Klaasen Kenneth P, A'Hearn Michael F, Baca Michael, Delamere Alan, Desnoyer Mark, Farnham Tony, Groussin Olivier, Hampton Donald, Ipatov Sergei, Li Jianyang, Lisse Carey, Mastrodemos Nickolaos, McLaughlin Stephanie, Sunshine Jessica, Thomas Peter, Wellnitz Dennis
Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 306-392, 4800 Oak Grove Dr., Pasadena, California 91109, USA.
Rev Sci Instrum. 2008 Sep;79(9):091301. doi: 10.1063/1.2972112.
Calibration of NASA's Deep Impact spacecraft instruments allows reliable scientific interpretation of the images and spectra returned from comet Tempel 1. Calibrations of the four onboard remote sensing imaging instruments have been performed in the areas of geometric calibration, spatial resolution, spectral resolution, and radiometric response. Error sources such as noise (random, coherent, encoding, data compression), detector readout artifacts, scattered light, and radiation interactions have been quantified. The point spread functions (PSFs) of the medium resolution instrument and its twin impactor targeting sensor are near the theoretical minimum [ approximately 1.7 pixels full width at half maximum (FWHM)]. However, the high resolution instrument camera was found to be out of focus with a PSF FWHM of approximately 9 pixels. The charge coupled device (CCD) read noise is approximately 1 DN. Electrical cross-talk between the CCD detector quadrants is correctable to <2 DN. The IR spectrometer response nonlinearity is correctable to approximately 1%. Spectrometer read noise is approximately 2 DN. The variation in zero-exposure signal level with time and spectrometer temperature is not fully characterized; currently corrections are good to approximately 10 DN at best. Wavelength mapping onto the detector is known within 1 pixel; spectral lines have a FWHM of approximately 2 pixels. About 1% of the IR detector pixels behave badly and remain uncalibrated. The spectrometer exhibits a faint ghost image from reflection off a beamsplitter. Instrument absolute radiometric calibration accuracies were determined generally to <10% using star imaging. Flat-field calibration reduces pixel-to-pixel response differences to approximately 0.5% for the cameras and <2% for the spectrometer. A standard calibration image processing pipeline is used to produce archival image files for analysis by researchers.
美国国家航空航天局（NASA）深度撞击号航天器仪器的校准，使得从坦普尔1号彗星返回的图像和光谱能够得到可靠的科学解读。已对四台机载遥感成像仪器在几何校准、空间分辨率、光谱分辨率和辐射响应等方面进行了校准。已对噪声（随机噪声、相干噪声、编码噪声、数据压缩噪声）、探测器读出伪像、散射光和辐射相互作用等误差源进行了量化。中分辨率仪器及其双撞击器目标传感器的点扩散函数（PSF）接近理论最小值[半高宽（FWHM）约为1.7像素]。然而，发现高分辨率仪器相机失焦，其PSF的FWHM约为9像素。电荷耦合器件（CCD）的读出噪声约为1 DN。CCD探测器象限之间的电串扰可校正至<2 DN。红外光谱仪响应的非线性可校正至约1%。光谱仪的读出噪声约为2 DN。零曝光信号电平随时间和光谱仪温度的变化尚未完全表征；目前校正效果最好时约为10 DN。波长在探测器上的映射已知在1像素范围内；光谱线的FWHM约为2像素。约1%的红外探测器像素表现不佳，仍未校准。光谱仪在分束器反射处呈现出微弱的重影图像。使用恒星成像一般确定仪器绝对辐射校准精度<10%。平场校准将相机的像素间响应差异降低至约0.5%，光谱仪降低至<2%。使用标准校准图像处理管道生成存档图像文件，供研究人员进行分析。
