# Small Satellite Tools for High-Resolution Infrared Fire Monitoring
## 6 Overview of the FireBIRD Satellite Busses  
The concept of compact segment construction was retained for the TET-1 and the BIROS satellite busses, providing time and cost saving advantages for (i) the DLR space agency ordering the TET-1's development by German Small and Medium Enterprises /SMEs/ (see [[https://www.astrofein.com/2728/dwnld/admin/AstroFein_TET_EN.pdf](https://www.astrofein.com/2728/dwnld/admin/AstroFein_TET_EN.pdf)]([https://www.astrofein.com/2728/dwnld/admin/AstroFein_TET_EN.pdf](https://www.astrofein.com/2728/dwnld/admin/AstroFein_TET_EN.pdf)), accessed on 9 December 2021) and (ii) the DLR R&D branch during BIROS's development at the DLR Institute for Optical Sensor Systems.  
This new satellite design approach was comprehensively investigated in a study on \"Affordable Space Missions\" conducted at DLR Berlin-Adlershof [13] on behalf of the DLR R&D program directorate \"Earth Observation\". It was shown that new payloads can be accommodated more easily by a modular segment design combined with a maximum decoupling of the satellite bus and the payload compartment. As a result, there are fewer or no repercussions for or modifications to the satellite bus, which in turn leads to high re-usability of the satellite bus components. Thus, on the TET-1 satellite ten different payloads, including the multi-spectral camera system, could be accommodated in the payload compartment without changes to the bus design. The segment design of the BIRD, TET-1, and BIROS satellites also allows for the highest integration densities, i.e., an optimum utilization of the volume of the overall satellite, which reduced launch costs. The modular segment design of BIROS, which was adopted from BIRD and TET-1, comprising bus, payload, and propulsion segments, is shown in Figure 12.  
Figure 11: Panel design using the Myriad small satellite as an example [12].  
Figure 10: Segment construction of the BIRD satellite (without payload).  
The BIROS bus consists of the Service Segment (in German the \"Dienst\" segment, DS) and the Electronics Segment (ES). The DS contains the batteries (see Figure 13, marked in red), the four reaction wheels, the Inertial Measurement Unit (IMU), and several electronic boxes.  
The Electronics Segment (ES) has two parts (see Figure 14): the electronics boards for the Satellite Bus Computer (SBC) and the payload computer, i.e., the Pre-Processing Unit (PPU). Figures 13 and 14 illustrate that the components are arranged very close to each other, resulting in (i) a very high degree of integration and (ii) a lightweight satellite support structure that is minimized in terms of the required component dimensions and mass.  
The BIROS payload segment (PS) consists of the main payload, i.e., the multi-spectral camera system (see Figures 1, 4 and 5), and several secondary payloads. The BIROS propulsion system is mounted on top of the payload support structure (see Figure 15).  
Figure 14: BIROS electronic segment (ES).  
Figure 12: Modular segment design of BIROS comprising bus, payload, and propulsion segments.  
Figure 13: BIROS service segment (DS).  
In the following subsections, we will focus on the attitude and orbit control subsystem of BIROS, because this subsystem is very important for the exact pointing of the multi-spectral camera system.