Payload Assessment Skill

Read CONVENTIONS.md at the repo root before proceeding.

This skill sizes the mission payload — the instruments or systems that fulfill the mission's primary objective. Every other subsystem exists to support the payload, so this skill's outputs drive the bus design.

Before You Begin

Ask the user (if not already known):

1. What is the mission objective? (Earth observation, science, comms relay, technology demo, ISRU, etc.)
2. What type of payload?
   • Optical: Camera, spectrometer, lidar, telescope
   • RF: SAR, radiometer, transponder, antenna
   • In-situ: Mass spectrometer, drill, sample handler, seismometer
   • Communication: Relay transponder, inter-satellite link
   • Other: Robotic arm, 3D printer, biological experiment
3. What are the key performance requirements? (resolution, coverage, sensitivity, data rate)
4. What orbit/altitude? (Drives ground resolution for remote sensing)
5. What design phase?

Applicable Phases

• Primary: Phase A (payload trade, first-order sizing), Phase B (preliminary design)
• Supporting: Phase C (performance verification), Phase D (calibration planning)

Analysis Workflows

1. Optical Payload Sizing

• Ground Sampling Distance (GSD): $GSD = h \cdot p / f$ where $h$ = altitude, $p$ = pixel pitch, $f$ = focal length.
• Diffraction limit: $\theta = 1.22 \lambda / D$ where $D$ = aperture diameter.
• Swath width: $W = 2h \tan(FOV/2)$ or $W = N_{pixels} \times GSD$.
• SNR estimation: Signal-to-noise ratio depends on solar irradiance, surface reflectance, atmospheric transmission, detector quantum efficiency, and integration time.
• MTF (Modulation Transfer Function): Budget for optics, detector, motion blur, and jitter (from gnc-assessment).

2. RF Payload Sizing

• SAR: Resolution = $\delta_r = c/(2B)$ (range) and $\delta_{az} = L_{ant}/2$ (azimuth). Power-aperture product drives overall system size.
• Radiometer: Sensitivity $\Delta T = T_{sys} / \sqrt{B \cdot \tau}$ where $B$ = bandwidth, $\tau$ = integration time.
• Communication relay: Size transponders, antennas, and link budget per communications-assessment.

3. In-Situ Instruments

• Mass spectrometer: Mass, power, and data rate estimates. Heritage instruments provide reference.
• Drill / Sample handling: Depth, torque, sample volume, contamination control requirements.
• Seismometer / magnetometer: Sensitivity, noise floor, deployment requirements.

4. Payload Resource Requirements

Derive the payload's demands on the bus:

• Mass: Instrument mass + optics + baffle + electronics + harness.
• Power: Continuous and peak power during observation modes.
• Data rate: Raw data rate = pixels × bits/pixel × frame rate (for imagers) or bandwidth × bits/sample (for RF).
• Data volume: Data rate × observation time per orbit. Feed to communications-assessment for downlink sizing.
• Thermal: Instrument dissipation and temperature limits. Feed to thermal-assessment.
• Pointing: Required accuracy, stability, and knowledge. Feed to gnc-assessment.

Output Format

1. Payload Sizing Report (payload_report.md): Instrument parameters, mass/power/data estimates, key performance metrics.
2. Bus Requirements Flowdown: Table of payload-driven requirements for each bus subsystem (mass, power, thermal, pointing, data).
3. Trade Notes: If multiple instrument options were considered, document the trade rationale.

Interface

• Reads from: /requirements/ (mission objectives, performance requirements)
• Writes to: /analysis/payload-assessment/
• Consumed by: systems-engineering-assessment (mass/power budget), thermal-assessment (dissipation), gnc-assessment (pointing requirements), communications-assessment (data volume), structural-assessment (CG impact), power-assessment (payload power)