TDRS desginations Re: Satellite designations in orbit

Philip Chien (
Sun, 25 Aug 1996 01:51:38 -0400

Regarding Philip Chien's...
>>The key confusion is the TDRS series.  TDRS-A became TDRS-1 in orbit.  Fine.
>>TDRS-B was lost in the Challenger accident.  TDRS-C was launched on STS-26,
>>and presumably should have been renamed TDRS-2, however it wasn't - it was
>>named TDRS-3.  So the designation TDRS-2 was never used, a contradiction of
>>how all other NASA satellite series have been named.

to which Lynn + Steve Walter / LAST Acre <> commented:

>... it IS proper to refer to TDRS-C as TDRS-3, since TDRS-2 still exists
>(in a concrete graveyard down at the Cape, I believe).  I have been VERY
>involved with each TDRS for about 10 years, now, and I've never heard of
>TDRS-3 being referred to with the number '2'!

But that's EXACTLY the issue!  On September 29, 1988 when TDRS-C reached
orbit, it should have been designated TDRS-2 --- not TDRS-3.  THERE HAS

Yes, it wasl always intended for TDRS-B to become TDRS-2 -- but _only_
after it achieved orbit.  A concrete graveyard in an old Minuteman silo is
_NOT_ in orbit.  (Well, it is in orbit around the sun, but you know what I
mean ...)

GOES-G is in some scrap bins and at the bottom of the Atlantic Ocean (some
of the debris probably fell on top of the TDRS debris but that's besides
the point), and it certainly didn't deserve or get any numercial
designation - so why should TDRS-B??

Ditto every other case of a launch failure, and even in some cases
activation failure.  (Some spacecraft which have failed shortly after
reaching orbit, but not declared operational have not been given numercial

>As a slightly further elaboration on TDRS, there've been 7 of them launched
>to date, each essentially the same type of spacecraft (built by TRW).
>[Tho, there are some key differences (improvements?) in each subsequent craft.]

Well, I wouldn't exactly call them improvements.  More of 'oops why'd we do
that' type items.  From what I understand the TDRS-B launch was delayed
nine months (from April 1985 to January 1986) because of a problem with the
decoder box aboard TDRS-A, the TDRS-D and later spacecraft have different
wiring so one fuse doesn't shut down an entire transponder, etc.  And
TDRS-G doesn't have the commercial C and Ku transponders, so it has a bunch
of ballast on board.  And also cost a _BUNCH_ more than the others because
it was a one-of-a-kind spacecraft.

>Philip is correct in that each TDRS carries a sequential-letter-designation
>while on the ground.  And, I believe it is NASA's convention to change this
>letter into the number corresponding to the alphabetic character once the
>vehicle is on-orbit.

Which is the fundamental problem - TDRS-B never made it to orbit!  So it
never earned the TDRS-2 designation.  So TDRS-C should _NOT_ have been
labeled TDRS-3.

>This practice does NOT stop folks from mixing
>alphabet characters and their numbers, however -- it is, I'm afraid, such a
>day-to-day mixture at the TDRS White Sands Complex.  My own, personal push,
>is to steadily use the NASA convention of numbered craft once on-orbit.

And, unfortunately, because of the TDRS designation fiasco, I've kept to
letter designations because there's no conflict of confusion there, while
there is confusion with the numbers (e.g. why is TDRS labeled differently
from every other spacecraft series).

>FYI, by the way, the next 3 TDRS vehicles are being built by Hughes; they
>currently contain the 'HIJ' designations (on the ground), and I suspect
>will be referred to as TDRS-8,-9,-10 after launch.  These vehicles look
>VERY different from the current series.

And Hughes has artist's renditons of these spacecraft at its web site.

Philip Chien, Earth News - space writer and consultant  PCHIEN@IDS.NET
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