Regulation and debris mitigation

Two kinds of rules

Two bodies of rules shape a small-satellite mission beyond its engineering. Spectrum rules decide which frequencies it may use and how it must coordinate them. Space-debris rules decide how long it may stay in orbit after its mission ends, and therefore where it may fly without propulsion.

Spectrum

Radio spectrum is allocated internationally by the ITU Radio Regulations[1], and every satellite network is notified to the ITU through its national administration. Missions in the amateur-satellite service additionally coordinate their frequencies with the International Amateur Radio Union, whose satellite advisers check the proposed frequencies, modes and the amateur character of the mission[2]. The amateur service is restricted to non-commercial purposes: open, decodable telemetry and a service to radio amateurs are part of the bargain, and a reliable command that shuts the transmitter down is required.

Grizu-263A followed this path. Its frequencies were IARU coordinated (serial 775) with the support of TAMSAT, and the team published all telemetry formats without encryption[3]. The additional spectrum for telemetry, tracking and command of short-duration missions agreed at WRC-19 offers an alternative for missions that are not amateur in character[3].

Licensing

In the United States, any non-federal transmitter needs a licence from the Federal Communications Commission; experimental licences are common for university CubeSats[4]. Launch providers ask for the licence, the frequency coordination and the debris assessment before integration, so the paperwork has to start a year or more before launch[5].

The five-year rule

In September 2022 the FCC replaced the long-standing 25-year guideline with a five-year limit on post-mission disposal for satellites in low Earth orbit[6]. The rule applies to satellites launched after 29 September 2024, both US-licensed and non-US-licensed satellites that seek access to the US market; satellites already in orbit by that date are grandfathered[7]. International standards such as ISO 24113 keep the older 25-year limit[8], and NASA’s technical standard for limiting orbital debris sets agency requirements for its own missions[9].

A total orbital lifetime of five years is a conservative way to meet the rule: if the spacecraft re-enters within five years of launch, it re-enters within five years of the end of its mission.

What the rules mean for altitude

For a spacecraft without propulsion, the rules become an altitude ceiling that depends on the ballistic parameter and the Sun:

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

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 1P meets the five-year rule below about 560 km at moderate solar activity, but the ceiling moves from about 490 to 630 km between low and high activity[3]. Because a release orbit is chosen years before the activity it will meet is known, a margin of tens of kilometres is prudent. The sensitivity is visible in the lifetime chart:

• 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

Above the ceiling

A mission that must fly higher has three options: an operational altitude-lowering burn, a drag device or simply a smaller ballistic coefficient. Drag sails enlarge the area that the flow sees:

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.

Propulsion can lower the perigee at the end of the mission. From typical rideshare altitudes a single burn of 70–100 m/s brings the perigee to 250 km, which is a demanding budget for a PocketQube:

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).

The five-year rule article compares the three options for PocketQubes and CubeSats.

Being catalogued

Debris mitigation assumes that objects can be tracked. PocketQubes are catalogued routinely once deployed, but the accuracy of orbits derived from two-line elements degrades for light objects[10], and identification after large rideshares can take days. Operators help by publishing transmitter frequencies and beacon formats before launch, so that networks can match signals to catalogue objects quickly.

Short life as a feature

For the smallest spacecraft, the high area-to-mass ratio is the most reliable mitigation measure: from 450 km a fully loaded 1P re-enters in well under a year at moderate activity, and from 400 km in months. Low orbits shorten missions, which is the tension the propulsion entry describes: debris rules push PocketQubes down, where only micronewton propulsion could keep them working for long.