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Element Suppresion



Here's some info on the suppression of elements by USSPACECOM:

NEWS AND COMMENT by Dave Ransom

mailto:rans7500@spacelink.nasa.gov

[Reposted from the RPV Astronomy BBS @ (520) 282-5559]

31 MAR 99  Reliable sources inform me that USSPACECOM would like to
           change the orbital model used for all TLEs and do NOT plan
           to release the code for their new "Special Perturbations"
           model. Since the "General Perturbations" model, SGP4/SDP4,
           is used in STSPLUS and most other satellite tracking programs,
           such a change would render that software all but useless
           except for historical purposes. I'll continue to track the
           situation and post Bulletins on my RPV BBS and FLASH.TXT on
           my Home Page as I learn more.

23 MAR 99  My sources report that USSPACECOM has completed suppressing
           TLEs from their "hit list" and that no more TLEs should be
           doing a disappearing act. My contact continues "... there is
           now a feeling of paranoia in releasing anything for operating
           DOD satellites, even the Navstars which are used for civilian
           purposes". I fear the GPS TLEs are gone for good ...

22 MAR 99  I have received unofficial confirmation that the suppression
           of GPS and DMSP TLEs at NASA/GSFC Orbital Information Group
           is the result of a policy change at US Space Command. I (and
           others) view this as a most unfortunate precedent. Not only
           is it a stupid decision -- more accurate orbital data for the
           GPS satellites can be obtained with a GPS receiver -- but it
           denies unclassified data to satellite users and the general
           public, data which is paid for by the American taxpayer. GPS
           and DMSP TLEs are suppressed now, what next?

           This policy change should not be allowed to stand unchallenged.
           I suggest that satellite users and those interested in satellite
           tracking write to Congress demanding that it be reversed. It may
           even take the Freedom of Information Act to apply some real
           pressure on USSPACECOM. Those individuals in the SeeSat-L forum
           are welcome to repeat my comments.

19 MAR 99  GSFC/OIG has deleted all trace of GPS satellites from their
           on-line database accessible to registered users. This appears
           to be a permanent policy change from USSPACECOM, unfortunately.

           I have implemented new TLE processing software which checks
           the age of TLEs posted in my TLEnnn.ZIP, GSFCnnn.ZIP and
           TLyymmdd.ZIP files. TLEs are deleted which are more than 21
           to 60 days old as a function of Mean Motion; LEO satellites
           are dropped at 21 days and GEO satellites at 60 days with
           other orbits falling in between those two limits.

           The GSFC/OIG TLEs for today were processed with the new
           software and quite a few TLEs were dropped, some dating back
           as far as 1968! I hardly think TLEs of that age are of much
           value to anyone. Comments invited.

16 MAR 99  USSPACECOM has apparently decided to discontinue distributing
           current TLEs for all GPS satellites and a number of other
           satellites. GSFC/OIG reports "No elements available" and TS
           Kelso's current data includes TLEs that are at least 10 days
           old. Unless the situation is corrected, I will stop including
           these TLEs in the data I distribute rather than continue to
           post outdated data.

           There has been no explanation for this change in policy. I
           fail to understand the rationale behind it since the basic
           orbital data for GPS satellites are included in the data that
           is transmitted to GPS receivers continuously. Any skilled
           "potential adversary" could easily obtain the data. Only the
           rest of us are denied the information.
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