The rule#
In September 2022 the US Federal Communications Commission shortened the time a satellite may remain in low Earth orbit after its mission from the long-standing 25-year guideline to five years[1]. The operative text asks that disposal by atmospheric re-entry be completed “as soon as practicable” and no later than five years after the end of the mission. It amends the rules for experimental (Part 5), commercial (Part 25) and amateur (Part 97) space stations, the last two being the routes most PocketQubes and university CubeSats take, and compliance is required for satellites launched after 29 September 2024[2]. The rule applies to US-licensed satellites and to non-US satellites seeking access to the US market; satellites already in orbit by that date are grandfathered[3]. The Commission declined blanket exemptions and said that waivers for failures would not be liberally granted[2].
Elsewhere the numbers differ. ISO 24113:2023 keeps the 25-year limit for the protected region[4], while ESA shortened the disposal phase of its own missions to five years in November 2023[5]. Applicants commonly compute lifetimes with NASA’s Debris Assessment Software, but the FCC notes that its “compliant / not-compliant” verdict refers to NASA-STD-8719.14 and does not by itself establish compliance with the Commission’s rules[3][6]. What the reviewer needs is the lifetime itself, with its assumptions.
What five years means without a thruster#
A satellite without propulsion cannot act at the end of its mission: its remaining life was fixed when the deployer released it. Two readings of the rule follow:
- Strict. The whole orbital lifetime, from release to re-entry, stays below five years. Compliance then holds whenever the mission ends, including after an early failure.
- Literal. The lifetime stays below the planned mission duration plus five years. Each extra year of mission allows about 10 km more altitude for a 1P at moderate activity.
The strict reading is the robust one for a small team: it removes any argument about when the mission ended, and it costs little altitude. The tables below use it.
Altitude ceilings#
With the lifetime model of the PocketQube review[7], the ceiling is the circular altitude whose natural decay takes exactly five years:
| Form factor | Within 5 years | Within 25 years | ||||
|---|---|---|---|---|---|---|
| Low | Moderate | High | Low | Moderate | High | |
| 1P | 493 | 559 | 627 | 567 | 656 | 752 |
| 2P | 490 | 555 | 622 | 563 | 651 | 745 |
| 3P | 489 | 553 | 620 | 562 | 649 | 743 |
| 1U | 467 | 525 | 585 | 538 | 618 | 702 |
| 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.
At moderate activity a fully loaded 1P complies below 559 km, a 1U below 525 km, a 3U below 513 km and a 12U below 494 km. The order is set by the : a PocketQube has about twice the area per unit mass of a CubeSat at its mass limit, decays faster and may therefore be released about 35 km higher. The 2P and 3P differ from the 1P by less than 7 km, because mass and area grow together along the long axis. Under the 25-year guideline the same spacecraft could start 90–100 km higher.
- 1P, 0.033 m²/kg
- 3P, 0.030 m²/kg
- 1U, 0.018 m²/kg
- 3U, 0.014 m²/kg
- 1P, low to high activity
- 1U, low to high activity
Show the data as a table
| Initial altitude (km) | 1P, 0.033 m²/kg | 3P, 0.030 m²/kg | 1U, 0.018 m²/kg | 3U, 0.014 m²/kg |
|---|---|---|---|---|
| 350 | 0.08 | 0.09 | 0.14 | 0.18 |
| 400 | 0.23 | 0.26 | 0.42 | 0.53 |
| 450 | 0.64 | 0.71 | 1.18 | 1.49 |
| 500 | 1.70 | 1.89 | 3.12 | 3.92 |
| 550 | 4.26 | 4.72 | 7.82 | 9.82 |
| 600 | 10.13 | 11.23 | 18.59 | 23.35 |
| 650 | 22.87 | 25.35 | 41.97 | 52.72 |
The Sun moves the ceiling by more than 100 km#
Between low and high solar activity the ceilings move by 50–70 km either side of the moderate case. That spread is larger than any design choice, and the activity a spacecraft will meet is not known when its orbit is booked. Solar Cycle 25 illustrates the problem: it rose faster and peaked earlier and higher than forecast in 2019[8], and Grizu-263A, released near 525 km, re-entered after 21 months instead of the four years its team had expected[7].
For compliance the conservative assumption is low activity, which gives the longest life: a 1P must then start below about 490 km. For mission planning the opposite holds: the shortest plausible life follows from high activity, and a 1P released at 450 km may last only about four months.
| Purpose | Activity case | Question answered |
|---|---|---|
| Debris compliance | Low, or a conservative cycle projection | Will it re-enter within five years in the worst case? |
| Mission planning | Moderate, or the forecast for the mission | How long will it most likely operate? |
| Minimum mission duration | High | Will the mission finish before re-entry? |
Above the ceiling: drag augmentation#
A spacecraft released above its ceiling can raise its ballistic parameter by deploying a drag sail at the end of the mission:
| Altitude (km) | Required ballistic parameter (m²/kg) | 1P: sail area (m²) | 3P: sail area (m²) | 3U: sail area (m²) |
|---|---|---|---|---|
| 550 | 0.028 | Not needed | Not needed | 0.075 |
| 600 | 0.067 | 0.008 | 0.025 | 0.29 |
| 650 | 0.151 | 0.027 | 0.083 | 0.75 |
| 700 | 0.324 | 0.066 | 0.20 | 1.69 |
| 800 | 1.280 | 0.28 | 0.85 | 6.91 |
A flat sail that tumbles with the spacecraft (mean projected area half the sail area); a sail held face-on to the flow needs half as much.
At moderate activity a 1P at 600 km needs only about 80 cm² of tumbling sail, a little more than three of its faces, while at 700 km it needs 0.066 m² and at 800 km 0.28 m², nearly twenty times its own surface. Under constant low activity the areas grow six- to ninefold. A 3U at 700 km needs 1.7 m² even at moderate activity. Sails add a mechanism that must deploy after years in orbit, so they are a design for missions that need a high orbit, not a fix for an orbit chosen carelessly.
Above the ceiling: propulsion#
The other option is to lower the perigee at the end of the mission. A single burn that drops the perigee to 250 km brings re-entry within weeks:
| Altitude (km) | Perigee to 250 km (m/s) | Perigee to 180 km (m/s) | Low-thrust spiral to 250 km (m/s) | Propellant for a 1P, Isp 65 s (g) |
|---|---|---|---|---|
| 500 | 71 | 91 | 142 | 26.3 |
| 550 | 84 | 105 | 170 | 31.0 |
| 600 | 98 | 118 | 197 | 35.6 |
| 700 | 124 | 144 | 251 | 44.3 |
| 800 | 150 | 170 | 303 | 52.4 |
Single impulsive burn from a circular orbit; a 250 km perigee brings re-entry within weeks. Propellant from the rocket equation for a 250 g 1P with cold gas (Isp 65 s).
From 600 km the burn costs about 98 m/s, or 36 g of cold gas for a 250 g 1P, a seventh of its mass. A low-thrust spiral to the same altitude needs about twice the , but electric thrusters with a high specific impulse turn it into a small propellant mass[9]. What a fixed propellant load buys depends strongly on the technology:
| Technology | Isp (s) | Thrust | Δv (m/s) | Years of drag make-up at 450 km |
|---|---|---|---|---|
| Cold gasN₂, butane, R-236fa | 40–110 | 10 µN–3.6 N | 16–44 | 0.2–0.4 |
| ElectrothermalResistojets: water or gas heated electrically | 20–350 | 0.1 mN–1 N | 8–140 | 0.1–1.3 |
| Alternative mono- and bipropellantAF-M315E (ASCENT), LMP-103S | 150–310 | 50 mN–22 N | 60–124 | 0.6–1.2 |
| Electrospray and FEEPIonic liquids; indium or gallium in FEEP | 225–3,000 | 20 µN–20 mN | 90–1,201 | 0.9–11.6 |
| Pulsed plasma, vacuum arcAblation of PTFE or a metal cathode | 87–3,200 | 4–500 µN | 35–1,281 | 0.3–12.3 |
Ideal rocket equation, propellant only (tanks, power and thrust level ignored). Holding a 1P at 450 km under high solar activity costs about 104 m/s a year. Ranges from NASA’s State of the Art of Small Spacecraft Technology.
Ten grams of cold gas give a 1P 16–44 m/s, too little to deorbit from 600 km; electrospray, FEEP and vacuum-arc thrusters reach several hundred to more than a thousand metres per second with the same mass[10]. MEMS micropropulsion is the main route to fitting such systems into a PocketQube[11], but power, thrust duration and qualification remain open problems at this scale.
The opposite problem: staying up#
Propulsion is more often wanted to extend a short life than to end a long one. Holding a 1P at a low, compliant altitude costs:
| Altitude (km) | Drag force (µN) | Δv per year (m/s) | Total impulse per year (N·s) |
|---|---|---|---|
| 350 | 1.15–4.64 | 145–586 | 36.2–146.4 |
| 400 | 0.33–1.91 | 42–241 | 10.4–60.2 |
| 450 | 0.10–0.82 | 13–104 | 3.2–26.0 |
| 500 | 0.033–0.37 | 4.2–47 | 1.1–11.7 |
| 550 | 0.012–0.18 | 1.5–22 | 0.4–5.6 |
Ranges run from low to high solar activity; tumbling mean area A_tot/4, drag coefficient 2.2. Solar activity: low F10.7 = 70 sfu, Ap = 6; moderate 140 sfu, Ap = 12; high 210 sfu, Ap = 18.
At 450 km the yearly Δv ranges from 13 m/s at low activity to more than 100 m/s at high activity, the same order as a deorbit burn from 550–700 km. A PocketQube with propulsion is therefore best released low, where compliance is automatic, and spends its propellant on staying there.
A decision procedure#
flowchart TB
A["Release orbit offered by the launch"] --> B["Lifetime at low, moderate and high activity"]
B --> C{{"Within 5 years at low activity?"}}
C -- yes --> D["Compliant by natural decay"]
C -- no --> E{{"Does the mission need this altitude?"}}
E -- no --> F["Choose a lower release orbit and check again"]
E -- yes --> G["Drag sail or deorbit propulsion, sized for low activity"]
G --> H["Document lifetime, assumptions and disposal reliability"]
D --> HRecommendations#
- Start from the orbits actually on offer. Releases from the International Space Station near 400–420 km comply for every form factor; Sun-synchronous rideshares at 500–600 km comply for a 1P only below about 560 km at moderate activity, and not at all if low activity is assumed.
- Report lifetimes for three activity cases, and state the ballistic parameter with its range, including deployed antennas and panels, which raise it.
- Prefer the strict reading of the rule when the spacecraft has no means of disposal.
- Size any drag device or deorbit burn for low activity, because a compliance case must hold in the worst plausible atmosphere.
The lifetime calculator runs the same model for any spacecraft, the lifetime article derives it, and the regulation entry places the rule among the licensing and frequency-coordination steps of a mission.