## 3 Materials and Methods
### Components
The tether spool incorporates  
Figure 4: RAATM anchor sleeve assembly components in the _rooted_ (**left**) and the _stowed_ (**right**) positions. a latching mechanism to relieve tension from the spindle actuator (7) in the fully retracted, _stowed_ position. The anchor assembly consists of three sub-assemblies (a-c) as depicted in Figure 5: (a) the anchor spike sub-assembly, (b) the wire root array sub-assembly, and (c) the anchor plug sub-assembly. The anchor assembly components are depicted in Figure 6 and labeled with red numbers. Figure 5: RAATM anchor sub-assemblies in the _stowed_ position. Figure 6: RAATM anchor assembly components in the _tethered_ position. The anchor plug (16) forms the body of the anchor assembly and retains the anchor cap (17), with its embedded anchor spike (6), and the wire root array (18). It is seated at the base of the anchor sleeve (8) inside the beveeled anchor port (9), and it is held in position by rare-earth (permanent) magnets (not depicted). Vertical splines (aa) on the anchor plug exterior align with corresponding beveled, vertical slots (ab) in the anchor port (9) to resist rotation during anchor cap (17) rotation. These grooves help guide and re-seat the anchor plug in position during the retraction of the tether. The anchor plug (16) and anchor cap (17) are made of Teflon to reduce fouling and minimize friction during the re-seating of the anchor plug into the anchor port, the passage of the anchor spike through the spike well (19), and the passage of the wire root array (18) through the root tunnels (20) in the anchor plug. The outer surface of the head of the anchor cap is ribbed with vertical splines (bb) that mate with the corresponding splines (bc) of the concave interior surface of the anchor cap coupler, thereby enabling the anchor cap coupler to transmit torque to and rotate the anchor cap (17). The anchor spike (6) is rigidly affixed to the anchor cap and is ideally made of a material such as stainless steel to provide weight and add resilience. Thus, the anchor cap retains the anchor plug and provides a mounting point for the swivel eyelet (5). The anchor tether is connected to the anchor spike via a free-spinning swivel eyelet (5) that enables the anchor spike to rotate without winding the tether. The anchor spike is shaped like an auger, and it passes through correspondingly shaped spike well (19) to enable the contraction of the anchor assembly while also serving as the primary means of attachment of the anchor assembly to the seabed. The wire root array sub-assembly (b) is depicted in Figure 7.  
The anchor spike passes through a non-rotating, rigid metal washer known as the wire root ring (21), which joins the wire brush anchor roots into an array (18). The wire root array consists of a set of thin, flexible, stiff wire brushes with interwoven synthetic bristles made of a corrosion-resistant metal, such as braided stainless steel. Each brush passes through a corresponding root tunnel (20) within the anchor plug (16), which angles gradually  
Figure 7: RAATM wire root array sub-assembly components in the _stowed_ position. outward from the vertical axis. The wire root ring (21) and wire root array (18) are stationary with respect to the anchor plug (16) as the anchor cap (17) and spike (6) are rotated, and are held in this position by the wire root array, which is fixed within the root tunnels of the anchor plug, as well as a set of root ring retention rods (22). The purpose of the retention rods (22) is to delay the injection of the wire roots until the anchor spike has been extended a preset depth into the seabed and then retract the wire root array during the retraction of the anchor by pulling up on the root ring (21). The retention rods should be free to move within a lipped groove set in the lower face of the anchor cap (17), which provides retention to the upper ends of the rods. The retention rods pass freely through the root ring (21) and into corresponding vertical retention rod tunnels (23) within the anchor plug in the _rooted_ position.