Director’s Discretionary Time

DDT may be requested at any time and is appropriate for the following cases:

  • Target of Opportunity (ToO) proposals are for unexpected or unpredicted phenomena such as, but not limited to, extreme X-ray or radio flares. ToO proposals are evaluated rapidly, with scheduling done as quickly as possible and as warranted by the nature of the transient phenomenon.
  • Exploratory Time proposals are normally for requests of small amounts of time, typically a few hours or less, in response to a recent discovery, possibly to facilitate a future submission of a larger proposal. In general, there will not be a need for immediate scheduling with these proposals but, for example, they may need to be observed in the current VLA configuration rather than waiting 16 months.
  • Proposals may be submitted for the purpose of education and public outreach - for example, to image an iconic source or to support a educational opportunity for students. These proposals must involve the Observatory’s Education and Public Outreach program.
  • Proposals for other science opportunities deemed sufficiently urgent to justify prompt action.
  • Proposals may be submitted in response to a Special Call announced by the Observatory. The announcement for the Special Call is available online at

While there is not an a priori limit to time that can be requested via DDT, it is expected that no more than 5% of the Open Skies time on each facility will be allocated for this purpose. DDT proposals cannot be joint proposals that request external telescope time; however, joint proposals between the Observatory’s facilities are allowed. For example, a DDT proposal cannot request HST orbits, but a DDT proposal can request joint observations with the VLA and VLBA.