Catherine DillCounting Type 094 Jin-class SSBNs with Planet Imagery

A quick post before the Thanksgiving holiday here in the U.S.

In my professional life, I am especially grateful for high frequency satellite imagery. This week Planet Lab’s SkySat sensor allowed us to make two very interesting observations about China’s SSBN program. Jeffrey Lewis and I both gave a few comments to Defense One, but I thought it might be useful to go into a bit more detail about using Planet imagery for monitoring China’s SSBNs.

In the most recent Annual Report to Congress on Military and Security Developments Involving the People’s Republic of China, the DOD assessed that China has four operational Type 094 Jin-class SSBNs. How do we know this? How can we monitor this? Colleagues like Hans Kristensen have done an exceptional job over the years of identifying areas where the Chinese SSBN fleet lives, starting from the production facilities through to the operational bases. Sightings of Chinese SSBNs are rare, and the context in which a sighting occurs can help analysts make judgements about the current status of the Chinese program to expand the country’s SSBN fleet to eventually reach eight operational Type 094 Jin-class SSBNs by 2020.

There is a list of haunts associated with the SSBN program in China, but there are two facilities in particular that are useful to monitor to track developments in the SSBN program: the Bohai Shipyard at Huludao where the submarines are built and maintained, and the Longpo Naval Base at the Hainan Island Naval Complex where there are four piers designed for docking nuclear submarines, like the Type 094.

As anyone who has ever listened to me speak before surely will know, one of the issues in using high-resolution commercial satellite imagery to monitor anything over a long period of time is that there is just not enough imagery, especially to monitor geographically distant but related facilities. The revisit rate for the high-resolution sensors simply is too infrequent to allow for certainty in analytic judgements, especially in areas of the world that are prone to more clouds.

On 16 November, the Planet SkySat sensor captured beautiful images of both the Bohai shipyard and the Longpo Naval Base, allowing us to count the Chinese SSBNs with much more certainty than if we only had imagery of one location.

Two Type 094 SSBNs are visible at the Bohai Shipyard on 16 November 2018, presumably for maintenance and/or repairs. Image © 2018 Planet Labs, Inc.

Jeffrey and I initially fixated on the two hulls back at the Bohai shipyard, typically used for maintenance and repairs, which leads to the first interesting observation: two of the SSBNs are not operational at the moment, contrary to the DOD assessment of four operational SSBNs. In reviewing imagery of the past year, we can observe that one of the hulls has been at the shipyard for some time, and the second hull arrived relatively recently. The next thing to monitor is how long the hulls will continue to be at Bohai, a statistic that might give some indications about potential maintenance and repair issues. (Bonus: we can observe that all 12 launch tubes in the top hull are open).

But after reviewing imagery of all the other facilities associated with SSBNs we observed something even more interesting: there are five 094s out in the wild, not four as analysts have been able to observe previously. There are three (3!) Type 094 submarines docked at Longpo, not the two we were expecting to see as we had a few weeks ago.

Three operational Type 094 SSBNs are visible at the Longpo Naval Station on 16 November 2018. Image © 2018 Planet Labs, Inc.

I measured the five submarines to persuade myself that they were all indeed 094s, and I have high confidence that they are.

High frequency imagery, like the imagery provided by Planet Labs, allows us to narrow analytic gaps that stem from simply not being able to see a location often enough. As a complement to the 70cm resolution SkySat imagery of Bohai and Longpo, we also reviewed the available 3m resolution Planetscope imagery of the locations, which is still quite useful for monitoring an SSBN. Between July 2017 and November 2018, Planetscope imagery was available on 244 days, which provides much more regular imagery for monitoring purposes.

With plentiful imagery, we can observe progress in the Chinese SSBN program that might be near impossible to observe only with high-resolution commercial satellites. In this case, what is particularly beautiful to me is that we have imagery from the same day in two locations that are geographically distant, providing the accurate count of five Type 094 SSBNs in various operational states.


  1. Raj @ Vinayak (History)

    The count is at least 6 if not more as of Nov 2018.

    • Catherine Dill (History)

      Then I’ve regrettably overlooked some. These are the five I’ve seen at one time. Feel free to cite other instances!

  2. noone (History)

    And in the same time, they have one or two under sea. So 5 + 1 or 5 + 2.

  3. Tom (History)

    The wording in the report to Congress is a little inconsistent. At first it says “It [PLAN] currently operates 4 nuclear-powered ballistic missile submarines” and “China’s four operational JIN-class SSBNs represent China’s first credible, sea-based nuclear deterrent.” But later it says “China continues to produce the JIN-class SSBN, with four commissioned and at least one other under construction.”

    The word “commissioned” is the operative one, because it means 4 hulls have been constructed, outfitted, undergone sea trials, and accepted into service by the PLAN. Given the length of time you observed the two SSBNs at Bohai, it could be that one of them is still in the outfitting/sea trials phase (not commissioned) while the other is a fleet asset that has returned for repairs. That assessment would be consistent with the DOD report to Congress.

    The simultaneous images do suggest, however, that the PLAN is not running continuous deterrence patrols, although that’s not the only way to operate a “credible sea-based deterrent.”

    • Catherine Dill (History)

      Thanks for the helpful point on the commissioned state and the observation on continuous deterrence patrols.

  4. Martin Tsien (History)

    The wording seems a bit ambiguous. Are there 5 total (2 operational, 2 under maintenance, and 1 under construction) or 5 under construction (that is 2+2+5=9 total)

    • Catherine Dill (History)

      5 completed in total, but not all operational. I’m still wrapping my head around the correct terminology for the various operational states. But I also can only count what I can see.

  5. Andrew Tate (History)

    Your analysis doesn’t seem to consider the possibility that one of the boats at Huludao is newly constructed and has been launched recently. Analysis of more Planet Labs images by Chris Bigger ( seems to show that one of the boats was launched on 31 Oct. The two images from 16 Nov certainly show that there are at least 5 Type 094, but if one (or more) are also at sea that number is incorrect. To establish the correct number it would be worth trying to repeat what Chris Bigger has done, but for previous launches – unlikely to be less than 12 months apart and post launch, a new boat is likely to remain in Huludao for at least a year. Also worth noting that the 2015 Annual Report to Congress (April 2015) stated that “four Jin-class SSBNs are currently operational”

    • Giovanni Martinelli (@giovamartinelli) (History)

      This consideration appears correct.
      According to many different sources, in fact, the number of Jin in service before the possible launch occurred on October 31 was already 5; if therefore that same launch was confirmed, it could be related to a sixth submarine.
      At that point, the PLA Navy could have a couple of Type 094 and at least 4 Type 094A; the latters, however, not all operational.

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