The VLBA is a stand-alone VLBI array that is useful for addressing many scientific questions. However, in some cases, more sensitive telescopes, longer baselines, or additional high-frequency antennas are necessary to reach science goals. Some additional opportunities are described in the following links:

• The High Sensitivity Array
• VLBI at the VLA
• Global mm-VLBI Array
• Global cm VLBI with VLBA+EVN--Proposal Instructions
• European VLBI Network

The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.