Calibration of Alignments of the MAXI/GSC
Abstract
One of the important goals of MAXI is to discover X-ray transient objects and inform the world of their positions. For follow-up observations with other satellites and telescopes, we must reduce the position uncertainties as small as possible. We therefore performed calibration of alignments of the MAXI/GSC. MAXI's field of view is restricted by the slats collimators to a narrow and long rectangle, which scans the sky in the direction perpendicular to the long dimension. The position of an X-ray source along the scan direction is determined by the time when the X-ray source crosses MAXI's FoV. To determine the position of the X-ray source perpendicular to the scan direction, we use the position of the X-ray image on the detector. The misalignment of a GSC camera around the orbital rotation axis is determined by the lag of the detection time of an X-ray source whose position is well known. One around another axis along the moving direction is determined by the shift of the X- ray image on the camera. The misalignment around the third axis is estimated by the change of incident angle caused by the precession of the ISS orbital plane. As a result, we reduced the systematic error in position determination from the initial uncalibrated value of 1.0 degree to 0.2 degree.
- Publication:
-
The First Year of MAXI: Monitoring Variable X-ray Sources
- Pub Date:
- December 2010
- Bibcode:
- 2010fym..confP..59S