NuSTAR Proposals and Tools

NuSTAR was initially approved by NASA for a 2-year Principal Investigator (PI) mission. In mid-2014, the NuSTAR Project received an extension of the mission, including the institution of a Guest Observer (GO) Program, based on its proposal to the NASA Astrophysics Senior Review of Operational Missions. A call for proposals from the community will be issued by the fall of 2014. The NuSTAR GO Cycle 1 proposal due date will likely be at the end of November 2014, with GO observations starting near the beginning of April 2015. Approximately 6.5 Ms of time will be available for GO proposals in Cycle 1.

Prior to this, there were opportunities to request NuSTAR time as part of joint observing programs with XMM-Newton in Fall 2013, and with Chandra in March 2014:

  • Joint XMM-Newton and NuSTAR observation time was made available in the XMM-Newton Cycle 13 AO which was released on 27 August 2013, and 62 such proposals were in fact submitted. Such joint observations began in spring 2014.
  • An opportunity to propose for NuSTAR observing time as part of a joint Chandra/NuSTAR observing program was described in the Chandra Cycle 16 Call for Proposals. Up to 500 ksec of NuSTAR observing time are to be made available through this AO, which closed on March 13, 2014.

To help potential proposers, the standard HEASARC count rate and spectral simulations tools, WebPIMMS and WebSpec, are available. WebSpec was updated on March 5, 2014 to include the most recent NuSTAR responses and background files. The NuSTAR responses and background files can also be downloaded directly from the Caltech web site and used to simulate spectra in spectral analysis software such as XSPEC.

Other issues which proposers should take under consideration are:

  • Target Visibility: The NuSTAR Science Operations Center Target Visibility checker allows input of the RA and Dec coordinates of a source and finds the times when it is visible to NuSTAR subject to viewing constraints.
  • Timing: The NuSTAR Clock Correction Files keep the NuSTAR relative time (after barycentric corrections) accurate to ~2 ms and account for drifts in the NuSTAR clock caused by temperature variations, etc. New clock files will be produced as the mission continues on a ~monthly basis.
  • Stray Light: Extremely bright X-ray sources (>100 mCrab in the 3-79 keV band) within 1 to 5 degrees of a target can cause issues with elevated backgrounds due to stray light.
  • Dead Time: NuSTAR has a triggered readout, similar to a proportional counter but unlike a CCD, so it does not suffer from pile-up effects. However, dead time becomes significant for sources above ~50 ct/s, and this must be factored into integration time estimates. Quantitative estimates of the effect of dead time on exposure estimates are included in the latest version of WebPIMMS. Further details of the effects of dead time on bright source count rates can be found in this memo (pdf).