task-search-approach

name	task-search-approach
description	Search for the target when it is initially outside the field of view, reacquire it safely, then approach to a stable front hold.
metadata	{"skill_kind":"task","routing_summary":"Use when the mission starts without the target in view and requires a bounded search before approaching.","routing_keywords":["search then approach","target not in view","find target first","reacquire then approach","explore then approach","no target in frame"]}

Task Goal

When the target is not initially visible, first regain a reliable observation, then approach to a safe near hold in front of the target spacecraft, and finally stop with terminate_navigation(...) when the final target-surface distance is about 2 meters.

Stage Policy

1. Treat the mission as two stages: search first, approach second.
2. Do not begin forward motion before the target is reacquired with usable evidence.
3. Once the target is found, switch immediately from search behavior to approach behavior.

Search Strategy

1. Sweep yaw to cover both sides of the starting heading, expanding outward until ±90° from start is covered.
2. Choose step sizes between 15° and 30°. Check the image and [Sensor] LiDAR block after every step — when LiDAR points appear or a spacecraft is visible, stop sweeping immediately.
3. Yaw accumulation rule — yaw deltas accumulate. Track your current heading offset from the start:
   • Example: three steps of dyaw=+30 puts you at +90° from start.
   • From +90°, three steps of dyaw=-30 only returns you to 0° (start), NOT to -90°.
   • To reach -90° from +90°, you need six steps of -30° (through +60, +30, 0, -30, -60, -90).
   • Returning to start is NOT the same as exploring the opposite side. You must continue past start.
4. A practical two-phase sweep: first go right to about +90° (e.g. +30, +30, +30), then keep turning left past the starting heading all the way to about -90° (e.g. continue with -30, -30, -30, -30, -30, -30). This ensures full ±90° coverage.
5. Complete the full ±90° range before concluding the target is not findable.

Transition: Search → Approach

• As soon as the target is detected (visually or via the LiDAR block), stop the search sweep.
• Before moving forward, check whether the target is centered. If it is off to one side (the LiDAR center_y value or image position tells you), correct yaw first.
• Only after centering, begin the approach phase.

Approach Strategy

1. Use the [Sensor] LiDAR distance reading (updated every step) to guide closing and verify the final surface-distance band.
2. Keep the target observable during approach. If it drifts to a side, correct yaw before the next forward step.
3. Reduce move size as the target gets closer, and require a fresh check near the final hold point.

Loss During Approach

• If the target disappears from the image and LiDAR after a motion, first reverse that motion to return to the last known good state.
• After the reverse, re-check. If the target reappears, re-center and resume approach.
• If reversal fails, try a small yaw correction toward the last known direction (see target-recovery skill). Do not restart the full search sweep — that is only for the initial acquisition.

Completion and Abort

• The mission is complete only after reacquisition and the final target-surface distance is about 2 meters.
• If structured search or recovery repeatedly fails, terminate with a clear target-lost or observation-failed reason instead of drifting indefinitely.