57 
IMAGE RESTORATION OF CALIBRATION AND VALIDATION FOR KOMPSAT-2 
Dong-Han Leea, D.C. Seo, J.H. Song, J.H. Chung, S.Y. Park, M.J. Choi, H.S. Lim 
a Satellite Data Information Team, Korea Aerospace Research Institute (KARI), 45 Eoeun-dong Yuseong-gu, Daejeon 
305-333, South Korea - dhlee@kari.re.kr 
Commission I, WG 1/1 
KEY WORDS: Calibration, Passive Optical system, Image restoration, MTF, Radiometry, Camera, Sensor, KOMPSAT-2 
ABSTRACT: 
The image restoration of Calibration and Validation (Cal/Val) for the KOMPSAT-2 (KOrea Multi-Purpose SATellite-2) has six 
parameters; Linearity, Video processor gain/offset, Non-uniformity correction, De-noising, Butting zone, SNR and additionally 
MTF/MTFC. Before launched, Cal/Val site, equipments, code and procedure for the image restoration of Cal/Val and MTF/MTFC 
have been defined and developed. After launched, KARI Cal/Val team has done the image restoration of Cal/Val and MTF/MTFC 
for the KOMPSAT-2, and then can guarantees the KOMPSAT-2 radiometric image qualities and MTF for Users. 
1. INTRODUCTION 
1.1 Overview 
After KOMPSAT-2 launched, the Cal/Val for KOMPSAT-2 
image quality has been doing and implementing the 
KOMPSAT-2 image data processing system with it in KARI. 
Generally, because the present remote sensing satellite 
technique cannot satisfy user’s requirements for image quality, 
the Cal/Val for image quality must be carried out directly after 
launch before distributing the imagery to the users. In the broad 
concept of Cal/Val, the Cal/Val of the remote sensing satellite 
can be divided into two parts if we recognize the technical gap 
between the satellite technique and the user requirements; 
Cal/Val to validate and verify the requirements of satellite, and 
Cal/Val and image restoration to guarantee the image data 
quality for the users. After launch, we can immediately 
understand the gap between the real Cal/Val and our own way 
from the new and different phenomenon and our mistakes form 
analyzing the KOMPSAT-2 image data. The first gap between 
them is the radiometric Cal/Val; Linearity, Video processor 
gain/offset, Non-uniformity correction, De-noising, Butting 
zone and SNR (Signal to Noise Ratio). The second gap of it is 
MTF (Modulation Transfer Function) / MTFC (MTF 
Correction). The last gap of it is the geometric Cal/Val; Geo 
accuracy, Band-to-Band registration, Planimetric accuracy, etc. 
(for more detailed; Seo 2007) 
This paper explains de-noising, non-linearity and butting zone 
of the radiometric Cal/Val and MTF/MTFC of KOMPSAT-2, 
Lee 2007 does the overview of KOMPSAT-2 Cal/Val and the 
basic Cal/Val results. Seo 2007 paper explains the Geometric 
Cal/Val of KOMPSAT-2, and Song 2007 does NUC 
Radiometric Cal/Val. 
1.2 KOMPSAT-2 radiometric and MTF specification 
The next list explains the radiometric specification of the 
KOMPSAT-2 MSC (Multi-Spectral Camera); 
Linearity: < 4% (5%-95% sat.) 
SNR: > 100 
The next list explains MTF specification of the KOMPSAT-2; 
Line rate: up to 7100 lines/sec 
- Default value (at Nadir imaging): 6800 (PAN), 1700 
(MS) 
MTF (@ Nyquist freq.): ~8% 
Yaw steering accuracy shall < 0.05 degree (3a) 
2. RADIOMETRIC CAL/VAL 
2.1 De-noising 
The noise value of the KOMPSAT-2 specification, 1% after 
NUC, is too high to be accepted by the Users. Noise can be 
divided by the random noise and the pattern noise. The random 
noise can directly affect the SNR, and be reduced by some filter 
algorithm. The KOMPSAT-2 IRPE (Image data processing 
system) has a wavelet filter to reduce the random noise in the 
KOMPSAT-2 image data. The pattern noise within the 
KOMPSAT-2 noise requirement level has been found out after 
KOMPSAT-2 launch newly; Diagonal line, Vertical line and 
Horizontal line. Additionally, the pattern noise may depend 
upon the input radiance (DN; Digital Number). The vertical and 
horizontal noise may appear more at less than 200 DN 
(Residual NUC). The diagonal line appears periodically, and 
the vertical and horizontal noise non-periodically. 
The diagonal line has been removed by the FFT algorithm 
developed from the periodic pattern of it (Figure 1). In Figure 1, 
the non-periodical horizontal line can be found out easily after 
the diagonal line removed. 
a. Diagonal line noise 
Non-uniformity correction before compressing 
Residual Non-Uniformity: < 1%