Navigable Classification System

Star systems containing exoplanets are identified from Earth-based deep space observatories.

While much can be speculated at this distance, confirmation of what exactly these planets are like – and whether they support life – must wait until Endeavour reaches orbit.

Priority is typically given to systems containing exoplanets likely to support life and suitable for direct exploration.

Classification Codes

To keep track of all these exploration targets, a classification system designed specifically for deep space navigation has been developed. Each astronomical object (AO) of interest is assigned a multi-part code.

An example of a classification code is: S1-F53T-P3M

Reading left to right, each part of the code adds greater specificity.

Galactic Sector

The left -most part of the code specifies the galactic sector. Sectors are an arbitrary division of the galaxy into more manageable chunks, based on bearing and vector from Galactic Normal.

A sector code always begins with the letter S and otherwise only contains numbers.

This part of the code is not typically included in normal notation unless that level of specificity is required. Galactic sectors are sufficiently large that vessels are not expected to regularly interoperate between them.


The next part of the code identifies the astronomical system, usually based on a star (and so typically referred to as a star system).

The code is a sequence of alphanumeric characters, generated randomly to avoid possible confusion from implying proximity based on similarity of codes.

A four-character code provides over 9.7 million possibilities, which is not enough for every star system in a sector – but only systems of interest are classified.  Should more than 9.7 million systems be required, additional characters will be added to the code for those systems.

Navigable Astronomical Object

An AO on which a system is based is known as a Navigable Astronomical Object (or NAO).

Typically the NAO is identified by the system code and no additional code parts are required.


Where a system is based on a nebula rather than a star, additional code part can added, beginning with N and then including the nebula’s classification.

For example: GT6R-N4

Astronomical Objects

The remainder of the code identifies the specific Astronomical Object (AO). Each of the code’s three characters have a particular meaning.

The first character is the AO’s type:

  • A: Asteroid
  • C: Comet
  • P: Planet
  • S: Star

The second character is the AO’s identifier within the system.

The third character is the AO’s class.


For planets the AO code the first character is P (for planet).

The second character is the AO’s orbital order within the system.

The third character is the planet’s class.

For example: F53T-P3M

Asteroids and Comets

Asteroids and comets within a star system are identified using a code that begins with either A (for asteroid) or C (for comet), followed by a number based on the order of cataloguing.

For example, F53T-A325


Where a star system contains more than one star, stars other than the NAO are identified using the standard 3 character AO code.

For example: F53T-S1F

The first character is S (for star) which is followed by a unique number. As this cannot always be derived from orbital order it can be assigned arbitrarily. The assignment of this number has no impact on the orbital order assigned to the star system’s planets.

The final character is the star’s class.

Planetary Systems

Planets are often orbited by their own satellite AOs (moons). A planet and its satellites are known as a planetary system.

AO’s within a planetary system are identified using an additional 3-character sub-code.

For example: F53T-P3M-M2D

The first character is M (for moon) which is followed by its orbital order within the planetary system.

The final character is the moon’s class, which uses the planetary classification system.

Where a moon is too small for a planetary classification (ie under 100km) then class Z is used.

Stellar Classification

For descriptive navigation purposes stars are classified based on their spectral characteristics.

Planetary Classification

Planets are classified based on their geophysical and enviornmental characteristics.