unisat

CubeSat 12U — Operations Guide

Profile key: cubesat_12u · Mass cap: 24.0 kg · Volume: 17438 cm³ Template: mission_templates/cubesat_12u.json · BOM: hardware/bom/by_form_factor/cubesat_12u.csv

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1. Mission class

The largest standard CubeSat: 226.3 × 226.3 × 340.5 mm, 24 kg, up to 60 W with deployable arrays. Used for long-duration tech demos, deep-space precursors (lunar orbit, cislunar), interferometric Earth observation, and multi-payload science missions.

Radiation caveat. The STM32F446RE has published TID heritage of ~10 krad (see docs/hardware/radiation_budget.md). A 12U on a 5-year polar orbit at 700 km burns through 10 krad — right at the margin. For deep-space, an additional rad-hard secondary OBC is recommended but not in scope for UniSat 1.3.x.

2. Physical envelope

Parameter	Value
Mass cap	24.0 kg
Dimensions	226.3 × 226.3 × 340.5 mm
Volume	17438 cm³
Power generation	~50 W with full deployable arrays
Nominal consumption	35 W
Battery	16S4P Li-ion, ~200 Wh

3. Regulatory context

• CDS rev 14 §3.2 — 12U dispenser spec.
• ITU: UHF + S-band + X-band; for deep-space, DSN (NASA) or ESTRACK (ESA) frequency coordination.
• Launch: ESPA-class rideshare, Firefly, Electron, Falcon-9 rideshare.
• Planetary protection (for lunar / deep-space): COSPAR Category II or III depending on target body.

4. Subsystem matrix

Subsystem	Status
3-axis ADCS (wheels+star)	✅
Redundant star tracker	✅
UHF telemetry	✅
S-band downlink (10 W)	✅
X-band downlink (20 W dish)	✅
GNSS (LEO only)	✅
Deep-space radio	⚠ (requires X-band TX 20 W + 0.5 m dish)
Camera (64 MP telescope)	✅
Deployable solar arrays	✅
Cold-gas propulsion	✅
Electric propulsion	⚠ (BIT-3, PPT — budget-permitting)
Rad-hard secondary OBC	❌ (out of scope for UniSat 1.3.x)

5. Build

make target-cubesat-12u

Compile-time macro: MISSION_PROFILE_CUBESAT_12U=1.

6. Mission config

cp mission_templates/cubesat_12u.json mission_config.json

Fields specific to 12U:

• subsystems.comm_xband.frequency_mhz — default 8400 MHz.
• subsystems.adcs.star_tracker — typically two for redundancy.
• subsystems.payload.type — match your experiment (interferometer, lunar comms relay, etc.).
• orbit.type — LEO, SSO, GEO insertion (via rideshare + kick stage), or cislunar.
• orbit.expected_lifetime_years — default 5, adjust per propulsion budget.

7. Mass & volume validation

Metric	Value	Status
Total mass	16.0 kg	≤ 24.0 kg ✅ (33 % margin)
Volume used	5425 cm³	31 % of 17438 cm³ ✅

Very comfortable margin for a complex payload stack. Typical 12U missions budget 4–6 kg for the payload alone.

8. Typical mission phases

Same as 6U in LEO mode. Cislunar / deep-space missions add:

initial_orbit → transfer_burn → cruise → science_arrival → science → eol

Where transfer_burn is an external propulsion event (rideshare upper stage or on-board electric propulsion) and cruise can be weeks or months.

9. Testing checklist (ground qualification)

Legend: [x] = verified in software / CI / SITL (passes in the current release); [ ] = requires bench hardware, RF range test, or flight-day field activity — team must sign off manually.

Everything from 6U plus:

• Extended TVac: 10 cycles, -30 °C to +65 °C, 8 h dwell.
• Radiation test to 5 krad TID (deep-space) or 2 krad (LEO).
• SEU cross-section characterisation at proton energies ≥ 65 MeV.
• Propulsion firing verification on air-bearing table (cold-gas) or vacuum chamber (electric).
• Star-tracker sky-field + stray-light tests in dark chamber.
• End-to-end SITL with full phase sequence including transfer_burn.

10. Flight-day checklist

Same as 6U plus:

• Planetary-protection certificate (for lunar / deep-space).
• DSN / ESTRACK tracking time scheduled.
• Redundant OBC path tested during the final pre-ship review.
• Propellant loaded per cold-gas / electric manifest; leak-test signed off.

11. Known limitations

• No rad-hard OBC in UniSat 1.3.x — long-duration deep-space missions accept TID risk on the STM32F446RE. Plan for a soft failure mode (fallback to safe-mode + survival beacon) at end of life.
• DSN/ESTRACK scheduling can limit science duty cycle for cislunar and beyond; budget accordingly.
• Thermal gradient across the 226 × 226 mm footprint under asymmetric illumination can exceed 30 °C; design the thermal strap network carefully.
• Deployable retention mass scales quickly with array size; budget 0.5 kg per panel articulation mechanism.

12. Post-flight debrief

Same as 6U plus:

• Deep-space radio link-budget verification per pass.
• Star-tracker cross-check over thermal swings.
• Propulsion consumption vs. plan (delta-V delivered).
• TID dose estimate from on-board radiation sensor (FAULT_RADIATION_* grayscale reports — see docs/hardware/radiation_budget.md).

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