## 1 Introduction
### MODIS \"Aqua\"-TET-1 Data Comparison in Low-Temperature Peat Fire Scenes in Borneo  
Peatlands naturally have a high water table, lying at or just below the forest-covered surface. Drainage infrastructure, such as canals, can contribute to lowering the water table, which is then compounded by drought periods coinciding with climatological events such as El Nino-Southern Oscillation (ENSO). The reduced water table allows drying of the peat layer, often for the first time in centuries, thus becoming more susceptible to catching fire. Fire is often utilized as a cheap, effective method to clear and maintain land for both agricultural and plantation development. In Borneo, slash-and-burn techniques often result in fires spreading into surrounding un-slashed peat swamp forests. Peatland fires are characterized by low-intensity burning, which can spread into peat deposits up to 0.5 m below the surface and can burn for long periods of time, often being very difficult to extinguish. Smoldering peatland fires produce large amounts of particulate matter, CO and other gas compounds [10].  
Figure 2 shows MODIS images and hot spot data compared with a TET-1 imagery overlay from [10]:  
N\({}^{\circ}\) (a)--a MODIS \"Aqua\" true color image from 24 September 2015, with the smoke from the fires (the smoke is dominating in the true color images, i.e., in the 0.4-0.65 wavelength region; the smoke is nearly transparent in the 3.6-4 \(\upmu\)m wavelength region, as can be seen in the center MIR band stripe of Figure 2b,d), superimposed with same-day MODIS hot spot data (red dots).  
N\({}^{\circ}\) (b)--The MODIS image N\({}^{\circ}\) (a) overlaid with a same-day TET-1 MIR band image fragment. MODIS hot spot data appear to omit low-intensity fire fronts visible in the TET-1 imagery (fire intensity is indicated by the yellow gradient).  
N\({}^{\circ}\) (c)--a MODIS \"Aqua\" true color image from 21 October 2015, superimposed with same-day MODIS hot spot data.  
N\({}^{\circ}\) (d)--the MODIS image N\({}^{\circ}\) (c) overlaid with a TET-1 MIR band image fragment, which shows MODIS hot spot active fire detection being inhibited by thick smoke and haze.  
Figure 3 illustrates the rapid peat fire front growth over two weeks showing two TET-1 MIR band image fragments from 24 September and from 15 October 2015. Red dots show--in contrast--the small number of active peat fires detected nearly simultaneously by MODIS \"Aqua\". The location of the image extent within the study area is indicated in the lower inset of Figure 3.  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Fire Cluster** & **Fire Radiative** & **Fire Front** & **Fire Front** & **Fire Front** \\
**(Number in** & **Power (FRP)** & **Length** & **Strength** & **Effective Depth** \\
**Figure 1, BIRD)** & **(MW)** & **(km)** & **(kW/m)** & **(m)** \\ \hline
1 & 1829 & 8.2 & 223 & 7.7 \\
2 & 150 & 5.8 & 26 & 1.9 \\
3 & 409 & 6.5 & 63 & 3.2 \\
4 & 111 & 4.8 & 23 & 1.1 \\
5 & 126 & 3.4 & 37 & 1.3 \\
6 & 568 & 5.0 & 114 & 3.8 \\
7 & 136 & 6.3 & 22 & 1.2 \\ \hline \end{tabular}
\end{table}
Table 4: Attributes of numbered forest fire fronts in the BIRD image fragment in Figure 1 (right) of the Lake Baikal area in Siberia, Russia, obtained on 16 July 2003.  
Figure 3: TET-1 MIR band image fragments from 24 September and 15 October 2015 showing the rapid fire front growth over 2 weeks. Red dots show the small number of active fires registered by MODIS nearly simultaneously with TET-1 [10].  
Figure 2: Mosaic of MODIS “Aqua” and TET-1 image fragments obtained on 24 September 2015 (**a**,**b**) and on 21 October 2015 (**c**,**d**) over Borneo’s region indicated in top right. Red dots are detected, hot spots based on MODIS data. The intensity scale of numerous peat fires derived from TET-1 data is also shown on the right [10].  
This example demonstrates the improved FireBIRD fire detection and analysis capabilities compared to MODIS due to its IR sensor's higher saturation temperature and finer spatial resolution (see Table 1).