unisat

CubeSat 1U — Operations Guide

Profile key: cubesat_1u · Mass cap: 1.33 kg · Volume: 1135 cm³ Template: mission_templates/cubesat_1u.json · BOM: hardware/bom/by_form_factor/cubesat_1u.csv

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1. Mission class

Entry-level orbital mission for universities or first-launch teams. 100 × 100 × 113.5 mm standard CubeSat cell with a single-board OBC, minimal ADCS (magnetorquer only), and a tech-demo payload. Typical mission life 3–12 months in a ≤ 450 km decaying LEO.

2. Physical envelope

Parameter	Value
Mass cap	1.33 kg (CDS rev 14)
Dimensions	100 × 100 × 113.5 mm
Volume	1135 cm³
Power generation	~2.5 W orbit-average, body-mounted
Nominal consumption	2.0 W
Battery	2× 18650 Li-ion, ~20 Wh

3. Regulatory context

• CubeSat Design Specification rev 14 §3.1 (Cal Poly SSDL).
• ITU frequency coordination required for amateur UHF 435–438 MHz (typical 1U amateur-radio allocation).
• Launch provider: NanoRacks / ISS Kibo, SpaceX Rideshare, ISRO PSLV, etc. — each has its own qualification matrix (ICD, thermal-vac, random-vibration).
• License: national space agency approval, FCC experimental licence (US), UK Space Agency license, etc.

4. Subsystem matrix

Subsystem	Required	Allowed	Forbidden
OBC (STM32F446)	✅
EPS	✅	4-panel body-mounted
UHF beacon	✅
Magnetorquer ADCS		✅
GNSS		✅
Camera		⚠ (space tight)
S-band downlink			❌ (registry gate)
Reaction wheels			❌ (registry gate)
Propulsion			❌

The registry’s form-factor gate refuses to enable S-band or reaction wheels on a 1U — there is neither the volume nor the power budget to support them.

5. Build

make target-cubesat-1u

Compile-time macro: MISSION_PROFILE_CUBESAT_1U=1. Sets:

• PROFILE_FEATURE_SBAND=0
• PROFILE_FEATURE_WHEELS=0
• PROFILE_FEATURE_ADCS_ACTIVE=1 (magnetorquers only)
• PROFILE_FEATURE_ORBIT_PREDICTOR=1
• PROFILE_FEATURE_RADIATION=1

6. Mission config

cp mission_templates/cubesat_1u.json mission_config.json

Fields to review:

• orbit.altitude_km / inclination_deg — defaults 400 / 51.6° (ISS-like).
• subsystems.comm_uhf.frequency_mhz — ITU-coordinated amateur allocation.
• subsystems.adcs.tier — magnetorquer (enforced by registry).
• subsystems.payload.type — describe your experiment.
• ground_station.location — your antenna coordinates.

7. Mass & volume validation

With the default subsystem set:

Metric	Value	Status
Total mass	1.258 kg	≤ 1.33 kg ✅ (limited margin)
20 % margin	0.210 kg	included
Volume used	365 cm³	32 % of 1135 cm³ ✅

A 1U has very tight mass margin. Adding a camera typically requires dropping one solar panel and accepting a 10 % power cut.

8. Typical mission phases

Inherited from the cubesat_leo mission type:

startup → deployment → detumbling → nominal
               ↓ timeout / fault
             safe_mode ⇌ low_power
             science / comm_window (from nominal)

Entry points:

Phase	Trigger	Duration
startup	T+0 s after release	5 min
deployment	antennas open + body solar cells deployed	30 min
detumbling	B-dot controller reduces rates < 0.5 °/s	≤ 60 min
nominal	long-term operations	ongoing
safe_mode	beacon-only when ground contact lost > 24 h	until ack

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.

• Thermal-vacuum cycle: -20 °C to +60 °C, 3 cycles × 4 h, no faults.
• Random vibration 14 g-rms @ 20 Hz – 2 kHz, 3 axes × 2 min.
• Sine sweep 5 Hz – 100 Hz at 2 g, check structural resonances.
• EMC: conducted + radiated emissions per MIL-STD-461 E or equivalent.
• Deployment dry-run: antennas + solar panels release within 30 s of timer expiry.
• 48-hour soak test (UNISAT_SOAK_SECONDS=172800 pytest flight-software/tests/test_long_soak.py).
• End-to-end SITL mission (scripts/simulate_mission.sh mission_config.json).

10. Flight-day checklist

Spacecraft delivery to launch provider:

• All ICD-required signatures on airworthiness certificate.
• Flight key loaded; KeyRotationPolicy reports ok.
• Remove-before-flight pin installed and tagged.
• Battery charged to 80 % (long-duration storage floor).
• Ground-station tracking software loaded with the launch TLE.
• ITU frequency coordination confirmed in writing.

11. Known limitations

• No redundancy in OBC / EPS / comms — every subsystem is a single point of failure. Suitable for low-cost first missions, not high-reliability flights.
• Passive thermal control: the MLI + kapton heater handles eclipse / insolation swings but cannot respond to prolonged off-nominal attitude. Rely on ADCS to keep the sun-side within 30° of the solar panel normal.
• Magnetorquer-only ADCS: no 3-axis pointing, only detumble + sun-tracking. Any imaging payload is coarse (≥ 1° pointing jitter).
• No S-band: downlink ≤ 9.6 kbps UHF. Budget imagery accordingly.

12. Post-flight debrief

For CubeSats the “post-flight” is the whole mission: debriefs happen after each ground-station pass.

Per pass, capture:

• AX.25 downlink (PCAP in flight_logs/<date>_<pass>.pcap).
• Beacon parameters (voltage, temperature, fault log tail).
• Command log (which commands were sent, how many replies received).

Weekly summary:

• Orbit-average SoC trend (should trend up post-detumble, stable in nominal).
• Fault counts from FDIR telemetry (any escalation?).
• Reboot count from FDIR persistent meta (reboot-loop guard should read 0).

File monthly mission-status reports under docs/operations/flight_reports/.

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