**2. University of Surrey heritages**

University of Surrey is known as one of the pioneers in the design and build of microsatellite in the 1990s. It started launching microsatellite in 1991 with amateur


**Table 1.**

*Sample for the University of Surrey microsatellite system design.*

radio missions. To simplify the satellite design, the first microsatellite generation has passive attitude control system, that is, using gravity gradient telescopic boom. The university provided microsatellite development and building capabilities to many emerging space countries, including Thailand, Malaysia, South Korea, Algiers, Turkey, and Nigeria. At the time, such countries started to use remote sensing satellites, mostly from the United States and European, for various land-based applications. Therefore, they required remote sensing payloads to include in their satellite missions. Such mission elevates the design requirements to active attitude control system and higher data rate downlink system.

Thailand's Mahanakorn University collaborated with the University of Surrey to jointly develop TMSat that was launched in 1998 [9]. TMSat focuses on remote


#### **Table 2.**

*Sample for the University of Surrey microsatellite heritage system design.*

sensing and amateur radio mission. Since Thailand did not continue building its subsequent satellites, TMSat is not selected as satellite design heritage sample in this chapter.

Singapore's Nanyang Technology University (NTU) collaborated with the University of Surrey to jointly develop satellite subsystem for UoSAT-12. However, the satellite is not a microclass and therefore is not selected as a sample for the University of Surrey's satellite system design in this chapter. The satellite subsystem from NTU is a communication payload with S-band downlink and L-band uplink, which provides the Internet protocol communication operating at 1 Mbps. Since the experience with the University of Surrey only in subsystem design and development, the subsequent NTU satellite, that is, XSAT, is also not considered as the University of Surrey heritage satellite [10, 11].

South Korean experience with the University of Surrey satellite design is when Satellite Technology Research Center (SaTReC), an institution under Korea Advanced Institute of Science and Technology (KAIST), jointly built KITSAT-1 and KITSAT-2 and launched it in 1992 and 1993. Both satellites have store-forward communication amateur payload and low-resolution imagers. Since the KITSAT-1 and KITSAT-2 development time does not match with other microsatellite design sample, only the design of KITSAT-3 is used in this chapter. SaTReC then developed STSAT series as its second generation microsatellites. Since STSAT-2 experienced launch failure, only STSAT-1 and STSAT-3 are selected as satellite design samples [12–15].

Turkey's experience with the University of Surrey satellite design is when its space research institute, TUBITAK-UZAY (previously named BILTEN TUBITAK-ODTU), jointly developed BILSAT-1. The satellite was part of DMC-1 constellation [16–19]. After BILSAT-1, the institute then built its second generation microsatellite, RASAT. Therefore, both microsatellites are used as sample for the University of Surrey design heritage [20–23].

Fifteen satellite bus design parameters are selected for the comparison, including 14 mechatronics component parameters in the satellites' design. For the University of Surrey satellite heritage, the parameters are tabulated in **Tables 1** and **2**. Structure design from four of the five microsatellites is shown in **Figures 2** and **3**. Payload parameters also noted in **Tables 1** and **2** to explain the similarity (or differences) in the mission requirements and their impacts to satellite bus parameters. The weight and dimensions are, in additional of drawings, noted in to explain the satellite

**Figure 2.** *Mechanical design of KITSAT-3 and STSAT-3.*

**Figure 3.** *Mechanical design of BILSAT-1 and RASAT.*

structure design aspects. The satellite operation years are noted in the tables to show the context of available technology.

As shown in **Figures 2** and **3**, the University of Surrey heritage satellites use electronic trays for its satellite bus electronics. The aluminum trays also function as load bearing structure, so that the rest of the satellites components, such as reaction wheels and attitude sensors, can be laid out around them. After all components integrated, the solar panels and/or other outside panels that are made of lighter materials can be used to cover the satellites.
