Wichmann 
ODIS SC. 
Juergen Oberst 
  
GEOMETRIC CALIBRATION OF THE MICAS CCD SENSOR 
ON THE DS1 (DEEP SPACE ONE) SPACECRAFT: LABORATORY VS. IN-FLIGHT DATA ANALYSIS 
Jürgen OBERST, Bärbel BRINKMANN, Bernd GIESE 
German Aerospace Center (DLR), Institute of Space Sensor Technology and Planetary Exploration 
Berlin, Germany 
Juergen.Oberst@dlr.de 
  
Working Group IC - 4 
KEY WORDS: CCD, Camera, Calibration 
ABSTRACT 
We have carried out a geometric calibration of the CCD sensor of MICAS (Miniature Integrated Camera Spectrometer), 
a 4-inch aperture reflecting telescope on board the DS1 (Deep Space One) spacecraft, using laboratory data and in-flight 
images of star fields. The images suffer from significant distortion up to 4 pixels near the margins, an effect which we 
modelled by two-dimensional polynomials of 10th degree. The focal length of the camera is determined to be f = 
686.55 +/- 0.05 mm, clearly above the nominal design value. In-flight images show that the geometric properties of the 
camera essentially have not changed. Following image geometric corrections on the basis of the laboratory data, 
positions of stars in the images can be predicted to within 0.5 pixels (1 6). The analysis demonstrates that ground 
calibration data which can be obtained and processed very rapidly constitutes an important basis for the evaluation of 
camera geometric properties. 
I INTRODUCTION 
The DS1 (Deep Space One) spacecraft was launched on October 24, 1998 from Cape Canaveral Air Station, FL. This 
mission is part of the New Millenium program of NASA, which has the goal to test new technologies for future space 
and Earth-observing missions [Nelson, 1998; Nelson et al., 2000]. The spacecraft encountered the 2-km asteroid Braille 
on July 28, 1999 and is now on a trajectory to an encounter with the comet Borrelly in September 2001. 
DSI is equipped with an onboard camera for imaging of the flyby targets. The camera is also used to support the 
navigation of the spacecraft. The onboard flight software (one of several technology experiments of DS1) is intended to 
measure positions of solar system objects relative to the background stars with the goal to autonomously determine the 
spacecraft's position and trajectory. For precise navigation, it is absolutely required that the imaging sensor is 
geometrically calibrated precisely. An effort was therefore made by members of the DS1 science and navigation teams 
to study the geometric performance of this sensor, specifically, to find algorithms to correct for possible image 
distortion 
2 MICAS CAMERA AND CCD SENSOR 
The spacecraft camera, MICAS (Miniature Integrated Camera Spectrometer, Fig. 1), combines the functionality of a 
framing camera with that of an imaging spectrometer. Two array sensors (briefly termed "APS" and "CCD") with two 
spectrometers ("UV" and "IR") share one common 4-inch aperture optical system. The "CCD" array sensor with a size 
of 1024 x 1024 pixels, and a nominal focal length of 677 mm (Table 1) is the prime instrument to obtain frame images. 
Owing to the compact design of the camera, the light path is complicated (Fig. 1, right). 
3 LABORATORY DATA 
Comprehensive laboratory studies of camera performance were carried out at JPL (Jet Propulsion Laboratory) in 
summer 1998, before the camera was mounted on the spacecraft. These included evaluations of the geometric 
properties of images obtained by the CCD sensor. Images of a geometric calibration target, placed in a collimator, were 
taken. The target, made photolithographically to high accuracy, shows a 5 x 5 pattern of "holes" which were very 
nearly equally spaced (Fig. 2). The target was initially centered in the field of view, then shifted to the upper left, top, 
upper right, lower left, bottom, lower right. Finally, the target was turned by 90°. Multiple exposures at each target 
position were taken; three sets of exposures, 21 images, were finally used in this analysis. 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B1. Amsterdam 2000. 221