Documents and Tools for Proposers

• Please see the Proposer's page for detailed information on how to submit a proposal.
• The Proposers' Observatory Guide (POG) is the primary HETG reference manual.
• ProVis is the Chandra target visibility tool. It gives target visibility, roll and pitch angle as a function of time. Pitch angle can be important for a time constrained observation (see notes on time constrained observations and POG chapter on visibility and constraints)
• PIMMS is the Chandra count rate simulator
• Response files (ARFs, RMFs) are available for spectral simulations and analyses.
• ObsVis allows Chandra instrument fields-of-view to be overlaid on sky images.
• The Spectrum Visualization Tool shows the location of the spectral features on the ACIS-S detector as a function of Y-offset and redshift.

HETG Observing Strategies

Before submitting a proposal, HETG proposers should consider the following:

• ACIS Considerations (see the POG Section 8.5 and the HETG observation planning page)
  • ACIS Subarray Size and Readout Time: Users can reduce first order pileup by selecting a subarray. See the HETGS Subarray page and the POG Chapter 6.12
  • TE mode vs. CC mode: To reduce pileup for very bright sources, users might consider using CC mode. Please see POG Section 6.12.
    
    In CC mode it is possible to place the 0th order image off of the ACIS-S array, and have only the dispersed orders fall on the array. This mode reduces telemetry and leads to simpler order sorting. It is useful for observing the brightest X-ray sources in the sky. (E.g., this mode was used to observe Sco X-1.) Please consult the instrument team via Helpdesk if you are considering viewing such bright sources.
  • Offsets: Offsets are used to move the dispersed spectrum closer to the CCD readout for improved order sorting. In addition, they are used to center the zeroth order within a subarray and avoid placing lines of interest in chip gaps (see next bullet).

• Instrument Features and Gaps:

  Observers should ensure that spectral features of interest do not fall on instrument gaps or features. These are listed in Tables 8.2 of the POG and discussed in Section 8.2.1. See the Spectrum Visualization Tool for ACIS-S observations. Offset Pointing (see POG section 9.4.2) can be used to move source features away from instrument gaps or artifacts.

• Background Rates:

  In combination with ACIS-S, the HETG spectrometer has very low background rates and this is not a primary concern in observation planning.