Wednesday, November 01, 2023

Space-ground optical (laser) communication


Inter-satellite laser links are in use now, but the technology for optical links to the ground is still being developed and tested. 

Optical frequency laser communication links have many advantages over radio frequency (RF) links:
  • Optical transmission is much faster than RF communication.
  • Optical terminals are smaller and cheaper than RF terminals and use less power.
  •  It's harder to intercept or jam optical signals so they are more secure and, conversely, better for clandestine use.
  • Multiple optical beams can be transmitted simultaneously to multiply speed.
  • Optical transmission is license-free. (There isn't enough RF spectrum to accommodate all of the currently proposed satellites).
SpaceX is equipping its new satellites with inter-satellite laser links (ISLLs). They now have over 8,000 optical terminals in orbit (3 per satellite) and they communicate at up to 100 Gbps. The other low-Earth orbit Internet service providers will follow SpaceX's lead.

Optical communication works well between satellites in the vacuum of space, but optical signals are weakened and distorted by clouds, rain, water vapor, dust, heat gradients, pollen, etc. in the atmosphere so today SpaceX and others use RF frequencies for communication between space and the ground.

Optical space-ground projects

Given the long list of optical advantages, many organizations are working on technology to adjust for atmospheric interference and use optical communication between space and the ground. The following are a few examples of optical communication research and development by NASA, universities, the military, private industry, and the Chinese. 

Ten years ago, NASA demonstrated optical communication between a satellite orbiting the moon and Earth, and they are updating that now. They have a data relay satellite in geosynchronous orbit for relaying data from other satellites to the ground and they are working on transmission from deep space beyond the Moon so we will be able to see video from Mars when we land there. They have also transmitted data between a cubesat with a 2.3 kg payload and the ground at a rate of 200 Gbps. 

ETH Zurich test site
Researchers at ETH Zürich have transmitted data from a mountaintop to their lab 53 kilometers away at up to 0.94 Tbit/s/channel. (Note that the top of the stratosphere is only 50 km from the ground). They adjust for atmospheric variance using sophisticated algorithms and terminals with adaptive optics that can correct the wave phase 1,500 times per second. Their technology can scale up to 40 channels and they are working on more efficient modulation schemes.

The ETH Zürich transmission was from a fixed point on top of a mountain to their lab – how about from a moving satellite? LEO satellites move across the sky at an angular tracking rate of ∼1 deg/s and researchers at the University of Western Australia have demonstrated that they can maintain contact with a drone moving back and forth at that rate. 

In Ukraine, SpaceX Starlink has demonstrated both the military value of satellite Internet and the drawback of being dependent on a private company.

SDA Tracking Layer constellation (source)
The Space Development Agency (SDA) of the Space Force is developing two constellations, a Tracking Layer constellation for warning of, tracking, and targeting advanced missile threats and a Transport Layer constellation providing connectivity to the full range of warfighter platforms. 

There will be ISLLs, using SDA standard optical communication terminals, within and between the early constellations. The early satellites will use RF links to the ground, but optical links are planned.

Tracking plus transport to intercept missiles with planned
optical links to the ground (source)
Space Force policy is to scale up its use of commercial capabilities and Mynaric has been awarded Tracking and Transport Layer contracts for their CONDOR Mk3 optical terminal. CACI International and Tesat terminals have also been certified and will be used -- standards enable competition.

Mynaric has also been selected to participate in a demonstration of links between various space-based optical terminals and an optical ground station they will design. 

The SDA is also working with Aalyria, a startup with two products, Tightbeam and Spacetime, that are based on intellectual property acquired from Google. 

Tightbeam is an optical communication technology that sounds similar to that of ETH Zürich. Using adaptive mirrors and proprietary algorithms, they have transferred data to and from a local mountain at 400 Gbps per channel, (They can use four channels simultaneously). They recently signed a maritime contract for connectivity "starting at" 100 Gbps. 

Tightbeam is only available through Spacetime, an extremely ambitious network operating system for controlling fixed and mobile assets and the links between them on Earth, in the air, and in space. Spacetime runs a simulation of the network and if an upcoming problem is predicted -- for example a weather event or an airplane banking -- Spacetime will reconfigure the network to route around it in 200 ms

(Spacetime is open source with open APIs and Spacetime networks can “federate,” accessing each other’s assets to create a “network of networks.” Sound familiar? APIs are open and they hope to establish standards -- reminiscent of Ethernet vs early proprietary LAN technology. I recommend watching this Spcetime presentation).

Intelsat has provided geostationary satellite communication since the 1960s and is also working with Aalyria on multi-orbit service and space-to-ground optical communication. (They are also considering a medium Earth orbit constellation -- could federating with SES's mPower constellation be an alternative to creating their own)?

I searched for and found two Chinese optical space-ground experiments, one by Beidou in 2021 and a recent test by The Chinese Academy of Sciences with a 10 Gbps transmission rate. I checked with Blaine Curcio, an expert on Chinese space, and he does not know of other tests.

Ground infrastructure

If projects like the above succeed in developing cost-effective space-ground optical communication technology, we will need significant investment in well-designed ground infrastructure. Optical antennas can be added to existing RF ground stations or new optical ground stations can be built.

World cloud cover map (source)
Augmenting existing ground stations makes sense if they are in suitable locations because they already have real estate, power, and Internet connectivity. For example, SpaceX has 75 gateways in North America, several of which are in arid regions of northern Mexico and the US southwest.

New ground stations with optical gateways will also be needed. They should be in relatively cloud-free places and, if possible, near centers of demand and locations with access to high-speed terrestrial Internet connections and power. The current locations of astronomical observatories might be considered.

African gateways
One of the United Nations Sustainable Development Goals is "to build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation" -- to reduce the digital divide. The needs of underserved areas should also be considered in locating ground stations. Today, SpaceX has only two RF ground stations in Africa, and there are arid regions in the north and south that might be suitable locations for optical ground stations.

ISLL path between arid areas in Mexico and Africa (source).
Such opportunities will increase as ISLLs proliferate.
Even if locations are carefully selected, routing around unfavorable weather or other atmospheric problems will occur at times. That will be facilitated by the proliferation of ISLLs. Furthermore, the addition of ISLLs to sharply inclined orbits will facilitate routing around winter in the northern and southern hemispheres.


This post is based on a presentation at a recent UN Internet Governance Forum panel but it has been significantly revised and extended. You can get a copy of the revised PowerPoint presentation here.

The presentation includes a Frequency terminology cheat sheet.

For an excellent tutorial on the properties of laser light, click here.

Thanks to Brian Barrit of Aalyria and Shane Walsh of The University of Western Australia for their input.

Update 11/3/2023

NASA's ILLUMA-T optical terminal will be delivered to the International Space Station in a SpaceX Cargo Dragon launch scheduled for no earlier than November 5. Once installed on the exterior of the space station it will enable two-way communication through the data relay satellite mentioned above to and from optical ground stations in Hawaii and California at 1.2 Gbps.

Monday, September 18, 2023

Will Telesat survive?

In 2017, Telesat, an established Canadian geostationary satellite operator, announced a planned low-Earth orbit Internet service constellation. The plan called for 117 satellites with inter-satellite laser links in a mix of inclined and polar orbits, enabling global coverage. They planned to ignore the consumer market and designed for the enterprise, government, mobile backhaul, mobility, and rural community markets. The mass of their production satellites would be roughly four times that of SpaceX's first-generation satellites. Telesat orbited their first test satellite a month before SpaceX. 

Today, there are over 5,000 Starlink satellites in orbit and Telesat plans to begin launching production satellites in 2026 and won't begin service until 2027. How did Telesat fall so far behind?

Unlike SpaceX, which is fully integrated, Telesat sought vendors for satellite manufacturing, antennas, and launch service, and spent time and money on collaborative design with potential contractors and soliciting and evaluating bids. In February 2021, Telesat selected Thales Alenia Space as the prime contractor for an initial constellation of 298 satellites. (Musk's integrated approach to manufacturing cars or rockets is reminiscent of Henry Ford)

In 2022, Covid, supply chain shortages, inflation, and financing difficulties, led Telesat to cut the constellation to 198 satellites. The schedule slippage raised concerns over Telesat's spectrum licenses (they will have to apply for an extension), and they needed additional capital while their geostationary satellite revenue was declining slightly. Telesat stock, which was offered at $40 per share was trading for a fourth of its initial price and bonds were trading well below par. 

The stock price doubled with the Hail Mary announcements. 
Telesat recently announced two decisions that Tim Farrar, President of TMF Associates, characterizes as a Hail Mary play. 

Last month, MDA, which had been selected to provide Telesat antennas last year, replaced Thales Alenia Space as the prime contractor and manufacturer of the satellites. Telesat expects the new satellites to be about 750 kg -- around the mass of SpaceX's second-generation "Mini" satellites. With these changes, Telesat has funding for the first 156 satellites with the remainder to be paid for from revenue once 156 are in service. 

This month, Telesat announced that they had contracted with SpaceX for fourteen launches starting in 2026. (Note that SpaceX is also launching satellites for competitor OneWeb and Amazon is being sued by shareholders for not considering SpaceX to launch their competing Project Kuiper satellites).

Telesat has lost valuable time. The delay has given SpaceX time to sign over 1.5 million customers, enter the non-consumer markets Telesat is focusing on, and begin launching their second-generation satellites equipped with inter-satellite laser links in both polar and inclined orbits. OneWeb will also be in service and competing with Telesat by 2026. Telesat also says that, despite having geostationary satellites, they will not provide multi-orbit service, while others will

I was on a podcast panel a while back with a Canadian colleague, and he believes the Canadian government will keep Telesat going if needed. I hope Telesat completes its Hail Mary pass -- we need all the competition we can get and the government and military need alternatives to Starlink.

Update 10/19/2023

Telesat explains the benefits of its Lightspeed constellation over rival LEO broadband constellations.

  • Lightspeed satellites orbit at higher altitudes than the others therefore each satellite can serve a larger area with fewer gateways, handoffs are less frequent, and collision risk is lower.
  • Each satellite has four inter-satellite antennas, creating a fixed mesh in space (SpaceX satellites have three).
  • There are only 198 satellites, but Lightspeed antennas can provide nearly 300,000 beams and aggregate up to 15 Gbps within a hot spot like an airport.
  • They will offer service-level agreements including committed information rates.
  • They will work with existing service providers and equipment manufacturers. 

These points are intended to differentiate Telesat from SpaceX, which has a head start in consumer and non-consumer markets, but the stock market is not impressed.

Thursday, July 20, 2023

Google Bard fails to answer satellite Internet questions

Bard made false, inconsistent statements, overlooked pertinent evidence, and overlooked expertise.

In an earlier post, I asked whether electronically steered antennas (ESAs) would replace parabolic antennas in satellite ground stations. I did some research and concluded that it is likely that they will. Next, I discussed the same question with ChatGPT and, while it made several false statements, it made a relevant point that I had overlooked. The relevant addition was positive, but the errors were troublesome, so I decided to try ChatGPT's competitor Google Bard.

Since the P in Chat GPT stands for "pre-trained," I began by asking Bard if it was more up-to-date than ChatGPT and it replied, "Bard is able to access the internet in real-time, while ChatGPT-4 is limited to a dataset that only goes up to late 2021." It added that it had last been updated on June 7, 2023.

That was encouraging since antenna technology has improved since late 2021 and at least two new products incorporating ESAs have been announced since that time, BlueHalo's mobile ground station and Thinkom's gateway array.

But my optimism faded when I began by asking Bard to "list the advantages of electronically steered antennas over parabolic antennas in ground stations for LEO Internet service constellations" and then asked it to "list the advantages of parabolic antennas over electronically steered antennas." The results of the two queries are shown here.

The replies are less complete and specific than those given by ChatGPT, and they are inconsistent -- Bard credits both ESAs and parabolic antennas as being cheaper. Furthermore, there was no indication that Bard was aware of the BlueHalo or Thinkom products, so I asked three leading questions:

  • Have there been recent satellite ground station innovations?
  • Any new hardware?
  • Any innovative new products?
It did not mention either BlueHalo or Thinkom, but after the third try it suggested that I try a Google search for "Innovative new products for satellite ground station" and that returned many links, including one to the Thinkom array of antennas.
My next query demonstrated an extreme lack of awareness. I asked if China's Long March 5B rocket would be used to launch their GuoWang satellite constellation. Bard answered that it would and added that it "will be the first time that a country has launched such a large constellation of satellites." 
Evidently, GuoWang is more frequently associated with Chinese propaganda than the SpaceX Starlink constellation in the Bard training set. (Garbage in, garbage out).
Red and blue text indicates errors (source)

A final example illustrates Bard's inability to recognize expertise. I asked Bard "Who is Larry Press", and it answered with the error-ridden professional biography shown here. The red text highlights statements that are false and the blue highlights work done in collaboration with others, not by me alone.

One can understand some of the errors. For example, I got my Ph.D. from UCLA, not USC, but I did teach at USC for a while and that may be more frequently mentioned in the training set. Similarly, I have been on several editorial boards, but I no longer am. I am an expert on my own biography and a simple Google Search would have found a somewhat dated, but accurate short biography on the Web. 
I was also disappointed in the promise that Bard would provide links to references. It only cites references when it "directly quotes at length from a webpage". I only saw one reference during my experimentation, and it was irrelevant.
"Artificial intelligence" programs have succeeded over the years in many specific tasks. As an undergraduate, I had the privilege of taking a course from Herbert Simon and learned about his chess-playing and theorem-proving programs. Arthur Samuel's checker playing program learned to beat him, and expert systems assist doctors in making some diagnoses. I even wrote an interactive program based on concept acquisition models that assisted researchers in multivariate data analysis. (It could be an Internet service today).
Artificial neural nets have also had success in specific tasks from recognizing zip codes on envelopes to playing Go and Chess and helping robots do back flips and they will succeed at other tasks like helping Microsoft Windows users or writing poetry. (I submitted haikus written by Bard and ChatGPT to the AI detector GPTZero and it reported that they were "likely to have been written entirely by a human").
But none of these programs are generally intelligent.
The illusion of intelligence results from the ability to generate responsive grammatical sentences in a conversation, but that is a low bar. Many years ago, I placed Teletype terminals in a public library and people conversed, sometimes for hours, with ELIZA, a simple simulation of a non-directive therapist. You can try ELIZA for yourself here.
The common practice of referring to errors as "hallucinations" furthers the illusion of intelligence.

Update 9/27/2023
I could not recall the verb "scrub" for navigating through a timeline, so I asked ChatGPT and Bard for help. ChatGPT got it;

Update 10/25/2023

A colleague told me that Bard had cited him as the author of a journal article. I searched for it using Google and could not find it so I asked him about it. It turned out that he had never written an article with the cited title and that the journal it cited had gone out of print two years before the cited publication date.

Friday, June 16, 2023

Will Electronically Steered Antennas Replace Parabolic Antennas in Satellite Ground Stations? (ChatGPT-Assisted Version)

In a previous post, I asked whether electronically steered antennas (ESAs) would replace parabolic antennas in satellite ground stations. I read a few articles suggested by others and by Google search, used some common sense, produced a list of advantages of ESAs, and concluded that it was likely they would eventually replace parabolic antennas for many applications. 

Many of the articles I found were written by companies selling products or services and I'm not an antenna expert -- more a curious journalist. ChatGPT has access to the entire Internet, and I wondered if it could have helped me improve what I wrote or convinced me to reach a different conclusion, so I queried it three times

Since I had listed the advantages of ESAs over parabolic antennas, I began by asking ChatGPT to list the advantages of electronically steered antennas over parabolic antennas for satellite ground stations.

In my post, I listed twelve bullet-point advantages. The ChatGPT answer was more verbose, beginning with a restatement of the question and listing and elaborating on seven advantages. The elaborated replies included all but one of my bullet points, spectral efficiency, and it included an advantage that I had overlooked, interference mitigation, and explained why that was so.

In spite of these glitches, ChatGPT reached nearly the same conclusion as I had, saying "It's worth noting that while electronically steered antennas offer numerous advantages, they also have some limitations, such as higher cost and complexity compared to parabolic antennas. However, ongoing advancements in technology are continuously addressing these challenges, making electronically steered antennas increasingly attractive for satellite ground station applications."

Since it had failed to mention spectral efficiency, I asked, "What about spectral efficiency?" and it replied with an apology for missing the point and went on to list and elaborate on five ways in which ESA made more efficient use of bandwidth.

You can see the dialog here

Since ChatGPT generally agreed with me, I asked it to play devil's advocate and list the advantages of parabolic antennas over electronically steered antennas for satellite ground stations. 

Perhaps I was biased by the experience of having written my earlier post, but I found myself questioning some of its cited advantages. For example, one was "wide coverage" but that would not apply to Thinkom's array of arrays. Another was "simplicity ... making them easier to manufacture, install and maintain." ChatGPT was contradicting its previous response in which it said ESAs were more reliable and required because parabolic antennas "have mechanical parts that can be subject to wear and require regular maintenance."

I also realized that my question was a bit off -- it focused on the antenna rather than the entire ground station -- so I asked it to "list the advantages of satellite ground stations that use parabolic antennas over satellite ground stations that use electronically steered antennas". One of the advantages it listed was suitability for high-frequency Ka and Ku bands, but both Thinkom and BlueHalo use those bands and Thinkom is targeting even higher frequencies. It also repeated the simplicity advantage.

You can see the dialog here.

Finally, I asked the title question from my previous post -- will electronically steered antennas replace parabolic antennas in satellite ground stations?

It listed points under three headings -- advantages of ESAs, limitations of ESAs, and application-specific considerations and concluded that:

"While there is potential for Electronically Steered Antennas to replace parabolic antennas in certain satellite ground station applications, it is not a straightforward or immediate transition. The adoption of ESAs will depend on factors such as technology advancements, cost reductions, performance improvements, and specific application requirements."

It reversed itself once more by listing improved reliability as an advantage of ESAs, but the conclusion was similar to the conclusion in my original post. It also revealed a shortcoming in my formulation of the question. Since I have been writing a lot about Internet service constellations, I overlooked other applications in my previous post and did not specify that I was interested in broadband Internet service. (A human editor would have known that I was writing for an Internet-related publication, would have been aware of my previous writing, and assumed I was focused on Internet applications).

It pointed out that parabolic antennas had an advantage for deep space communication, so I asked a more fully qualified question -- Will electronically steered antennas replace parabolic antennas in ground stations for LEO, MEO, and GEO Internet service constellations?

The reply seemed vaguer and non-committal this time, but was also similar to mine:

"Considering these factors, it is likely that a combination of ESAs and parabolic antennas will be employed in future ground stations for LEO, MEO, and GEO internet service constellations. The specific configuration and utilization of each technology will depend on various factors, including cost, performance requirements, deployment scenarios, and network architectures." 

You can see the dialog here.


So, what is the role of ChatGPT in this sort of journalism? It served me as an editor or referee reviewing what I had written. I would have made two changes after getting feedback from ChatGPT -- I would have mentioned that I was focused on LEO, MEO, and GEO Internet service applications, and I would have included interference mitigation as one of the advantages of ESAs.

ChatGPT made a couple of misstatements and did not "know" about the possibility of an array of antennas like that of Thinkom with its wide elevation angle range. To its credit, I liked the way it apologized for overlooking spectral efficiency as an advantage for ESAs and it was an indefatigable and patient interviewee. It was also free (for the time being).

I consulted ChatGPT after drafting my article, but I could have used it as a research tool before writing. Had I done so, I might have been misled by some of its mistakes and I wouldn't have discovered Thinkom's innovation. Furthermore, its prose was not clear and concise -- I don't think it could pass a Turing Test on writing style. In this case, an old-fashioned Internet search engine was a far better pre-writing tool.

ChatGPT would be improved if it gave links to the sources of its assertions. Like autocomplete, it generates sentences by repeatedly appending the most probable next word in text documents found on the Internet, so the final string is novel. (That's not the way I generate sentences -- they follow from an idea). Might a list of the documents providing the most words be useful? (Google Bard adds citations, but I've not tried it out yet).

While ChatGPT helped me, I don't believe a ground station expert would have learned anything new by interacting with it and a beginner like a student writing a term paper would have been misled. The curious journalist was the sweet spot in this case, but this is version 3.5 of ChatGPT, which had a data-cutoff date before BlueHalo and Thinkom announced the products I've mentioned. I'll revisit it when I get access to ChatGPT4.

PS -- Let me know if you read the dialogs I linked to and notice something I missed,

Thursday, June 08, 2023

Will electronically steered antennas replace parabolic antennas in satellite ground stations?

ThinKom gateway -- an array of electronically steered arrays

Might ChatGPT, which has access to the entire Internet, have come to a different conclusion than me? Stay tuned.

Three recent developments make me wonder whether we are on the cusp of a shift in satellite ground station technology from parabolic to electronically steered antennas (ESAs). 
The Space Force Satellite Control Network (source)

The U.S. Space Force operates the Satellite Control Network, with 19 parabolic antennas at seven locations around the world. The network was established in 1959 and a report by the Government Accountability Office found that it should be updated to help the Space Force better manage future efforts. Last year, The Space Force awarded BlueHalo a $1.4 billion contract to modernize space operations using their software-defined ESAs and the OpenSpace software-defined satellite ground system from Kratos. This article says they will upgrade 12 "ground stations" starting in 2025, which I assume means they will install 12 ESAs at the seven locations shown here.

In March, the Air Force Research Lab selected ThinKom for its next-generation gateway solution -- an integrated array of ESAs. The following month, ground station operator Kongsberg Satellite Services (KSAT) and ThinKom announced a partnership to bring ThinKom’s gateway array to the commercial ground station market. The Air Force contract will help fund the development of the gateway and the partnership plans to have a fully operational system in 2024.

ThinKom antenna design (source video)
ThinKom and KSAT are a good match. KSAT has experience operating ground stations with 270 antennas at 26 locations and ThinKom has a hybrid mechanical/phased array antenna design utilizing three rotating platters. Rotating the feed and aperture platters together steers the beam in azimuth; rotating them relative to each other steers beam elevation; and rotating the polarizer platter selects between left and right polarization. The partnership's first commercial "customer" will likely be KSAT itself.

Finally, OneWeb will soon be online globally. Arctic Space Technologies is building a 27-antenna ground station for them, and it will be operational in the third quarter of this year. Given the short timeline, the antennas will probably be parabolic, but OneWeb is committed to and has signed a contract for multi-orbit service. I asked about the possibility of ESAs and got no reply.

I wrote the following list of advantages of ESAs in ground stations after visiting the sites and reading the articles I've linked to above and using a little common sense:
  • Reliability (though ThinKom's hybrid antenna may be less reliable than a pure ESA)
  • Wide elevation angle range (in a ThinKom array)
  • Wideband (Thinkom is targeting Q and Vbands -- what about atmospheric interference)?
  • Multiple beams
  • Instant switching between frequency bands
  • Spectral efficiency
  • Instant switching between LEO, MEO, and GEO orbits (a "selling point" for OneWeb)
  • Fast handoffs between satellites
  • Compact and small footprint (especially with ThinKom gateway)
  • Reduced power requirement
  • Lower installation cost
  • Portability
Prices may be high today and standards not solidified, but with technical progress and increased production quantities, parabolic ground station antennas seem likely to go the way of vacuum tubes, mag tape, and core memories. 
But the articles I read were about ESA projects so the advantages may have been overstated. Might ChatGPT, which has access to the entire Internet, have done better or come to a different conclusion than me? Stay tuned.

Sunday, April 23, 2023

China and Taiwan recognize Starlink's military value

Starlink has a conflict of interest.

Ukrainian Starlink traffic March 6-May 22, 2022 (source)
When Russia invaded Ukraine, SpaceX had around 2,000 satellites in orbit. It was clear from the first day of the war that a low-Earth orbit (LEO) constellation of around 2,000 satellites would be a valuable military and civilian asset. The first truckload of Starlink terminals arrived in Ukraine on February 28, 2022, four days after the invasion. By March 19, there were 5,000 terminals in Ukraine and 150,000 active daily users by May 2nd.
China and Taiwan have both seen the strategic value of 2,000 Starlink satellites.

Initially, China planned two LEO Internet service constellations, but they were abandoned in favor of a single constellation, GuoWang, which would be operated by a state-owned company called China SatNet. Since satellite Internet had been deemed critical infrastructure China SatNet was not placed under The China Aerospace Science and Technology Corporation (CASC), China's main state-owned space conglomerate, but was made an independent entity at the same level as CASC, empowered to select its own government and privately-owned launch providers, satellite producers and other vendors. 

China space consultant Jean Deville thinks it is likely that the GuoWang satellite constellation will start to deploy this year on a Long March 5B rocket. The mass of Starlink Gen 2 v 9-1 satellites is 303 kg and the mass to LEO of a Long March 5 is 25,000 kg. If GwoWang's satellites had the same mass, it would take 83 fully packed launches to orbit 2,000 satellites, and doing that in five years would require developing reusability.

China sees Starlink as a weapon (source
The Chinese assessment of Starlink as a military threat is found in articles like:

The Taiwan Ministry of Digital Affairs has noted that since the Russian invasion, Ukraine "has depended on Starlink satellite communications to connect to the world" and they have an $18 million plan to place satellite receivers in 700 places at home and abroad, to maintain government communications "during emergencies such as natural disasters or wars." The ministry said it was "willing to cooperate with any qualified satellite service provider" and that is wise because Elon Musk would have a conflict of interest in the case of a war between China and Taiwan and we may have already seen evidence of that conflict.

Taiwan's vulnerable undersea cables (source)
In February 2023, SpaceX’s chief operating officer Gwynne Shotwell said "We know the military is using [Starlink satellites] for comms, and that's ok ... But our intent was never to have them use it for offensive purposes" and they began geofencing satellites when they were above water or Russian-occupied territory inside Ukraine. 

In March 2022 I wrote that the Ukrainian army was using drones to spot targets and relay their coordinates over Starlink to "the artillery guy and create target acquisition” and they were also using drones equipped with bombs. 

That sounds "offensive" to me, but more likely Shotwell was going along with the peace plan Elon Musk tweeted calling for Ukraine to cede Crimea and holding UN-supervised elections by the people who remained and were still alive in the "annexed regions."

More cynically, there may have been pressure from Russia's ally China. Tesla plans a large battery factory in China and makes and sells a lot of cars there, and Shotwell knew that the Chinese government had stalled Tesla's plan to expand auto production there because of concerns about Starlink in January. (I wonder if Ukraine was discussed during Musk's recent trip to China).

The above is speculative and indirect, but the threat to Tesla would be direct if Starlink were to aid Taiwan in the event of a Chinese invasion. (Tesla would be in jeopardy in the case of a Chinese invasion regardless Starlink). Taiwan should be talking with OneWeb, Telesat, Amazon Project Kuiper, and the European Union's recently approved IRIS² project and consult the technicians and military people working with Starlink in Ukraine.

Saturday, March 04, 2023

Connecting every home in Africa -- Starlink backhaul?

Pia! runs fiber to an area and the "last mile" is wireless.
The vision of Kenyan ISP Poa! Internet is "to bring internet to every home in Africa."

Poa! offers unlimited, uncapped, 4 Mb/s fixed wireless connectivity to homes for 1,500 KSh ($11.64) per month plus a one-time installation fee of 3,500 KSh ($27.16). But wait, there's more. They provide a dual-SSID router and the home SSID is used by trusted family members and the open street SSID is for others. Street users get 100 MB of free data each day and are charged 15 KSh ($.16) per GB with no expiry .data if they exceed 100 MB on a given day
ASR 33 Teletype
Depending upon your age, 4 Mb/s may sound exceedingly slow, but my first home Internet connection was using an ASR 33 Teletype that printed ten upper-case characters per second -- about as fast as I could read. This enabled me to use email, Usenet, Telnet, FTP, etc. and, most importantly, to collaborate with remote colleagues. My first professional home computer had an 8-bit CPU, 64 KB memory, two 8-inch floppy drives, and a 300-baud modem. It enabled me to quit my day job and program, write and consult -- I owned my own professional tools.

A low-cost Windows PC and a 4 Mb/s connection would allow all that I did at that time and so much more today -- download software, articles, books, movies, etc., stream HD 720p video, make voice-over-IP calls, listen to podcasts, read newspapers, etc. and, importantly, create content and invent applications and services that are relevant to Africa. It would be fascinating to conduct a study of Poa! users to see what they are using the Internet for and how it is impacting their lives.

One thing we know for certain is that people do different things with a computer at home than with a phone on a mobile network or at a Wi-Fi hotspot. For example, I could not write this post on my Android phone.

This point is underscored by the experience of Poa!. Poa! CTO Mike Puchol said that when they deployed about 160 outdoor Wi-Fi hotspots in Kibera, a district of Nairobi, users consumed "very little" data despite the price being 10% of the mobile network operator’s rate.  When Poa! deployed residential broadband in Kibera, average consumption hit ~140 GB/month right away and is now over 200 GB/month. (In 2021, average mobile data consumption in sub-Saharan Africa was 2.9 GB per month).

Puchol provisions 1.5 Mb/s per 4 Mb/s account and he says there is "very little" contention. No doubt that contention grows during busy hours and days, but if they can add capacity as quickly as they add customers, they would be able to maintain that contention ratio without alienating too many customers.

They have fiber loops between their data center and points of presence in each network area they serve and use wireless links to reach individual houses. The service seems to be financially viable in urban areas like Kibera. Puchol reports that they currently have 20,000 home users and last December 27,000 people used the public street service. Poa! has received over $42 million in funding 


SpaceX recently began offering Starlink Internet service in Nigeria and Rwanda and several South American nations and will begin service in Kenya next quarter. Could they substitute Starlink connectivity for fiber and offer their service in rural Kenya

Today, they could not. Today, there is only one Starlink ground station in Africa and it is in Nigeria. The only way a Starlink user in Kenya can reach the Internet is via inter-satellite links from a visible satellite to a remote ground station. I just ran Mike Puchol's Starlink simulation for one hour at a random location in central Kenya and there was no available coverage six percent of the time.

Since SpaceX has committed to offering connectivity in Kenya during the second quarter of this year, I assume they will have reachable ground stations by then. The same goes for Angola, Eswatini, Mozambique, and Zambia, which will have connectivity during the second quarter, and many other African nations that are slated to connect later in 2003 and in 2004. A rural village with access to a ground station could be used for Starlink backhaul.

If there is excess constellation capacity over a village location, the marginal cost of serving a new terminal will be near zero and an ISP can count on adding users at a predictable cost. I've seen a Nigerian Speedtest result showing a download rate of 238 Mb/s, an upload rate of 45 Mb/s, and a latency of 42 ms. At those speeds, a terminal could theoretically support 188 4 Mb/s customers, but that test was run on an unloaded terminal at a particular time of day. 

During a day, the available capacity at a given location varies as the satellites move and the number of users online varies. (Large files should be transferred late at night). 

In the long run, capacity increases as more satellites are launched and technology improves. SpaceX just began launching second-generation Starlink satellites which provide four times the capacity of the first generation and the next generation is expected to more than double that. The number and capacity of ground stations will also continue to increase, and more satellites with inter-satellite laser links will make it possible to reach them from remote sites. We will also see optical links to some ground stations and terminal cost and performance are also improving.

SpaceX is the only company offering low-Earth orbit broadband connectivity today, but they will have low and medium Earth orbit competitors and several of those future competitors are designing their constellations for organizations and enterprises which may make them better suited than SpaceX for backhaul from a village. For example, OneWeb will offer service-level agreements, which will take some of the uncertainty out of pricing decisions and SES will offer software-defined beam capacities and shapes.

The one prediction I can make given all this variability is that the prices SpaceX is charging in Rwanda and Nigeria today will change over time as they have in the US and other nations.

Poa! staff
In Kibera, Poa! provides both the fiber link to an area and the wireless links to the homes in the community, but decentralized alternatives where the community contracts with Poa! for the satellite link but installs, owns, and operates the local network should be considered. Whether operated by the local government or a private company, local community networks could coordinate to share expertise, training, and purchase equipment and tools in quantity. There could be variations on this theme. For example, Poa! could offer discount purchasing as a service to community networks.
The orbit-inclinations and marketing efforts of SpaceX's constellation were focused on affluent nations at first, but nearly all the African and South American nations will have Starlink service next year and OneWeb and SES will be serving many of them as well. Necessity is the mother of invention, and I can't wait to see the technology, organizations, and applications invented in the global south and their social impact.
PS -- The closest I can come to an English translation of poa is our slang term cool.
Update 3/24/2023
Several people wrote telling me that the Poa! example was unfeasible because the Starlink customer agreement prohibits reselling connectivity and Kenya would require rural community ISPs to have international gateway licenses.
This is true in Kenya today, but SpaceX will change Starlink prices and policy as they have done in the past and will be operating in many if not all African nations. The Kenyan government may modify licensing regulations to allow a provider like Poa! to obtain a single license covering their retail customers, and other nations have different regulations. 
As noted above, SpaceX's global capacity is increasing but they will have competitors with different technologies, strengths, organizational structures, market emphases (OneWeb, Amazon Project Kuiper, and Telesat), and political interests (China SatNet). The title of a future post may be "Connecting every home in rural Africa -- LEO satellite backhaul."