline intensive sessions yield one UT1 measurement daily. Monday through Friday Mark 5 is used on the Kokee-Wettzell baseline, and on Saturday and Sunday K5 is used on the Wettzell-Tsukuba baseline. The data of all intensive sessions are e-transfered from the stations directly to the target correlator.

Session Days Baseline Correlator
I1 Monday-Friday Wettzell-Kokee WACO
I2 Saturday-Sunday Wettzell-Tsukuba GSI
I3 Monday Wettzell-Tsukuba-NyAlesund BONN


The primary purpose of the APSG sessions is to continue monitoring the relative motions of the plates in the Asia-Pacific region. These sessions involve sites on the four plates. Hobart and Parkes are on the Australian Plate; Tsukuba, Seshan, and Urumqi are on the Eurasian Plate, and Kokee is on the Pacific Plate. Thus, these sessions will produce critical data for the investigation of the current crustal motions in the Asia-Pacific region combined with the data from the APSG SLR and GPS campaigns which will also be performed in the same month as the APSG experiments. Also, these experiments will improve the accuracy of the geocentric coordinates of the participating stations, especially Urumqi and Tsukuba.

The purpose of this experiment is to determine the station coordinates and their evolution in the Australia (AuScope) and New Zealand geodetic VLBI network. This process will be done with the highest precision possible.

The purpose of this experiment is to determine the station coordinates and their evolution in the European geodetic VLBI network. This process will be done with the highest precision possible.

The purpose of the IVS-OHIG (Southern Terrestrial Reference Frame) sessions is to tie together optimally the sites in the southern hemisphere. The participating sites include all the sites in the south: O'Higgins, Syowa, Fortaleza, Hartebeesthoek, Hobart, TIGO—as well as Kokee Park. The last two sites are the southern-most of the northern sites and have been included to make the geometry more robust and to increase the number of observations per scan. Because these sessions concentrate on the southern sites and do not use observing time to accurately tie these sites to far northern sites (as the Global Sessions do) they should yield a very accurate regional TRF around the South Pole. The characteristics of this network have changed slightly due to more weight of the southern part.

There are six bi-monthly coordinated astrometric/geodetic experiments this year that use the full 10-station VLBA plus up to 10 geodetic stations.

These experiments are being coordinated by the geodetic VLBI programs of three agencies: 1. USNO will perform repeated imaging and correction for source structure.; 2. NASA will analyze this data to determine a high accuracy terrestrial reference frame.; and 3. NRAO will use these sessions to provide a service to users who require high quality positions for small numbers of sources.

The Celestial Reference Frame (CRF) sessions and the CRF deep-south (CRFDS) and CRF median-south (CRFMS) sessions are intended purely to provide astrometric observations useful in improving the current CRF, and in extending and densifying the CRF by observing "new" sources. The CRF, CRFDS, and CRFMS sessions are scheduled 19 times this year.

The goal of the 2011 R&D sessions will likely be to test and validate the observing mode to be used during the CONT11 campaign. Other R&D sessions may be done to observe occultation and/or close approach events. There are 10 R&D sessions.