BeamDesk Articles

The only project writing the method for measuring a power beam has no draft and fifteen months left

2026-09-27T00:00:00Z

No recognised body has published a method for measuring whether a power beam meets the

exposure limits it must meet. One project was chartered to write it. That project has been

an Active PAR since June 2023, has no public draft, and its authorisation runs out in

December 2027.

This matters more than it sounds. Everyone arguing about power beaming argues about the

limit, and the limit is the settled part. What is missing is the boring half: where to put

the probe, over what area to average, and what a regulator accepts as proof that the fence

is in the right place.

A limit is not a method

Start with the numbers, because they are documented and they are not controversial.

ICNIRP's 2020 radiofrequency guidelines set a general public whole-body reference level of

10 W/m² incident power density between 2 and 300 GHz, averaged over 30 minutes, and 50 W/m²

for occupational exposure. IEEE Std C95.1-2019 is the second document to cite. Read on

27 September 2026, its IEEE SA page gives it as an Active Standard, board approval

8 February 2019, published 4 October 2019, with Cor 1-2019 and Cor 2-2020 as the only

corrigenda and the working group showing "No Active Projects".

Those documents tell you the number. They do not tell you how to obtain it in the field.

They do not say what area to spatially average over when the field varies across the width

of a person, what to do about a 30-minute averaging time when the field is steady and the

person is not, what instrument to use, at what height, or with what uncertainty budget.

IEEE Std C95.3-2021 is the general answer to that question and is deliberately not a

procedure. Its IEEE SA page gives board approval 25 March 2021 and publication 28 May 2021,

and the scope says plainly that detailed methodology is not described: best practice is

expressed through guidance and references to other documents. That is the right document

for a specialist and the wrong one to attach to a licence application.

The document that does give procedures is IEC 62232, fourth edition, published 29 April 2025

by IEC TC 106 and titled "Determination of RF field strength, power density and SAR in the

vicinity of base stations for the purpose of evaluating human exposure". It covers 110 MHz

to 300 GHz for intentional transmissions, it distinguishes product compliance boundaries

from installation compliance and in-situ measurement, and it handles time-varying

beam-steering including massive MIMO. Every piece of that is close to what a power beaming

site needs. None of it is scoped to a transmitter whose purpose is to deliver power, and a

rectenna field is not a base station.

The project that would close the gap has produced nothing public in three years

IEEE P63480 is the project. Its IEEE SA page, read on 27 September 2026, gives the title as

"Assessment of Human Exposure to Electromagnetic Fields from Radiative Wireless Power

Transfer Systems: Measurement and Computational Methods", for the frequency range 30 MHz to

300 GHz. Status: Active PAR. PAR approval date: 29 June 2023. Sponsor: the IEEE SA Board of

Governors through ICES, the International Committee on Electromagnetic Safety. Working group

chair: Andreas Christ. The scope covers incident field strength, incident power density,

specific absorption rate and absorbed power density, from the reactive near field out to the

far field.

The page shows no draft, no ballot state and no publication date. It has shown none on every

reading this project's daily scan has made since 30 August 2026.

One honest caveat before that is over-read. IEEE drafts are not public before ballot, so the

absence of a visible draft is not proof that nobody is writing one. What is public, and what

is checkable, is the clock.

The IEEE SA Standards Board New Standards Committee recommendations carrying SASB approval

date 29 June 2023 list P63480 under ICES among the new PARs, with the recommendation

"Approve new PAR until December 2027." The IEEE SA Standards Board Operations Manual,

clause 5.2, sets the rest: a project not completed by the four-year deadline authorised in

the PAR needs the Standards Committee to file an extension request with NesCom, which may be

granted for one or more years, and a project that reaches its deadline without one "shall be

subject to administrative withdrawal".

Fifteen months, from today, on the authorisation as originally granted. Two limits on that

sentence. The project page publishes no expiry date, and searches of published NesCom

papers did not surface an extension for P63480 in either direction. If an extension has been

granted since 2023, it is not visible on the pages checked here.

The same committee shipped the other half of this job last year

The gap is not a failure of the machinery, and the evidence is that the machinery already

delivered the adjacent standard. IEC/IEEE 63184:2025 was published on 25 February 2025 by

IEC TC 106, titled "Assessment methods of the human exposure to electric and magnetic fields

from wireless power transfer systems", covering models, instrumentation, measurement and

computational methods for the range 3 kHz to 30 MHz. It handles SAR, internal electric

fields and contact currents, and it is aimed at inductive systems.

That is the low-frequency, near-field half of exposure assessment for wireless power, it is

finished, and it carries both logos. So the joint IEC and IEEE route works, and the people

who know how to write these documents are in the room.

The half that is missing is precisely the half power beaming needs. The most likely reading

is not competence but priority. The market behind 63184 is electric vehicle and consumer

charging, shipping in the millions of units, with manufacturers who need a compliance test

today. The market behind 63480 is a small number of funded demonstrations. Standards follow

units, and there are no units yet.

What an operator is holding while that runs

Put rough numbers on the thing being measured. What follows is estimated, and it is

arithmetic on a hypothetical rather than anybody's published system.

Take a transmitting aperture 1 km across in geostationary orbit at 5.8 GHz. Before going

further: 5.8 GHz is not regulatorily available for space-to-Earth power transmission. It is

the band the engineering literature uses, it sits in an ISM allocation intended for

industrial, scientific and medical use, and using it in a study is not permission to radiate

from orbit.

At a 5.17 cm wavelength over 35,786 km, the first-null main lobe from a 1 km aperture is

roughly 2.44 λR/D, which is about 4.5 km across. Spread a radiated gigawatt across that, and

the average is around 60 W/m², with an on-axis peak perhaps twice that under a tapered

illumination. Both figures are estimates. Radiated is not delivered, and neither number is a

rating of any real machine.

Against a general public reference level of 10 W/m², the consequence is geometric. The

boundary of the publicly accessible area is a flux contour lying a kilometre or so outside

the nominal spot, and where exactly it lies depends on the aperture taper, the pointing

error and the atmosphere on the day. That contour is the fence. It is also a site's largest

land cost and its licence condition.

Now ask the questions the limit does not answer. Over what area is the average taken. What

counts as compliance for a person crossing the contour for two minutes rather than thirty.

Who measures it, with what instrument, traceable to what, and what uncertainty does the

regulator accept. Those are exactly the questions P63480 was chartered to answer. Until it

lands, every demonstration negotiates its own method with its own regulator, and every one

of those negotiations sets a precedent that no committee voted on.

The ITU side does not fill the gap either. The in-force Recommendation ITU-R SM.2151-0

(09/2022) is titled "Guidance on frequency ranges for operation of wireless power

transmission via radio frequency beam for mobile/portable devices and sensor networks",

which is its scope as well as its title. WRC-31 preliminary agenda item 2.2, under

Resolution 910 (WRC-23) and led by Working Party 1A, reads "to consider the possible

[frequency bands] for [non-beam and beam] wireless power transmission to avoid harmful

interference to the radiocommunication services", brackets in the original. That is

interference between services, not human exposure, and it is not yet agreed text.

What would change my mind

A public draft or a ballot state appearing on the P63480 project page would change the

strongest sentence here immediately, and I would say so.

A NesCom record extending the PAR past December 2027 would change the framing even without a

draft, because it would show a committee that intends to finish rather than one drifting

into administrative withdrawal. That record is the single piece of evidence this article

most wants and does not have.

The IEC side is unchecked and could contradict me. The IEC TC 106 project dashboard returned

HTTP 403 to this run, so the IEC-side stage for 63480 was not read. If it shows a committee

draft in circulation, then "no draft in three years" is wrong as written and should be

retracted rather than softened.

A regulator publishing guidance that extends IEC 62232's base-station procedures to power

beaming would close the gap in practice without any new standard. That would be the quiet

outcome, and it is plausible, because it is what regulators usually do.

What would not change my mind is another funded demonstration, another award, or another

company announcing a megawatt of anything. Money is not a method, and a compliance

demonstration that cannot be repeated by a second party with published procedures is a

private arrangement wearing a standard's clothes.

Sources

The Pentagon did not buy orbital power beaming this week. Its own solicitation says it bought a robot.

2026-09-26T00:00:00Z

On 21 September 2026 Katalyst Space announced that the US Department of Defense had selected it to

demonstrate space-based power beaming. The government's own solicitation for that programme is

public, and it says something narrower: the primary focus is the platform, and power beaming is the

payload that proves it.

Figures below are labelled documented where a source states them and estimated where I have

calculated them from stated assumptions. Nothing here is a measurement.

What the government asked for, in its own words

Katalyst's release of 21 September 2026 says the company will build and launch a robotic spacecraft

that will "assemble a large-format power beaming system on orbit and transmit power back to Earth",

under a programme called ASGARD, funded by the Operational Energy Capability Improvement Fund, using

modular tiles built by the US Naval Research Laboratory. It publishes no power level, no frequency,

no altitude, no tile count, no contract value and no demonstration year. RuthAnne Darling, the

Director of Operational Energy - Innovation, is quoted in it saying the work "opens new pathways for

operational energy in space".

The office she directs published the solicitation. Request for Project Proposal HQ0034269ASGD,

issued by Washington Headquarters Services on behalf of that office and still linked from the fund's

own portal at oecif.org, carries the same expansion of the acronym, Advanced Scalable Growth

Architecture for Robotic Deployment, and describes the same LEO spacecraft assembling

government-furnished modular panels with robotic arms. It sets a white paper deadline of 24 June

2026 and anticipates a prototype Other Transaction agreement under 10 U.S.C. § 4022.

Its framing is the interesting part. The document says the platform could host applications such as

on-orbit solar power collection and beaming, and then states that "the primary focus of the ASGARD

program is the demonstration of the foundational persistent platform itself". Power beaming appears

as the second of three key objectives, under the heading of demonstrating application-specific

operation as a testbed. The tiles are not the contractor's to design: the solicitation says the

"high efficiency Solar to RF tiles to beam power from LEO to the ground" will be government

furnished and integrated into government-furnished panels.

None of that makes the award less real, and it is not a discrepancy with the company's release.

Assembling a large structure in orbit is the harder and more general problem, and it is the one the

government wrote down first. But it changes what a reader should expect to see at the end. A

programme whose primary objective is a persistent modular platform succeeds if panels get joined,

powered and pointed. It does not need a single watt to arrive anywhere useful on the ground.

The fund has been buying in this direction deliberately. Its FY26 call for proposals, dated 7 May

2025, lists under the emerging-battlefields priority: "Space - advanced space qualified photovoltaic

(PV); in-space recharging/refueling; power beaming". That call caps a multi-year OECIF contribution

at $3m a year for up to three years, or $5m for a one-year surge, though ASGARD arrived through a

targeted solicitation rather than the annual cycle, so whether those caps bind it is not established

here. The novelty is not that the Pentagon is interested in beamed power. It is the robot.

The one physical dimension in the document decides the rest

The solicitation contains exactly one hard physical number, and it is a good one. The robotic arms

must "manipulate government furnished modular panels with a maximum dimension of 0.7m x 0.9m x

0.2m". That is documented. Everything from here is estimated, and the assumptions are stated as they

are used.

A 0.7 by 0.9 metre panel presents at most 0.63 square metres of aperture. A hundred of them, joined

edge to edge with no loss, make 63 square metres, which is a circle about 9 metres across. Assume a

500 kilometre orbit, which is the middle of LEO and the solicitation names no altitude. At that

range a 9 metre aperture is comfortably in the far field, so the ordinary expressions apply.

The width of the beam at the ground follows from the aperture and the wavelength, not from the

power. For a uniformly illuminated circular aperture the first null sits at about 2.44 λR/D. The

solicitation names no frequency, so take the two that the field actually uses. At 2.45 GHz that

hundred-panel array puts a spot about 16.7 kilometres across on the ground. At 10 GHz it is about

4.1 kilometres.

Now the power density, which is what a receiving station cares about. On axis it is roughly

P·A/(λR)², where A is the transmitting aperture. Radiate a kilowatt from those 63 square metres at

2.45 GHz from 500 kilometres and the peak at the ground is about 17 microwatts per square metre. A

generous 100 square metre rectenna sitting exactly under it collects about 1.7 milliwatts. At 10 GHz

the same array gives about 0.28 milliwatts per square metre and about 28 milliwatts captured. These

are estimates, and they are dominated by the aperture, so an error in my assumed efficiency does not

move them. An error in the assumed frequency moves them by the square of the ratio.

Run it backwards and the scale of the ambition becomes legible. To put a 100 metre spot on the

ground from 500 kilometres you need a transmitting aperture of about 366 metres at 10 GHz, or about

1.5 kilometres at 2.45 GHz: roughly 167,000 panels of 0.63 square metres for the first, and 2.8

million for the second. That is why the programme is about robotic assembly rather than about

transmitters. Nobody launches that aperture. ASGARD asks whether a machine can build one a panel at

a time, and nobody has yet built anything at all that way.

There is a second requirement in the document that tells you where the risk sits. The spacecraft

must "incorporate a sensor on the bus to measure planarity of the payload's antenna (non-PV)

surface". Planarity is a proxy for phase. If the panels are to combine coherently, their placement

error has to be a small fraction of a wavelength. Take a sixteenth of a wavelength as a working

tolerance, which is estimated and on the loose side: that is about 7.6 millimetres at 2.45 GHz and

about 1.9 millimetres at 10 GHz. A robot arm placing panels across tens of metres to millimetre

flatness is the actual experiment. The beam is the instrument that reads out whether it worked.

A band nobody has named, and no allocation to name it in

Neither the company nor the solicitation names a frequency, and there is a reason it is easier to

leave blank. Wireless power transmission has no status in the Radio Regulations. The current text is

the Edition of 2024, which the ITU describes as the Regulations adopted by WRC-95 and reviewed by

the conferences through WRC-23, and it carries no allocation for beaming power from space to Earth.

The band most often assumed for this work, 5.8 GHz, is not regulatorily available for space-to-Earth

transmission, and saying so is not a technicality: it is the difference between an experiment under

a national licence and a service.

The only ITU-R Recommendation naming frequency ranges for beam wireless power transmission is

SM.2151-0 of September 2022, listed as In force when I checked the editions page on 26 September

2026, and its title scopes it to "mobile/portable devices and sensor networks". A solar-to-RF tile

array in low Earth orbit is not that. The broader question is queued behind a conference: WRC-31

preliminary agenda item 2.2, under Resolution 910 (WRC-23) and assigned to Working Party 1A, is

framed as considering bands for non-beam and beam wireless power transmission "to avoid harmful

interference to the radiocommunication services". That is a protection item, not an enabling one,

and there is no space-based solar power item beside it.

Domestically the record is just as empty. A full-text search of the Federal Register for "power

beaming", across every agency, for anything published since 1 January 2026, returned zero documents

when I ran it on 26 September 2026. The venue for a demonstration like this is an experimental

licence, and an experimental licence is not a rulemaking. So the first real space-to-Earth power

beam over US soil may well be authorised without any public rule ever being written. Whoever

publishes the conditions attached to that licence, with the band and the permitted power flux

density in them, will have done the field a larger favour than the demonstration itself.

What this demonstration can honestly prove

Two constraints decide what the phrase "power to remote locations" can mean here, and neither is

efficiency.

The first is exposure, and it is the constraint that turns out not to bind. ICNIRP's 2020

guidelines set, in Table 5, a whole-body incident power density reference level of 10 watts per

square metre for the general public and 50 for occupational exposure, between 2 and 300 GHz,

averaged over 30 minutes. IEEE C95.1-2019 sits alongside them, still an active standard, board

approved in February 2019 and published in October 2019. Put the estimate above beside the limit:

17 microwatts per square metre is roughly 600,000 times below the general public reference level.

Nothing about a hundred-panel array in LEO is an exposure problem. The exposure problem arrives with

the kilometre-scale aperture, not with this one, and it will be a genuine one then.

The second is geometry, and it binds hard. A spacecraft in a 500 kilometre circular orbit has a

period of about 94.5 minutes and is above the horizon of a fixed ground site for at most about 11.6

minutes, on the single pass that goes through the zenith. Most passes are shorter and most are not

overhead. That is estimated from circular-orbit geometry alone, not from any access model of ours.

A single spacecraft therefore delivers minutes per day to any one place, separated by hours, and the

number that matters operationally is the typical worst gap in a day rather than any average. Beamed

power from one LEO platform is not a substitute for a generator at a forward site. It is a

demonstration of a link, on a schedule someone has to plan around, which is the same scheduling

problem every other orbital service has.

The case against everything I have written here is worth stating plainly, because it is decent. If

the objective is to prove robotic assembly and coherent operation, then the spot size at the ground

is beside the point, and criticising the delivered milliwatts is like criticising the first

transatlantic cable for its bit rate. That is fair. It is also exactly why the framing in the

solicitation deserves to travel further than the framing in the press release. The document says the

platform is the product. Read that way, the programme is well posed. Read the other way, as the

Pentagon buying beamed power for remote sites, it invites a disappointment it did not earn.

BeamDesk has no involvement in this programme and no relationship with any organisation named here.

Everything above comes from published material and from the issuing bodies' own documents. One loose

end, stated as loose: the solicitation does not identify the tile design, and the US Navy's own

DVIDS entry of 18 May 2020 records its Photovoltaic Radio-frequency Antenna Module being deployed

aboard an X-37B, with the aim of a later spacecraft "to test the transmission of energy back to

Earth". Whether ASGARD's tiles descend from that module is not stated in any source I have seen,

and I am not going to assume it.

What would change my mind

If the government or the contractor publishes a target power flux density at the ground, with the

band and the assembled aperture area, the second section becomes checkable rather than indicative,

and if those figures imply a spot far smaller than my estimate then the assumption that broke is

probably the panel count or the frequency, and I would want to know which.

If the demonstration turns out to be aimed at a receiving site with a rectenna measured in hectares

rather than in hundreds of square metres, the captured-power figures move by orders of magnitude and

the "milliwatts" framing here is too harsh.

If a follow-on production transaction under 10 U.S.C. § 4022(f) is announced with a power delivery

requirement in it, then the platform-first reading of this programme was correct only for the

prototype, and the fund is buying beamed power after all.

If the FCC grants an experimental licence for a space-to-Earth power beam and publishes the

conditions, or if Working Party 1A receives a contribution proposing a space-to-Earth band rather

than an interference-protection study, then the regulatory vacuum described above has started to

close, and that is the single most consequential thing that could happen in this field.

Sources

ITU-R approved three Recommendations on 8 September. Its own editions pages still show the old ones.

2026-09-21T00:00:00Z

On 8 September 2026 the ITU Radiocommunication Sector approved revised editions of three

propagation Recommendations. Eleven days later, on 19 September, the ITU pages that tell you

which edition is in force list none of them. That is not a website defect. It is where a

standards register quietly goes stale, and two revisions worth reading are sitting in the same

gap today.

What was approved, and what the pages say

Administrative Circular CACE/1206, dated 16 September 2026, is one page and an annex. It

records that three draft revised Recommendations were put through simultaneous adoption and

approval by correspondence under Circular CACE/1198 of 8 July 2026, and states, in the

circular's own words, "The conditions governing this procedure were met on 8 September 2026."

The annex gives the numbers and titles: P.372-18, radio noise; P.2041-1, path attenuation on

links between an airborne terminal and space; and P.311-20, the acquisition and presentation of

propagation data.

Now check the pages that a citation would point at. On 19 September 2026, the editions list for

P.372 gives P.372-17 (08/2024) as In force (Main) and shows no -18 at any status. P.311 gives

P.311-19 (11/2025). P.2041 gives P.2041-0 (09/2013), still under the older title, which says

airborne platform where the approved revision says airborne terminal. Three for three, eleven

days after approval.

The two ITU surfaces also disagree about their own dates. The circular index lists CACE/1206 as

2026-09-10. The circular's own first page is dated 16 September 2026. Where they differ, the

document is the record and the index is a listing.

None of this is misconduct, and the mechanism is not hidden. A Recommendation is approved first

and published after, and the editions page is a publications page. But the page does not say

that about itself. It says In force, which is a legal claim, on a date that is a publishing

fact. Anyone who builds a register by reading those pages, and that includes the standards

labelling it as current.

The leading indicator is free, public and needs no login: the administrative circular stream at

itu.int/md/R00-CACE-CIR-NNNN/en, with the PDF one path below it. Each circular names the

Recommendations in an annex. As of today the index tops out at CACE/1206, so nothing has been

approved since 8 September that this route would show.

A revision that adds a band, and drops a paragraph

Administrative Circular CACE/1203, dated 26 August 2026, covers Study Group 1 and is a step

earlier in the same procedure: two draft revisions adopted by the Study Group and sent to Member

States, who are asked to reply by 26 October 2026. One of the two is a draft revision of

Recommendation ITU-R SM.2151-0.

SM.2151 matters to anyone in power beaming because it is the only ITU-R Recommendation that

names frequency ranges for beam wireless power transmission. The 2022 text scopes itself to

wireless charging of mobile and portable devices and to powering sensor networks, explicitly not

electric vehicles, and its Table 1 lists four ranges: 915-921 MHz, 2 410-2 483.5/2 486 MHz,

5 725-5 875 MHz and 61-61.5 GHz. Its recognizing a) says plainly "that WPT has no status in the

RR".

The annex to CACE/1203 summarises what the revision does. Two items stand out. The first is an

addition: "added a new frequency range, 24.1-24.15 GHz, to Table 1 based on the completion of

impact studies in Report ITU-R SM.2505", with a new note beneath the table. That is a fifth band

named for beam WPT, and the study that justified it is the same Report whose 2026 revision added

a United States study at 24.1-24.15 GHz.

The second is a subtraction. The same annex records that the revision "removed ICNIRP and WHO

from the Abbreviations and Glossary section", because those acronyms were deleted from

considering g), and separately that it "deleted considering h)". In the 2022 text, considering

h) is the paragraph reading "that administrations wishing to introduce and bring into use beam

WPT applications should consider the exposure limits for non-ionizing electromagnetic fields".

The summary lists that paragraph as deleted, and lists the h) slot as refilled by the old

recognizing c), on the benefits of harmonised frequency ranges.

Be careful about how far that goes. The draft text itself is Document 1/85, restricted to ITU

members, so what is established here is what the public summary says: one deletion, and no

relocation named for it. The obligation may well reappear elsewhere in the revised text. The

summary does not say where, and I have not seen the draft.

It changes no exposure limit either way. Exposure limits do not come from SM.2151. ICNIRP's 2020

radiofrequency guidelines set a general public whole-body reference level of 10 W/m² incident

power density between 2 and 300 GHz, averaged over 30 minutes, and IEEE C95.1-2019 is the other

instrument a regulator will reach for. A Recommendation that drops a pointer to them does not

move either number. What it moves is what a spectrum administration reads when it first opens

the only ITU-R text naming bands for this technology.

One caveat that this site attaches every time the band comes up. The 5 725-5 875 MHz row is ISM

beam WPT between devices on the ground. 5.8 GHz is not regulatorily available for space-to-Earth

power transmission: there is no Article 21 space-to-Earth power flux-density row for it in the

Radio Regulations, Edition of 2024, and wireless power transmission has no status in the

Regulations at all.

The clutter model that is about to reach 5.8 GHz

Administrative Circular CACE/1205, dated 9 September 2026, is the Study Group 3 twin of the

above: one draft revision adopted, Member States asked to reply by 9 November 2026. It is a

revision of P.2108-1, "Prediction of clutter loss", and its annex is specific: "The revision

extends the lower frequency limit of the method from 10 GHz down to 500 MHz." The same annex

says the clutter loss distribution, today a function of elevation angle and frequency, becomes

additionally a function of ground station height and median clutter height.

The current text bounds that model tightly. Section 3.3 of Annex 1 in P.2108-1 covers the case

where one end of the path is inside man-made clutter and the other is a satellite, aeroplane or

other platform above the Earth, and states its validity as 10 to 100 GHz, elevation angles 0 to

90 degrees, applicable to urban and suburban environments. So today, for an Earth-space path at

5.8 GHz, the model does not apply. There is no ITU-R statistical clutter figure to cite. After

approval there would be one.

The magnitude is worth knowing before deciding whether to care. Evaluated at the model's own

lowest valid frequency, 10 GHz, for a 10 degree elevation angle and the median location,

equation (7) of P.2108-1 gives roughly 14 dB of clutter loss. That figure is an estimate

computed from the published equation, not a measurement, and it sits at the edge of the model's

stated range. At 5 degrees it is near 21 dB. Tens of decibels, in other words, for a terminal

low down among buildings and trees, falling away quickly as the elevation rises.

Here is the case against caring. This is a model of clutter loss on an interference path in

urban and suburban surroundings. The sites anyone would actually put a rectenna on are open

land, chosen precisely to have no clutter, and this revision does not change a power link

budget, a beam, or a safety case. What it changes is the arithmetic available to whoever has to

show that a ground station in a town neither causes nor suffers harmful interference, at a

frequency where that arithmetic currently has no ITU-R method at all.

How to read the stream

Approval by correspondence is a quiet procedure and its calendar is public. Two deadlines are

live now: 26 October 2026 for the SM.2151 revision, and 9 November 2026 for the P.2108

revision. In both cases Member States are asked to tell the Secretariat whether they approve,

the results are announced in a later circular, and the approved text is published after that.

The publication step is the one the editions pages report, and it is the last event in the

chain.

The practical consequence is small and worth doing. If you maintain a list of the editions you

cite, do not refresh it from the editions pages alone. Read the circular index, note the Study

Group and the annex, and treat a circular dated last week as better evidence than a publications

page dated today. It cost two fetches to establish everything above.

What would change my mind

Three things, and each is checkable by somebody other than me.

If the ITU's editions pages pick up P.372-18, P.311-20 and P.2041-1 within a day or two of

publication, and publication itself follows approval by a predictable interval, then the

complaint shrinks to a labelling matter: the page means published and says In force. I would

still want the page to say which it means, but "lagging indicator" would be the wrong phrase for

a queue that moves on schedule. The test is the next approval round.

If someone with ITU member access reads Document 1/85 and finds that the duty to consider

non-ionising exposure limits survives elsewhere in the revised SM.2151 text, then the second

section above is describing a tidy-up rather than a removal, and I would correct it. The public

summary is all I have, and a summary is not a text.

And if a Member State objects before 26 October, the SM.2151 revision does not enter into force

as adopted, in which case the band that is not yet in Table 1 stays out of it and the argument

about what the revision does becomes hypothetical. Objections are rare in this procedure. They

are not impossible.

Sources

https://www.itu.int/dms_pub/itu-r/md/00/cace/cir/R00-CACE-CIR-1206!!PDF-E.pdf

https://www.itu.int/dms_pub/itu-r/md/00/cace/cir/R00-CACE-CIR-1205!!PDF-E.pdf

https://www.itu.int/dms_pub/itu-r/md/00/cace/cir/R00-CACE-CIR-1203!!PDF-E.pdf

https://www.itu.int/md/R00-CACE-CIR/en

https://www.itu.int/rec/R-REC-P.372/en

https://www.itu.int/rec/R-REC-P.311/en

https://www.itu.int/rec/R-REC-P.2041/en

https://www.itu.int/rec/R-REC-P.2108/en

https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.2108-1-202109-I!!PDF-E.pdf

https://www.itu.int/rec/R-REC-SM.2151/en

https://www.itu.int/dms_pubrec/itu-r/rec/sm/R-REC-SM.2151-0-202209-I!!PDF-E.pdf

https://www.itu.int/pub/R-REP-SM.2505

https://www.itu.int/pub/R-REG-RR

https://www.icnirp.org/cms/upload/publications/ICNIRPrfgdl2020.pdf

https://standards.ieee.org/ieee/C95.1/4940/

A £1.3m contract points a 5.8 GHz beam up at the stratosphere. The design is settled on the ground.

2026-09-21T00:00:00Z

On 15 September 2026 Space Solar announced a £1.3m research contract from the UK's Advanced

Research + Invention Agency to develop RF power beaming to high-altitude platforms, at 5.8 GHz.

The interesting number is not the money and not the wattage. It is how much ground the

transmitter needs.

Figures below are labelled documented where a source states them and estimated where I have

calculated them from stated assumptions.

What was actually bought

Documented, from the company's own news page dated 15/09/2026: a £1.3m contract, one of 18

funded R&D Creators in ARIA's Enduring Atmospheric Platforms programme, to take rectenna work

from TRL 3 to TRL 7 over 36 months, at 5.8 GHz, ending in an integrated flight demonstration

aboard a PHASA-35. The named partners are Prismatic Ltd, which develops that aircraft, and

MuWave Limited, which is to develop the ground transmitter. Space Solar's release quotes co-CEO

Martin Soltau saying "Energy is one of the central constraints for HAPS." The release gives no

rectenna area, no range and no efficiency.

ARIA's own documents give the target the work is aimed at. The call for proposals, version 1.0

dated 3 December 2025, sets a primary metric of 300 W delivered continuously to a payload in the

sky for a full week while holding line of sight to a fixed point on the ground, with a 20 kg

payload as the tertiary metric. The programme runs 3.5 years. The proposed budget in that

document is £50m, split £6.1m to enabling technologies, £37.7m to system integration and

testing, £3.1m to deployment planning and £3.1m to programme partners; the programme's public

page now gives £70m. Orbital systems are explicitly out of scope, air-breathing very low Earth

orbit satellites included.

One small thing for anyone quoting the forward target. The programme thesis, version 2.0, puts

the future goal at 3 kW over one week and gives it as 0.5 MWh, which is right. The call for

proposals gives the same target as 840 kWh, which is not. Three kilowatts for 168 hours is

504 kWh. Use the energy figure that matches the power figure you are quoting.

Two limits on the award itself. ARIA has not published a Creators list for this programme: the

path that carries one for its sibling programme returns HTTP 404 here, checked on 20 September

And the company's release is first-party for the award and for the frequency, but it is

the only account of either. Nothing below depends on a second source for those two facts.

The aperture, not the wattage, sets the price

A ground-to-stratosphere power link is not a far-field radio link and Friis will mislead you.

Take a 100 m ground array at 5.8 GHz. Its far field begins at roughly 2D²/λ, which is about

387 km, so a receiver at 20 km sits deep inside the near field, where the beam can be focused

and where the right expression is the classical beam-efficiency result for two apertures: with

τ² = A_t·A_r / (λR)², the captured fraction is approximately 1 − exp(−τ²).

Everything in this section is estimated. The assumptions are: 5.8 GHz, so λ = 51.7 mm; a

vertical range of 20 km, which is the best case, since a slant path is longer; a rectenna of

20 m² on the underside of the aircraft, which is generous for a 35 m wing that BAE Systems

publishes as weighing 150 kg all-in and which already carries photovoltaics on top; and a

rectenna converting RF to DC at 70%. λR is then about 1,030 m².

A 30 m ground array is 707 m². That gives τ² ≈ 0.013 and a captured fraction of about 1.3%. To

land 300 W of DC in the payload you radiate about 33 kW.

A 100 m array is 7,850 m². Capture rises to about 14%, and the radiated power falls to about

3.1 kW.

A 217 m array is 3.7 hectares. Capture reaches about 50%, the radiated power is about 860 W,

and the wall-plug draw is about 1.2 kW if the transmitter converts DC to RF at 70%. That is an

end-to-end efficiency near 25%.

Seven times the array width buys a fortyfold cut in radiated power. That is the whole design

conversation, and it is a trade of land against watts. Electricity is not what is being traded.

Even the wasteful case draws about 47 kW, which at 25p per kilowatt-hour is about £12 an hour,

against the programme's own gross operating cost target of under £500 an hour. That target is

ARIA's threshold for the platform, not a forecast of anything, and the electricity line is not

where it will be won or lost.

The same choice decides the exposure question

ICNIRP's 2020 radiofrequency guidelines set, for 2 to 300 GHz, a whole-body incident power

density reference level of 10 W/m² for the general public and 50 W/m² for occupational

exposure, each averaged over 30 minutes. IEEE C95.1-2019 sits alongside them. Those are the

numbers a site is assessed against, not a reassurance about beam density being low.

Now put the estimates beside them. The 30 m array radiating 33 kW is about 47 W/m² averaged

across its own face. That is just under the occupational reference level, about 4.7 times the

general public one, and a tapered illumination is higher than the average on axis. It implies a

fenced, controlled, access-managed site, with the exposure case made at the array rather than

at the aircraft.

The 100 m array radiating 3.1 kW is about 0.4 W/m² across its face, a factor of 25 below the

general public level. The 217 m array is lower again by more than an order of magnitude.

So the aperture decision and the exposure decision are the same decision. A small array is a

regulated industrial site. A large one is a field with a low-power emitter in it and a planning

problem instead. At the far end, 300 W into 20 m² is about 15 W/m² at an uncrewed airframe,

which is a hardware and airframe question rather than a human exposure one. The column of air

between the two is inside UK controlled airspace, which is why ARIA's solicitation offers

Creators segregated airspace at a UK test range during defined testing windows, and names the

Civil Aviation Authority.

The good news is that there is a regulator at all

This beam points up and stays inside one jurisdiction, and that is a materially better

regulatory position than the one a satellite downlink is in. 5.8 GHz is not regulatorily

available for space-to-Earth: the Radio Regulations, Edition of 2024, carry no space-to-Earth

power flux-density row for the band, and wireless power transmission has no status in the

Regulations at all. None of that binds a ground-to-air link. What binds it is Ofcom, and ARIA's

own milestone list requires TA3 teams to reach a critical design review with plans for spectrum

licensing and buy-in from the CAA and Ofcom.

The international instruments are thinner than the size of the beam suggests. The only ITU-R

Recommendation naming frequency ranges for beam wireless power transmission is SM.2151-0

(09/2022), still listed In force (Main) on the ITU's editions page when I checked it on 20

September 2026, and its title scopes it to mobile and portable devices and sensor networks. Tens

of kilowatts aimed at an aircraft is not that. A draft revision is in the approval queue:

Administrative Circular CACE/1203 of 26 August 2026 records Study Group 1 adopting it, with

Member States asked to reply by 26 October 2026, and the annex says it adds 24.1-24.15 GHz to

Table 1 on the strength of the impact studies in Report ITU-R SM.2505. The scope in the title is

unchanged.

The broader question is queued behind a conference. WRC-31 preliminary agenda item 2.2, under

Resolution 910 (WRC-23) and assigned to Working Party 1A, covers possible bands for non-beam and

beam wireless power transmission, and its published framing is avoiding harmful interference

caused by such transmission rather than enabling it. A 36-month project starting now finishes

years before that item reaches a conference. The demonstration will exist before the band

question is answered, which is an argument for doing the demonstration under a national licence

with published conditions, and for publishing what those conditions turn out to be.

What it does not say about orbit

Run the same formula at 400 km and λR becomes about 20,700 m², so the aperture product required

for a given capture fraction grows by a factor of 400. The 217 m ground array that reaches 50%

at 20 km becomes about 4.3 km across at 400 km against the same 20 m² receiver. Stratospheric

power beaming is not a scale model of orbital power beaming. It is a different problem that

happens to use the same hardware vocabulary, and the honest reading of this contract is as a

test of rectennas, phased arrays and beam control at a range where the arithmetic closes.

BeamDesk has no involvement in this programme and no relationship with any organisation named

here. Everything above is from their published material and from the issuing bodies' own

documents.

What would change my mind

A measured end-to-end DC-to-DC efficiency at kilometre-scale range, published with the aperture

areas and the illumination taper, would test the whole of the second section. If it beats these

estimates materially, the assumption that broke is probably the rectenna area or the taper, and

I would want to know which.

If the flight demonstration meets the metric in bursts rather than continuously, or fractionally

across several platforms, which the programme explicitly permits, then the land-against-watts

trade is not the one being made and the exposure arithmetic changes with it.

If ARIA publishes its Creators list and more than one award is power beaming, particularly an

optical one, then treating this as an RF bet is too narrow and the story is RF against laser at

the same altitude.

If Ofcom authorises the transmission with published EIRP or power density conditions, that is a

concrete national answer to a question the ITU has parked until WRC-31, and it would be the most

useful document anyone in this field could read this decade.

Sources

https://www.spacesolar.co.uk/space-solar-wins-1-3m-aria-contract-to-help-power-enduring-stratospheric-flight-over-britain/

https://www.spacesolar.co.uk/category/news/

https://aria.org.uk/opportunity-spaces/scoping-our-planet/enduring-atmospheric-platforms

https://aria.org.uk/media/xiukdjjv/enduring-atmospheric-platforms-programme-solicitation_accessible.pdf

https://aria.org.uk/media/et5hsubs/programme-thesis-enduring-atmospheric-platforms.pdf

https://www.baesystems.com/en/product/phasa-35

https://www.itu.int/rec/R-REC-SM.2151/en

https://www.itu.int/dms_pub/itu-r/md/00/cace/cir/R00-CACE-CIR-1203!!PDF-E.pdf

https://www.itu.int/en/ITU-R/study-groups/rcpm/Pages/wrc-31-preliminary-studies.aspx

https://www.itu.int/pub/R-REG-RR

https://www.icnirp.org/cms/upload/publications/ICNIRPrfgdl2020.pdf

https://standards.ieee.org/ieee/C95.1/4940/

Space mirrors offer a faster route to orbital power than microwave transmission

2026-09-18T00:00:00Z

The return of the space mirror

Reflect Orbital, an aerospace company headquartered in Hawthorne, California, is preparing to launch a satellite designed to reflect sunlight onto the night side of Earth. Founded in 2021 by Ben Nowack and Tristan Semmelhack, the privately held firm aims to provide responsive lighting after dark and increase the effective hours of solar energy production. Nowack, who previously worked at Zipline and interned at SpaceX, serves as chief executive, while Semmelhack is the chief product officer. The company has attracted significant investment, raising $35.2 million in Series A funding from venture capital firms including Sequoia Capital, Lux Capital, and Climate Capital.

In July 2026, the Federal Communications Commission granted the company a license to launch its first demonstration satellite, Eärendil-1. The spacecraft is scheduled to fly aboard a SpaceX Falcon 9 rideshare mission later this year. Eärendil-1 is designed to operate at an altitude between 500 and 650 kilometres. The 134-kilogram satellite will unfurl four triangular panels to create an 18-by-18-metre square of highly reflective material, constructed with an aluminium front and a space-grade plastic backing. Once deployed, the satellite will use oversized reaction wheels (components typically used in 650-kilogram-class spacecraft) to angle its mirrors without burning fuel. The resulting illumination will cover an area about five kilometres wide and is expected to provide brightness comparable to a full moon. Because the satellite moves at approximately 7.5 kilometres per second, it will illuminate a single target on the ground for only a few minutes before passing over the horizon. The company received a $1.25 million award from the United States Air Force in 2025 to support this initial demonstration. Nowack has stated that the prototype cost around $2 million to build, but future production units are estimated to cost roughly $300,000 each.

The commercial case for artificial daylight

The primary market for this technology is utility-scale solar farms. Humanity consumes less than one trillionth of the sun's output, and solar energy currently represents a small fraction of global electricity production. Reflect Orbital intends to extend the productivity of existing solar infrastructure without requiring new land use or additional ground equipment. By 2030, the company aims to field enough satellites to supply solar farms with about 200 watts per square metre during the evening peak in electricity demand. This intensity is comparable to sunlight at dawn or dusk.

To achieve continuous illumination, a massive constellation is required. Reflect Orbital plans to launch 36 satellites by 2027, expanding to 5,000 by 2030, and ultimately operating up to 50,000 reflector satellites by 2035. Arranged in a continuous chain, these larger production satellites, which would measure 54 metres across, could keep solar farms illuminated for hours as new mirrors come into view just as previous ones set. The company also envisions selling its lighting services to emergency response crews, remote industrial sites, and outdoor events.

This architecture contrasts sharply with traditional space-based solar power, which involves collecting solar energy in orbit, converting it to microwaves, and beaming it to a ground rectenna. Such microwave systems face immense regulatory and technical hurdles. For instance, engineers frequently propose using the 5.8 GHz frequency for power transmission. However, 5.8 GHz is not regulatorily available for space-to-Earth, and securing spectrum rights remains a massive barrier. By merely redirecting natural sunlight, Reflect Orbital bypasses the need for complex orbital power conversion and ground rectennas entirely.

The historical precedent of Znamya

The concept of placing reflective surfaces in orbit to redirect sunlight to the ground predates Reflect Orbital by a century. The physicist Hermann Oberth first proposed large orbital mirrors in 1923. However, the only successful deployment of such a device was achieved by the Soviet Union and Russia during the 1990s under the Znamya project. Led by aerospace engineer Vladimir Syromyatnikov, who famously designed the docking system for the 1975 Apollo and Soyuz mission, the initiative originally sought to test solar sail propulsion but was repurposed to demonstrate artificial orbital illumination.

On 27 October 1992, the uncrewed Progress M-15 cargo spacecraft launched from the Baikonur Cosmodrome to resupply the Mir space station. After completing its primary logistical mission, the spacecraft undocked on 4 February 1993 and deployed Znamya 2. The device was a 20-metre-wide circular mirror made of aluminium-coated plastic that weighed less than four kilograms. Because the mirror lacked a rigid frame, the spacecraft had to spin to deploy the fragile material using centrifugal force. The experiment succeeded, reflecting a five-kilometre-wide beam of light that traversed Europe from southern France to western Russia at eight kilometres per second.

Despite this technical triumph, the project ultimately collapsed. Russia launched a larger successor, Znamya 2.5, in October 1998 aboard a Progress M-40 spacecraft. This 25-metre reflector was designed to produce a bright spot seven kilometres in diameter with a luminosity between five and ten full moons. During its deployment on 4 February 1999, the delicate mirror snagged on a spacecraft antenna and tore apart. After several failed attempts by Russian mission control to free the material, Znamya 2.5 was de-orbited and burned up upon re-entry, effectively ending the Russian space mirror programme.

The regulatory and environmental backlash

Reflect Orbital faces fierce opposition from astronomers, environmentalists, and dark sky advocates. The core argument against the constellation is that scattered light from thousands of orbital mirrors will significantly increase skyglow and degrade ground-based astronomical observations. Astronomer Miroslav Kocifaj and his research team calculated the illumination from these satellites and concluded that light pollution would extend well beyond the targeted areas. Critics warn that the proposed fleet could add several hundred objects as bright as Venus to the night sky by 2035. Moving beams of light from space-based mirrors could also create sudden flashes or glare, posing risks to night vision, aircraft operations, and wildlife ecosystems, including bird migration patterns.

Jonathan McDowell, an astrophysicist who has tracked human-made space objects since 1989, publicly criticised the initiative. In September 2026, he described the system to Science News as an insane project, arguing that the company fails to understand that darkness is a beneficial state. Furthermore, some astronomers assert that viewing the reflected beam through a moderate-sized telescope could damage observers' eyes or harm sensitive research equipment. Reflect Orbital counters that the risk of eye damage is extremely low, calculating that intentionally tracking the satellite for 100 seconds through a 12-inch diameter telescope would still stay within international eye-safety limits.

In March 2026, the American Astronomical Society petitioned the Federal Communications Commission to deny Reflect Orbital's request to operate its test satellite. When the agency granted approval in July, nonprofit organisations including DarkSky International formally asked the regulator to reverse its decision. The Federal Communications Commission concluded that it lacks the authority to evaluate the environmental impacts of an orbital solar reflector, limiting its review strictly to radiofrequency spectrum usage. DarkSky International continues to demand a full environmental risk evaluation by independent experts.

Reflect Orbital has defended its approach, stating that it engaged with the astronomical community before filing its licensing request. Christopher Buscombe, a spokesperson for the company, wrote in an email to Science News in September 2026 that "exploring how new technologies can help the world forgo fossil fuels is a responsible application of the scientific process." The company insists its service will be controllable, transparent, and avoidable. The reflectors are motorised and steerable, which the firm claims will ensure that reflected light is visible only in targeted areas and kept away from observatories and dark sky parks. Furthermore, the company plans to share its satellite positions in advance so that researchers can plan their observations around the brief windows of operation.

What would change my mind

The commercial viability of orbital mirrors depends entirely on achieving a massive scale while navigating an ambiguous regulatory environment. My current view is that Reflect Orbital offers a more immediate path to space-based solar power than microwave transmission, but several factors could alter this assessment.

First, the regulatory loophole that allowed Eärendil-1 to be licensed might close. If the Federal Communications Commission or international bodies assert jurisdiction over orbital light pollution, the company could be blocked from launching its planned 50,000-satellite constellation. Without the ability to deploy in vast numbers, the service cannot provide continuous illumination.

Second, the operational reliability of the constellation remains unproven. If the typical worst gap in a day between satellite passes is too long, utility-scale solar farms will not be able to rely on the service to meet evening peak demand. A failure to provide consistent, uninterrupted light would destroy the economic justification for the project.

Finally, the physical risks of operating massive, fragile structures in low Earth orbit cannot be ignored. The failure of Znamya 2.5 demonstrates how easily thin reflective membranes can snag and tear. Furthermore, as low Earth orbit becomes increasingly congested, the large surface area of these mirrors makes them highly vulnerable to space debris. A catastrophic collision could generate a debris field that endangers other assets, prompting immediate regulatory intervention that would ground the entire enterprise.

Sources

Orbital Reflectors Expose a Regulatory Vacuum Over Light Pollution

2026-09-18T00:00:00Z

The First Orbital Reflector

The US Federal Communications Commission approved a demonstration satellite on July 9, 2026, that is designed to reflect sunlight onto the Earth after dark. The spacecraft, named Earendil-1, is built by the California-based startup Reflect Orbital. It will carry an 18-by-18-metre thin-film mirror made of glossy mylar plastic into an orbit 600 kilometres above the surface. The satellite will launch folded like origami and deploy its flat mirror in space. The company intends to test the feasibility of redirecting natural sunlight to terrestrial solar farms, extending their operating hours past sunset. The license permits Reflect Orbital to test the technology for up to two years.

Reflect Orbital envisions a future constellation of up to 50,000 mirrors by 2035. The economic premise relies on capturing peak electricity pricing. Ben Nowack, the chief executive of Reflect Orbital, told Sky & Telescope in July 2026 that it would be beneficial to capture solar energy outside daylight hours because operators could "charge higher prices and make a lot more money." Extending the daily generation window improves the utilisation of existing solar infrastructure without requiring additional ground-based construction. By selling sunlight on demand, the company hopes to provide an alternative to massive battery storage facilities. The company also suggests the technology could illuminate disaster zones after dark for free to assist rescue teams.

The approval marks a significant milestone for the orbital power industry, but it has triggered intense opposition. The FCC received over 1,800 public objections to the application. The debate has exposed a critical gap in how emerging space technologies are governed, pitting the commercial drive for renewable energy against the preservation of the night sky.

The Limits of the FCC

The Federal Communications Commission regulates the use of the radio spectrum. It does not regulate visual light. When the American Astronomical Society petitioned the agency in July 2026 to deny the license for Earendil-1, the organisation warned that the satellite carries the "potential for eye damage to amateur astronomers looking through reasonably sized telescopes." They also cited the risk of flash-blinding pilots and drivers, alongside the broader implications for optical astronomy.

The FCC approved the satellite despite these warnings. In its July 2026 ruling, the agency stated that the effects on optical astronomy are beyond its scope of review. The regulator concluded that harm from the reflector is not likely to occur, and that the deployment of a solar reflector is beyond its authority to regulate. The FCC did stress that approving this single demonstration satellite does not predetermine the outcome of any future application for a larger constellation.

This decision rests on a long-standing precedent. In the United States, satellite projects are exempt from the National Environmental Policy Act. This exemption has been in place since the 1980s, an era when only a handful of satellites were launched each year. Today, the astronomical community argues that this logic leaves regulators powerless. The American Astronomical Society noted in its July 2026 statement that the FCC's logic implies the commission would have no ability to consider the severe implications of a 50,000-satellite constellation. The society also expressed dismay that the FCC did not require a formal coordination agreement to protect federally funded astronomical facilities, a step the agency has historically taken when observatories are at risk.

The Case Against Artificial Twilight

The visual impact of a massive space mirror extends far beyond its intended target. A study by astrophysicist Gaspar Bakos of Princeton University and František Kundracik models the exact light pollution these satellites would generate. The research, accepted for publication in The Astrophysical Journal and available on arXiv, calculates the effects of atmospheric light scattering.

The researchers focused on Reflect Orbital's planned operational mirrors, which would measure 54 by 54 metres. According to their models, an observer standing at the centre of the mirror's 5.4-kilometre-wide beam would see a light 40 times brighter than the full moon. The sky would become as luminous as after-sunset twilight, completely wiping out the stars. Bakos told Space.com in August 2026 that the situation "will be worse than big cities like London" because observers would not see any stars if they were in the beam.

The problem is compounded by the atmosphere. As photons bounce off particles in the air, the light spreads. The study found that even 14 kilometres away from the beam, the sky would remain brighter than during a full moon. At a distance of 34 kilometres, the light-polluted area above the horizon would still appear brighter than the night sky during a full moon.

A single mirror is not enough to generate commercial power. Bakos estimates that triggering energy generation in modern solar panels would require the combined reflected light from at least 400 mirrors simultaneously. The resulting beam would be 10,000 times brighter than the full moon. The researchers found that the sky glow from these combined beams would be visible from 80 kilometres away. The light pollution from a town illuminated by the beam would be ten to twenty times brighter than the artificial lighting in that same town. Artificial light only illuminates streets and sidewalks, but the orbital beam would illuminate every backyard, park, roof, and river.

The overall effect depends heavily on the ground surface and the weather. A dense forest might absorb most of the light, while snow-covered fields or concrete city streets would scatter it further into the atmosphere. Biologists have also raised concerns. Brett Seymoure, a biologist at the University of Texas at El Paso, noted in a September 2026 Science News interview that nighttime light can disrupt circadian rhythms, the behaviour of nocturnal animals, and the migration patterns of birds and insects.

For comparison, SpaceX currently operates around 11,000 Starlink satellites. While astronomers complain that Starlink leaves streaks on telescope images, those satellites are much smaller and dimmer than the proposed orbital reflectors. A constellation of 50,000 massive mirrors represents a fundamentally different scale of light pollution.

The Industry's Defence

Reflect Orbital disputes the findings of the Princeton study. The company argues that the models rely on inaccurate assumptions and that the vast majority of people will never see the light.

Christopher Buscombe, a spokesperson for Reflect Orbital, told Science News in September 2026 that "exploring how new technologies can help the world forgo fossil fuels is a responsible application of the scientific process." The company maintains that the service locations will be remote solar farms and large construction projects. They state that only the satellites required to serve approved locations would be active, and that inactive satellites would remain below the threshold of naked-eye visibility. The mirrors are steerable and can be tilted away from the Earth instantly to turn off the beam.

The company insists it is engaging with the scientific community. Reflect Orbital says it is working on a coordination agreement with the National Science Foundation. It is also commissioning third-party research through independent scientists to verify its own operational plans. The industry's broader argument is that orbital reflectors are a necessary step to make solar power dispatchable, reducing the need for fossil fuels during peak evening demand.

The Microwave Alternative

Most space-based solar power architectures do not rely on reflecting raw sunlight. Instead, they propose capturing solar energy in orbit, converting it to microwaves or lasers, and beaming it to a ground rectenna. This approach bypasses the visual light pollution problem entirely.

Microwave transmission is invisible to the human eye and does not scatter through the atmosphere in a way that disrupts optical astronomy. However, it requires massive orbital infrastructure to perform the conversion, making it technologically and financially daunting. Reflecting sunlight requires only a thin-film mirror, drastically reducing the mass and complexity of the spacecraft.

Microwave architectures also face their own regulatory barriers regarding spectrum allocation. For example, while 5.8 GHz is frequently discussed as an ideal frequency for wireless power transmission, 5.8 GHz is not regulatorily available for space-to-Earth. Any commercial microwave beaming system will require international coordination to secure a dedicated frequency, a process that could take years. Reflect Orbital's approach attempts to sidestep spectrum allocation for power transmission, using radio frequencies only for telemetry and control. This strategy has successfully secured a license for a demonstration, but the resulting visual light pollution has created a fierce backlash.

What would change my mind

If the Federal Communications Commission or another US agency is granted explicit statutory authority to regulate visual light pollution from orbit, the current regulatory vacuum would close. This would force orbital reflector companies to undergo rigorous environmental reviews before launching massive constellations.

If Reflect Orbital publishes peer-reviewed technical data proving that their mirrors can operate without causing the severe atmospheric scattering modeled by Bakos, the threat to optical astronomy might be manageable. The current debate relies heavily on models generated by the company's critics, and empirical data from Earendil-1 could disprove the worst-case scenarios.

If the cost of ground-based battery storage continues to plummet, the economic case for orbital reflectors may collapse. The entire business model depends on sunlight-on-demand being cheaper than storing daytime solar energy for nighttime use. If batteries win the economic race, the constellation of 50,000 mirrors will never leave the drawing board.

Sources

A Report is not a Recommendation, and the difference is the whole regulatory question

2026-08-30T00:00:00Z

The ITU has identified 5.8 GHz for space-based solar power. Every word of that

sentence traces to a real document, and the claim is false.

The document is ITU-R Report SM.2392, "Applications of wireless power transmission via

radio frequency beam". A new edition appeared in June 2026, superseding the 2021 text.

Its Section 5 addresses spectrum for RF-beam wireless power transfer and names 915 MHz,

2.45 GHz, 5.8 GHz and 24 GHz as the bands the field uses. Section 2.9 is titled "Space

based solar power via satellite". If you work on power beaming, this is a genuinely

useful document, and until it existed much of the frequency discussion in this field

cited nothing at all.

None of that makes it permission.

Reports describe. Recommendations bind.

The ITU-R publishes several kinds of text, and two of them are easy to confuse.

A Recommendation is a technical standard. Other instruments incorporate it by

reference. When a national regulator writes a licence condition that points at ITU-R

P.618, the propagation model in P.618 acquires legal force in that jurisdiction through

the pointer. Recommendations are what the phrase "the ITU says" usually means when

somebody says it and is right.

A Report is a description of a state of affairs. It surveys, it summarises, it

records what practitioners do. It recommends nothing and it binds nothing. SM.2392

behaves like one throughout. It observes that 2.45 GHz is more desirable than the higher

bands because propagation impairments are smaller, which is a statement about physics

rather than about spectrum.

One of these you can cite in a licence application. The other you can cite in a

literature review.

Why 5.8 GHz is the one that will catch people

Take the tempting inference at face value and follow it. The ITU has named 5.8 GHz among

the bands used for RF power transfer. Space-based solar power appears in the same

document. Therefore 5.8 GHz is a candidate for space-to-Earth power beaming.

The first two steps are accurate. The third does not follow, and the reason is in a

different document entirely.

5.8 GHz sits in an ISM band: industrial, scientific and medical, shared, unlicensed for

many uses, and busy. What matters for a satellite is not the ISM status

but the Radio Regulations, and specifically Article 21, which sets power flux-density

limits on what a space station may deliver to the Earth's surface in a given band. The

Radio Regulations carry no Article 21 space-to-Earth power flux-density row for 5.8 GHz.

There is no limit written for it because the Regulations do not contemplate a space

station transmitting at these power levels into that band at all.

So the honest statement is that **5.8 GHz is not regulatorily available for

space-to-Earth power beaming today.** The band is not restricted or subject to

coordination; there is no framework in which to ask the question at all. A Report naming

it as the band the field uses on the ground describes engineering practice. It is not an

allocation and not a change to Article 21, and a regulatory assumption built on it rests

on nothing.

That sentence is uncomfortable if you are raising money on a 5.8 GHz architecture. It is

considerably more uncomfortable to discover it at the point where a regulator asks.

The ISM problem cuts the other way too

There is a second reason to be careful with 5.8 GHz, and it is not regulatory at all.

The Radio Regulations designate certain bands for industrial, scientific and medical

applications, and the arrangement comes with a condition attached: radiocommunication

services operating in an ISM band must accept harmful interference from ISM equipment.

The band is shared on the understanding that nobody in it is protected.

For a microwave oven that is a reasonable bargain. For a power link it is a strange one.

A receiving site is being asked to accept interference from every other user of the band

while delivering a service somebody is paying for, and the whole commercial case for

beamed power rests on the delivery being predictable enough to contract against. Choosing

a band precisely because it is lightly regulated means choosing a band in which you have

no standing to complain.

That is not an argument against 5.8 GHz on physics. Propagation at 5.8 GHz is workable

and the hardware is mature, which is exactly why the field converged on it for ground

demonstrations. It is an argument that the band's convenience on a test range and its

suitability for a contracted service are different questions, and the second one has

barely been asked.

What we did with it

We file the documents we cite in a public registry, with a column recording how far we

actually go with each one. The categories are deliberately unflattering to ourselves:

whether a method is computed in our code, whether we parse data in that format, whether

we merely use the vocabulary accurately without executing anything.

SM.2392 went in as vocabulary. We cite it for its terms, which are the ITU's own

description of the application, and we execute nothing from it, because there is nothing

in it to execute. Our Article 21 caveat stayed exactly where it was, because nothing in

the new edition touched it.

That is the whole of what a Report can do to a system like ours. It improved the

citation behind a definition. It did not move a limit, enable a band, or alter a

constraint.

The narrower trap, for anyone flying low

There is a second inference in this document worth ruling out, and it is subtler than

the spectrum one.

Section 2.9 describes a geostationary system. Most published work on beamed power at

scale is geostationary, for the good reason that a satellite parked over one spot solves

the intermittency problem that a low orbit creates. Ground-footprint figures in that

literature follow from aperture and range, and at geostationary range the numbers are

large.

If you fly in low Earth orbit, your range is two orders of magnitude shorter. Should one

of the areas stated in a geostationary study happen to sit near a number in your own

model, that agreement is a coincidence of scale across a fundamentally different link.

It is not the ITU validating your case. Citing it as though it were is the kind of error

that survives internal review precisely because the citation is real and the number

matches.

Take a citation for what it covers, and no further.

What would change my mind

A Recommendation. If ITU-R published one governing RF power transfer from a space

station to the ground, or if a World Radiocommunication Conference agenda item opened

work on a space-to-Earth allocation for power beaming, the regulatory position in this

piece would change materially and I would say so here.

A power flux-density row in Article 21 covering these bands for this use would do it

too, and would be the single clearest signal available that the question has moved from

description to permission.

Short of that, a national regulator granting an experimental licence for a space-to-Earth

power beaming demonstration would not change the international position, but it would be

the first real evidence of how a regulator intends to reason about one — and that is

worth more than another survey.