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What is a Space Object?

There was a recent article on[1] discussing the definition of a satellite. The article was very good but didn’t discuss the legal situation. This has prompted this post. However, there’s more to consider especially as discussion of in-space manufacturing of satellites is becoming a ‘hot topic’ (note the recent article in the Financial Times[2]). In this post I will discuss the legal definition of a ‘space object’ and the issues that could be provoked by making a ‘space object’ in outer space and from space materials.

The treaties don’t use the term satellite, instead opting for ‘object launched into outer space’ in the Outer Space Treaty or ‘space object’ in the Liability and Registration Conventions[3]. In line with a general trend the Outer Space Treaty doesn’t really provide a definition for ‘object launched into outer space’ other than an indication in Article VIII that it includes the ‘component parts’ of the ‘object launched into outer space’. To add to the mix Article V of the Outer Space Treaty uses the term ‘space vehicle’ and the Rescue Agreement (which is essentially an elaboration of Article V OST) uses the term ‘spacecraft’.


A British space object Prospero launched into outer space 46 years ago on 28/10/71

However, there is a definition of sorts of ‘space object’ provided by Article I(d) of the Liability Convention and Article I(b) of the Registration Convention: “The term ‘space object’ includes component parts of a space object as well as its launch vehicle and parts thereof.” Now strictly speaking this definition only applies to the Liability and Registration Conventions but it conforms with the piecemeal definition ‘provided’ by the Outer Space Treaty and therefore can be used for space law as a whole, although as Professors Diederiks-Vorschoor[4] and Kopal wrote in An Introduction to Space Law “the term ‘space object’ is indeed the commonly used expression, but it must always be borne in mind that its exact meaning is still not quite clear.”[5] I would posit that a useable working definition of a ‘space object’ is the one given by Professor Hobe in the Cologne Commentary that a ‘space object’ is a human made object launched into outer space intended to be used in (as opposed to merely transit through) outer space.[6] This is backed up by now over sixty years of practice and the launch and operation of thousands of space objects.

A key point here is launched into outer space. There are now people and companies actively discussing in-space manufacturing of satellites and other objects, some even going so far as to discuss making them out of material sourced from outer space. This also has implications for things like the Moon Village or Elon Musk’s Mars colony, especially if they make some habitats out of locally sourced material, because then they won’t have been launched into outer space, so will they be ‘space objects’? This is important because if not then they may fall outside of the existing space governance regime.

There is also potentially a split between objects manufactured in space and on a celestial body. Article VIII of the Outer Space Treaty stipulates that “ownership of objects launched into outer space, including objects landed or constructed on a celestial body, and of their component parts, is not affected by their presence in outer space or on a celestial body or by their return to the Earth.” Now presumably this was about bases constructed from prefab units a la the ISS but on, say, the Moon but as it doesn’t stipulate it is possible to extend it to objects constructed or 3D printed from locally sourced material, so your home on Mars built out of local material could still be a space object under existing space law.[7]

There is also a potential argument to be made that materials launched into outer space from Earth are ‘component parts’ and the final product could therefore be a space object of sorts. However, that seems like it’d be a paperwork nightmare at the very least, and is probably a rather tenuous stretching of the existing definitions. But an object manufactured in space from material sourced from space (provided by, say Deep Space Industries) really exists in a legal vacuum (pun intended) as it was not manufactured on a celestial body and was not launched into outer space… If the object manufactured in space from space sourced material was manufactured in a space object that itself was launched from Earth it is possible that the manufactured object could be a ‘component part’ of the ‘space factory,’ although again that seems tenuous and not without problems of its own…

As is usually the case, I advocate for further discussion of this issue, particularly at the Legal Subcommittee of UNCOPUOS. However, I will note that there has already been discussion of this issue at the most recent Practitioners Forum held by the European Centre for Space Law, and The Hague Space Resources Governance Working Group have also discussed this issue, and they have posited the term ‘space product’ in their Draft Building Blocks[8] defining it as a “product made in outer space wholly or partially from space resources”[9] although given that the note on the definition of ‘space object’[10] says that “according to the understanding of the Working Group, this includes objects made wholly or partially from space resources” it is unclear from the Building Blocks themselves what the distinction is. The term ‘space product’ is only used in Building Block 13(f) requiring the notification of the presence of ‘space objects or space products, or parts thereof’ in the event of the termination of space resource activities.

Personally, I support a simple tweak to the definition of space object to: a space object is a human made object in outer space intended to be used in (as opposed to merely transit through) outer space. Of course, this definition has issues of its own, such as what constitutes ‘in outer space’ and ‘merely transiting through outer space,’ but it avoids the creation of entirely new definitions and regimes. I expect that customary development will somewhat resolve this issue, but that doesn’t negate the importance nor the necessity of discussing the issue at the various international forums where space governance is discussed. There’s also an incentive for industry to promote discussion of the topic as the space law regime actually has a very strong property rights regime for ‘space objects’ so there’s an incentive for them to have this maintained for objects constructed in space.




[3]I’m going to stop linking to the treaties, they’re easily googleable and all available as PDFs on

[4]She sadly passed away recently, see her obituary here:

[5]I.H.Ph. Diederiks-Verschoor and V. Kopal, An Introduction to Space Law (3rd edn, Kluwer Law International, 2008), 89

[6]Stephan Hobe ‘Article 1’ 25-43 in Stephan Hobe, Bernhard Schmidt-Tedd and Kai-Uwe Schrogl eds., Cologne Commentary on Space Law, vol 1 (1st edn, Carl Heymanns Verlag, 2009), 32

[7]For further discussion of some of these issues see my previous post on ‘building a space nation’


[9]Building Block 2.5

[10]Building Block 2.4

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