NASA Network Site Selection Criteria / Preliminary Examination of Existing Sites

Generalized layout for an integrated site with all space geodesy techniques, including a local control-survey network. Individual instruments are spread far enough to avoid interference with each other, but close enough to allow local survey measurements to be performed at the sub-millimeter level. Each technique has a dedicated set of survey pillars.

The Network Design Simulations studies within SGP will provide general information on how many global integrated stations will be needed, and their approximate geographic locations, in order to meet the requirement for the ITRF. It is expected that NASA will contribute some fraction of the stations needed, but certainly not all. The example SGP described in Appendix A assumes a contribution of 10 next generation NASA Space Geodetic Stations, which may be 1/3 the total number needed (~30 based on preliminary results). Because a global network already exists (see Figure 2.1) it may be possible to utilize sites already occupied by one or more techniques; this gives the added advantage of a side-by-side co-location of next generation and current generation systems. Alternatively, it may be necessary to develop some entirely new sites to insure proper geographic distribution.

Conditions that need to be considered are listed below. An overriding constraint will likely be national and local political considerations. Stations already established by NASA or network partners may be more mature in many respects than a new facility. However, some existing sites have already demonstrated severe shortcomings. For example neither Concepcion nor Arequipa are included in the current reference frame models due to their geological instability.

Simulations provide general areas where stations should be located; specific locations will depend upon local conditions. Deployment of NASA stations will be carried out in concert with the activities and plans of foreign partners. However, it may be most effective to deploy some of the NASA Stations in Africa, South America, and India where voids would otherwise occur.

NASA’s space geodesy program has great experience in selection and implementation of observing sites. This includes developing site criteria, actual site selection, obtaining the necessary MOUs and other agreements, partnering with national and international organizations, obtaining site permits, arranging for on-site construction, utilizing local personnel and infrastructure, and finally operating geodetic systems.

To establish criteria for and identify and select likely sites for the future NASA Space Geodetic Network, a working group will be formed consisting of technical experts representing each of the space geodetic techniques, network operations personnel, and local experts as needed.

The site selection activity will begin the process of selection of sites for next generation NASA Space Geodetic Stations by examining which of the existing NASA or NASA partner sites may be suitable. Specific work to be carried out will include:

  1. Develop site selection criteria and requirements documents including global geometry, weather, geologic stability, accessibility, local infrastructure including power and other utilities, voice and high speed data communications, access roads, local manpower needs, site security, political issues, property ownership and ability to obtain long term agreements, ITAR issues, shipping constraints, etc., that takes into account the physical, operational, and other needs of the different systems and the need for vector ties between them. Results of site design studies will be important input into this. A document describing the criteria will be provided.
  2. Determine which if any of the currently available VLBI and SLR sites belonging to NASA meet these criteria (for all systems) and also satisfy the results of the Network Design Simulations and the Generalized Station Design.
  3. Where opportunities permit, begin discussions with existing and possible new partners on possible availability of alternative existing or new sites and the requirements for use of those prospective sites.
  4. Work with GGOS (IAG) and other international organizations to develop plans for international participation and partnerships within their established framework [note: GGOS will be issuing a Call for Participation for fundamental co-located stations this Fall with the same intent of developing the next generation global geodetic network].

A product of this study will be a report describing the suitability of current NASA sites as locations for the integrated multi-technique stations for NASA’s contribution to the next generation Space Geodetic Network.