From this answer to the question What artificial satellite has the farthest orbit around the Earth?:
I found the following "far out" spacecraft:
- TESS (Transiting Exoplanet Survey Satellite) recently launched, not in final orbit yet
- IBEX or Interstellar Boundary Explorer
Here are there IDs:
TESS 43435 2018-038A Spektr-R 37755 2011-037A IBEX 33401 2008-051A Geotail 22049 1992-044A
I downloaded both TLEs and orbit data from JPL Horizons in order to piece together this qualitative data.
All four of these are without question in Earth orbit, or at least have been until recently.
As I describe in the (currently unanswered) question “Deep space” corrections in SGP4; how does it account for the Sun's and Moon's gravity? the "deep space corrections" of SDP4 are already included in modern implementations of SGP4.
To my knowledge none of these four spacecraft are actually lost.
Question: So why does Celestrak show three of them as lost? What does "lost" mean in Celestrak-speak?
I'm not looking for guesses or free-form interpretations, I'd like to know how Celestrak uses the term "lost" in this case, and what it means specifically.
GEOTAIL 1 22049U 92044A 19100.47047473 -.00001329 00000-0 00000+0 0 9998 2 22049 16.9903 61.2002 5647056 148.0163 356.4514 0.19163824 10715