Glossary

Terms and acronyms

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78 terms

Orbit and environment

ApPlanetary geomagnetic index: Daily measure of geomagnetic activity. Storms heat the upper atmosphere and raise drag; in the Kennewell model each unit of Ap adds 1.5 K to the exospheric temperature.
Ballistic parameterC_D·A/m: Drag coefficient times mean projected area over mass. A fully loaded 1P has 0.033 m²/kg, almost twice a 1U (0.018), so it decays about twice as fast. Its reciprocal is the ballistic coefficient m/(C_D·A).Encyclopedia entry
Beta angleβ: Angle between the Sun vector and the orbit plane. As β grows the eclipse shortens; beyond a threshold the satellite stays in sunlight for whole orbits.
Eclipse fractionf_e: Share of an orbit spent in Earth’s shadow: about 0.36–0.37 for a 500–550 km orbit at β = 0°, the worst case for power and the strongest thermal cycle.
F10.710.7 cm solar radio flux: Solar radio flux at 2.8 GHz in solar flux units (sfu), a proxy for the EUV that heats the thermosphere. It drives the density models; 70, 140 and 210 sfu are low, moderate and high activity on nadir lab..Encyclopedia entry
LEOLow Earth orbit: Orbits between about 160 and 2000 km. Almost all CubeSats and PocketQubes fly at 350–600 km, where atmospheric drag sets their lifetime.
NORAD IDSatellite catalogue number (SATCAT): Unique catalogue number of every tracked object, used as the key in TLEs and tracking software. Grizu-263A is NORAD 51025.
NRHONear-rectilinear halo orbit: A long-period halo orbit of the Earth–Moon L1/L2 family that passes over the lunar poles; CAPSTONE was the first spacecraft to fly one.
Scale heightH: Altitude change over which atmospheric density falls by a factor e. In the Kennewell model it is H = T/(27 − 0.012 (h − 200)) km, about 40–60 km at 400–550 km.
SGP4Simplified General Perturbations 4: Analytical propagator that turns a TLE into position and velocity, with J2–J4 zonal harmonics and a simplified drag term (B*).
SSOSun-synchronous orbit: A near-polar orbit whose plane precesses 360° per year through J2, so it keeps the same local solar time. At 525 km the inclination is about 97.5°.
TLETwo-line element set: Mean orbital elements of a tracked object in a fixed two-line format, meant to be propagated with SGP4. Their accuracy degrades for small, light objects.

Communications

AX.25Amateur packet-radio link-layer protocol: HDLC-framed link layer derived from X.25 that uses call signs as addresses; common for CubeSat telemetry.
BERBit error rate: Fraction of received bits in error. Without forward error correction it sets the frame loss of AX.25-type links directly.
DigipeaterDigital repeater: A store-and-forward relay that retransmits short packets uplinked by radio amateurs; Grizu-263A offered one.
Doppler shiftΔf = −f·ṙ/c: Frequency offset caused by the range rate between satellite and station; at 437 MHz from a 525 km orbit it reaches about ±10 kHz at the horizon.
Eb/N0Energy per bit to noise density: Normalized signal-to-noise ratio that sets the bit error rate: C/N0 minus the data rate in dB. Non-coherent FSK needs 13.4 dB for a BER of 10⁻⁵.Encyclopedia entry
EIRPEquivalent isotropically radiated power: Transmitter power minus line losses plus antenna gain, in dBW or dBm. Grizu-263A radiated 20 dBm (100 mW into a 0 dBi monopole).Encyclopedia entry
FSKFrequency-shift keying: Digital modulation that sends bits as discrete frequency shifts; non-coherent 2-FSK is simple and robust to Doppler, at a cost of about 3 dB against coherent BPSK.Encyclopedia entry
FSPLFree-space path loss: Geometric spreading loss, 20·log₁₀(4πd/λ). At 437 MHz and 951 km slant range it is 144.8 dB.
G/TGain-to-noise-temperature ratio: Figure of merit of a receiving station in dB/K: antenna gain minus 10·log₁₀ of the system noise temperature. A 13 dBic Yagi at 350 K gives −12.4 dB/K.Encyclopedia entry
GMSKGaussian minimum-shift keying: Continuous-phase binary FSK with Gaussian filtering; its narrow spectrum and constant envelope suit efficient non-linear amplifiers.
IARUInternational Amateur Radio Union: Coordinates frequencies for satellites in the amateur-satellite service, which must be non-commercial under the ITU Radio Regulations.Encyclopedia entry
LoRaLong Range chirp spread spectrum: Chirp spread-spectrum modulation that decodes below the noise floor at low data rates; FossaSat-1 tested it from a 1P. Doppler and ionospheric scintillation must be budgeted.
SatNOGSSatellite Networked Open Ground Station: Libre Space Foundation’s open network of volunteer ground stations and the open database of their observations, waterfalls and decoded telemetry.Encyclopedia entry
Turnstile antennaCrossed dipoles: Two perpendicular dipoles fed 90° apart, giving circular polarization over a wide beam.Encyclopedia entry

Power

BOL / EOLBeginning / end of life: Start and end of the mission; cell efficiency and battery capacity are lower at EOL because of radiation and cycling.
DoDDepth of discharge: Share of battery capacity used in one discharge. With about 5500 eclipses per year in LEO, a low DoD extends battery life markedly.Encyclopedia entry
MPPTMaximum power point tracking: Converter control that keeps the solar array at the point of its current–voltage curve where it delivers the most power.Encyclopedia entry
OAPOrbit-average power: Electrical power averaged over sunlight and eclipse. For body-mounted cells on a tumbling body it is S·η·p·(A_tot/4)·(1 − f_e): 0.55 W for a fully loaded 1P.Encyclopedia entry
Triple-junction cellInGaP/InGaAs/Ge: III-V solar cell grown on germanium with three stacked junctions, about 28–32% efficient. Germanium expands at 5.9 ppm/K, against 14–17 ppm/K for FR-4.Encyclopedia entry

Attitude

ADCSAttitude determination and control system: Sensors, actuators and algorithms that measure and control where a spacecraft points; the subsystem most constrained by PocketQube size, weight and power.Encyclopedia entry
B-dotm = −k·Ḃ: Detumbling law that commands a magnetic dipole opposing the measured rate of change of the field, removing rotational energy with only a magnetometer and magnetorquers.Encyclopedia entry
CoercivityH_c: Field needed to reverse a material’s magnetization. In dampers it trades despin speed (loss grows with H_c) against a residual dead band θ ≈ arcsin(H_c/H⊥).Encyclopedia entry
Demagnetizing factorN: Geometric factor relating a body’s internal field to its magnetization, H_i = H_a − N·M. A 45 mm, 1 mm rod has N ≈ 9.8 × 10⁻³; slender strips reach about 10⁻³.Encyclopedia entry
Detumbling: Removing the tip-off rates a spacecraft has after deployment, typically several degrees per second, before any pointing mode starts.Encyclopedia entry
Hysteresis rodSoft-magnetic damper: A slender soft-magnetic element (HyMu-80, mumetal, amorphous ribbon) that turns rotational energy into heat as the field along it cycles. In a 1P its loss is set by demagnetization and magnet bias.Encyclopedia entry
IMUInertial measurement unit: Accelerometer and gyroscope package, often with a magnetometer; near a PMAC magnet the magnetometer may saturate or read a millitesla bias.
MagnetorquerMTQ: A coil or rod electromagnet whose dipole produces torque m × B in the geomagnetic field; the only practical actuator for detumbling a PocketQube, sometimes printed in PCB layers.Encyclopedia entry
PMACPassive magnetic attitude control: A permanent magnet aligns one axis with the geomagnetic field and soft-magnetic hysteresis dampers dissipate rotational energy, with no power or software.Encyclopedia entry
Reaction wheel: A motor-driven flywheel that exchanges angular momentum with the spacecraft for fine three-axis pointing; the Unicorn-2 3P flies them.Encyclopedia entry
Residual dipole: Unintended magnetic moment of a spacecraft’s electronics, batteries and ferromagnetic parts. It does not shrink with size, so it dominates the disturbance torques of a 1P.Encyclopedia entry

Avionics and software

COTSCommercial off-the-shelf: Commercial parts not qualified for space; cheap and capable, with radiation behaviour managed by testing and architecture.
FDIRFault detection, isolation and recovery: On-board logic that detects anomalies, isolates the faulty unit and restores service, from watchdogs to safe modes.Encyclopedia entry
OBCOn-board computer: The processor that runs flight software, formats telemetry, executes commands and supervises the other subsystems.Encyclopedia entry
RTOSReal-time operating system: A kernel that schedules tasks deterministically; FreeRTOS and Zephyr are common on CubeSats.Encyclopedia entry
SEESingle-event effect: Instantaneous effects of a single charged particle: bit flips (SEU), latch-up (SEL) and functional interrupts (SEFI).Encyclopedia entry
SELSingle-event latch-up: High-current state of a CMOS device triggered through a parasitic thyristor; needs current limiting and a power cycle.Encyclopedia entry
SEUSingle-event upset: A bit changed in memory or a register by a particle strike; mitigated with EDAC, scrubbing and triple redundancy.Encyclopedia entry
TIDTotal ionizing dose: Ionizing dose accumulated by electronics over a mission, in krad(Si); it shifts thresholds and raises leakage currents.Encyclopedia entry

Thermal

MLIMulti-layer insulation: Stacked metallized films separated by low-conductance spacers that block radiative heat exchange.Encyclopedia entry
Thermal time constantτ = m c_p / (4 ε σ A T₀³): Time scale on which a lumped body follows its radiative environment: about 56 min for a fully loaded 1P against 104 min for a 1U, so the PocketQube swings harder through eclipse.Encyclopedia entry
TVACThermal vacuum: Test that cycles a unit between hot and cold plateaus in vacuum; Delfi-PQ was cycled four times between −20 and +50 °C.Encyclopedia entry

Materials

Atomic oxygenAO: The dominant species of the LEO thermosphere; it erodes exposed polymers at a rate set by their erosion yield (Kapton H: 3.0 × 10⁻²⁴ cm³ per atom).Encyclopedia entry
Cold welding: Solid-state adhesion of clean metal surfaces in vacuum once fretting or impact has broken their oxide films; a risk at deployer rails and contact faces.Encyclopedia entry
CTECoefficient of thermal expansion: Linear expansion per kelvin. Mismatch between joined materials, such as germanium cells (5.9 ppm/K) on FR-4 (14–17 ppm/K), fatigues solder joints over eclipse cycles.Encyclopedia entry
Fretting: Small-amplitude oscillatory sliding between clamped surfaces, as under launch vibration; it wears away protective films.Encyclopedia entry
Hard anodizingMIL-A-8625F Type III: Thick, hard porous oxide (typically 25–75 µm) grown on aluminium; required on PocketQube contact surfaces. About half the film grows outward, so parts are machined undersize.Encyclopedia entry
OutgassingTML · RML · CVCM: Release of water and volatiles from materials in vacuum. Screening accepts RML (or TML) below 1.0% and CVCM below 0.10% after 24 h at 125 °C.Encyclopedia entry
SCCStress-corrosion cracking: Intergranular cracking under sustained tension in a corrosive environment. ECSS-Q-ST-70-36C rates 7075-T6 as low resistance and 6061-T6 or 7075-T73 as high.Encyclopedia entry
Tin whiskers: Filamentary crystals that grow from pure-tin finishes under compressive stress and can short circuits; space specifications require at least 3% lead.Encyclopedia entry

Propulsion

IspSpecific impulse: Impulse per unit weight of propellant, in seconds; from 40–110 s for cold gas up to thousands of seconds for electric thrusters.Encyclopedia entry
PPTPulsed plasma thruster: Electric thruster that ablates a solid propellant such as PTFE with short discharges; sub-joule PocketQube versions gave impulse bits near 0.65 µN·s.Encyclopedia entry
Resistojet: Thruster that heats a propellant, often water, electrically before expanding it; TU Delft built MEMS micro-resistojets for very small spacecraft.Encyclopedia entry
ΔvVelocity change: Total velocity change a propulsion system can deliver, from the rocket equation Δv = Isp·g₀·ln(m₀/m_f). Holding a 1P at 400 km needs 42–241 m/s per year.Encyclopedia entry

Standards and interfaces

AlbaPodAlba Orbital PocketQube deployer: Deployer that clamps PocketQube backplates; the v2 version, printed in Windform XT 2.0, carries up to six units and weighs under 500 g.Encyclopedia entry
CDSCubeSat Design Specification: Cal Poly’s document defining CubeSat envelopes, mass limits, rails and test rules; Rev. 14.1 (2022) allows 2.00 kg per unit.Encyclopedia entry
ECSSEuropean Cooperation for Space Standardization: European space standards; the PocketQube Standard cites ECSS-Q-ST-70-36C (stress corrosion) and ECSS-Q-ST-70-02C (outgassing).Encyclopedia entry
Kill switch: Mechanical switches held open by the deployer that keep the spacecraft off until ejection; the PocketQube Standard requires at least two at the Z− end.Encyclopedia entry
P-PODPoly Picosatellite Orbital Deployer: The original spring-loaded tube deployer for three 1U CubeSats that set the rail interface of the CubeSat standard.Encyclopedia entry
PocketQube StandardIssue 1, 2018: Mechanical standard by Alba Orbital, TU Delft and GAUSS: a 50 mm cube of at most 250 g per unit, held by a 1.6 mm sliding backplate.Encyclopedia entry
PQ9PocketQube avionics interface: TU Delft’s lean subsystem bus for PocketQubes: RS-485 data and a few unregulated power lines instead of PC/104 stacks; flown on Delfi-PQ.Encyclopedia entry
RBFRemove before flight: A pin or jumper that keeps the spacecraft unpowered during handling and is removed before integration into the deployer.
Sliding backplate: The 1.6 mm plate (58 × 64 mm for a 1P) whose 2 mm edges are clamped by the deployer rails; the whole mechanical interface of a PocketQube.Encyclopedia entry

Launch and operations

AITAssembly, integration and test: The sequence from parts to a qualified flight model: bench, engineering-model, thermal-vacuum and vibration tests.Encyclopedia entry
Five-year ruleFCC 22-74: FCC requirement (2022) that US-licensed LEO satellites leave orbit within five years of mission end. A 1P meets it by total lifetime below about 560 km at moderate activity.Encyclopedia entry
OTVOrbital transfer vehicle: A free-flying carrier, such as D-Orbit’s ION, that releases satellites after the rideshare; it carried every PocketQube launched in 2023.Encyclopedia entry
Rideshare: A launch shared by many payloads, such as SpaceX Transporter missions; it made PocketQube launch prices of about 20 k€ per 1P possible.Encyclopedia entry