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Invited Article: Deep Impact instrument calibration.

Authors :
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
Source :
Review of Scientific Instruments. Sep2008, Vol. 79 Issue 9, p091301. 77p. 9 Color Photographs, 22 Black and White Photographs, 11 Diagrams, 22 Charts, 61 Graphs.
Publication Year :
2008

Abstract

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 [∼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 ∼9 pixels. The charge coupled device (CCD) read noise is ∼1 DN. Electrical cross-talk between the CCD detector quadrants is correctable to <2 DN. The IR spectrometer response nonlinearity is correctable to ∼1%. Spectrometer read noise is ∼2 DN. The variation in zero-exposure signal level with time and spectrometer temperature is not fully characterized; currently corrections are good to ∼10 DN at best. Wavelength mapping onto the detector is known within 1 pixel; spectral lines have a FWHM of ∼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 ∼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. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00346748
Volume :
79
Issue :
9
Database :
Academic Search Index
Journal :
Review of Scientific Instruments
Publication Type :
Academic Journal
Accession number :
34647296
Full Text :
https://doi.org/10.1063/1.2972112