IVS Observing Program

Session Descriptions: 2007

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
• IVS-T2
• IVS-INT1 and IVS-INT2
• APSG
• EUROPE
• Ohiggins
• RDV: R&D with VLBA
• IVS-CRF and IVS-CRD
• IVS-R&D

Session Types and Data Rates in 2007

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 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 tapes to the correlator as rapidly as possible. Tapes from the Monday session should arrive no later than Friday, tapes 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 7 or 8 stations. There is a core network for each day plus one or two other stations. The R1 will be recorded with a data rate of 256 Mbit/s. The R4s will be recorded with a data rate of 128 Mbit/s.

The networks and correlators are:

IVS-T2:
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.

IVS-INT1 and IVS-INT2:
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 K4/K5 is used on the Wettzell-Tsukuba baseline. The data of all intensive sessions are e-transfered from the stations either directly to the target correlator (INT2) or to a node in the vicinity of the correlator (INT1), where it is written to disk and picked up by the correlator.

APSG:
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. Tsukuba and Fairbanks are on the North American Plate, Hobart is on the Australian Plate, 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 Tuskuba.

EUROPE:
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.

OHIGGINS:
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, 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. Syowa will participate when the station is available. 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. Syowa (Japan/Antarctica) are willing to participate in this experiment. The characteristics of this network have changed slightly due to more weight of the southern part.

RDV:
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.

IVS-CRF and IVS-CRD:
The Celestial Reference Frame (CRF) sessions and the CRF deep-south (CRD) 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 and CRD sessions are scheduled 17 times this year.

IVS-R&D:
The goal of the 2007 R&D sessions, as decided by the IVS Program Committee, is to record at a Gbit/s data rate to evaluate the geodetic results. These experiments will also test the entire data flow from scheduling through analysis for the higher data rate. There are 10 R&D sessions. Participating stations will vary depending on when stations are equipped with Mark 5 systems.