Restoration of the ASCA Source Position Accuracy
Restoration of the ASCA Source Position Accuracy
复制标题
ASCA 源位置精度的恢复
DOI：
10.1086/317093
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
K. Yamaoka
中科院分区：
文献类型：
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作者：
E. Gotthelf;Yoshihiro Ueda;Ryuichi Fujimoto;T. Kii;K. Yamaoka
我们提出了一个校准的绝对指向精度的先进卫星宇宙学和天体物理学（ASCA），使我们能够补偿一个很大的误差（高达1 '）在派生的源坐标。我们参数化的温度依赖性偏差的态度的解决方案，这是负责这个错误。通过分析100个明亮活动星系核的ASCA坐标，我们表明可以将任何给定观测的天空位置的不确定性降低4倍。修正后的90%误差圆半径为12“，与飞行前的规格一致，有效地恢复了ASCA的全部指向精度。在这里，我们推导出一种算法，补偿这种姿态误差，并提出了一个基于互联网的表，用于纠正事后的所有ASCA观测的坐标。虽然上述误差圆严格适用于机载固态成像光谱仪（SIS）采集的数据，但对于气体成像光谱仪（GIS）获得的数据也推导出了类似的坐标校正，但这些数据具有额外的仪器不确定性。GIS中心20“直径的90%误差圆半径为24”。这两种仪器的误差圆面积的大幅减少为极大地增强对其他波长的X射线对应物的搜索提供了机会。这对当前和未来的ASCA源目录和调查具有重要意义。
We present a calibration of the absolute pointing accuracy of the Advanced Satellite for Cosmology and Astrophysics (ASCA) which allows us to compensate for a large error (up to 1') in the derived source coordinates. We parameterize a temperature dependent deviation of the attitude solution which is responsible for this error. By analyzing ASCA coordinates of 100 bright active galactic nuclei, we show that it is possible to reduce the uncertainty in the sky position for any given observation by a factor of 4. The revised 90% error circle radius is then 12'', consistent with preflight specifications, effectively restoring the full ASCA pointing accuracy. Herein, we derive an algorithm which compensates for this attitude error and present an internet-based table to be used to correct post facto the coordinate of all ASCA observations. While the above error circle is strictly applicable to data taken with the on-board Solid-state Imaging Spectrometers (SISs), similar coordinate corrections are derived for data obtained with the Gas Imaging Spectrometers (GISs), which, however, have additional instrumental uncertainties. The 90% error circle radius for the central 20' diameter of the GIS is 24''. The large reduction in the error circle area for the two instruments offers the opportunity to greatly enhance the search for X-ray counterparts at other wavelengths. This has important implications for current and future ASCA source catalogs and surveys.