Marengo

You are a mission/orbit design engineer. Propose 2–3 viable orbit options for a spaceborne SAR mission and justify the trade.

Mission needs:
- Target latitude range: [e.g., global / ±70° / specific region]
- Required revisit: [e.g., <24 h / 3 days / weekly] at [incidence angle range]
- Desired ground resolution: [m] and swath: [km]
- SAR band: [X/C/L], imaging modes: [Stripmap/Spotlight/ScanSAR]
- Spacecraft constraints: mass [kg], max power [W], max downlink [Mbps], max slew rate [deg/s]
- Ground segment: # ground stations and latitude(s)

Deliver:
1) A short list of candidate orbits with (altitude, inclination, LTAN if SSO, repeat cycle, max access/revisit, beta angle implications).
2) For each orbit: expected coverage/revisit for the target region, key SAR geometry impacts (look/incidence angle ranges, Doppler/PRF considerations, shadow/layover risk).
3) A decision matrix (revisit, coverage, resolution geometry, downlink opportunity, drag/lifetime, radiation, cost/complexity).
4) Final recommendation and what requirements it best satisfies. State assumptions explicitly.

Compare reaction-wheel ADCS vs magnetorquer-only ADCS for a nanosatellite and recommend an architecture for the stated mission.

Inputs:
- Platform: [1U/3U/6U/12U], inertia estimate or dimensions: [ ]
- Pointing: accuracy [deg/arcmin], stability [deg/s or arcsec/s], knowledge [ ], jitter limit [ ]
- Agility: max slew [deg] in [s], retarget frequency [per orbit/day]
- Environment: orbit [LEO/SSO], altitude [km], geomagnetic latitude range (if relevant)
- Payload sensitivity: [imager exposure time / antenna beamwidth / SAR?]
- Constraints: power average/peak [W], volume [U], cost, reliability class

Deliver:
1) Disturbance torque estimate (aero, gravity-gradient, magnetic residual dipole, SRP) and control authority comparison.
2) Mode table (detumble, coarse point, fine point, momentum management) for each architecture.
3) Sizing guidance: wheel torque/momentum capacity and required magnetic dipole moment; duty-cycle and power impacts.
4) Risks/failure modes and mitigations (wheel saturation, bearing failures, MTQ-only limitations, eclipse operations).
5) A decision matrix + recommended architecture for the given pointing/agility needs.
Assume reasonable values if inputs are missing and show sensitivity to key assumptions.