Store-and-Forward Communication Buffer
Persistent CCSDS/CFDP Transaction Buffer with EDAC
Dedicated non-volatile and volatile memory pool storing outbound telemetry, queued CFDP file segments, in-flight transactions, and received command frames during ground station visibility gaps and contingencies.
Purpose
Decouple data generation rate from communication windows; protect against data loss during occultation, link outages, or transmitter faults; enable autonomous resume of file transfers across days/weeks of degraded link.
Context
Used by L3-COM-EARTH-PROC for CFDP transaction state and AOS queue management; mirrored at lower priority to L1-DVT (Data Vault) for long-term storage. Sized to cover 2 weeks of full-rate telemetry without any DSN/relay contact (worst-case ESS outage + lunar libration extreme).
Principles
- ▸Store-and-forward decouples producer/consumer rates, essential when link is intermittent
- ▸Non-volatile storage (NAND flash, MRAM, FRAM) preserves state across power events; volatile DRAM/SRAM provides working scratch with EDAC
- ▸Reed-Solomon or BCH ECC inside flash, plus SECDED (single-error-correct, double-error-detect) at the controller level, protects against SEU and wear-out
- ▸Wear leveling (dynamic + static) and bad-block management extend NAND life to tens of thousands of P/E cycles
- ▸Write amplification factor must be kept low (<2x) to maximise flash endurance for the lifetime of the mission
- ▸Sized as Σ(data rate × max outage duration) + reserve for retransmission queue
Typical implementations
- ▸3D-Plus 3DSR16G08VS rad-tolerant NAND flash modules (used on JUICE, Sentinel)
- ▸Honeywell HXNV 4Mb MRAM (non-volatile, infinite endurance, used on multiple GEO comsats)
- ▸BAE 3DSEU-tolerant SRAM with SECDED EDAC (RAD750 family heritage)
- ▸Cobham Gaisler GRLIB IP cores for memory controllers with scrubbing
Lunar considerations
- ▸Total Ionizing Dose ~10–30 krad over 100 years with regolith shielding — NAND flash typically tolerates 30–50 krad before erase failure dominates
- ▸Single-Event Upsets in DRAM/SRAM require continuous scrubbing (period < few seconds for high-LET environments)
- ▸Single-Event Functional Interrupts (SEFI) in NAND can require power-cycle recovery — need watchdog and redundant pages
- ▸Thermal cycling between –40°C (controlled enclosure) accelerates flash gate wear-out — keep operating range conservative
- ▸Lunar-night low-power mode must preserve buffer contents — non-volatile storage essential
Specifications
Functional
| primary function | Reliable persistent buffering of communication payloads and transaction state |
| inputs | Write requests from L3-COM-EARTH-PROC (frames, file segments, transaction state), Periodic scrub commands from memory controller, Power from L1-PDM (always-on rail) |
| outputs | Read responses to L3-COM-EARTH-PROC, Buffer fill telemetry, ECC error counters, wear-level statistics, Critical-state replication to L1-DVT for long-term backup |
| non volatile capacity gb | 64 |
| volatile working set mb | 256 |
| sequential read bandwidth mbps | 400 |
| sequential write bandwidth mbps | 200 |
| uncorrected ber target | 1e-15 |
| retention years unpowered | 10 |
| endurance pe cycles | 50000 |
| max outage supported hours | 336 |
Physical
| mass kg | 0.5 |
| dimensions | 100 × 100 × 15 mm SBC mezzanine card |
| materials | Rad-tolerant 3D NAND flash modules, MRAM (Magnetoresistive RAM) for critical state, Rad-hard SRAM for working set, Ceramic capacitors for power hold-up, Aluminum shielding (5 mm equivalent) over flash dice |
| operating temperature c | -40, 70 |
| non operating temperature c | -55, 85 |
| radiation tid krad | 50 |
Operational
| power consumption w | 2.5 |
| power consumption w idle | 0.3 |
| thermal range c | -40, 70 |
| lifetime years | 25 |
| mtbf hours | 400000 |
Interfaces
Provides
- Persistent storage and retrieval for in-flight CFDP transactions, AOS queues, and command history
- Replicated copies of mission-critical buffer state for long-term preservation
Requires
- 3.3 V and 1.8 V supplies, ~2.5 W active
- Memory controller interface (SPI/parallel NAND/PCIe-class)
- Cold-plate or radiator interface to maintain flash within endurance temperature window
Cite this entry
Lunar Ark Codex. "Store-and-Forward Communication Buffer" (L3-COM-EARTH-BUF). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-COM-EARTH-BUF
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.