GCAT: General Catalog of Artificial Space Objects

Jonathan C. McDowell


Phases and Status Values

Each entry in the General Catalog represents a time period or phase in the flight history of an object. The !b status value describes the status of the object at the end of the phase. Typical values of the status are 'O' (still in orbit) and 'R' (reentered). But it can get a lot more complicated.


Each time an object transitions to another state (undocks, is attached to something, reenters, changes which body it is orbiting, etc.) marks the beginning or end of a phase. Most objects in GCAT have only a single phase - they separate from an object (launch vehicle) and then are either still in free flight or have reentered. However, some objects go through many phases.

The phase is defined by a set of fields in the object catalog entry.

ParentPEJCAT/Bodythe parent can be an extended JCAT ID (EJCAT) or a body name.
SDatet1VagueDatethe phase start time. This can be the time the object separated from the parent EJCAT or the time the object departed the parent body's gravitational sphere of influence (SOI)
PrimaryCBodythe name of the central body for this phase
DDatet2VagueDatethe phase end time
StatusSPhase Status Codea code describing the event that ends the phase
DestDLocation/Body/JCAT`destination', a string whose definition depends on the Status value. It can be empty, a Location, a body, or a JCAT.

The symbols in the table above are used in the discussion below for conciseness. A location can be expressed as a string (uncontrolled text, e.g. 'W Atlantic') or as longitude/latitude coordinates (e.g. 74W 22S). The Dest field may be blank if reentry location is unknown.

The different kinds of phases are defined by the Status field. They are given in a somewhat arbitrary order that makes sense to me, and grouped by what kind of Dest field is used. The state of an object includes its `externality' - is it free, attached to a parent object externally, or is it inside its parent object. This externality is also described in the following table defining the different Status codes. The table assumes (in the interpretation of t1 and t2) that P is a EJCAT rather than a body. If P is a body then t1 represents the time the object went from P's SOI to C's SOI; if D is a body then t2 represents the time the object went from C's SOI to D's SOI.

(Added 2021 Oct:) For cases where a vehicle is reused in a new launch (e.g. Space Shuttle Orbiter), the REFLT status is used to connect the objects. For example, the Space Shuttle OV-102 Columbia flew on mission STS-1 as orbital launch 1981-034, catalog S12399, piece designation 1981-034A. When it flew again on STS-2, NORAD gave it a new launch number 1981-111, catalog number S12953, and piece designation 1981-111A. Understandably the NORAD (now Space Force) tracking system cannot know from tracking data that the objects are the same vehicle - but historians do. I add an extra phase to S12399 (STS-1) after the landing, with zero duration, status REFLT, and dest equal to S12953, to signal that S12399 later got relaunched as S12953. Note that only a few entries of this kind have been added at the time of this writing.

I acknowledge that there is a bit of a `ship of Theseus' problem here: is the orbiter that flew on STS-93 really the `same object' as the one that flew STS-1?

The case of re-launches from other worlds is slightly different, in that Space Force does NOT assign a new catalog number, but I do - when the launch is from a world, not a small rock. For Apollo 11, three objects get new catalog numbers: the LM 5 Eagle ascent stage and the two EVA suits. EVA suit A7L-056 was given auxiliary catalog A01625 for its launch from Earth (launch designation 1969-059). On reaching deep space aboard Eagle it is given designation D00265. The last A01625 phase has status DSA with dest D00265 to tie the two together. The suit retains its D00265 designation through the lunar surface EVAs. Then it has a phase with the REFLT tag reassigning it to a new catalog number D01053 associated with a new launch, 1969-U01, corresponding to the launch of Eagle from the lunar surface. This follows the spirit of what NORAD did with STS-1 - when relaunching the same thing it gets new launch designations and catalog numbers - even though NORAD does not actually do this when the launch is not from Earth. Suit A7L-056 retains the new D01053 catalog number and 1969-U01 launch designation through its landing in the Pacific aboard D00273/1969-059A Columbia.

For the actual extraterrestrial re-launching itself, I retain the `LO' status tag used previously but add a dest value. `LO' should now be considered as equivalent to REFLT for such cases. Thus, for Eagle's ascent stage we have: launched from Earth as 1969-059C, catalog S04041. Reached deep space and reassigned as 1969-059C, catalog D00274, via a DSA status tag to connect the catalog numbers. Relaunched from the Moon as new launch 1969-U01, catalog D01052. The final D00274 phase has status LO with dest D01052 to connect it to the new catalog number.

For `launches' (departures) from low gravity objects that I don't count as worlds, I don't give new launch designations. I think of it more like an undocking in such cases! In these cases, the LO status tag does not have a new catalog number in the Dest field.

Status valueDescriptionInterpretationExternality
Cases with t2 and Dest both empty
OIn orbitSep from P at t1, still in free flightFree
AOAttached in orbitAttached to P from t1 to presentExternal
AO INAttached insideInside P from t1 to presentInternal
UDKUndockedDocked to P from t1 to t2, sep from P at t2External to free
RELReleasedAttached to P from t1 to t2, sep from P at t2External to free
DEPDeployedSame as REL but for objects on planetary surfaceExternal to free
LOLiftoffLaunch from C surface (C is a small body, not a world)Free
ALOAttached at liftoffAttached to P from t1 to t2 including at launch from C surface.External
Dest is always blank but t2 is not
EExplodedSep from P at t1, free in orbit until breakup at t2. Next phase of this object is a debris fragment.Free
NRenamedIn orbit from t1 to t2, name or owner changed at t2. Next phase reflects new name and ownerFree
LEASELeaseTemporary lease from main owner from t1 to t2. SatType code is PA. Free
Dest is a location on C, or C itself, or blank
RReenteredSep from P at t1, destroyed in C's atmosphere at t2 after natural decayFree
DDeorbitedSep from P at t1, destroyed in C's atmosphere at t2 via active deorbit maneuverFree
LLandedSep from P at t1, landed or splashed down on C's surface at t2Free
ARReentered attachedAttached to P from t1 to t2 when P reenteredExternal
AR INReentered insideInside P from t1 to t2 when P reenteredInternal
ALLanded attachedAttached to P from t1 to t2 when P landedExternal
AL INLanded insideInside P from t1 to t2 when P landedInternal
TXTransmission endedOperated on C's surface from t1 to t2Free
FFailedSep from P at t1, crashed or destroyed at t2 during launch failureFree
AFFailed attachedAttached to P at all times until it and P crashed or destroyed at t2 during launch failureExternal or internal.
Dest is a JCAT from D catalog (deep space). JCAT ID used in deep space catalog for this object is given by the Dest value.
DSODeep spaceSep from P at t1, passed deep space boundary at t2. Free
DSADeep space attachedAttached to P since t1, passed deep space boundary at t2.External
DSA INDeep space inside Inside P since t1, passed deep space boundary at t2. Internal
LOLiftoffLaunch from C surface (C is a world but not Earth), catalog reassigned to destFree
REFLTReflightLaunch from C surface (C is a world but not Earth) aboard parent object, catalog reassigned to destExternal or Internal
Dest is a JCAT from the main catalogs (not from D catalog)
DKDockedSep from P at t1, docked with D at t2Free to External
GRPGrappledSep from P at t1, docked with D at t2Free to External
ATTAttachedWas attached to P at t1, then attached to D at t2External.
TFRTransferInside P at t1, moved inside D at t2Internal
TFR ETransfer externalInside P at t1, moved to exterior of D at t2Internal to External
RETRetrievedAttached to P at t1, moved inside D at t2External to Internal
CCollidedCollided with D at t2Free
EVASpacewalkMoved outside P at t1, returned inside D at t2Internal to tethered or free to Internal
REFLTReflightObject reassigned to a new catalog number on its next flightNot applicable
Dest is a body name
EOEscapeLeft P's SOI at t1, In C's SOI from t1 to t2, entered D's SOI at t2Free
EAOEscape attachedAttached to P from t1 to t2. In C's SOI till t2, then in D's SOIExternal

For case C (Collision) the collision can result in the destruction of the object, in which case there is no subsequent phase; or the object can survive, in which case t2 starts a new phase. If object A collides with object B, there is a C status for each of the objects A and B. That is, A has a phase that ends with 'A collides with B', and B has a phase that ends with 'B collides with A'. If A survives, B is the parent object for A's next phase, and vice versa.

For cases R, D, AR, AR IN: if C has no atmosphere, t2 is the time of impact on C's surface. Natural decay includes orbit perturbation due to mascons, and direct impact without first entering bound orbit.

For cases DSO, DSA, DSA IN; the object is considered to have left the main part of GCAT at t2. Its old JCAT ID no longer applies and the Deep Space Catalog JCAT ID is used for further phases of its history.

The cases EO and EAO are only used in the Deep Space Catalog and the heliocentric and lunar-planetary registers.