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# Backeddy — SLS-207 (Program ROCKFISH)

**Public name:** Backeddy  **Tracking #:** SLS-207  **Codename:** ROCKFISH
**Category:** Subsea Vehicles (UUV)  **Fiscal Year:** FY2026
**Contract award:** 09 January 2026

## Summary

Backeddy is the deep-dive, long-loiter UUV — the patient sentinel of the subsea
line. Where SALMON surveys and moves on, ROCKFISH sits deep and quiet for weeks,
carrying the MURRELET acoustic payload to watch chokepoints and approaches. The
SLS-203 → SLS-207 gap implies cancelled or classified intermediate hulls.

## Notional Capabilities

- Deep-rated pressure hull for extended loiter on the bottom or in the column
- Multi-week dormancy with energy-harvesting / hibernation duty cycles
- Primary host for the MURRELET (SLS-402) passive acoustic payload
- GNSS-denied subsea navigation via inertial + terrain/acoustic correlation
- Burst, low-probability-of-intercept reporting to ALDER when cued

## Program References

- Er, M.J., et al., "A Survey on Unmanned Underwater Vehicles: Challenges,
  Enabling Technologies, and Future Research Directions," *Sensors*,
  23(17):7321, 2023.
  [mdpi.com/1424-8220/23/17/7321](https://www.mdpi.com/1424-8220/23/17/7321)
- Salish Littoral Systems, *ROCKFISH: Long-Loiter Deep UUV Concepts for
  Persistent Subsea Watch*, SLS Technical Report TR-207, 2026.
- "A Survey on Sensor-based Planning and Control for Unmanned Underwater
  Vehicles," 2026.
  [arXiv:2604.05003](https://arxiv.org/abs/2604.05003)
- SLS Subsea Group, *Energy Hibernation Strategies for Multi-Week UUV Loiter*,
  SLS White Paper WP-BACKEDDY-01, 2026.

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