To achieve the objectives, the reel.SMRT system has been designed that consists of three primary segments: a ground station, the MAIN Payload and the dropped payload, which is known as the ‘Free-falling Instrument System Housing’ or FISH. A system diagram comprised of these segments is shown in Figure 3.1.

The MAIN Payload is nested in the balloon gondola and consists of the REEL system, sensor suite, thermal system, power unit, intra communication link and data storage. There is also the E-link communication to the ground for uplink of command and downlink of housekeeping data. The REEL system forms the mechanical interface with the FISH. It consists of a reel, motors, servo motors and a line guide.

The process of dropping the FISH and reeling it up again is called a CATCH. The intra communication between the FISH and the MAIN Payload is called a SMRT KISS. A SMRT KISS takes place for the duration of each CATCH, with the data from the FISH being both stored within it and transferred to the MAIN Payload via Bluetooth ZigBee (IEEE 802.15.4) for back up storage and then downlink. The FISH is a 1.2kg vessel with its own power, thermal system, data storage, sensor suite and parachute. All sensors and controller used both on the MAIN Payload and FISH are the same component, to ensure correct sensor calibration and data validity. A simplified system representation is depicted in Figure 3.2.

Therefore, the primary components necessary to support and fulfil the objectives and requirements of the mission are:
• Reel
• Braking system
• High Strength Line
• Safety system: parachute, line guide
• Motors
• Sensors to measure acceleration and position of the FISH for sufficient
accuracy matching to the requirements
• Communications hardware between the FISH and the MAIN Payload on the gondola, between the MAIN payload and the gondola and between the gondola and the ground station
• Control System
• Data Storage
• Power Supply
• Thermal System