Observing Program

CONT08

Continuous VLBI Campaign 2008

This web page will undergo frequent updates as the planning of the CONT08 campaign progresses. Please send a message to the Coordinating Center if you have updates or links to be included on this page.

Purpose

CONT08 is a two-week campaign of continuous VLBI sessions, scheduled for observing during the second half of August 2008. The CONT08 campaign will continue the series of the very successful continuous VLBI campaigns that were observed at irregular intervals: CONT94 (January 1994), CONT95 (August 1995), CONT96 (fall 1996), CONT02 (October 2002), and CONT05 (September 2005).

Goals

The plan for the CONT08 campaign is to acquire state of the art VLBI data over a two-week period to demonstrate the highest accuracy of which VLBI is capable. Further, it shall support high resolution Earth rotation studies. As the diurnal and sub-diurnal signals in the atmospheric excitation functions are large in the northern hemisphere summer months, an observation period during the summer is preferable. 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 previous CONT campaigns allowed already to study high frequency EOP variations to some extend. With the planned 512 Mb/s recording and a network with larger geographical coverage the sub-daily precision is expected to be better than earlier CONT campaigns, thus clarifying even more the deviations from the ocean tide model and allowing for testing further theoretical models. First detection of ter-diurnal signals related to M3 and S3 tidal phenomena in the oceans and the atmosphere was achieved with the CONT94, CONT02, and CONT05 data. The anticipated precision of the CONT08 will allow investigating these phenomena in much more detail.
  Previous CONT campaigns were also successfully used to monitor ionospheric activity with geodetic VLBI and in particular to derive maps of total electron content (TEC). The planned CONT08 network will have a larger geographical coverage than pervious CONT campaigns, and thus promises to be more sensitive to smaller scale features in the ionospheric activity. Also a combination with complementary techniques like GPS for the derivation of TEC maps will be possible.
• 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. Comparison with WVR measurements where possible will be especially useful. 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.
  Besides comparisons to WVR results, comparisons with GPS estimates and with Numerical Weather Models (NWM) will be of great importance. First investigations to use high resolution numerical weather models to derive mapping functions were tested with previous CONT data. This approach proved to be successful and should be continued more intensively with CONT08 and combined with modeling of atmospheric turbulence. Also the application of NWM derived tropospheric gradients for the geodetic VLBI analysis shall be further tested.
• Accuracy assessment: Analysis of reference frame repeatability day to day can be made and compared with previous continuous VLBI series. In particular the rigorous combination of reference frame realizations can be investigated. Continuous VLBI sessions have proved 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 15 days of continuous VLBI observation have been fixed as follows:

• first observation: Tuesday August 12, 2008 @ 00:00:00 UT
• last observation: Tuesday August 26, 2008 @ 23:59:59 UT

Network Resources

The following network resources will be used during the CONT08 campaign:

• Observation network: 11 stations alloted observing time for the 15 session days of the CONT08 campaign. The stations are:
  
  

  Name	Code	Observatory name and location
  HARTRAO	Hh	Hartebeesthoek Radio Astronomy Observatory, South Africa
  KOKEE	Kk	Kokee Park Geophysical Observatory, Kauai, HI, USA
  MEDICINA	Mc	Medicina Radio Astronomy Station, Italy
  NYALES20	Ny	Ny Ålesund Geodetic Observatory, Spitsbergen, Norway
  ONSALA60	On	Onsala Space Observatory, Sweden
  SVETLOE	Sv	Svetloe Radio Astronomy Observatory, Russia
  TIGOCONC	Tc	Transportable Integrated Geodetic Observatory (TIGO), Concepción, Chile
  TSUKUB32	Ts	Tsukuba VLBI Station, Japan
  WESTFORD	Wf	Westford Antenna, Haystack Observatory, MA, USA
  WETTZELL	Wz	Fundamentalstation Wettzell, Germany
  ZELENCHK	Zc	Radioastronomical Observatory Zelenchukskaya, Russia

  
  The geographical distribution of these stations is depicted in the network map.
  
  
  
  
• The CONT08 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.

Station Testing

In order to make sure the stations are in good operating condition before CONT08, 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 three years ago.

Expected Accuracies

The schedule will be a standard geodetic schedule which achieves simulated EOP results of at least as good as 35 micro-arcsec for pole position and 1.3 micro-sec for UT1. The recording mode will be the Mark 5 non-fanout mode with 512 Mb/s data rate.

Shipping

The media usage plan and shipment schedule as of July 7, 2008 is posted. The information will be updated when new information comes in.

Schedules

The detailed observing schedules for CONT08 will be generated using the automatic scheduling algorithms of the NASA sked program. We will investigate the best combination of scheduling parameters, minimum SNR levels, source list, and flux models. The "best" schedule will be determined as a compromise between the optimum simulated formal errors, number of observations, number of scans per hour, sky coverage, and robustness.

The schedule and corresponding notes files are available from the Data Centers. Each CONT08 day has its own schedule. A detailed description of the observing schedule is available in the CONT08 session notes .

Performance Plots

From the log files submitted by the stations performance plots have been created (PostScript format). Please follow the link to the respective station.