Technical Specification · VC-ENG-2101

PhytoSense Mesh Sensor Network

The facility-wide distributed plant-health sensor network. 48,900 deployed nodes carry a six-sensor phytophysiology suite, reporting plant state to the Mycelial Data Fabric for ingest by CHLORA.

Doc ID: VC-ENG-2101 Rev: F · 2089-10-22 Owner: K. Aldous, Sensing & Imaging Group Approver: Dr. H. Voss, Director Classification: INTERNAL // CHLOROPHYLL-EYES-ONLY Supersedes: VC-ENG-2101 Rev E

1. Overview

The PhytoSense Mesh provides continuous, per-specimen-cluster measurement of plant physiological state. Nodes self-organize into a wireless mesh and forward time-stamped, signed telemetry packets upstream. The network spans all 14 greenhouse zones plus the GCL-1…GCL-4 containment vaults, with hardened variants in the Toxin Yield Reactor and Phyto-Synthesis Bay.

● 48,610 nodes online 📡 6 sensors / node ⚘ 1 node : ~26 specimens Rev F

Scope. This spec covers node hardware, the sensor suite, placement density, calibration, telemetry schema, power budget, failure modes, and maintenance. Transport SLAs are defined in VC-ENG-2200; alarm thresholds in VC-ENG-2400; canonical units in Botanical Metrics.

2. Hardware & Sensor Suite

Standard node model PS-Node M4. Ruggedized vault variant PS-Node M4-V adds a chemically inert PTFE shroud and gamma-tolerant MCU for GCL-3/4 service.

Channel	Sensing Method	Range	Accuracy	Sample Rate	Power (avg)
Sap flow	Heat-ratio thermal pulse, dual-probe	0–120 cm/h	±2.0% rdg	0.1 Hz (10 s)	41 mW
Stem turgor	Magnetic leaf/stem patch-clamp pressure	5–600 kPa	±1.5 kPa	0.2 Hz (5 s)	12 mW
Leaf-surface temp	NDIR thermopile, 8–14 µm	−10 … +65 °C	±0.2 °C	1 Hz	6 mW
Stomatal conductance	Differential leaf-chamber porometry	0–1000 mmol·m⁻²·s⁻¹	±3.0% rdg	0.033 Hz (30 s)	58 mW
VOC / ethylene	MOS + electrochemical C₂H₄ cell	0–10 ppm C₂H₄; 0–50 ppm VOC	±0.05 ppm	0.1 Hz	33 mW
Chlorophyll fluorescence	Pulse-amplitude-modulated (PAM), 650 nm excite	Fv/Fm 0.000–0.850	±0.005 Fv/Fm	0.0167 Hz (60 s)	74 mW (pulsed)

2.1 Platform

Attribute	Specification
MCU	RV64 low-power core @ 96 MHz, 512 KB SRAM, hardware AES-256 + Ed25519
Comms	2.4 GHz IEEE 802.15.4 mesh (primary) + sub-GHz 868 MHz LoRa fallback
Mesh hop budget	≤6 hops to nearest MDF edge gateway; auto re-route on link loss
Local buffer	8 MB FRAM ring buffer — ≥72 h store-and-forward at nominal rate
Enclosure	IP67, food-grade; M4-V variant chemically inert to alkaloid aerosols
Time source	PTP (IEEE 1588) disciplined, ±1 µs to MDF grandmaster

3. Node Placement Density

Placement is risk-weighted: denser instrumentation in high-value and high-hazard zones.

Zone Class	Density	Node : Specimen	Notes
General greenhouse (GCL-1)	1 / 6 m²	~1 : 32	Cluster-averaged; canopy + root-zone pair
Cultivar nursery	1 / 3 m²	~1 : 14	Per-tray instrumentation
Containment vault (GCL-2/3)	1 / 1.5 m²	~1 : 6	Redundant pair per specimen, M4-V
GCL-4 / weaponized cultivar	1 / specimen + 2 spares	3 : 1	Triple-redundant, 2-of-3 voting
Toxin Yield Reactor	Inline + headspace	n/a	VOC/ethylene emphasis, hardened

Facility-wide mean: 1 node : ~26 specimens across 48,900 deployed nodes.

4. Calibration Procedure

Nodes run continuous self-checks against on-board references and are wet-lab re-calibrated on a rolling schedule. Procedure CAL-PSM-07:

Pre-check — confirm node reports firmware ≥ 4.6.2 and PTP lock < ±1 µs.
Thermopile — two-point against NIST-traceable blackbody at 15.00 °C and 45.00 °C; accept if residual ≤ ±0.15 °C.
Turgor — apply 50 / 300 / 550 kPa reference; fit linear gain/offset, accept R² ≥ 0.999.
Sap flow — heat-pulse on a reference stem analog at known 0 / 40 / 90 cm/h; accept ±2%.
Stomatal — null against sealed dry/wet chamber; zero-drift < 5 mmol·m⁻²·s⁻¹.
VOC/ethylene — span gas: 1.00 ppm C₂H₄ + 10 ppm isoprene; zero with scrubbed air.
Fluorescence — dark-adapt 20 min, verify Fv/Fm against reference leaf (0.832 ± 0.005).
Sign-off — write calibration record to node EEPROM; push cal cert to MDF; node returns to service.

Rolling wet-lab cal: 5% of fleet / quarter (full coverage every 5 quarters).
Auto self-cal nightly; node flagged CAUTION if any channel drifts > 1.5× spec.
Calibration coverage target: ≥ 98% of nodes in-window at all times.

5. Telemetry Data Schema

Each node emits a signed CBOR packet; the JSON projection below is the canonical decoded form ingested by the MDF.

{
  "schema": "vc.psm.telemetry/4",
  "node_id": "PSM-0712-A3F",
  "node_model": "PS-Node-M4-V",
  "zone": "GCL-4/VAULT-03",
  "specimen_cluster": "TX-RADICANS-W7",
  "ts": "2089-11-04T08:42:17.044Z",
  "ptp_offset_us": 0.7,
  "seq": 884213,
  "readings": {
    "sap_flow_cm_h":        38.4,
    "stem_turgor_kpa":      412.6,
    "leaf_surface_temp_c":  24.81,
    "stomatal_cond_mmol":   318.0,
    "voc_ppm":              0.42,
    "ethylene_ppm":         0.07,
    "chl_fluor_fvfm":       0.821
  },
  "qc": { "drift_flag": false, "channels_ok": 6, "battery_pct": 87 },
  "health": "OK",
  "sig": "ed25519:5f3c...a91d"
}

Quality-control fields drive node-level health badges; drift_flag:true raises a CAUTION in the Alarm Matrix. A missing seq or stale ts (> 90 s) marks the node offline.

6. Power Budget

Nodes run on a 3.6 V Li-SOCl₂ primary cell with a supercapacitor buffer for the fluorescence pulse. Energy is harvested where canopy light allows.

State / Load	Avg Power	Duty	Notes
Six-sensor sampling	224 mW	continuous	Sum of channel table above
Mesh radio (802.15.4)	38 mW	~6%	Listen + forward
MCU + QC + sign	21 mW	continuous	Ed25519 sign per packet
Sleep floor	0.9 mW	idle	FRAM retention + RTC
Node total (nominal)	~283 mW	—	Battery life ≥ 14 months; +6 mo with harvesting

Fleet mean battery state of charge: 62% · low-battery alarm at 15%

7. Failure Modes & Redundancy

Failure Mode	Detection	Mitigation	Residual Risk
Node offline (radio/power)	Missed heartbeat > 90 s	Mesh re-route; neighbor coverage; FRAM replays on return	Low
Single-channel drift	Nightly self-cal > 1.5× spec	Channel masked; CAUTION raised; cal dispatch	Low
Sensor failure (GCL-4)	2-of-3 voting disagreement	Failed sensor voted out; node stays live on 2	Managed
Edge gateway loss	MDF gateway timeout	Sub-GHz LoRa fallback to alternate gateway	Watch
Mesh partition	Topology audit (weekly)	Store-and-forward up to 72 h; bridge node dispatch	Watch
Spoofed packet	Ed25519 signature mismatch	Packet dropped; node quarantined; security event	Low

GCL-4 rule. No GCL-4 specimen may run below two healthy redundant channels per measurement. Falling to a single channel raises a CRITICAL and dispatches a field technician under SOP within the escalation window in VC-ENG-2400.

8. Maintenance Intervals

Daily — NOC offline-node sweep; auto-dispatch if > 0.8% of any zone is dark.
Weekly — mesh topology audit; calibration-window coverage report (target ≥ 98%).
Monthly — firmware patch train; battery state-of-charge survey; gateway link-margin review.
Quarterly — wet-lab gravimetric re-cal of 5% sample; M4-V shroud chemical-integrity inspection.
Annual — full fleet cal-cert reconciliation; battery replacement campaign for nodes < 20% SoC.

→ Transport: Mycelial Data Fabric → Reasoning: CHLORA → Alarm Matrix → Botanical Metrics