As described in the previous paper (Park et al. 2013), the detector subsystem of optical wide-field patrol (OWL) provides many observational data points of a single artificial satellite or space debris in the form of small streaks, using a chopper system and a time tagger. The position and the corresponding time data are matched assuming that the length of a streak on the CCD frame is proportional to the time duration of the exposure during which the chopper blades do not obscure the CCD window. In the previous study, however, the length was measured using the diagonal of the rectangle of the image area containing the streak; the results were quite ambiguous and inaccurate, allowing possible matching error of positions and time data. Furthermore, because only one (position, time) data point is created from one streak, the efficiency of the observation decreases. To define the length of a streak correctly, it is important to locate the endpoints of a streak. In this paper, a method using a differential convolution mask pattern is tested. This method can be used to obtain the positions where the pixel values are changed sharply. These endpoints can be regarded as directly detected positional data, and the number of data points is doubled by this result.

1. INTRODUCTION
 2. OWL DATA REDUCTION
  2.1 Reduction Procedure
  2.2 Streak Detection and Length Determination UsingSExtractor
  2.3 Combining Positional Data with Time Log Data
  2.4 Ambiguity of Length Determination
 3. RELATED STUDIES
  3.1 Using "Tepui" Function as PSF
  3.2 Harris Corner Detector
  3.3 Phase Congruency
 4. REVISED REDUCTION ALGORITHM
  4.1 “Differential” Convolution Mask
  4.2 Measuring the Lengths of Streaks and Making theFinal Reduction Result
  4.3 Comparison with the Old Method via Simulation
 5. SUMMARY
 REFERENCES

• Sun-Youp Park(Korea Astronomy and Space Science Institute, Daejeon 34055, Korea) Corresponding Author
• Jin Choi(Korea Astronomy and Space Science Institute, University of Science and Technology)
• Dong-Goo Roh(Korea Astronomy and Space Science Institute, Daejeon 34055, Korea)
• Maru Park(Chungbuk National University, Cheongju 28644, Korea)
• Jung Hyun Jo(Korea Astronomy and Space Science Institute,University of Science and Technology)
• Hong-Suh Yim(Korea Astronomy and Space Science Institute, Daejeon 34055, Korea)
• Young-Sik Park(Korea Astronomy and Space Science Institute, Daejeon 34055, Korea)
• Young-Ho Bae(Korea Astronomy and Space Science Institute, Daejeon 34055, Korea)
• Jang-Hyun Park(Korea Astronomy and Space Science Institute, Daejeon 34055, Korea)
• Hong-Kyu Moon(Korea Astronomy and Space Science Institute, Daejeon 34055, Korea)
• Young-Jun Choi(Korea Astronomy and Space Science Institute, Daejeon 34055, Korea)
• Sungki Cho(Korea Astronomy and Space Science Institute,University of Science and Technology)
• Eun-Jung Choi(Korea Astronomy and Space Science Institute, Daejeon 34055, Korea)