Palomar Observatory

Keck Observatory

Caltech Optical Observatories

Caltech Astronomy

California Institute of Technology

Caltech-Internal Target of Opportunity (ToO) Policy

Caltech Optical Observatories (COO) supports a Caltech-internal Target of Opportunity (ToO) program to enable its researchers to acquire data on unexpected, transient events by allowing interruption of regularly scheduled programs of Caltech observers at the Keck telescopes and the Palomar 200-inch telescope. In such cases, the observer at the telescope is obliged to set aside his or her program and make specific observations on behalf of the ToO researcher.

Caltech-Internal ToO Program Policies:

  • NEW: ToO projects are restricted to Caltech (and Northwestern -- see below) researchers as designated by the appropriate selecting official.
  • Such projects must be among the applicant's highest priority requests for time on the telescope involved.
  • NEW: ToO interrupts may be invoked only when a Caltech (or Northwestern -- see below) is observing with the telescope. All Caltech observers shall support requested interrupts from authorized Caltech-Internal ToO program advocates.
  • NEW: Caltech's Keck Partnership with Northwestern includes Northwestern participation in Caltech's internal ToO program on Keck Telescopes. Keck ToO requests from designated Northwestern ToO program advocates shall be supported by Caltech observers, and Northwestern Keck observers shall similarly honor authorized Caltech ToO requests (up to negotiated program limits).
  • Each ToO interrupt should be restricted to a reasonable total time per night so as not to undermine community support. A maximum of 2 hours per night is suggested except in exceptional circumstances. Shorter interrupts are the norm.
  • There will be no payback time or other compensation for interrupted observers.
  • Unused time assigned to a ToO program will not be carried forward to the next semester.
  • All PIs who are allocated observing time will be given brief details of the successful ToO programs from previous years.
  • An override may be activated only when the available equipment and moonlight conditions are consistent with the TAC recommendations. Seeing and photometric conditions are not a condition for any override.
  • When a ToO PI wishes to activate her or his program, it will be sufficient to telephone the observatory and describe the requirements to the observer. Observers who are supporting ToO observing must comply with the request regardless of the state of her or his program after completing the exposure then in progress and any necessary calibration exposures that cannot conveniently be completed in twilight. If the exposure is part of a longer sequence, that sequence must nevertheless be curtailed.
  • Interrupt time is measured from the completion of the regular observer's exposure and necessary calibration, to the same point for the ToO override.
  • The scheduled observer will send an e-mail to the ToO PI [copies to S. Kulkarni (srk [at] and A. Boden (bode [at]] immediately upon completion of the observing run, reporting on the time devoted to ToO observations and other relevant comments. The observer will deliver the necessary data to the ToO PI. Similarly, the ToO PI will send an e-mail to A. Boden (bode [at] [copy to S. Kulkarni (srk [at]] reporting on the time used for each interrupt, with an account of the status of the ToO project. Finally, the ToO PI will also report to the Director at the end of each observing semester with a complete account of the status of his/her ToO projects, time invoked, etc.

The log of active and past ToO projects, go to COO ToO Log.

COO ToO Policy / v 0.2
Last updated: 27 February 2018 AFB/RJB/ACM