Terms and acronyms used across THHOR-BOLT documentation. When in
doubt, check here first.
For deeper-than-a-definition treatment, follow the linked
documents.
Term
Definition
THHOR TUHH Orbital Research
HST Hamburg Space Team, the umbrella student organisation
THHOR-BOLT This project: Beamed Optical Light Transmission demonstrator on REXUS 37
REXUS Rocket EXperiments for University Students; suborbital sounding-rocket programme operated by DLR and SSC
REXUS 37 The specific REXUS flight THHOR-BOLT is manifested on, planned for Q1 2027 from Esrange Space Center, Sweden
THHOR-HANS A follow-on satellite mission that consumes BOLT's results
REXUS User Manual The operational and interface specification document maintained by the REXUS programme
Term
Definition
SDR Student Application Document, the entry-level proposal review
PDR Preliminary Design Review
CDR Critical Design Review
IPR Integration Progress Report
EAR Experiment Acceptance Review
Term
Definition
BTC Bifröst Test Controller. STM32L476-class master controller and downlink gateway
EXP1 "Space Disco" -- spectral characterisation experiment
EXP2 "Bouncy Castle" -- bit-error-rate experiment with floating particles
EXP3 "Floaty Boi" -- wireless power + LiFi demonstration with magnetometer comparison
RXI REXUS Interface; the bulkhead and structural interface to the rocket
RXSM REXUS Service Module; provides power, discrete signals, and the PCM downlink path
Wired Stack EXP3 sensor PCB powered and signalled over cable plus LiFi A
Wireless Stack EXP3 sensor PCB powered through a solar cell + supercapacitor, signalled over LiFi B
Term
Definition
LO Lift-Off discrete signal from RXSM; defines t = 0 for the science timeline
SODS Start of Data Storage discrete signal from RXSM
SOE Start of Experiment discrete signal from RXSM
T-, T+ Time before (T-) or after (T+) the LO event
tick The 25 Hz, 40 ms cycle that drives every flight controller
science window The ~600 s interval around apogee where useful microgravity science is collected
Term
Definition
FlightComputer Abstract base class that owns the 40 ms tick loop and PacketBuilder
NodeComputer Intermediate base class that adds the sensors and SD shared by every node
BtcComputer Concrete class running on the BTC
ExpComputer Abstract CAN-slave framework shared by Exp1/2/3
Platform Function-pointer abstraction over delay/tick/watchdog/LED primitives, makes host testing possible
on_tick() Pure virtual hook called once per 40 ms; implements per-controller behaviour
on_init() One-shot initialiser called before the tick loop
PacketBuilder Producer that writes a downlink packet into a caller-owned buffer
GAP_MARKER Special downlink packet that flags a known on-board failure or missed slot
BOOT packet Sent at startup, carries reset reason and reboot count
Design Principles and Invariants
Term
Definition
P-1 ... P-4 The four design principles in docs/standards/system-invariants.md
I-1 ... I-7 The seven testable invariants that operationalise the principles
Three-strike rule A sensor is permanently disabled after 3 consecutive read failures
Autonomous mode An experiment controller's fallback after 5 missed CAN SYNC frames (200 ms)
Term
Definition
CAN Controller Area Network; BTC <-> experiments at 1 Mbit/s (ICD-002 )
RS-422 The differential serial link from BTC to RXSM (ICD-001 )
I2C / I2C Inter-Integrated Circuit; Fast Mode (400 kHz) sensor bus (ICD-005 )
UART Universal Asynchronous Receiver/Transmitter; used for LiFi transceiver links
SDMMC STM32 peripheral that drives the microSD card in 4-bit mode at 16 MHz
SYNC packet CAN broadcast at 25 Hz from BTC carrying the current tick value
Term
Definition
LittleFS Power-fail-safe filesystem used on every microSD (ADR-003 )
log.bin The per-controller append-only LittleFS log file
Ringbuffer Producer-consumer RAM buffer between on_tick() and SdStore (ADR-004 )
.noinit Linker section in SRAM that survives software resets (ADR-008 )
Term
Definition
MS5611 Pressure + temperature sensor, I2C 0x77
TMP117 Precision temperature sensor, I2C 0x48
ICM-42686-P +-32 g / +-2000 dps IMU on BTC and EXP3 controllers
ICM-42688-P +-32 g / +-2000 dps IMU on EXP3 stacks (different part, similar interface)
AS7265X 18-channel spectrometer on EXP1, I2C 0x49
MMC5983MA Magnetometer on the EXP3 stacks
LP5810 LED driver IC, two instances on EXP1 (C at 0x14, D at 0x15)
STM32L476RGT6 Main MCU on BTC, EXP1, EXP2, EXP3
STM32U031F8 Small MCU on the LiFi transceivers and EXP3 stacks
VBPW34S Photodiode used on the LiFi transceiver receive side
Term
Definition
HIL Hardware-in-the-Loop test platform, see bolt-thhor-hil
clang-tidy Static analyser; runs on every PR and targets HIC++ compliance
clang-format Code formatter; the team-standard style
Catch2 Host-side unit test framework
HIC++ High Integrity C++; the coding standard we adapt for flight code
Term
Definition
sensor-api The bridge that decodes packets and serves SSE to the dashboard
sensor-dashboard The React + Vite frontend used by operators
SSE Server-Sent Events; how live packets reach the dashboard
PCM Pulse Code Modulation; the REXUS-side RF chain that carries our downlink
Term
Definition
ADR Architecture Decision Record; one decision, one document, one PR
ICD Interface Control Document; the contract between two parties
CDR document The CDR LaTeX source under docs/cdr/