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1 Korean Journal of Remote Sensing, Vol.27, No.2, 2011, pp.163~170 Change of Refractive Index of Air in X-band due to Atmospheric Humidity, Temperature and Pressure measured by GB-SAR Interferometry Jae-Hee Lee*, **, Hoonyol Lee*, Seong-Jun Cho**, Nak-Hoon Sung** and Kwang-Eun Kim** *Department of Geophysics, Kangwon National University **Mineral Resources Research Division, Korea Institute of Geoscience and Mineral Resources Abstract : In this paper, we analyzed the phase change of 5-triangular trihedral corner reflectors by using X-band Ground-Based Synthetic Aperture Radar (GB-SAR) system. Each reflector was set as a stationary target at a different distance from the system. We obtained total 123 full-polarization images during 40 hours continuously at 20 minute interval. Results of SAR interferometric analysis showed phase changes of maximum 2 radians and followed similar pattern with atmospheric data. Through a GB-SAR phase formula that includes refractive index in the air, we performed regression analysis for refractive index as a function of atmospheric humidity, temperature and pressure. As a result, refractive index of air in X-band showed relatively high coefficient of determination with humidity and temperature (0.72 and 0.76 on average, respectively) but not so with pressure (0.34). The refractive index of air in X-band changed by _ 5 during the measuring time with a humidity range of 50% ~ 90% and a temperature range of -1 ~ 9. We expect that a total expression of refractive index of air including humidity, temperature and pressure can be calculated when more extensive data would be collected at various atmospheric conditions. Key Words : synthetic aperture radar, interferometry, humidity, temperature, pressure, refractive index hoonyol@kangwon.ac.kr 163

2 Korean Journal of Remote Sensing, Vol.27, No.2,

$Change of Refractive Index of Air in X-band due to Atmospheric Humidity, Temperature and Pressure measured by GB-SAR Interferometry Fig. 1. Photo of the experiment location.$

3 Change of Refractive Index of Air in X-band due to Atmospheric Humidity, Temperature and Pressure measured by GB-SAR Interferometry Fig. 1. Photo of the experiment location. 5 red triangles indicate triangular trihedral corner reflectors that used as stationary targets. Table 1. Parameters for the GB-SAR Experiment Date and Time 5 PM Feb. 6, 2009~9 AM Feb. 8, 2009 (40 hours) Humidity 50.4~90.1 % Atmosphere Temperature -1.2~9.0 Pressure ~ hpa Center frequency 9.65 GHz Bandwidth 600 MHz Range Polarization HH, VV, HV, VH Range sampling 1601 Power 37 dbm Azimuth scan length 5 m Azimuth Azimuth step 5 cm Azimuth sampling

4 Korean Journal of Remote Sensing, Vol.27, No.2, 2011 (a) HH-polarization (b) VV-polarization (c) VH-polarization Fig. 2. GB-SAR amplitude images. (d) HV-polarization (a) HH-polarization (b) VV-polarization (c) VH-polarization (d) HV-polarization Fig. 3. Phase changes relative to the first image in (a) HH, (b) VV, (c) VH and (d) HV during the experiment. 166

5 Change of Refractive Index of Air in X-band due to Atmospheric Humidity, Temperature and Pressure measured by GB-SAR Interferometry f = _ 4p nr (1) l l R n Df = _ 4p DnR (2) l (a) (b) (c) Fig. 4. Atmospheric conditions during the GB-SAR experiment. (a) Atmospheric humidity, (b) Temperature and (c) Pressure. 167

6 Korean Journal of Remote Sensing, Vol.27, No.2, 2011 Fig. 5. Changes of refractive index of air in X-band as a function of humidity, temperature and pressure at various channels. Dn = _ l Df (3) 4pR Dn 168

7 Change of Refractive Index of Air in X-band due to Atmospheric Humidity, Temperature and Pressure measured by GB-SAR Interferometry Table 2. Results of regression and coefficients of determination (R 2 ) between refractive index of air in X-band and humidity (h), temperature (T) and pressure (P). Dn = ah + b, [50.4 h 90.1%] Dn = ct + d, [ _ 1.2 T 9.0 ] Dn = ep + f, [ P hPa] humidity (h) temperature (T) pressure (P) a 10 7 b 10 5 R 2 c 10 6 d 10 5 R 2 e 10 6 f 10 3 R 2 HH VV VH HV Dn = ah + b, [50.4 h 90.1%] Dn = ct + d, [ _ 1.2 T 9.0 ] (4) Dn = ep + f, [ P hPa] a b c d e f h T P 169

8 Korean Journal of Remote Sensing, Vol.27, No.2, 2011 Leva, D., G. Nico, D. Tarchi, J. F. Guasch, and J. Sieber, Temporal analysis of a Ground- Based SAR interferometry, IEEE Transactions on Geoscience and Remote Sensing, 41(4): Luzi, G., M. Pieraccini, D. Mecatti, L. Noferini, G. Guidi, F. Moia, and C. Atzeni, Ground- Based Radar interferometry for landslides monitoring: Atmospheric and instrumental decorrelation sources on experimental data, IEEE Transactions on Geoscience and Remote Sensing, 42(11): Luzi, G., M. Pieraccini, D. Mecatti, L. Noferini, G. Macaluso, A. Tamburini and C. Atzeni Monitoring of an Alpine glacier by means of Ground-Based SAR interferometry, IEEE Transactions on Geoscience and Remote Sensing, 4(3): Noferini, L., M. Pieraccini, D. Mecatti, G. Luzi, C. Atzeni, A. Tamburini, and M. Broccolato, Permanent Scatterers analysis for atmospheric correction in Ground-Based SAR interferometry, IEEE Transactions on Geoscience and Remote Sensing, 43(7): Noferini, L., M. Pieraccini, D. Mecatti, G. Macaluso, C. Atzeni, M. Mantovani, G. Marcato, A. Pasuto, S. Silvano and F. Tagliavini, Using GB-SAR technique to monitor show moving landslide, Engineering Geology, 95(3-4): Pieraccini, M., D. Mecatti, L. Noferini, G. Luzi, G. Franchioni, and C. Atzeni, SAR interferometry for detecting the effects of earthquakes on buildings, NDT&E International, 35(2002): Pipia, L., X. Fabregas, A. Aguasca, and C. L. Martinez, Atmospheric artifact compensation in Ground-Based DInSAR application, IEEE Transactions on Geoscience and Remote Sensing, 5(1): Tarchi, D., N. Casagli, R. Fanti, D. D. Leva, G. Luzi, A. Pasuto, M. Pieraccini, and S. Silvano, Landslide monitoring by using Ground-Based SAR interferometry: anexample of application to the Tessina landslide in Italy, Engineering Geology, 68(1-2): Zebker, H. A., P. A. Rosen, and S. Hensley, Atmospheric effects in interferometric synthetic aperture radar surface deformation and topographic maps, Journal of Geophysics Research, 102(B4):

07이재희(3p)(123~131)ok

07이재희(3p)(123~131)ok Korean Journal of Remote Sensing, Vol.26, No.2, 2010, pp.123~131 Detection of Artificial Displacement of a Reflector by using GB-SAR Interferometry and Atmospheric Humidity Correction Jae-Hee Lee*, **,