2nd SDP failure case revisi

ROB MATSON (ROBERT.D.MATSON@cpmx.saic.com)
31 Mar 1997 19:41:14 -0800

Hi Curtis,

Well, I guess there's more to creating these test cases than meets the eye! 
The problem is that the quadrant problem with XNODES will either manifest
itself when the old (unperturbed) XNODES crosses zero, or the new one does,
depending on whether the original XNODES has been maintained in the range of 0
to 2*Pi.  The XNODES in SR #3 could come into DPPER with a value greater than
2*Pi.  And this is the case for you.  But T.S. Kelso later modified DPPER to
make sure XNODES was from 0 to 2*pi.  If you've got this mod, the test case I
gave will fail as advertised.  (This is why TRAKSTAR fails -- it's got the
Kelso mod).  But without Kelso's mod, the code will *still* exhibit the bug. 
It just occurs when the perturbed XNODES crosses zero.  In the case of the
second example I cited, it happens a little less than an hour later.  I
recompiled my code to match yours in order to find the quadrant crossing time
on the perturbed XMODES.  It occurs between 14:42:30 and 14:43:

UTC Date:  1/17/97      position in km

UTC Time         X                   Y                   Z
--------  ----------------   -----------------   -----------------
14:40:00  12058.6968436073   -9088.05059434088   -1604.73341693802
14:40:30  12207.3904182008   -9040.79898042420   -1596.37913955513
14:41:00  12354.8551383471   -8992.63608004684   -1587.86366489113
14:41:30  12501.0976325425   -8943.58238643458   -1579.19061502540
14:42:00  12646.1245522158   -8893.65787621351   -1570.36352079508
14:42:30  12789.9425652844   -8842.88202551640   -1561.38582463892
(jump)
14:43:00  13726.9960697113   -7532.85729295977   -1330.06349285878
14:43:30  13862.6766127548   -7467.35366752016   -1318.48402930620
14:44:00  13997.0964328723   -7401.16989068805   -1306.78421250686
14:44:30  14130.2638901796   -7334.32287724387   -1294.96703273207
14:45:00  14262.1872942258   -7266.82911673137   -1283.03540513679

So run your code at the later time.  I'll bet you see the jump...  --Rob

Note to Bruno Tilgner:  Could you try it also?  Yours should fail too.