UVIT在ASTROSAT上的在轨性能
In-orbit Performance of UVIT on ASTROSAT
摘要：
我们目前的在轨性能和第一批结果，从紫外成像望远镜（UVIT）的ASTROSAT。UVIT由两个相同的38厘米共对准望远镜组成，一个用于FUV通道（130- 180 nm），另一个用于NUV（200- 300 nm）和VIS（320- 550 nm）通道，视场为28 $arcmin$。FUV和NUV探测器在高增益光子计数模式下操作，而VIS探测器在低增益积分模式下操作。FUV和NUV通道具有滤光片和光栅，而VIS通道具有滤光片。ASTROSAT于2015年9月28日发射。UVIT的性能验证是在UVIT门于2015年11月30日打开后进行的，直到2016年3月底，在50天的指定校准时间内进行。船上所有系统均运作良好。在PV阶段，UVIT观察了几个校准源以校准仪器，并观察了几个物体以证明UVIT的能力。在FUV和NUV中发现UVIT的分辨率约为1.4 - 1.7 $arcsec$。使用标准恒星（白矮星）校准各种滤波器的灵敏度，以估计零点星等以及通量转换因子。光栅也被校准，以估计其分辨率以及有效面积。滤波器的灵敏度相对于地面标定降低了15%。敏感度变动按月监控。UVIT将以其良好的分辨率和大视场成像能力，使用不同滤光片对紫外光谱区域进行采样的能力以及在紫外线中进行可变性研究的能力，推出科学成果。
英文摘要：
We present the in-orbit performance and the first results from the ultra-violet Imaging telescope (UVIT) on ASTROSAT. UVIT consists of two identical 38cm coaligned telescopes, one for the FUV channel (130-180nm) and the other for the NUV (200-300nm) and VIS (320-550nm) channels, with a field of view of 28 $arcmin$. The FUV and the NUV detectors are operated in the high gain photon counting mode whereas the VIS detector is operated in the low gain integration mode. The FUV and NUV channels have filters and gratings, whereas the VIS channel has filters. The ASTROSAT was launched on 28th September 2015. The performance verification of UVIT was carried out after the opening of the UVIT doors on 30th November 2015, till the end of March 2016 within the allotted time of 50 days for calibration. All the on-board systems were found to be working satisfactorily. During the PV phase, the UVIT observed several calibration sources to characterise the instrument and a few objects to demonstrate the capability of the UVIT. The resolution of the UVIT was found to be about 1.4 - 1.7 $arcsec$ in the FUV and NUV. The sensitivity in various filters were calibrated using standard stars (white dwarfs), to estimate the zero-point magnitudes as well as the flux conversion factor. The gratings were also calibrated to estimate their resolution as well as effective area. The sensitivity of the filters were found to be reduced up to 15\% with respect to the ground calibrations. The sensitivity variation is monitored on a monthly basis. UVIT is all set to roll out science results with its imaging capability with good resolution and large field of view, capability to sample the UV spectral region using different filters and capability to perform variability studies in the UV.
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