Introduction MOMS-02 r r

Ž . ISPRS Journal of Photogrammetry Remote Sensing 54 1999 332–341 Orientation of MOMS-02rD2 and MOMS-2PrPRIRODA imagery 1 H. Ebner a,2 , W. Kornus b , T. Ohlhof c, , E. Putz d a Chair for Photogrammetry and Remote Sensing, Technische UniÕersitat Munchen TUM , D-80290 Munich, Germany ¨ ¨ b German Aerospace Center DLR e.V., Institute for Optoelectronics, PO Box 1116, D-82230 Wessling, Germany c Elektroniksystem-und Logistik ESG , System DeÕelopment, Reconnaissance and Remote Sensing Systems, PO Box 800 569, D-81605 Munich, Germany d Starkstrom-Anlagen-Gesellschaft SAG , Landshuter Str. 65, D-84030 Ergolding, .Germany Received 13 June 1998; accepted 15 February 1999 Dedicated to Dr.-Ing. Otto Hofmann Abstract This paper deals with the orientation of three-line imagery which has been taken during the MOMS-02rD2 experiment in spring 1993, and during the MOMS-2PrPRIRODA mission since April 1996. The reconstruction of the image orientation is based on a combined adjustment of the complete image, ground control, orbit and attitude information. The combined adjustment makes use of the orientation point approach or the orbital constraints approach. In the second case, the bundle adjustment algorithm is supplemented by a rigorous dynamical modeling of the spacecraft motion. The results of the combined adjustment using MOMS-02rD2 imagery and control information of orbit a75b are presented. Based on the Ž . orientation point approach an empirical height accuracy of up to 4 m 0.3 pixel is obtained. In planimetry the empirical Ž . Ž . accuracy is limited to about 10 m 0.7 pixel , since the ground control points GCP and check points could not be identified in the imagery with the required accuracy. Computer simulations on MOMS-2PrPRIRODA image orientation based on realistic input information have shown that good accuracies of the estimated exterior orientation parameters and object point coordinates can be obtained either with a single strip and a few precise GCP or even without ground control information, if a Ž . block of several overlapping and crossing strips with high geometric strength q f 60 is adjusted. q 1999 Elsevier Science B.V. All rights reserved. Keywords: image orientation; Three-line CCD cameras; Bundle block adjustment; MOMS; Orbital constraints Corresponding author. Fax: q49-89-9216-2732; E-mail: tohlhofesg-gmbh.de 1 Updated version of a paper presented at the ISPRS Congress in Vienna, 1996. 2 Tel.: q49-89-2892-2671; Fax: q49-89-280-9573; E-mail: ebnphoto.verm.tu-muenchen.de.

1. Introduction

During the 2nd German Spacelab mission D2, successfully flown in AprilrMay 1993, the Modular Optoelectronic Multispectral Stereo Scanner MOMS- 02 acquired digital high resolution, along track, three-fold stereoscopic and multispectral imagery of the earth surface. The MOMS-02rD2 experiment was the first use of a three-line camera in space. 0924-2716r99r - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 9 2 4 - 2 7 1 6 9 9 0 0 0 3 4 - 9 Although the results of this experiment are remark- able, the high accuracy potential of the MOMS-02 sensor could not be exhausted due to several prob- lems. These problems, however, have been an impor- tant experience in the preparation phase of the MOMS-2PrPRIRODA mission from the Russian space station MIR, launched in April 1996. The photogrammetric processing of the MOMS- 02rD2 and MOMS-2PrPRIRODA data is con- ducted by several German university institutes and the DLR. The major aim is to realize the entire photogrammetric processing chain, which starts with radiometrically corrected image data and ends up Ž . with digital terrain models DTM , orthoimage maps Ž . and vector data for geo-information-systems GIS . Within the science team the Chair for Photogramme- try and Remote Sensing of the TUM is responsible for the reconstruction of the exterior orientation by combined adjustment and the semi-automatic extrac- tion of linear objects for updating the German GIS ATKIS-DLM25. After a description of the two camera experiments MOMS-02rD2 and MOMS-2PrPRIRODA and the combined bundle adjustment concept, the results of the adjustment using MOMS-02rD2 imagery of or- bit a75b are presented and assessed. Then the results of computer simulations on MOMS-2PrPRIRODA image orientation are discussed. Finally the experi- ences are summarized and an outlook is given.

2. MOMS-02 r r

r r r D2 and MOMS-2P r r r r r PRIRODA camera experiments 2.1. MOMS-02 r D2 experiment The optical system of MOMS-02 consists of a Ž . stereo module and a multispectral module Fig. 1 . In seven different imaging modes certain combinations of the panchromatic stereo and the multispectral channels can be selected. The three lenses of the Ž stereo module with 1 CCD sensor array Fairchild . 191 each provide three-fold along track stereo scan- ning with different ground resolutions. The nadir Ž . looking CCD array 4.5 m ground pixel size com- prises two arrays with 6000 sensor elements each, which are optically combined to one array with 9000 sensor elements. The other CCD arrays of the stereo Fig. 1. Optical system of the MOMS-02 camera. The two inclined Ž . 21.98 stereo lenses are depicted in the background. In the foreground, the high resolution lens is visible, arranged between two lenses for multispectral data recording. Ž module consist of 6000 sensor elements 13.5 m . ground pixel size . In stereo imaging mode 1 8304 sensor elements of the HR channel and 2976 sensor elements of the stereo channels are active. In the course of the 10 day lasting D2 mission, 48 data takes with a data volume of 300 GB were recorded during 4.5 h, covering an area of about 7 Mio. km 2 . Due to the orbital inclination of 28.58 industrial countries in Europe and North America have not been imaged. More detailed information about the MOMS-02rD2 camera experiment is given Ž . by Ackermann et al. 1989 , Seige and Meissner Ž . Ž . 1993 and Fritsch 1995 . To demonstrate the combined adjustment of im- age, orbit and attitude data, one imaging sequence Ž . 2 mode 1 with 32 120 rows covering 37 = 430 km Ž . in Northern Australia orbita75b has been chosen Ž . see Section 4 . 2.2. MOMS-2P r PRIRODA experiment The MOMS-2P camera is part of the PRIRODA module, which is equipped with several remote sens- ing instruments. Overall goals of the PRIRODA Ž . Russ. nature project are to investigate nature pro- cesses and to further develop remote sensing meth- Ž . ods Armand and Tishchenko, 1995 . The m ain param eters of the M O M S- 2PrPRIRODA experiment are listed in Table 1. In contrast to the D2 mission, the MIR orbital inclina- tion of 51.68 also allows for imaging of industrial Table 1 Main parameters of MOMS-02rD2 and MOMS-2PrPRIRODA MOMS-02rD2 MOMS-2PrPRIRODA Camera carrier Space shuttle MIR space station Mission duration 10 days at least 18 months Data storage HDT recorder onboard mass memory and telemetry to ground stations w x Orbital height km 296 400 w x Orbital inclination 8 28.5 51.6 w x Ground pixel size nadirrstereo m 4.5r13.5 6.0r18.0 w x Swath width nadirrstereo km 37r78 50r105 Geometric camera calibration laboratory laboratory, inflight Orbit information TDRSS tracking GPS Attitude information IMU IMU, star sensor countries in Europe and North America. Due to several problems, only a few MOMS-2PrPRIRODA images were acquired between September 1996 and April 1997. Since January 1998 MOMS-2P is operat- ing again. The camera geometry including the alignment of the MOMS-2P camera axes has been determined not only by calibration in the laboratory, but also by Ž . inflight calibration Kornus and Lehner, 1997 . A special navigation package MOMSNAV con- sisting of high precision GPS and Inertial Measure- Ž . ment Unit IMU ensures precise orbit and attitude data, synchronized with the MOMS-2PrPRIRODA imagery to 0.1 ms. Based on GPS observations during a time interval of ca. 5 min and a sophisti- cated short arc modelling, the MIR orbit has been determined with 5 m absolute accuracy. The Astro 1 star sensor, which is mounted on the QUANT mod- ule of the MIR station provides 10 Y . attitude accu- racy. The alignment, however, between the QUANT and the PRIRODA module is known only in the order of 200 Y .

3. Combined bundle adjustment