# State-of-the-Art Mobile Radiation Detection Systems for Different Scenarios
## 3 Mobile Platforms
### Challenges and Research  
The use of unmanned systems in extreme environment missions and scenarios (e.g., nuclear disasters) still presents some challenges that need to be overcome [80]. In the same way, urban operation poses similar challenges, in particular, by the use of micro air vehicles (MAV), also known as drones (with dimension less than 1 m and speed lower than 10 m/s) [15], and by the use of SUAS [69]. Some issues must be overcome, such as:  
* Communications [15; 80]--use of payloads, like cameras (electro optic multi or hyperspectral cameras), light detection and ranging (LiDAR), and micro radio detection and ranging (RADAR), transmits high data volume and difficulties may arise due to limited bandwidth and possible interference or failure, particularly in operations \"beyond line of sight\". The latter may require separate frequency band or the use of satellite communications, which have higher latency, operational costs, and reliability issues. The requirements of higher bandwidth and secure communications are of special concern for robots that are based on distributed systems. * Autonomous vs semi-autonomous--currently, robots need a high degree of human supervision and control, particularly in urban areas [80]. Due to low altitude flights (0.3-40 m) and proximity to urban structures (1.5 m) new challenges arise in vehicle and navigational autonomy. In such environments, five autonomous navigational capabilities must be considered: scan, obstacle avoidance, contour following, environment-aware return to home, and return to highest reading. In addition, the vicinity of buildings and other structures decreases the GPS satellite coverage. Therefore, autonomous capabilities should have the goal to increase the human skills, not to replace them, highlighting the human-robot teaming [69]. For indoor environments, GPS signal is not available. * Data-to-decision process--improvement is needed in autonomous data analysis (visual and radiation data) for prompt use by mission commanders [69]. * Environmental sensors [80]--fast, cheap, and reliable sensors and associated electronics for real-time response are needed. * Energy storage and management [15; 80]--the current endurance of a battery powered rotary wing can vary between 10-60 min (depending on the payload). * Weather conditions--in most cases, the operation of unmanned systems, particularly air-based platforms, are limited by adverse weather conditions (e.g., precipitation, wind, fog, haze, and pollution). The data collected by the sensors, the communications, and navigation systems might also be affected [15]. * Regulatory restrictions--safety regulations and operational procedures are necessary to avoid collisions of drones with ground obstacles (people and structures) and other aircrafts [15]. * Radiation damage [44; 48; 81]--when exposed to high radiation fields, the platform's operational life is limited. This is due to microscopic damage caused by the radiation interaction with the platform materials. Therefore, it is important to predict the radiation damage in the platform materials and sensors to accomplish the planned mission tasks. Three ways are available to reduce the effects of radiation in critical components: increase the distance to source, reduce time exposure, and/or using shielding materials. * Noise--low altitude and various UAVs might cause a significant level of annoyance (e.g., propellers rotation of a multi-rotor or airframe vibrations). Research may fall on both drone design (reducing the noise source) and flight paths [15]. Some examples of research projects and future technological breakthrough advances in the field encompass:
* Hybrid vehicles--e.g., commercially available unmanned VTOL fixed-wing, which does not need a runway (can hover) and has a flight time in the order of hours; or the use of a small agile ground robot carried by a multi-rotor type aircraft (Figure 5a) [80]. * Ducted fan drones--the ducted fan can produce more thrust than a open propeller with less power.