CubeSat
Also known as Cube satellite, U-class spacecraft
Nanosatellite standard built from 10 cm units (U). Cal Poly’s CubeSat Design Specification defines the envelope, mass and centre-of-mass limits, rails and separation switches from 1U to 12U.
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- SQ-FF-002
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Definition
A CubeSat is a nanosatellite built from cubic units of about 10 cm, written "U". The standard says almost nothing about the inside of the spacecraft. It specifies the interface with the launcher: the external envelope, mass and centre-of-mass limits, the rails that touch the deployer, the separation switches and the timers that keep the spacecraft silent and folded until it is clear of the rocket[1]. Because that interface is common, a CubeSat can fly in any compatible deployer of its size without changing the primary payload.
History
Jordi Puig-Suari of California Polytechnic State University and Robert J. Twiggs of Stanford University proposed the standard in 1999, as a platform on which students could design, build and launch a satellite within a degree programme[2]. Cal Poly developed the Poly Picosatellite Orbital Deployer (), a spring-loaded tube for three 1U units that became the model for every later deployer[3].
The first CubeSats were launched from Plesetsk on a Rockot on 30 June 2003. One of them, the University of Tokyo’s XI-IV, is still listed as operational in the database in 2026[4]. In the following two decades CubeSats became carriers for commercial Earth-observation constellations, science missions and deep-space demonstrations: in 2018 the two 6U MarCO spacecraft relayed InSight’s landing on Mars almost in real time, the first interplanetary CubeSat mission[5], and in 2022 the 12U CAPSTONE became the first spacecraft to enter a near-rectilinear halo orbit around the Moon.
The early years were also a lesson in reliability. A large share of the first hundred CubeSats failed early, many of them in the first days, which showed that cheap and fast development carries its own risks[6]. Statistical studies traced most early failures to the power and communication subsystems and to insufficient system-level testing[7].
Size family
The base unit is 1U. The 1.5U, 2U and 3U sizes grow along the long axis; 6U and 12U are double-row structures that also widen the cross-section. The CubeSat Design Specification Rev. 14.1 defines mass and centre-of-mass limits from 1U to 12U. Fractional sizes such as 0.25U and 0.5U, and larger structures from 16U up, are outside the document; their interface is set by the deployer provider[1].
CubeSat and PocketQube
The PocketQube grew out of the same community and keeps the same philosophy at half the edge length[8]:
| Attribute | 1U CubeSat | 1P PocketQube |
|---|---|---|
| Governing document | CubeSat Design Specification Rev. 14.1 | PocketQube Standard, Issue 1 |
| External envelope | 100 × 100 × 113.5 mm | 50 × 50 × 50 mm |
| Volume / external surface | 1135 cm³ / 654 cm² | 125 cm³ / 150 cm² |
| Maximum mass per unit | 2.00 kg | 0.25 kg |
| Maximum bulk density | 1.76 g/cm³ | 2.00 g/cm³ |
| Deployer interface | Four rails | Sliding backplate |
| Avionics interconnect | PC/104-derived stacks (de facto) | PQ9/CS14 proposed; otherwise vendor-specific |
Dimensions and mass
| Size | Envelope (mm) | Volume (cm³) | Mass limit (kg) | Deployers |
|---|---|---|---|---|
| 1U | 100 × 100 × 113.5 | 1,135 | 2.00 | P-POD, ISIPOD, NRCSD, EXOpod |
| 1.5U | 100 × 100 × 170.2 | 1,702 | 3.00 | P-POD, ISIPOD |
| 2U | 100 × 100 × 227 | 2,270 | 4.00 | P-POD, ISIPOD |
| 3U | 100 × 100 × 340.5 | 3,405 | 6.00 | P-POD, ISIPOD, NRCSD |
| 6U | 226.3 × 100 × 366 | 8,283 | 12.00 | 6U dispensers (e.g. CSD, EXOpod) |
| 12U | 226.3 × 226.3 × 366 | 18,743 | 24.00 | 12U dispensers |
PocketQube Standard Issue 1 (2018); CubeSat Design Specification Rev. 14.1 (2022). The 2P length is indicative.
The long-axis dimension is the envelope including the rail standoffs: the 113.5 mm of a 1U are the 100 mm structure plus the rail ends. The mass limits of Rev. 14.1 are typical maxima; heavier designs can be accepted with the launch provider’s agreement. The 1U limit rose from 1.33 kg in earlier revisions to 2.00 kg, which matters for every scaling comparison: at 1.33 kg a 1U has a bulk density of only 1.33 g/cm³[1].
Centre of mass
The centre of mass must lie within the following distances of the geometric centre, so that the spacecraft does not bind in the rails and leaves the deployer with a small tip-off rate[1].
| Size | X | Y | Z |
|---|---|---|---|
| 1U | ±2 cm | ±2 cm | ±2 cm |
| 1.5U | ±2 cm | ±2 cm | ±3 cm |
| 2U | ±2 cm | ±2 cm | ±4.5 cm |
| 3U | ±2 cm | ±2 cm | ±7 cm |
| 6U | ±4.5 cm | ±2 cm | ±7 cm |
| 12U | ±4.5 cm | ±4.5 cm | ±7 cm |
Interface requirements
| Topic | CDS Rev. 14.1 requirement |
|---|---|
| Rails | At least 8.5 mm wide from the edge to the first protrusion; surface roughness below 1.6 µm recommended |
| Rail material | Aluminium surfaces in contact with the deployer hard anodized against cold welding |
| Separation switch | At least one; disconnects the power system from all loads while the spacecraft is in the deployer |
| Remove-before-flight pin | Cuts all power while inserted; protrudes no more than 6.5 mm from the rail surface |
| Deployables | May deploy no earlier than 30 minutes after separation |
| Radio transmission | May start no earlier than 45 minutes after separation |
Deployers
| Deployer | Developer | Notes |
|---|---|---|
| P-POD | Cal Poly | The original 3U-capacity tube |
| ISIPOD | ISISPACE | 1U–3U spacecraft |
| NRCSD | NanoRacks | Release from the International Space Station |
| CSD | Planetary Systems Corporation, now Rocket Lab | Tab-and-clamp "canisterized" interface instead of rails |
| EXOpod | Exolaunch | Common on rideshare launches |
Mass and volume
Mass is the earliest and hardest constraint in choosing a form factor. Inside a 2 kg 1U, what remains for the payload after structure, power and radio is a few hundred grams. Saving mass is not always a gain: a lighter spacecraft has a higher and comes down sooner.
Power
With body-mounted cells and a random tumble, Eq. 1 of the PocketQube review gives the orbit-average power of fully loaded CubeSats[8]:
| Form factor | Surface (cm²) | Mean projected area (cm²) | Mean in sunlight (W) | Orbit average (W) | Specific power (W/kg) |
|---|---|---|---|---|---|
| 1U | 654 | 163.5 | 3.74 | 2.39 | 1.20 |
| 2U | 1,108 | 277.0 | 6.33 | 4.05 | 1.01 |
| 3U | 1,562 | 390.5 | 8.93 | 5.71 | 0.95 |
| 6U | 2,841 | 710.3 | 16.24 | 10.39 | 0.87 |
Eq. 1 of the review: solar constant 1361 W/m², triple-junction cells with η = 0.28, packing factor 0.6.
Deployable, Sun-pointed arrays raise these values several times, at the price of attitude control, hinges and release mechanisms, each a single point of failure.
Launch safety
Separation switches, the remove-before-flight pin and the timers ensure that a CubeSat cannot endanger the primary payload or the other passengers. If a separation switch opens even briefly, the spacecraft must return to its pre-launch state, timers included. Batteries, pressure vessels and propellants need extra documentation and tests from the launch provider[9].
Thermal response
A fully loaded 1U has a lumped of about 104 minutes, twice that of a 1P, so it averages out more of the eclipse:
| Form factor | Mass (kg) | Surface (cm²) | Time constant (min) | Longest eclipse ÷ time constant |
|---|---|---|---|---|
| 1U | 2.00 | 654 | 104 | 0.34 |
| 2U | 4.00 | 1,108 | 122 | 0.29 |
| 3U | 6.00 | 1,562 | 130 | 0.27 |
c_p = 900 J/(kg·K), ε = 0.8, T₀ = 290 K. The longest eclipse at 525 km lasts 35.7 min; the larger the ratio, the deeper the spacecraft cools in it.
Orbital lifetime and debris
Without propulsion, the lifetime of a CubeSat depends on its release altitude and on the Sun:
| Form factor | Mass (kg) | Ballistic parameter (m²/kg) | From 450 km | From 500 km | From 550 km | From 600 km | From 650 km |
|---|---|---|---|---|---|---|---|
| 1U | 2.00 | 0.0180 | 14.2 months | 3.1 years | 7.8 years | 18.6 years | 42 years |
| 2U | 4.00 | 0.0152 | 16.7 months | 3.7 years | 9.2 years | 22 years | 50 years |
| 3U | 6.00 | 0.0143 | 17.8 months | 3.9 years | 9.8 years | 23 years | 53 years |
| 6U | 12.00 | 0.0130 | 19.6 months | 4.3 years | 10.8 years | 26 years | 58 years |
Kennewell density model, drag coefficient 2.2, mean tumbling area A_tot/4, re-entry at 180 km, spacecraft at the mass limit of its standard. Solar activity: low F10.7 = 70 sfu, Ap = 6; moderate 140 sfu, Ap = 12; high 210 sfu, Ap = 18.
Heavier spacecraft live longer, so the altitude ceiling for natural compliance drops as the form factor grows:
| Form factor | Within 5 years | Within 25 years | ||||
|---|---|---|---|---|---|---|
| Low | Moderate | High | Low | Moderate | High | |
| 1U | 467 | 525 | 585 | 538 | 618 | 702 |
| 2U | 460 | 516 | 574 | 531 | 608 | 689 |
| 3U | 457 | 513 | 570 | 528 | 604 | 685 |
| 6U | 453 | 508 | 564 | 524 | 598 | 677 |
| 12U | 442 | 494 | 546 | 511 | 583 | 657 |
Bisection on the lifetime model of the review (Eqs. 5–6). The FCC five-year rule applies to satellites launched after 29 September 2024 that are licensed in or serve the United States; ISO 24113 keeps 25 years. Solar activity: low F10.7 = 70 sfu, Ap = 6; moderate 140 sfu, Ap = 12; high 210 sfu, Ap = 18.
A fully loaded 3U exceeds the above roughly 510 km at moderate activity, and above 460 km if the Sun is quiet. Altitude selection, drag devices and propulsion therefore become design questions; the five-year rule article works through the options.
Technology maturity
The CubeSat ecosystem has matured to the point where most subsystems can be bought off the shelf. NASA’s State-of-the-Art of Small Spacecraft Technology report, updated in 2026, compiles current performance ranges for power, propulsion, attitude control, communications and avionics products[10]; the subsystem entries of this encyclopedia draw on its chapters.
Missions in the index
| Mission | Size | Launch | Operator | Status |
|---|---|---|---|---|
| XI-IV | 1U | 30 Jun 2003 | University of Tokyo (ISSL), Japan | Active |
| CUTE-I (CO-55) | 1U | 30 Jun 2003 | Tokyo Institute of Technology, Japan | Active |
| CanX-1 | 1U | 30 Jun 2003 | UTIAS Space Flight Laboratory, Canada | In orbit, inactive |
| AAU CubeSat | 1U | 30 Jun 2003 | Aalborg University, Denmark | Completed |
| DTUsat-1 | 1U | 30 Jun 2003 | Technical University of Denmark (DTU), Denmark | In orbit, inactive |
| QuakeSat | 3U | 30 Jun 2003 | Stanford University / QuakeFinder, United States | Completed |
| GeneSat-1 | 3U | 16 Dec 2006 | NASA Ames Research Center, United States | Re-entered |
| Delfi-C3 | 3U | 28 Apr 2008 | TU Delft, Netherlands | Re-entered |
| ITU-pSAT1 | 1U | 23 Sept 2009 | Istanbul Technical University, Türkiye | Not verified |
| SwissCube | 1U | 23 Sept 2009 | EPFL, Switzerland | Active |
| TURKSAT-3USAT | 3U | 26 Apr 2013 | ITU, Türksat, TAMSAT, Türkiye | In orbit, inactive |
| ESTCube-1 | 1U | 7 May 2013 | University of Tartu, Estonia | Completed |
| FUNcube-1 (AO-73) | 1U | 21 Nov 2013 | AMSAT-UK / AMSAT-NL, United Kingdom | Active |
| Flock-1 / Dove (SuperDove) | 3U | 9 Jan 2014 | Planet Labs, United States | Completed |
| GOMX-3 | 3U | 19 Aug 2015 | GomSpace / ESA, Denmark | Re-entered |
| Lemur-2 (Spire Constellation) | 3U | 28 Sept 2015 | Spire Global, United States | Active |
| Nayif-1 (EO-88) | 1U | 15 Feb 2017 | MBRSC / American University of Sharjah, United Arab Emirates | Re-entered |
| BeEagleSat (QB50 TR01) | 2U | 18 Apr 2017 | Istanbul Technical University (İTÜ) & HAVELSAN, Türkiye | Re-entered |
| HavelSat (QB50 TR02) | 2U | 18 Apr 2017 | HAVELSAN & Istanbul Technical University (İTÜ), Türkiye | Re-entered |
| ASTERIA | 6U | 14 Aug 2017 | MIT & NASA JPL, United States | Re-entered |
| UBAKUSAT | 3U | 2 Apr 2018 | Istanbul Technical University (İTÜ) / TAMSAT, Türkiye | Re-entered |
| MarCO-A / MarCO-B | 6U | 5 May 2018 | NASA JPL, United States | Completed |
| RainCube | 6U | 21 May 2018 | NASA JPL, United States | Re-entered |
| PW-Sat2 | 2U | 3 Dec 2018 | Warsaw University of Technology, Poland | Re-entered |
| OPS-SAT | 3U | 18 Dec 2019 | European Space Agency (ESA ESOC), European Union | Re-entered |
| ASELSAT | 3U | 24 Jan 2021 | ASELSAN & Istanbul Technical University (İTÜ), Türkiye | Not verified |
| GRBAlpha | 1U | 22 Mar 2021 | Konkoly Observatory and partners, Hungary | Re-entered |
| LICIACube | 6U | 24 Nov 2021 | ASI (Italian Space Agency) & Argotec, Italy | Completed |
| Connecta T1.1 | 3U | 25 May 2022 | Plan-S Satellite and Space Technologies, Türkiye | Re-entered |
| CAPSTONE | 12U | 28 Jun 2022 | Advanced Space / NASA, United States | Completed |
| ISTSat-1 | 1U | 9 Jul 2024 | Instituto Superior Técnico (ULisboa) / ESA, Portugal | Active |
| Milani | 6U | 7 Oct 2024 | European Space Agency (ESA) & Tyvak International, European Union | Active |
| Juventas | 6U | 7 Oct 2024 | European Space Agency (ESA) & GomSpace, European Union | Active |
| ERMIS-3 | 8U | 30 Mar 2026 | National and Kapodistrian Univ. of Athens (NKUA) / ESA, Greece | Active |
| MARMOTSat (CO-128) | 3U | 7 Jul 2026 | University of Victoria (CfAR) / CSA CUBICS, Canada | Active |
Status from SatNOGS DB, operator pages and Gunter’s Space Page; open a mission for its sources.
The CubeSats in the index are reference points rather than a census: the first launch group (XI-IV), early university missions from Delft, Istanbul and Lausanne, the first Turkish 3U and the deep-space MarCO and CAPSTONE missions. The mission index lists them with their sources.
References
- [1]The CubeSat Program, Cal Poly SLO. (2022). CubeSat Design Specification, Rev. 14.1 (CP-CDS-R14.1). California Polytechnic State University.nasa.gov
- [2]Heidt, H., Puig-Suari, J., Moore, A. S., Nakasuka, S., & Twiggs, R. J. (2000). CubeSat: a new generation of picosatellite for education and industry low-cost space experimentation. In: 14th Annual AIAA/USU Conference on Small Satellites (SSC00-V-5).
- [3]Puig-Suari, J., Turner, C., & Ahlgren, W. (2001). Development of the standard CubeSat deployer and a CubeSat class PicoSatellite. In: 2001 IEEE Aerospace Conference Proceedings, vol. 1 (347–353).doi:10.1109/AERO.2001.931726
- [4]Libre Space Foundation. (2026). SatNOGS DB — satellite and transmitter database.db.satnogs.org(accessed 20 October 2026)
- [5]NASA Jet Propulsion Laboratory. (2019). The MarCO mission comes to an end.jpl.nasa.gov
- [6]Swartwout, M. (2013). The first one hundred CubeSats: a statistical look. Journal of Small Satellites, 2, 213–233.
- [7]Langer, M., & Bouwmeester, J. (2016). Reliability of CubeSats — statistical data, developers’ beliefs and the way forward. In: 30th Annual AIAA/USU Conference on Small Satellites (SSC16-X-2).
- [8]nadir lab. (2026). PocketQube-class picosatellites: architecture, flight heritage, and a multi-method post-flight analysis of Grizu-263A [Preprint]. nadir lab. Research Monographs (SQ-R-001).Read on nadir lab.
- [9]NASA CubeSat Launch Initiative. (2017). CubeSat 101: Basic Concepts and Processes for First-Time CubeSat Developers. NASA.nasa.gov(accessed 20 October 2026)
- [10]NASA Small Spacecraft Systems Virtual Institute. (2026). State-of-the-Art of Small Spacecraft Technology (2026 edition). NASA Ames Research Center.nasa.gov(accessed 20 October 2026)
Cite this SatWiki entry
@misc{nadirlab2026cubesat,
author = {{nadir lab.}},
title = {{CubeSat}},
year = {2026},
month = oct,
howpublished = {nadir lab. SatWiki SQ-FF-002 (Rev. 6)},
url = {https://nadirlab.space/wiki/cubesat/}
}nadir lab. (2026). CubeSat. nadir lab. SatWiki (SQ-FF-002, Rev. 6). https://nadirlab.space/wiki/cubesat/
TY - ENCYC AU - nadir lab. TI - CubeSat T2 - nadir lab. SatWiki PY - 2026 ET - Rev. 6 C1 - SQ-FF-002 UR - https://nadirlab.space/wiki/cubesat/ ER -