Hello all,

I got a request to post new elements on-list. If you use the first set
of elements below (epoch 26 June) to compute positions for 27 June, you'll
be off by about a quarter of a degree. So use the first set until 26.5
June or so, the second set after that.

Properly speaking, we should be using geocentric elements, what with
this object being within the earth's sphere of influence (about 920000 km).
But most software won't handle those... just for yuks, though, I've
added them at the bottom of this message.

The perturbations are really pretty strong at this point, of course.
But they're mostly in the direction toward us... because, of course,
that's the direction in which the earth is pulling this thing. Which is
why you can still get decent RA/dec values with these elements; almost
all the error will be radial.

Adding last night's DOU decreased the sigmas about fourfold. However,
bumping the epoch up a couple of days doubled the sigmas, which are
higher when one is near a planetary encounter or further outside the
observation arc. And you can also see that the U parameter goes up from
4.6 for one epoch, to 5.1 for the next day's epoch. Which is one reason
one shouldn't rely on the U parameter to mean much of anything.

Anyway. The extra data also turns the "maybe it's an encounter" 1962
pass into a very clean miss at .064 AU. So this object is a for-real
rock. (I don't see Tabare Gallardo's 1978 encounter at all... dunno
what's going on there.)

-- Bill

Orbital elements:
2011 MD
Perihelion 2011 Aug 19.615850 TT = 14:46:49 (JD 2455793.115850)
Epoch 2011 Jun 26.0 TT = JDT 2455738.5 Earth MOID: 0.0002
M 308.981769 (2000.0) P Q
n 0.934128655 Peri. 231.789816 0.842745464 0.534660243
a 1.036409979 Node 95.806600 -0.472138395 0.789992521
e 0.02968618 Incl. 3.607480 -0.258583481 0.300083722
P 1.06/385.38d H 28.3 U 4.6 q 1.005642920 Q 1.067177039
From 122 observations 2011 June 22-25; mean residual 0".445.

Orbital elements:
2011 MD
Perihelion 2011 Aug 10.325120 TT = 7:48:10 (JD 2455783.825120)
Epoch 2011 Jun 27.0 TT = JDT 2455739.5 Earth MOID: 0.0002
M 319.510282 (2000.0) P Q
n 0.913471135 Peri. 223.208871 0.750511790 0.656650808
a 1.051976803 Node 95.591627 -0.584130302 0.711836000
e 0.04466404 Incl. 4.289671 -0.309069316 0.249197159
P 1.08/394.09d H 28.3 U 5.1 q 1.004991263 Q 1.098962343
From 122 observations 2011 June 22-25; mean residual 0".445.

Sigmas (for 27 June elements):
sigma_Tp 0.00336 days
sigma_e 8.21e-6
sigma_q 6.62e-7 AU (99.1 km)
sigma_Q 1.74e-5 AU (2603 km)
sigma_1/a 7.58e-6 1/AU
sigma_i 0.000393 deg
sigma_M 0.00355 deg
sigma_omega 0.00289 deg
sigma_Omega 0.000245 deg
sigma_n: 1.09e-5
sigma_a: 8.39e-6 AU (1255 km)
sigma_P: 0.00472 days

Orbital elements (geocentric):
2011 MD
Perigee 2011 Jun 27.708875 TT = 17:00:46 (JD 2455740.208875)
Epoch 2011 Jun 27.0 TT = JDT 2455739.5 Find_Orb
q 18627.9 +/- 5 km (2000.0) P Q
H 28.3 G 0.15 Peri. 281.756305 -0.188192857 -0.781210704
Node 43.407969 0.791883657 -0.479189217
e 1.10208155 Incl. 119.982878 -0.580950704 -0.400109395