unisat

CubeSat 2U — Operations Guide

Profile key: cubesat_2u · Mass cap: 2.66 kg · Volume: 2270 cm³ Template: mission_templates/cubesat_2u.json · BOM: hardware/bom/by_form_factor/cubesat_2u.csv

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1. Mission class

First CubeSat size that fits an 8 MP imaging payload, an S-band downlink, and a 3-channel magnetorquer stack comfortably. Sweet spot for universities that want to upgrade from educational 1U missions to a meaningful science / Earth-obs demonstration.

2. Physical envelope

Parameter	Value
Mass cap	2.66 kg
Dimensions	100 × 100 × 227.0 mm
Volume	2270 cm³
Power generation	~5.0 W orbit-average
Nominal consumption	4.0 W
Battery	4× 18650 Li-ion, ~40 Wh

3. Regulatory context

• CDS rev 14 §3.1 — same dimension/mass contract as 1U/1.5U.
• ITU coordination: UHF amateur band and S-band 2.4 GHz (licence required, NOT amateur-only).
• US FCC Part 25 (commercial) or Part 97 (amateur), depending on payload.

4. Subsystem matrix

Subsystem	Status on 2U
Magnetorquer ADCS	✅ (3 axes)
Reaction wheels	❌ (gate: needs 3U)
UHF telemetry	✅
S-band downlink	✅ (first allowed)
GNSS	✅
Camera (8 MP)	✅
Payload module	✅
Propulsion	❌

5. Build

make target-cubesat-2u

Compile-time macro: MISSION_PROFILE_CUBESAT_2U=1. S-band gate is enabled (PROFILE_FEATURE_SBAND=1).

6. Mission config

cp mission_templates/cubesat_2u.json mission_config.json

Edit as for 1.5U, plus:

• subsystems.comm_sband.frequency_mhz — your coordinated channel (typical 2400 MHz).
• subsystems.camera.resolution_mp — match your optical chain.
• mission.telemetry_hz — 1.0 Hz is reasonable; 2 Hz requires S-band.

7. Mass & volume validation

Metric	Value	Status
Total mass	2.30 kg	≤ 2.66 kg ✅ (14 % margin)
Volume used	735 cm³	32 % of 2270 cm³ ✅

8. Typical mission phases

Same cubesat_leo / cubesat_sso profile as 1U/1.5U. With S-band enabled, the comm_window phase becomes more interesting: image downlink happens in discrete windows when ground tracks the pass.

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.

Same as 1.5U plus:

• S-band end-to-end link budget verified on a 2 m range with a 1.2 m parabolic dish (expected SNR ≥ 10 dB).
• Image pipeline (imagery_pipeline feature flag) processes 100 frames at 10 fps without drop.
• Camera temperature stays within 5 °C of the OBC temperature during capture burst.

10. Flight-day checklist

Same as 1.5U plus:

• S-band ground antenna pointed within 3° of first expected pass.
• TLE < 72 hours old.

11. Known limitations

• Still no reaction wheels — attitude pointing from magnetorquers alone is typically ≥ 2° jitter. Not suitable for narrow-field science imaging.
• Battery charge during full S-band transmit can go negative under worst-case eclipse — budget a duty cycle of ≤ 15 % per orbit.
• No propulsion — orbit decay is unavoidable; plan for a 2-year natural decay from 550 km SSO.

12. Post-flight debrief

Same as 1.5U plus image-downlink analytics: measured BER on S-band, frames received per pass, average pass duration.

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