HXD: Angular response

Calibration status and caveats

• Angular response of HXD-PIN
  Individual field of view of the 64 PIN diodes are collimated with 64 fine collimators to 34'. The optical axes of all fine collimators were measured based on multiple pointing observations of the Crab Nebula, consisting of various offset positions in the Satellite's X- and Y- directions (Figure 1). The resultant optical axes of 64 fine collimators on the X-Y plane are shown in Figure 2. The alignment of each collimator is measured with a typical error of 1' and the overall scatter of all units is within 3'.5 (FWHM).
  The current response files for the XIS and HXD nominal pointings have been built incorporating the information on the collimator alignment. The effect of thermal wobbling of the satellite's attitude control is not included, which would thus induce a systematic error of **
  In the case that users wish to calculate the response for largely extended sources, the following provisional method is possible: **.
  
  Figure 1: Typical angular response of a fine collimator along the Satellite X-axis.
  
  Figure 2: Distribution of the optical axes of 64 fine collimators.