Satellite Development¶
Last updated: 2026-04-10
Last updated: 2026-04-11
Focus: small satellites (CubeSat, microsat), LEO missions, on-board software.
Recent Finds¶
Model-Based ADCS Design-to-Verification for INHA RoSAT 3U CubeSat (MDPI Aerospace, Feb 2026)¶
Reusable end-to-end ADCS pipeline: algorithm design in Simulink → simulation → automatic C code generation → integration into flight software, bypassing manual C coding entirely. Validated on INHA RoSAT, a 3U CubeSat with rollable solar panels to overcome the chronic power constraint of standard body-mounted cells. The paper's contribution is a verified MBD (model-based design) framework applicable to any team building ADCS from scratch — the verification framework is the deliverable, not just the algorithm. Key practical note: the Simulink-to-C path requires careful fixed-point arithmetic configuration to avoid numerical drift on embedded targets.
LeLaR: First In-Orbit AI Attitude Controller via Deep Reinforcement Learning (arXiv 2512.19576)¶
Landmark result: a DRL controller trained entirely in simulation was deployed to InnoCube (3U nanosatellite, launched Jan 2025) and successfully commanded reaction wheels in orbit on October 30, 2025 — the first confirmed in-orbit AI attitude control demonstration. Sim2Real transfer worked without any fine-tuning in orbit. The training domain randomized over inertia tensor uncertainty, actuator noise, magnetic disturbances, and thruster faults. Implication: DRL-trained attitude controllers may eventually replace hand-tuned EKF + PID stacks for ADCS in CubeSats, especially for missions with uncertain or time-varying inertia (deployable structures, fuel slosh). Open question: how does it perform during detumble (high angular rates post-deployment), where classical B-dot controllers are most reliable?
CubeSat Standard¶
Unit (U) = 10×10×10 cm, ~1.33 kg max. Common form factors: 1U, 2U, 3U, 6U, 12U.
1U CubeSat mass budget (~1.3 kg):
- Structure + panels: 0.3 kg
- EPS + batteries: 0.3 kg
- OBC + comms: 0.2 kg
- ADCS: 0.2 kg
- Payload: 0.3 kg
Subsystems¶
| Subsystem | Acronym | Function |
|---|---|---|
| Electrical Power System | EPS | Solar panels, battery, power regulation/distribution |
| On-Board Computer | OBC | Central processor, data handling, software |
| Communications | COMMS | RF transceiver, antenna deployment |
| Attitude Determination & Control | ADCS | Orientation sensing + control (magnetorquers, reaction wheels) |
| Thermal Control | TCS | Passive (coatings) or active (heaters) |
| Structure | STR | Mechanical frame, deployment mechanism |
| Payload | PL | Mission instrument (camera, spectrometer, SDR...) |
EPS Architecture¶
- MPPT (Maximum Power Point Tracking) — extracts max power from solar cell I-V curve
- Battery: typically Li-ion or LiFePO4 — must survive LEO thermal cycles (-40°C to +80°C)
- Power budget: 1U gets ~2–5W average orbital power
ADCS Basics¶
Determination (where am I pointing?): - Magnetometer → magnetic field vector - Sun sensor → sun direction - Gyroscope → angular rate - Star tracker → precision pointing (expensive)
Control (change my pointing): - Magnetorquers — coils generate torque against Earth's B-field. Simple, low power, slow. - Reaction wheels — momentum exchange. Faster, needs desaturation via magnetorquers. - Thrusters — active orbit control, rare in CubeSats (cold gas, electrospray)
Modes: 1. Detumble — kill post-deployment tumble with B-dot controller 2. Nadir pointing — always face Earth 3. Sun pointing — maximize power during eclipse recovery 4. Target pointing — point payload at target
On-Board Software¶
Architecture Patterns¶
Monolithic RTOS (most CubeSats): - FreeRTOS / ChibiOS / RTEMS - Tasks: EPS monitor, ADCS loop, comms handler, payload manager - Simple, deterministic, easy to certify
Linux-based (larger small sats, payload-heavy): - Yocto/Buildroot custom image - Run ML inference (TFLite/NCNN) on payload processor - More complex reliability story (kernel panics, filesystem corruption)
Fault Tolerance Patterns: - Watchdog timers — hardware kicks OBC if software hangs - Safe mode — minimal power draw when anomaly detected - Command & Data Handling (C&DH) — centralized state machine - Triple Modular Redundancy (TMR) — vote among 3 results for critical decisions
Key Open Source Flight Software¶
| Framework | Language | Notes |
|---|---|---|
| NASA cFS (core Flight System) | C | NASA open-source, POSIX + RTOS, production-used |
| FPrime | C++/Python | JPL-developed, component-based, used on Mars Ingenuity |
| OpenSatKit | Ruby/C | cFS-based toolkit with GCS |
| LibCSP | C | CSP protocol stack, runs on bare metal + Linux |
| SatOS (EnduroSat) | C | Commercial, free for non-profit |
NASA cFS is the gold standard open-source FSW framework. Steep learning curve but production-proven.
Common OBC Hardware (Open Source / COTS)¶
| Board | CPU | OS | Notes |
|---|---|---|---|
| GomSpace NanoMind | ARM | FreeRTOS | Industry standard |
| ISIS iOBC | ARM9 | Linux/FreeRTOS | Common in 3U+ |
| Raspberry Pi CM4 (for payload) | ARM Cortex-A72 | Linux | High performance, thermal challenge |
| STM32-based custom | ARM Cortex-M | FreeRTOS | DIY, good learning platform |
Orbit Mechanics (LEO Basics)¶
Typical LEO: 400–600 km altitude, ~90–95 min period.
Key parameters: - Semi-major axis (a): orbital size - Eccentricity (e): 0 = circular, <0.1 for LEO - Inclination (i): angle to equatorial plane. Sun-synchronous: ~97° - RAAN: Right Ascension of Ascending Node — where orbit crosses equator northbound
Sun-Synchronous Orbit (SSO): - Precesses ~0.9856°/day to match Earth's orbit around Sun - Same local solar time over every pass → consistent lighting for imaging - ~96-100° inclination depending on altitude
Ground Track Coverage: - Single LEO sat: ~10 min pass window, revisit ~14×/day globally - Constellation needed for continuous coverage
Tools: STK (AGI), GMAT (NASA open-source), Orekit (Java), Poliastro (Python)
Licensing & Regulation¶
- ITU frequency coordination — must file for frequency allocation before launch. 2–3 year process.
- FCC (US) or national regulator — need license to operate transmitter.
- ITAR/EAR — US export controls apply to satellite components and software.
- Debris mitigation — LEO satellites must deorbit within 5 years (per new FCC rule, IADC 25-year guideline still common).
Open Questions¶
- What's the realistic cost breakdown for a 3U CubeSat mission end-to-end (hardware + launch + ops)?
- How does on-board ML inference (NCNN/TFLite) fare under space radiation — bit flips, latch-up?
- What's the maturity of inter-satellite links (ISL) for small constellation coordination?
- Electrospray thrusters — are they reliable enough for CubeSat propulsion in 2026?