Frame and Packet Processor
CCSDS AOS/SCPS Framing Engine with CFDP File Transfer
Software/firmware that frames, multiplexes, and de-multiplexes CCSDS Telemetry (TM), Telecommand (TC), and Advanced Orbiting Systems (AOS) transfer frames, plus the CCSDS File Delivery Protocol (CFDP) layer for reliable file transfer of data vault contents.
Purpose
Convert the Ark's application data (commands, telemetry, file payloads) into standards-compliant frames suitable for modulation, and reconstruct received frames into commands and files, providing automatic retransmission and store-and-forward capability.
Context
Layered between L3-CDH-SW (application layer source/sink) and L3-COM-EARTH-MOD (coding/modulation layer). Coordinates with L3-COM-EARTH-BUF for queueing and prioritisation. Implements CCSDS 732.0-B (AOS Space Data Link Protocol), 232.0-B (TC), 133.0-B (Space Packet Protocol), 727.0-B-5 (CFDP), and 734.2-B-1 (Bundle Protocol gateway for DTN).
Principles
- ▸CCSDS frame hierarchy: Application Packets → Space Packets → Transfer Frames → Channel Access Data Units
- ▸AOS frames carry multiple virtual channels (VCID 0–63), each with its own multiplexer for different data classes (real-time telemetry, file dump, fill)
- ▸CFDP provides Class 1 (unreliable, single-hop) and Class 2 (reliable, ACK-based) file transfer with optional store-and-forward Extended Procedures
- ▸CFDP segmentation handles files larger than a single PDU, with negative acknowledgement (NAK) lists for missing segments
- ▸Frame Error Control Word (FECW, CRC-16) detects bit errors at the frame level after FEC decoding
- ▸Bundle Protocol Version 7 (BPv7, RFC 9171) is the LunaNet network layer; gateway converts CFDP/Space Packet ↔ BPv7
Typical implementations
- ▸NASA's cFS (core Flight System) – ci_lab, to_lab, cf (CFDP) apps used on numerous missions
- ▸ESA's SAVOIR CCSDS Software Stack on JUICE, Sentinel
- ▸ION (Interplanetary Overlay Network) open-source BP/CFDP stack — used by NASA PACE mission (Feb 2024, first Class-B routine DTN operations, 34M+ bundles, 100% delivery)
- ▸NASA's HDTN (High-Data-Rate DTN) for high-throughput surface-to-orbit relay applications
- ▸Surrey Satellite's CFDP implementation on Lunar Pathfinder
Lunar considerations
- ▸Round-trip light-time Earth-Moon ~2.6 s makes per-segment ACK feasible (unlike Mars where DTN/BP store-and-forward is essential)
- ▸Earth-Moon visibility gaps from south-pole topography mean buffer storage and resume-from-checkpoint are required between passes
- ▸Lunar surface to relay (Lunar Pathfinder/LCRNS/Moonlight) link uses DTN BPv7 — Ark must speak both DSN-direct CCSDS and LunaNet BPv7
- ▸100-year mission requires backward-compatible frame parsing for legacy formats and forward-compatible for future LunaNet revisions
- ▸Long mission means file system journaling and SEU-tolerant data structures for CFDP transaction state are critical
Specifications
Functional
| primary function | Frame and de-frame CCSDS transfer frames and CFDP file transactions across virtual channels |
| inputs | Application packets and file references from L3-CDH-SW, Decoded transfer frames from L3-COM-EARTH-MOD, Buffer pool from L3-COM-EARTH-BUF for outgoing queue and incoming reassembly, Crypto services from L3-COM-CRYPT-PROT (SDLS authentication/encryption tags) |
| outputs | Encoded transfer frames to L3-COM-EARTH-MOD for transmission, Reconstructed packets and files to L3-CDH-SW, CFDP transaction telemetry (open transactions, NAK history, throughput), Bundle Protocol PDUs to L3-COM-MESH-ROUT for LunaNet relay path |
| supported protocols | CCSDS Space Packet Protocol (133.0-B-2), CCSDS AOS Space Data Link (732.0-B-4), CCSDS Telecommand Space Data Link (232.0-B-4), CCSDS CFDP (727.0-B-5) Class 1 & 2, Bundle Protocol v7 (RFC 9171) gateway, CCSDS SDLS (355.0-B) for security |
| virtual channels supported | 64 |
| max transfer frame size bytes | 2048 |
| throughput mbps min | 10 |
| cfdp concurrent transactions | 32 |
| ack timeout s default | 6.0 |
Physical
| mass kg | 0.0 |
| dimensions | Software running on L3-CDH-PROC SBC |
| materials | Code stored in radiation-hardened NOR flash and EDAC-protected RAM |
| operating temperature c | -40, 70 |
Operational
| power consumption w | 4 |
| thermal range c | -40, 70 |
| lifetime years | 100 |
| mtbf hours | 500000 |
| software loc | 80000 |
| verification standard | NASA-STD-8739.8 / DO-178C Level B equivalent |
Interfaces
Provides
- Encoded CCSDS transfer frames for modulation
- Reconstructed commands, telemetry packets, and file completion events
- BPv7 bundles destined for LunaNet relay path
Requires
- Persistent buffer storage for outgoing queues and partial CFDP transactions
- SDLS security tags and authenticated encryption services
- Host CPU cycles and OS services for processing
Cite this entry
Lunar Ark Codex. "Frame and Packet Processor" (L3-COM-EARTH-PROC). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-COM-EARTH-PROC
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.