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Spy Balloons: The Alternative to Spy Satellites

NASA Super Pressure Balloon -Loft  Capacity 5000lbs
Look Familiar? NASA Super Pressure Balloon -Loft Capacity 5000lbs

The Chinese Spy Balloon incident has caused shock and alarm in the US and the western world. As if this incident wasn’t bad enough, three additional objects have been intercepted and destroyed over the US and Canada. The US leads the world in using balloons for intelligence, communications, and scientific measurements while simultaneously operating a vast array of spy satellites. Why is it a surprise that the Chinese are emulating our methods? This blog will look at US balloon systems and technology to extrapolate the likely capabilities of the now-destroyed Chinese Spy Balloon.

Before we begin our survey of US balloon systems, let’s briefly review what w know about the Chinese Spy Balloon Incident.

The Chinese Spy Balloon Incident

Path of the Chinese Spy Ballon -  January 28  to February 4, 2023 ( Source Statisica)
Path of the Chinese Spy Balloon - January 28 to February 4, 2023 ( Source Statistica)

Per the BBC, “From January 28 to February 4, 2023, a Chinese-operated, large white high-altitude balloon was seen in North American airspace, including Alaska, western Canada, and the contiguous United States.” On February 4th, as the balloon finally reached the South Carolina coast, a US Air Force F22 interceptor fired an AIM-9 sidewinder missile and shot down the balloon.

The US Navy immediately performed a recovery operation shipping the balloon debris to the FBI in Quantico, Virginia, for analysis.

Based on the US Defense department briefings, the balloon was helium-filled and approximately 200 feet in diameter. As a data point for comparison, a mid-sized version of NASA’s own Super Pressure Balloon Program (SPB), of roughly the same size, can loft nearly 2000 lbs of payload.

Telephoto Image of Chinese Spy balloon over Wyoming
Telephoto Image of Chinese Spy balloon over Wyoming

The Chinese Balloon carried a payload ( “gondola”) roughly “two to three school buses in length” ( ~30 meters). Based on a US U2 spy plane flyby, the balloon carried antennas and equipment capable of locating electronic communications devices, including mobile phones and radios. A DoD spokesperson noted that the balloon’s instrument package was “clearly for intelligence surveillance” and inconsistent with the weather-balloon equipment. The balloon’s payload included 12 solar panels estimated to generate the power necessary to operate multiple intelligence-gathering systems.

Spy Balloon Architecture  (Source BBC)
Spy Balloon Architecture (Source BBC)

So at a gross level, the Chinese spy balloon clearly had signals intelligence capability with antennas to collect RF and cellular traffic and transmit that intelligence via satellite up-link back to China. The balloon likely had hyperspectral imaging equipment for detailed images of the flyover areas. While there is no confirmation, the balloon could have LiDAR ( Laser Radar) an all-weather radar imaging capability similar to Lower Earth Orbit Earth observation satellites.

For more information on LEO Earth observation sensors used satellites, please watch the following: Video Presentation: Imagery versus SAR for Military Applications.

Four US Airspace Breach Incidents Resulting in Shootdowns – (Source WSJ)
Four US Airspace Breach Incidents Resulting in Shootdowns – (Source WSJ)

In late-breaking news – A US F22 shot down a 2nd object over Canada on February 11th. A briefing by Canadian Defence Minister Anita An noted that the unidentified object was smaller than the Chinese Spy Ballroom but similar in appearance and represented an immediate hazard as it was lofted at 40,000 feet (12,200 m), posing a risk to civilian air traffic.

In even later breaking news - 2 similar smaller “objects” have been destroyed over Alaska and Michigan. NORAD and the US airforce have been very busy

In each of these cases, the additional “objects” were detected after the US Defense Department changed the detection parameters of the North American air defense and early warning systems If you want to know more about these early warning and defense systems, check out: Missle Defence – An Imperfect Shield.

Did the US Have a Legal Right to Shoot Down the Spy Balloon?

International law states that a nation “has complete and exclusive sovereignty over the airspace above its territory”, which corresponds with the maritime definition of territorial waters as being 12 nautical miles (22.2 km) out from a nation’s coastline.

Karman Line – layers of the Atmosphere and the boundary of Outer Space
Karman Line – layers of the Atmosphere and the boundary of Outer Space

The problem lies with the fact that the specific definition of “airspace” altitude is NOT DEFINED. You read that right; there is no international agreement on the vertical extent of sovereign airspace.

According to NOAA, the US National Oceanographic and Atmospheric Administration. “the common definition of space is known as the Kármán Line, an imaginary boundary 100 kilometers (62 miles) above mean sea level. In theory, once this 100 km line is crossed, the atmosphere becomes too thin to provide enough lift for conventional aircraft to maintain flight.”

High-altitude stratospheric balloons typically fly between 120,000 feet (37 Km) and 80,000 (24 Km). High enough to be safely out of Civilian and military air traffic, typically between 30,000 and 65,000 feet (~10 km to 20 km ), but far lower than the Kármán Line at 100km, which defines outer space.

In short, the Chinese Spy Balloon flew squarely in US airspace, and China needed to request overflight permission for this balloon to overfly the US. Lacking permission from the US for overflight, US air defense forces were within their rights to destroy the object violating our airspace.

A final note: There is an international ban on nuclear or other weapons of mass destruction in space. Unfortunately, there is no ban on air, ground, or conventional space-based anti-satellite or anti-missile weapons. However, unlike showdowns associated with airspace violations, since the dawn of the space age, an anti-satellite attack has been considered an act of war. You can read more about international space law from these two excellent papers: Reference 1, Reference 2

High Altitude (Stratospheric) Balloons – The Poor Man’s Satellite System

Why would China bother using a high-altitude balloon as a spy platform? Given all the new low-cost satellite launch capabilities, why would you bother using high-altitude balloons as earth sensors/spy/communications platforms?

There are several advantages to using a stratospheric balloon:

  1. Low radar cross-section, difficult to detect (STEALTH)

  2. Launch Costs of LEO satellites

  3. Range of sensors to a target (lowers cost and complexity of instruments)

  4. Dwell Time over a target

  5. The sensor package (the “gondola”) can be landed, and sensor equipment reused ( lowering cost)

As the Chinese spy satellite incident illustrated, balloons are stealthy despite their massive size. Most of a balloon’s composition, except the equipment package, is helium ( air) held in a non-radar reflective material. The US air defense system can detect these balloons closer to our airspace and sensors. The shortened detection range limits the time for defense authorities to react before our air space is breached.

There are no appreciable launch costs for a balloon. A SpaceX Falcon 9 rocket launch is roughly $50M to place a 34,000 lb payload into orbit, and this is approximately $1500/lb 0r $3300 /Kg (1 KG = 2.2 lbs). Given the estimate of a 2000 lb Chinese spy balloon payload, the equivalent launch cost would be $3M.

Spy satellites typically fly at 450 Km above the Earth, traveling at 7.6 Km/sec. An LEO satellite completes an orbit in just over 90 Minutes and can only observe a given location of the Earth for less than 5 minutes. That is a very short dwell time, considering a balloon can loiter for hours or even days over a given location gathering far more extensive information. Earth observation instruments collect RF or visible light energy. The range of an optical camera or RF antenna is proportional to the square of the distance. A Balloon sits ~35 km above a target location, while an LEO satellite distance is > 450 Km. That means an equivalent sensor on a balloon receives over 160 times more energy and, by extension, is more sensitive than an LEO satellite.

Put another way, a spy balloon can use cheaper, less sophisticated sensors than an LEO spy satellite, saving cost and weight while having far superior dwell time.

Finally, balloons can be landed safely. A balloon’s sensor package can be recovered and reused, further reducing costs. A spy satellite burns up in orbit after its service life is complete.

There are, however, two critical downsides to using balloons and a spy platform:

  • High-altitude balloons are easily within the range of low-cost weapons like Aim-9 sidewinder missiles, as the Chinese satellite incident clearly pointed out.

  • The platforms are subject to unexpected weather and air patterns changes - a reliability issue that LEO satellites do not have.

Still, it is no wonder spy balloons are thought of as “Poor man’s Satellites.”

The Chinese Balloon program is neither a new concept nor novel. As it turns out, US and US commercial companies have numerous balloon programs servicing a variety of applications. It is doubtful the US government will ever reveal all the details learned from the Chinese Spy Satellite. We can extrapolate by example the likely capabilities by reviewing a number of important balloon programs.

The remainder of the blog will do just that. We’ll be reviewing the following balloon systems to provide insight into what balloon platforms are capable of:

  • TARS (Tethered Aerostat Radar System)

  • Space Data

  • Google Project Loon

  • NASA Super Pressure Balloon

TARS (Tethered Aerostat Radar System)

TARS - Tethered Aerostat Radar System  ( source US Customs and Border Protection Agency)
TARS - Tethered Aerostat Radar System ( source US Customs and Border Protection Agency)

The TARS (Tethered Aerostat Radar System) is a tethered balloon lofted radar system. TARS began operations 1978 with a single site developed by the US Air Force to detect maritime and surface smugglers, narcotics traffickers, and other threats flying below the coverage of ground-based Radars. Once the system was qualified, construction commenced across the United States-Mexican border, the Florida Straits, and a portion of the Caribbean. The US Air Force managed the TARS program until July 2013, when the program was transferred to CBP(Customs and Border Patrol).

The TARS aerostat is a large fabric envelope (balloon) filled with helium that can rise to an altitude of 15,000 feet. The look-down radar and any communications signals detection equipment (SIGINT) is housed in the covered equipment bay(“bubble” at bay bottom of the aerostat. The maximum tether length ( altitude) for the system is 25,000 feet. The Radar has a detection range of roughly 200 nautical miles (400Km).

The Air Force initially considered crewed radar aircraft (AWACS) and drones for the southern border low-level surveillance mission. Analysis concluded that only a multi-site tethered look-down radar could cost-effectively maintain continuous coverage. Drones and aircraft would simply be too expensive to perform the mission. For example, In 2013, TARS was responsible for detecting 586 suspicious flights, representing 42 percent of all the suspect flights along the Southwest border tracked by the CBP that year.

As a starting point for balloon-based intelligence gathering, TARS gives us a glimpse of how effective a balloon platform can be for low-level airspace surveillance. What is little talked about is TARS SIGINT and COMINT capabilities. that is a conversation for another day.

TARS -Tethered Aerostat Radar System – US border coverage – Source( US border protection)
TARS -Tethered Aerostat Radar System – US border coverage – Source( US border protection)

Space Data

Space Data is a commercial company that develops and deploys Stratospheric, high-altitude wireless communications based on their SkySat balloon platform. Space Data has flown more than 25,000 missions lifting wireless communications systems to stratospheric altitudes using military-grade balloon technology. As an example, a SkySat repeater platform extends the range of commercial and military-grade UHF two-way radios from 10 miles to nearly 500 miles. Equipped with a WiFi access point, real-time voice and data services are possible over a similar area of coverage.

Space Data – US Marine Tactical UHF Communications Repeater
Space Data – US Marine Tactical UHF Communications Repeater

Unlike TARS or other systems we will discuss, Space Data SkySats are designed for a quick launch and a limited life span. A SkySat can be launched and reach an operating altitude of 60,000 to 100,000 feet in under 20 minutes. SkySat’s small size (<10m) and weight meet FAA rules for balloon fights and do not require flight approvals. Balloons typically loft for~7 days, are battery-powered, and are typically used for short-term communications. Example missions:

  • Tactical UHF military communications extension

  • Wide area IoT data communications

  • Wide area WiFi network for emergency communications services

The SkySat system is so inexpensive and quickly deployed that these systems could be launched in swarms to overload air defense with multiple targets. Considering events of recent days, imagine the crisis that would evolve if 100s or even 1000s of stratospheric breached US airspace over a period of days... Food for thought!

Google Project Loon

When the Chinese spy balloon was first spotted, and the first telephoto images hit the media, it immediately made me immediately think of Google’s Project Loon.

Google Project Loon Communications Balloon ( Source Google)
Google Project Loon Communications Balloon ( Source Google)

Before SpaceX ever conceived the StarLink Low Earth Orbit broadband data system, Google Project -X conceived a low-cost global network of stratospheric balloons to connect “the unconnected” with broadband wireless using LTE micro base station technology. Unlike LEO satellite networks like SpaceX StarLink requiring expensive custom user hardware, the Loon project team set out to use 4G LTE (and later 5G) and build a system compatible with smartphones WITHOUT MODIFICATION.

Google Loon Balloon Architecture ( Source Google)
Google Loon Balloon Architecture ( Source Google)

In 2011, Google envisioned creating worldwide cellular network coverage using stratospheric balloons, a slowly moving cell site. As we saw earlier with Space Data, each balloon’s “cell coverage” is approximately 400 miles in diameter. Live testing started in June 2013 in New Zealand and expanded to other sites around the world. Over a 9 year period, the Loon team solved a series of technical hurdles to field a full system, including:

  • Design and testing of LTE links to the users and high-speed data feeds to the balloons and between balloons (cross links)

  • Refinement of the Balloon design for long endurance – 100s of days, not 10s of days typical of weather and scientific balloons and, in the process, setting a record of over 300 days aloft

  • Predictable maneuvering and station-keeping of balloons to create continuous coverage between multiple balloon “Cells.”

Along the way, Loon provided practical services as an emergency communications system. First in 2017 during a major flooding event in Peru and later in Puerto Rico after a major hurricane.

Despite all the progress made, deployment and operating costs could not reach a point where a fully deployed loon system would be profitable. A brilliant set of technical success could not overcome an unworkable business case.

Google Loon Network Basics – (source: Google)
Google Loon Network Basics – (source: Google)

So, what does this have to do with Chinese Spy Satellites?

First, Loon proves that a spy satellite can easily listen in and intercept cellular and other communications. Further, communications links are readily supported to pipe those intercepts any place in the world.

Secondly, Chinese efforts in modern balloon surveillance platforms appeared to have begun in 2017, about the time Loon solved their technical problems and demonstrated practical solutions. Between Loon’s open communications about the project and a modicum of industrial espionage, it would be interesting to see what parts of the loon project made it into the Chinese Spy Satellite being examined by the FBI in Quantico, Virginia.

If you are interested in learning more about Loon, check out the following links:

NASA Super Pressure Balloon Program

NASA has been lofting stratospheric balloons for over 40 years. The NASA Balloon Program has provided high-altitude scientific balloon platforms for scientific and technological investigations, including fundamental scientific discoveries that contribute to our understanding of the Earth, the solar system, and the universe.

In particular, NASA developed a new generation of balloons capable of lofting Over 5000 lbs (2,5x the estimated weight of the Chinese Spy Satellite payload). The so-called “Super Pressure Balloon Program.” provides the lift necessary for NASA to loft an ambitious set of stabilized telescopes above the distortion of the Earth’s atmosphere to detect exoplanets in other star systems. SPB has also lofted and tested high-definition LIDAR ( Laser Radar) missions for highly accurate mapping of the earth’s surface.

In particular, NASA developed a new generation of balloons capable of lofting Over 5000 lbs (2,5x the estimated weight of the Chinese Spy Satellite payload). The so-calledSuper Pressure Balloon Program.” provides the lift necessary for NASA to loft an ambitious set of stabilized telescopes above the distortion of the Earth’s atmosphere to detect exoplanets in other star systems. SPB has also lofted and tested high-definition LIDAR ( Laser Radar) missions for highly accurate mapping of the earth’s surface.

In particular, the WASP - Wallops Arc-Second Pointer project perfected a platform that can point telescopes on balloon gondolas at inertial targets with arc-second accuracy. WASP is capable of compensating wind-driven motion of the gondola platform in the stratosphere. In particular, SPB and WASP are capable of providing meeting or exceeding the following system parameters:

  • Supporting 1 ton of science instruments (SPB can loft 2.5 tons)

  • Capable of sustained flight altitude of 110,000+ ft (33.53+ km).

  • Capable of sustained flight duration of up to 100 days.

  • Using the WASP platform – capable of sustained instrument pointing to within 1 arc second

NASA – Laser Radar (LiDAR) – Balloon Gondola Package
NASA – Laser Radar (LiDAR) – Balloon Gondola Package

As it turns out, these same system parameters are ideal for a spy surveillance balloon. After all, if you can accurately point a telescope at a star, you accurately point a telescope/hyperspectral imager at a target on the ground. Even more important, the NASA LIDAR experiments are identical to the equivalent functionality for mapping ( TARGET MAPPING) a spy satellite might perform.


As we speak, scientists and engineers in Quantico, VA, are gathering and dissecting the remnants of the Chinese Spy satellite recovered off the shore of South Carolina. With any luck, the components of 3 other “Spy Objects” that the US has shot down be added to the investigation.

What are the exact capabilities of these satellites? It is very unlikely that the US government will provide anything but the most general information to the public.

However, suppose we assume the Chinese can implement any of the ball0on technologies outlined here, you can extrapolate the possible capabilities of the Chinese Spy Satellite.

To summarize, any or all of the following are possible:

  • Intercept cellular, IoT, WiFi, & possibly Bluetooth data within a 200-mile radius of the flight path of the balloon and forward the intercept back, via satellite link, to the home base/control. – CLASSIC COMINT – COMMUNICATIONS INTELLIGENCE

  • Capture and analyze US air traffic and national defense radar systems, specialty radio links, and other command and control infrastructure – CLASSIC SIGINT – SIGNALS INTELLIGENCE

  • Capture High-Resolution Images/Hyperspectral images of structures, facilities, and other infrastructure tied to highly accurate GPS/GNSS location of the ballo0n platform - imaging for target classification and targeting selection in time of war.

  • Laser Radar (LIDAR) super high accuracy mapping - - imaging for target classification and targeting selection in time of war

To be clear, the US deploys an extensive array of spy satellites to achieve the same objectives and avoid violating Chinese airspace. As the old saying goes., “Big Brother Is Watching.”

These incidents are foolish and provocative and have resulted in the first cases of aircraft being shot down in US airspace in our nation’s history.

While we have concentrated on the Chinese Balloon Incident – if you are interested in understanding Earth Observation /Satelite Intelligence sensors, here are links to presentations, video presentations, and technical blogs which accessible to technical and non-technical readers:

As always, if you have any questions, or feedback, or are interested in a specific topic, please reach out to me via my contact page.

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