Observing Program

CONT11

Continuous VLBI Campaign 2011

This Web page will undergo frequent updates as the planning of the CONT11 campaign progresses. Please send a message to the Coordinating Center if you have updates or links to be included on this page.

Purpose

CONT11 is a campaign of continuous VLBI sessions, scheduled to be observed in the second half of September 2011 (15-SEP-2011 00:00 UT through 29-SEP-2011 24:00 UT). The CONT11 campaign will be a continuation of the series of very successful continuous VLBI campaigns that were observed at irregular intervals since 1994. The most recent CONT campaigns were observed in roughly three-year intervals as CONT02 (October 2002), CONT05 (September 2005), and CONT08 (August 2008). With a tentative network size of fourteen stations (nine in the northern hemisphere and five in the southern hemisphere) the observation mode will depend on the station capabilities, media resources, e-transfer capacities, and correlator resources. Resource limitations may make it necessary to reduce the network size or length of the campaign.

Goals

The plan for the CONT11 campaign is to acquire state-of-the-art VLBI data over a time period of about two weeks to demonstrate the highest accuracy of which the current VLBI system is capable. This will support high resolution Earth rotation studies, investigations of reference frame stability, and investigations of daily to sub-daily site motions, among other things. A number of scientific and technical goals are set for the campaign:

• Science: Analysis of the two weeks of continuous high frequency (sub-daily) Earth Orientation Parameters (EOP) will address the discrepancies seen between the theoretical models (ocean tidal and atmospheric) and the observations at the M2 and S1 frequencies as well as between long-term and short-term values of tidal amplitudes. The large network of CONT11, with the reasonably balanced geographical distribution between northern and southern hemisphere, is expected to provide an increased precision with respect to previous CONT campaigns and will thus allow further studies of high frequency EOP variations, analysis of ocean tide models, and tests of theoretical models. It is also expected that the precision of CONT11 will further the studies of ter-diurnal signals related to M3 and S3 tidal phenomena in the oceans and the atmosphere. For ionospheric research, the larger geographical coverage of CONT11 will allow the derivation of maps of total electron content (TEC) with an increased sensitivity to smaller scale features.
• Technique improvement: Continuous VLBI data allows comparison of estimates of troposphere zenith delay and gradients across experiment boundaries as a measure of the accuracy of the observations and analysis. Experience from previous CONT campaigns shows the importance of observing tropospheric parameters with several complementary instruments for the derivation of robust geodetic results in particular for reference frame investigations. Comparisons with GPS estimates and with Numerical Weather Models (NWM) will be of great importance. High-resolution NWM are being used for the derivation of mapping functions. CONT11 will be an excellent test bed to develop this approach further by investigating the inclusion of atmospheric turbulence models and/or NWM derived tropospheric gradients in the geodetic VLBI analysis.
• Accuracy assessment: Analysis of reference frame repeatability day to day can be made with CONT11 and compared with previous continuous VLBI series. In particular the rigorous combination of reference frame realizations can be investigated. Continuous VLBI sessions have proven to be a very important source of information for these investigations.
• Comparisons: All stations have IGS GPS systems relatively nearby that are considered Global Stations, three stations are co-located with an ILRS SLR system, and four stations are co-located with an IDS DORIS station. The continuous high accuracy allows investigation of daily and sub-daily site motions for comparison with external factors such as atmospheric effects and temperature distortions of the antennas or pedestals.

Observation Period

The fifteen days of continuous VLBI observation have been fixed as follows:

Network Resources

The following network resources will be used during the CONT11 campaign:

• Observation network: 14 stations alloted observing time for the 15 session days of the CONT11 campaign. The stations are:
  
  

  Name	Code	Observatory name and location
  BADARY	Bd	Badary Radio Astronomical Observatory, Russia
  FORTLEZA	Ft	Space Radio Observatory of the Northeast (ROEN), Fortaleza, Brazil
  HARTRAO	Hh	Hartebeesthoek Radio Astronomy Observatory, South Africa
  HOBART12	Hb	Mt. Pleasant Radio Astronomy Observatory, Hobart, TAS, Australia
  KOKEE	Kk	Kokee Park Geophysical Observatory, Kauai, HI, USA
  NYALES20	Ny	Ny Ålesund Geodetic Observatory, Spitsbergen, Norway
  ONSALA60	On	Onsala Space Observatory, Sweden
  TIGOCONC	Tc	Transportable Integrated Geodetic Observatory (TIGO), Concepción, Chile
  TSUKUB32	Ts	Tsukuba VLBI Station, Japan
  *WARK12M	Ww	Warkworth VLBI Station, New Zealand
  WESTFORD	Wf	Westford Antenna, Haystack Observatory, MA, USA
  WETTZELL	Wz	Fundamentalstation Wettzell, Germany
  YEBES40M	Ys	Astronomical Center at Yebes, Spain
  ZELENCHK	Zc	Radioastronomical Observatory Zelenchukskaya, Russia

  
  *WARK12M had to cancel participation due to technical problems.
  
  The geographical distribution of the CONT11 stations is depicted in the network map.
  
  
  
  
• The CONT11 stations committed to a pre-campaign station checkout to ensure that the data acquired during the campaign are of the highest quality. Instructions and advice about what to check and how are handled by the Network Coordinator.
• Rapid disk return for the "R" type sessions during the CONT period so that IVS can keep up its commitment for two rapid-turnaround sessions each week.
• Simultaneous acquisition of high quality GPS data during the campaign so that the comparison analyses can be done. Coordination with the IGS community will be done to make sure that the stations can be expected to produce good data reliably.
• Simultaneous observing by co-located SLR systems at TIGO, HartRAO, and Wettzell.

Station Testing

In order to make sure the stations are in good operating condition before CONT11, a set of tests is being developed under the direction of Brian Corey and Ed Himwich for each station to perform. These tests will be based on the similar tests that were done for previous CONT experiments, the last of which was the CONT08 campaign in 2008. The sixth Technical Operations Workshop (TOW), to be held at MIT Haystack Observatory in May 2011, will offer a troubleshooting class tailored to the CONT11 needs.

Correlator Resources

With a network size of fourteen stations, the CONT11 campaign can be viewed as a precursor of the observing mode of the next generation VLBI system (VLBI2010). In “VLBI2010 mode” networks of sixteen or more stations will observe continuously and transfer their data to a correlator facility for immediate correlation so that results become available within 24 hours of the end of observation. CONT11, of course, will have a lower data rate and a less stringent completion requirement than VLBI2010. It is expected that recording modules will store several campaign days of a given station in order to optimize the usage of media. Hence, for logistical ease, consistency of results, and to gain experience in VLBI2010-type load, correlation will be performed at a single correlator: the Washington Correlator will take on the large task of correlating the CONT11 data.

Expected Accuracies

The schedule will be a standard geodetic schedule which achieves simulated EOP results of at least as good as 35 µarcsec for pole position and 1.5 µs for UT1. The recording mode will probably be the 2-bit sampled version of the R1 mode (512 Mb/s data rate) which was successfully used in the CONT08 campaign.

Schedules

The detailed observing schedule for CONT11 was generated using the automatic scheduling algorithms of the NASA sked program. We investigated the best combination of scheduling parameters, minimum SNR levels, source list, and flux models. The “best” schedule was determined as a compromise between the optimum simulated formal errors, number of observations, number of scans per hour, sky coverage, and robustness. Gaps with no observational data was avoided by scheduling the daily station checks at non-overlapping, staggered time periods that are convenient for the stations.

The schedule and corresponding notes files are available from the Data Centers. Each CONT11 day has its own schedule. A detailed description of the observing schedule is available in the CONT11 session notes.

Ultra-rapid dUT1 Determination

For the length of the CONT11 campaign an ultra-rapid dUT1 determination will be performed on the basaline between Onsala and Tsukuba. The data will be e-transferred to the Tsukuba correlator, correlated, and analyzed in near real-time so that dUT1 estimates are available about 1 hour after the observation. More information is compiled in a dedicated Web page at GSI.