Letter designations for sources of elements - re: GPS Elsets C No

Philip Chien (kc4yer@amsat.org)
Wed, 9 Jun 1999 10:27:12 -0400

>JBARKER@arinc.com wrote:
>
>> All I'm asking is that consideration be given to the selection of
>> certain letters that may give the appearance that those of us who have
>> security clearances have broken the rules.

Jim Varney <sat_watcher@rocketmail.com>

>Since you are with ARINC I now see how this might be problem for you.
>Future releases of the GPS elsets will have the "U".

Hold on a second!  "U "has a very specific meaning - e.g. unclassified
objects generated by USSPACECOM.

I was unaware of the existence of "C" for classified or other designations
until it was brought up here recently, although I did find the background
information interesting.

I have seen "E" in previous elesets which I understand means Estimated
(e.g. sets generated for predictions or historic purposes either because
the original data is unavailable or prelaunch predictions).

And I certainly like the idea of using field 8 to identify the origins of
different element sets.  Certainly when I've got several different
predictions plus actual post-launch elsets there can be confusion.

The only concern I have is whether or not all of the common tracking
programs will accept other characters in field 8.  Obviously based on the
recent discussions since there are other valid characters no programmer
should check if character="U" to verify the validity of a set.

For me it would be highly desirable if those who generate predicted keps
(rockets before they launch, search orbits, predicted orbit after a
maneuver) would use some consistent letter ("P" for predicted?).  The
problem would be convincing *everybody* (Ken Ernandez, Gil Carman, NASA
JSC, Ron Lee, etc.) to use the same letter designator.

I do like Sue's suggestion to use "A" for amateur derived elements for
those objects where elements are unavailable from USSPACECOM where amateur
visual and radio observations were used to derive elements (USA objects and
even objects incorrectly identified by USSPACECOM)

How about "D" for derived for elsets generated through state vectors and
other analysis of refined orbital information (like GPS element sets
reverse engineered from the ephemeris data and even space shuttle elements
derived from the shuttle's state vector)?

We've got 26 letters in the Roman Alphabet (32 in ASCII) - surely they
can't all be in use by USSPACECOM!



JAY RESPLER <jrespler@superlink.net> said:

>Re: "U" vs "C" vs ... in elsets
>
>As far as that goes, If it's not broken, don't fix it. Forget all
>those extra letters. U works. Just leave it that way. The simplest
>way is the best way.

While it isn't broke - it doesn't hurt to make improvements.  My 286
computer wasn't broken when I changed out the motherboard.  Different
letters to indicate sources of elements will help define where they came
from, and whether or not they're still valid.


Philip Chien, KC4YER
Earth News
world (in)famous writer, science fiction fan, ham radio operator,
all-around nice guy, etc.