Talk:SDP4

"Any satellite with an orbital time of greater than 255 minutes should use this algorithm", that seems to be more opinion than fact Redconverse 19:00, 18 May 2006 (UTC)

The 255 minutes was wrong, it is 225 minutes and the choice is one made in the original design of the NORAD/AFSPC orbit determination system. For accuracy, you need to use the same model and assumptions in using the TLE as were made in generating them.--Pcrawford 11:14, 25 November 2006 (UTC)


 * The 255 minute figure is correct and is mentioned in multiple reference including Vallado's paper analyzing STR#3. It could be argued that the number is a bit arbitrary but it is the standard for ensuring that the correct model is selected.  Smaller periods mean near Earth orbit, larger periods for deep space orbits (a potentially misleading term but the right one to use here none-the-less).--RadioFan (talk) 18:14, 16 June 2010 (UTC)

Can someone post the actual algorithm ?
I see some links to source code. Can someone post the actual algorithm here? —Preceding unsigned comment added by 70.238.110.131 (talk) 21:20, 12 December 2007 (UTC)


 * If prefer looking at formulas with lots of Greek letters instead of source code, SpaceTrack Report #3 should give you what are looking though its not any easier to read than the source code.--RadioFan (talk) 18:14, 16 June 2010 (UTC)

New external link, please check COI
There seems to be no other Java implementation of SDP4/SGP4 other than my own. I've added the external link "SDP4 algorithm in Java". Can someone please check it's appropriate and remove the link if not? Chi And H (talk) 19:32, 21 May 2009 (UTC)

Proposed merger with SGP4 page
The proposed merger of this page with Simplified Perturbations models - recently renamed from SGP4 - makes good sense. Any literature or software is likely to deal with both. SGP4 and SDP4 are complementary to each other, dealing with low and high satellite orbits resp. Also, this page already deals with SDP8 in passing; best have all SGP/SDP versions dealt with in one page. Chi And H (talk) 16:17, 16 June 2010 (UTC)
 * ✅ --RadioFan (talk) 18:27, 16 June 2010 (UTC)