unisat

CanSat Minimal — Operations Guide

Profile key: cansat_minimal · Mass cap: 350 g · Volume: 226 cm³ Template: mission_templates/cansat_minimal.json · BOM: hardware/bom/by_form_factor/cansat_minimal.csv

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1. Mission class

A pared-down CanSat for first-time teams, school programmes, and educational outreach. No GNSS, no camera, no deployable payload — just the four sensors needed to describe a free-fall descent: accelerometer, gyro, barometer, and a UHF beacon.

Typical flight profile: released at ~500 m from a small rocket or drone, descends under a single parachute, transmits telemetry until landing.

2. Physical envelope

Parameter	Value
Mass (with 20 % margin)	≤ 350 g
Outer diameter	60 mm
Inner (usable) dia.	56 mm (2 mm wall)
Height	80 mm
Internal volume	226 cm³
Power generation	0 W (battery-only)
Nominal consumption	0.6 W
Battery	1× 18650 LiPo, ~2.5 Wh

3. Regulatory context

• Educational CanSat (looser than ESERO) — no mandatory rulebook.
• Radio: ISM 433 MHz LoRa module, ≤ 100 mW ERP. No licence required in EU / US / CIS for this band/power.
• Airspace: launch vehicle (rocket or drone) must comply with local aviation authority; the CanSat itself has no airspace burden below 500 m AGL.

4. Subsystem matrix

Subsystem	Required	Allowed	Forbidden
OBC (STM32F446)	✅
EPS (LiPo + regulator)	✅
IMU (MPU-6050 class)	✅
Barometer	✅
UHF 433 MHz telemetry	✅
Descent controller	✅	passive parachute
GNSS		⚠ (adds 40 g)
Camera			❌ (volume)
ADCS			❌ (no attitude control on CanSat)
S-band			❌ (no range benefit)

5. Build

make target-cansat-minimal
# produces firmware/build-arm-cansat-minimal/unisat_firmware.elf
# or a host binary if arm-none-eabi-gcc is absent

The compile-time macro is MISSION_PROFILE_CANSAT_MINIMAL=1. See firmware/stm32/Core/Inc/mission_profile.h for the full expansion. All orbital features (PROFILE_FEATURE_ORBIT_PREDICTOR, SBAND, IMAGERY, ADCS_ACTIVE, WHEELS) are 0; the DESCENT_CTRL gate is 1.

6. Mission config

cp mission_templates/cansat_minimal.json mission_config.json

Minimum fields to review and adjust:

• mission.operator — your team name.
• mission.competition.name — the event you are entering.
• subsystems.comm_uhf.frequency_mhz — pick a channel in the 433.05–434.79 MHz band that is free at your launch site.
• ground_station.location — coordinates of the launch pad (defaults to 0,0).

The configurator UI can generate the same file interactively:

make configurator
# Platform → "CanSat" → Form Factor → "cansat_minimal"

7. Mass & volume validation

Expected output from the validator with the default subsystem set (obc, imu, barometer, comm_uhf, descent_controller):

Metric	Value	Status
Total mass	0.288 kg	≤ 0.35 kg ✅
20 % margin	0.048 kg	included
Total volume	89 cm³	≤ 226 cm³ ✅
Utilization	39 %	plenty of headroom

If adding a GNSS module pushes the result over budget, disable the camera placeholder or drop to a 14500-cell battery.

8. Typical mission phases

The mission_types registry (flight-software/core/mission_types.py) defines these for cansat_standard; cansat_minimal inherits them:

pre_launch  →  launch_detect  →  ascent  →  apogee  →  descent  →  landed

Each phase gates which modules are active:

Phase	Active modules	Duration
pre_launch	telemetry, health, imu, barometer	until launch ARM
launch_detect	imu (accel threshold 3 g), barometer	≤ 10 min
ascent	+ data_logger @ 10 Hz	≤ 2 min
apogee	+ descent_controller (eject parachute)	≤ 30 s
descent	full telemetry, high-rate logging	≤ 5 min
landed	telemetry + comm only (conserve battery)	≤ 1 h

9. Testing checklist (bench)

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.

• make target-cansat-minimal completes with no warnings.
• ./scripts/verify.sh is green.
• Ground station receives telemetry on the chosen 433 MHz channel at ≥ -110 dBm.
• IMU detects a simulated 3 g launch event and transitions pre_launch → launch_detect in the SITL harness.
• Barometer reads pressure within ± 1 hPa of a reference device.
• Descent-controller fires within 50 ms of apogee detection (SITL-injected pressure profile).
• Battery survives 90 minutes of continuous operation on a single charge.
• Watchdog feeds for 30 minutes with no missed periods (check CommandDispatcher_GetStats).

10. Flight-day checklist

• Battery > 90 % charged.
• Configurator-generated mission_config.json flashed.
• Correct UHF channel programmed.
• Parachute folded and restraint verified.
• Ground station tracking the beacon for ≥ 5 min before integration.
• Arm switch in SAFE position until just before release.
• Ground-side clock synchronised with OBC within ± 1 s.
• HMAC key loaded; key_rotation policy reports ok (see ground-station/utils/key_rotation.py).

11. Known limitations

• No GNSS in the default BOM — position recovery relies on visual tracking + RF direction-finding.
• Single IMU (no redundancy) — an MPU-6050 failure ends the mission.
• No camera — descent video is not available on this profile. Upgrade to cansat_advanced for a 5 MP camera.
• ISM 433 MHz at 100 mW gives ≤ 5 km range in line-of-sight conditions; not suitable for stratospheric-balloon deployments.

12. Post-flight debrief

Capture and archive:

1. Full AX.25 ground-station capture (.bin + timestamp) under flight_logs/<YYYY-MM-DD>/.
2. On-board CSV log from the data_logger module (pull over USB post-recovery).
3. Photographs of any visible damage to the structure / electronics.
4. Completed flight-day checklist with any deviations noted.
5. Lessons-learned summary — file under docs/operations/flight_reports/.

Data to analyse:

• Launch-detect latency (ascent - pre_launch timestamp delta).
• Peak acceleration / angular rate during ascent and at apogee.
• Descent-rate profile (should be 5–12 m/s per the configured limits).
• Telemetry coverage (% packets received vs. expected at 5 Hz).

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