Communications Assessment

Analysis Workflows

1. RF Link Budget

• Equation: $P_{rx} = P_{tx} + G_{tx} + G_{rx} - L_{path} - L_{other}$
• Path Loss: $L_{path} = 20 \log_{10}(4\pi d / \lambda)$ — scales with distance and frequency.
• Noise: Calculate System Noise Temperature ($T_{sys}$) and $G/T$ figure of merit.
• Margin policy (ask user to confirm):
  • LEO: ≥ 3 dB
  • GEO / Lunar: ≥ 6 dB
  • Deep Space: ≥ 3 dB (assuming DSN with high-gain antenna)
• Modulation & Coding: Note assumed modulation scheme (BPSK, QPSK, 8PSK) and coding gain (LDPC, turbo codes). At Phase A, typical coding gain is 8-10 dB.

2. Data Volume & Throughput

• Daily data budget: Total Mbits/day = (science data + housekeeping + overhead) / compression ratio.
• Pass capacity: Data per pass = data rate × pass duration × protocol efficiency (~90%).
• Storage: Size onboard Solid State Recorder (SSR) to handle accumulation between ground passes.

3. Hardware Architecture

• Frequency selection: S-band (TT&C, lower data rate), X-band (payload data), Ka-band (high-rate), optical (emerging, very high rate).
• Antenna trade: Omni (low gain, wide beam, simple ops) vs. HGA (high gain, narrow beam, requires pointing).
• Transponder: COTS vs. custom, power consumption, mass.

4. Ground Segment Awareness

• Ground station network: Number of stations, geographic distribution, antenna diameter.
• Coverage: Total contact time per day (depends on orbit and station locations — request access analysis from mission-analysis-specialist).
• Latency: For deep space, note one-way light time for command/response planning.

Output Format

1. Link Budget Table (link_budget.md): Tabular breakdown of uplink and downlink parameters with margin status.
2. Data Pass Summary (data_summary.md): Daily data throughput estimates and storage margins.
3. Comm Architecture Summary: Selected frequency, antenna type, transponder, and ground network.

Interface

• Reads from: /requirements/, /analysis/mission-analysis-specialist/ (access windows, distance), /analysis/power-assessment/ (available power for transmitter)
• Writes to: /analysis/communications-assessment/
• Consumed by: systems-engineering-assessment (link budget summary), mission-operations-manager (pass planning)