Note that for catalog pieces in the SATCAT, the launch encoded in the international designation is not always the actual launch. In particular, all objects deployed from the ISS are give 1998-067 designations (the Zarya launch) even if they were launched on a much later cargo ship. However, the correct launch for an object can be found in the object catalogs by tracing back the Parent fields to the launch vehicle.
For launches, the scheme is of the form 'year - launch number in year'. For example, 2005-012 indicates the 12th launch to reach orbit in the year 2005.
For individual objects, a `piece designation' is used, with a sequence of letters appended to the launch designation; 2005-012E is the fifth (E) piece associated with that launch. The piece letters run from A to Z, then AA to AZ, BA ... to ZZ, AAA to AAZ, etc., always omitting the letters I and O. Usually, the first piece letters are reserved for the main payloads, followed by the rocket stages, followed by debris. However, there are frequent exceptions to this rule.
You can think of the piece letter scheme as a base 24 number. The largest number of pieces assigned to a launch as of 2020 is for 1999-025; object 1999-025EYS is the 3449th piece from the launch (5 x 24 x 24 + 23 x 24 + 17 = 3449 ). The mapping of piece number to piece letter for the first 72 objects of a launch is given in the figure below for convenience.
Usually the launch numbers are in chronological order within the year. There are, nevertheless, rare exceptions to this rule.
In principle, international designations are assigned to launches and pieces of launches which either complete a full orbit of the Earth or reach the Moon or beyond. Again, there are exceptions - launches which completed an orbit but did not get a designation, and launches or pieces which did not complete an orbit but got a designation anyway.
It is currently conventional to use three digits for the launch number, including leading zeros; e.g. 2020-005A. However, this is not part of the definition of the designation; e.g. 2020-05A is also a valid use and means the same thing.
As a special case, launch number 000 of the year is used for cataloged objects whose parent launch is unknown. This special case has been used very rarely and most of the relevant cases have since been identified with known launches and given revised designations. I tabulate all such cases here.
|US Satcat Number||Original designation||Current designation||Notes|
|S04924||1971-000A||1962 B LAM 2 (1962-059B)|
|S05310||1971-000E||maybe should be 1971-039D?|
This system was used for launches until the end of 1962, and the last launch to use the scheme was 1962 βω. which had two pieces, 1962 βω 1 and 1962 βω 2. However, in later years when new debris objects were discovered from those launches, NORAD (acting on behalf of COSPAR) also designated them using the Harvard scheme. For example, in 1992 a new debris object from the Ablestar 008 breakup was cataloged as NORAD number 21986 and given international designation 1961 ο 300 (1961 Omicron 300) using the Harvard scheme.
Designation of new objects had at some point been delegated to NORAD by COSPAR. However, it's not entirely clear that control of the scheme itself was designated. Thus, when in the late 1990s NORAD retrospectively reassigned all Harvard designations using the post-1963 scheme, it's not clear that was really a legitimate thing to do. From the point of view of historical consistency, I prefer to retain original designations rather than reassign them. Thus, although the US DoD now refers to object 21986 as 1961-015MM, I still use its original designation.
In most of my database files I map the Greek letters to an ASCII representation (mostly because I started this project long before Unicode was a thing). The representation used is indicated in the following table as `Code'. `Order' is the numerical order of launch (and the launch number in the new COSPAR scheme). I also provide the full English names of the Greek sequences, since the Greek alphabet may be less familiar to 21st-century readers.
You can call this the "JSR" scheme or even the "New Harvard" scheme (technically I work for the Smithsonian Institution's SAO, and I'm doing this on my own time, but to the extent that I'm on the Harvard campus and support space-related outreach inquiries for the Harvard-Smithsonian Center for Astrophysics, and recalling that Fred's satellite support team was an SAO program too, it's good enough.)
The only other comprehensive scheme for suborbital launch designations that I am aware of was from the World Data Center for Rockets and Satellites-A (WDC/RS-A) at NASA-Goddard. They assigned numbers to sounding rockets using a scheme of the form Ryymm-ddnn - example, R7402-1311 for the 11th cataloged launch on 1974 Feb 13. They only covered scientific sounding rockets (not, e.g., missile launches or failed orbital launches). I considered retaining these designations but instead have found it more useful to use a scheme similar to international designations for orbital launches.
My scheme is similar to the current international designation except that a `class letter' is added following the hyphen. The letter used indicates the type of launch, as described below. For example, the class letter F denotes a failed orbital launch attempt and the designation 2005-F03 indicates the third failed attempt in the year 2005.
Since the non-orbital catalog is incomplete, and I often identify previously undocumented historical launches, there are many more cases of launch numbers that are not chronological. Thus, 1961-S227 may have a launch date later than 1961-S511. Ordering within a year is therefore essentially arbitrary (although I start off *trying* to make it chronological).
Another wrinkle is that launches can change designation. If I've got documentation on a Nike Apache launch with no information on apogee, I may assume it worked and give it an S designation. If I later find it failed at low altitude, I will retire the S designation and assign a new A designation. I've been rather cavalier about this until now, but hope to be better in future about recording such changes explicitly.
Note that the JSR scheme is only for launches - there is no equivalent of the `piece letter', at least for now. For space catalog objects from such launches, my practice is to use the launch designation in the `piece designation' field. Thus, all objects from launch 2005-F03 have JSR designation 2005-F03, rather than being 2005-F03A, 2005-F03B, etc.
The categories used are presented in the following table:
|(none)||Orbital launch with COSPAR designation.|
|A||Endoatmospheric flight||apogee less than 50 km.|
|E||Pad explosion||rocket blew up, apogee in controlled flight less than a few cm|
|F||Failed orbital launch attempt|
|M||Mesospheric flight||apogee between 50 and 80 km|
|S||Suborbital space launch||apogee more than 80 km|
|U||Uncataloged orbital-energy launch||See below.|
|W||Mesospheric flight||same as M, obsolete|
|Y||Suborbital space launch||same as S, obsolete|
Orbital launch failures (class F) also satisfy the criteria for either A, M or S classes, but differ in that the intent was to achieve orbit. (F overrides A, M or S; but U overrides F.)
Some small meteorological rocket launches have W and Y class letters. I have discontinued assigning new launch designations in these classes, and the existing ones should be treated as if they were in classes M and S respectively.
I use 'U' to indicate a launch that should have received a regular designation but did not (e.g. 1995-U01). I also use it for a small set of interesting launches which had total energy (kinetic + potential) equal or greater than that needed for low Earth orbit with positive perigee. This includes some low-perigee orbital attempts that reentered within one orbit and some high speed reentry tests.
Launches from worlds other than the Earth are given 'U' designations and marked as 'LO' (liftoff) in the event catalog status. Departures from rocks (objects that are not large enough to be round due to self-gravity, working definition: objects with radius less than 200 km) are also marked as 'LO' but are not given launch designations; they are considered to be a new phase in the existing launch.