Methods
The SAR images were all co-registered using common ground control points. A speckle removal filter was applied. We identify eight land cover classes in the study area for JERS and ERS images by using the SPOT images as ground truths The SAR backscattering coefficient (s⁰ ) of every class is computed using the following equation,
s⁰ (dB)=10log₁₀(I_ave)-K
where I_ave is the average intensity value (square of pixel digital number) of each class, and the value of K is 68.20 for the JERS SAR images processed at NASDA and 59.75 for the ERS-2 SAR PRI images processed at CRISP.

Results and Discussions
The change in radar backscatter is evedent from the multitemporal SAR composite images of the study area. Fig. 4 shows the multitemporal colour composite of JERS SAR images (Red - 2 Feb 97, Green - 24 Oct 97, Blue - 7 Dec 97). The locations of the different classes (I to VII) are marked on this image. Fig. 5 shows the colour composite image of ERS SAR images (Red - 7 Nov 96, Green - 23 Oct 97, Blue - 27 Nov 97), with the location of Class VIII marked.

Figure 4. Multitemporal Composite of JERS SAR images (R-2 Feb 97, G-24 Oct 97, B-07 Dec 97) showing locations of different classes. The three display channels have been independently stretched to accentuate the different classes.

The values of radar backscatter coefficient for the different land cover classes are tabulated in Table 2. The time series of radar backscattering coefficient for these classes are shown in Fig. 6 and Fig. 7 for JERS SAR and ERS SAR respectively. The SPOT images acquired before, during and after the fire period are shown in Figs. 8, 9 and 10 respectively.

Table 2. Radar Backscatter of Different Land Cover Types in JERS and ERS Images.

Class	Satellite	Radar Backscatter(dB)
		Before-fire	Fire-burning	After-fire
I.Burnt Forests	JERS	-4.136	-8.602	-6.409
	ERS	-6.548	-9.096	-6.278
II.Cleared Land(Bright)	JERS	-6.290	-7.046	-6.437
	ERS	-6.240	-7.537	-5.746
III.Cleared Land (Dark)	JERS	-6.796	-9.573	-8.139
	ERS	-6.148	-8.738	-6.280
IV.Paddy Fields	JERS	-10.052	-12.125	-11.227
	ERS	-8.405	-10.176	-7.033
V.Peat Swamp Forests	JERS	-6.407	-6.713	-6.165
	ERS	-5.817	-6.954	-5.203
VI.Secondary Forests	JERS	-7.960	-8.317	-8.216
	ERS	-6.770	-7.734	-5.466
VII.Unburnt River Banks	JERS	-7.114	-6.843	-7.212
	ERS	-6.079	-6.410	-6.183
VIII.Very Bright Lands	JERS	-6.965	-6.413	-7.531
	ERS	-7.588	-4.398	-4.338

There are quite a number of differences between the ERS and JERS backscattering coefficients from various land cover classes. Except for two classes (Class VII and Class VIII), the C-band ERS SAR backscatter generally decreases during the fire period and increases after fire. For the L-band JERS SAR, only three classes (Classes I, III and IV) show a similar pattern while the backscatter of the other classes do not show significant changes. For the unburnt vegetation along the river banks (Class II), the C-band ERS SAR backscatter remains constant whereas for the cleared lands which appear very bright in ERS images (Class VIII), the ERS backscatter increases during fire and stay high after fire.

Figure 5. Multitemporal Composite of ERS SAR images (R-07 Nov 96, G-23 Oct 97, B-27 Nov 97) showing locations of class VIII.