unisat

HAB Payload — Operations Guide

Profile key (medium): hab_payload_medium · Mass cap: 2.0 kg · Volume: 6000 cm³ Template: mission_templates/hab_standard.json ·

Also covers hab_payload_small (1.0 kg, 2250 cm³) and hab_payload_large (5.0 kg, 18000 cm³). Pick the size that matches your balloon envelope + lifting gas.

1. Mission class

High-altitude-balloon (HAB) payload for educational / citizen- science flights. Typical mission profile: launch with a latex or mylar envelope, ascend at ~5 m/s to ~30 km, burst, descend under a parachute, recover 100–300 km downwind.

2. Physical envelope

Parameter	Small	Medium	Large
Mass cap	1.0 kg	2.0 kg	5.0 kg
Dimensions (mm)	150×150×100	200×200×150	300×300×200
Volume (cm³)	2250	6000	18000
Generation	0.5 W (small solar cell)	1 W	2.5 W
Consumption	1.5 W	3 W	6 W

3. Regulatory context

FAA Part 101 (USA): ≤ 6 lb / 2.7 kg per payload; ≤ 12 lb total; notify FSS 24 h before launch. Payload cord < 50 lb breaking strength.
EASA equivalent: UK CAA Article 166 (≤ 2 kg payload), EU EASA NfL (light unmanned balloons).
Radio: UHF 434 MHz or ISM 868 MHz for LoRa; APRS 144.39 MHz requires a licensed operator; amateur radio call-sign in beacon.
Airspace: notify local ATC for controlled airspace transits.

4. Subsystem matrix

Subsystem	Status
OBC	✅
Barometer (MS5611)	✅
GNSS	✅
UHF RTTY / LoRa	✅
APRS (licensed op.)	⚠
Camera (wide-angle)	✅
Environmental sensors (temp, humidity, UV, radiation)	✅
IMU	⚠ (optional)
ADCS	❌
Descent controller	❌ (passive parachute only)

5. Build

make target-hab-medium          # default for 2.0 kg envelope
# or configure small / large manually:
# cmake -B firmware/build-arm-hab-small -S firmware \
#       -DCMAKE_C_FLAGS=-DMISSION_PROFILE_HAB_PAYLOAD_SMALL=1

Compile-time macro: MISSION_PROFILE_HAB_PAYLOAD_MEDIUM=1 (or _SMALL / _LARGE).

6. Mission config

cp mission_templates/hab_standard.json mission_config.json

Key fields:

mission.competition.target_altitude_m — typical 30 000 m.
mission.competition.expected_ascent_rate_m_s — typical 5.
subsystems.comm_uhf.frequency_mhz — 434 MHz RTTY or 868 / 915 MHz LoRa.
subsystems.comm.aprs.callsign — YOUR licensed call-sign.
satellite.form_factor — hab_payload_small/medium/large depending on chosen size.

7. Mass & volume validation

Per form-factor (ALL_ENABLED subset relevant for HAB):

Size	Typical loaded mass	Limit	Volume used / total
Small	0.82 kg	1.0 kg	270 / 2250 cm³
Medium	1.45 kg	2.0 kg	475 / 6000 cm³
Large	2.90 kg	5.0 kg	850 / 18000 cm³

8. Typical mission phases

ground_setup → ascent → float → burst → descent → landed

Phase	Typical duration	Notes
`ground_setup`	30 min	Balloon inflation + checklist
`ascent`	90–180 min	~5 m/s nominal
`float`	0–120 min	Only if balloon is zero-pressure
`burst`	2–10 s	Sudden pressure spike
`descent`	30–90 min	~30 m/s initial, decreasing
`landed`	until recovery	Downlink GPS for chase team

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.

Cold test: place payload in freezer at -55 °C for 2 h. OBC continues to log.
Battery (Energizer Ultimate Lithium, -40 °C rated) survives 6 h at -40 °C without voltage sag.
GNSS retains fix through simulated stratospheric altitude by enabling “airborne < 1g” mode.
Telemetry link closes at 50 km slant range with a yagi on ground.
Camera SD card survives 6 h of -40 °C operation.
Pressure sensor reads 5 mbar ± 0.5 mbar at 30 000 m equivalent altitude in a vacuum chamber.

10. Flight-day checklist

FAA / CAA notification filed.
Chase team briefed on predicted landing zone (run APRS.fi flight predictor).
Helium / hydrogen tank pressure + valve checked.
Parachute attached to cord; cord to balloon via break-away line.
Payload battery voltage logged before sealing insulation.
Telemetry received by two independent ground stations for 15 min before release.
KeyRotationPolicy reports ok on ground console (ISM 868 / 915).

11. Known limitations

Thermal: inside the payload box the temperature swings from +30 °C (launch on sunny day) to -60 °C (tropopause) and back. Use foam insulation + chemical warmer if running low-temperature sensitive components.
GNSS “airborne mode”: consumer u-blox modules default to a max altitude of 12 km; the MAX-M10S accepts a dynamic model switch — issue it during ground_setup.
No active attitude control: payload spins randomly. Camera footage is shaky; panoramic photography requires a gimbal or a dedicated rotation-compensated mount.

12. Post-flight debrief

Capture:

GNSS ground track (upload to aprs.fi / habhub.org).
On-board pressure / temperature / UV / radiation CSV.
Camera SD card (wide-angle video + stills at 30 s interval).
Any damage on recovery (battery voltage, antenna integrity).

Publish:

Landing-point prediction accuracy (predicted vs. actual).
Burst altitude vs. balloon spec.
Science-payload results (photo processing, radiation profile, etc.).

File a flight report in docs/operations/flight_reports/.

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