[X] My Assistant

[slinted]

3 new (old) observations from Apache Point-Sloan Digital Sky Survey have been added to the arc, extending it back to 2007/11/08. I think JPL Horizons has an updated ephemeris, since it now shows closest approach at 2008-Jan-30 11:45 at a distance of 21,006 km from the center of Mars, down from the previous 51,722 km closest approach. This may or may not actually mean the chances of impact went up, but either way I can't wait to hear what the impact gurus have to say.

[ugordan]

Perhaps counterintuitively, these new observations might actually rule out an impact, despite the closer projected approach distance. How wide was the across-track uncertainty prior to this observation? Looking at SteveM's animation, it was huge. If the uncertainty now is less than +/- 21000 km the deal's off.

This would be truly a once in a lifetime event, but really, the odds are strongly against it.

[MarsIsImportant]

The cone of uncertainty from a couple of days ago extended over a million kilometers (700,000 miles) along a very slender ellipsoid only 1200 km (700 miles) wide. That's why they could say with certainty that Opportunity was safe. They knew where on Mars the asteroid could possibly hit.

I don't know the exact figures altered by these new earlier observations added to the equations, but my best guess is that Mars is still very much within the cone of uncertainty. And if that is true, then the odds of a hit just went dramatically up. The predicted path keeps getting closer and closer to Mars. First is was around 100,000 km; then it was 50,000 km; and now it is 21,000 km. Do you see the trend? The cone of uncertainty is too wide of a swath for it not to be still intersecting with Mars. Yet, how much of the cone is current filled by Mars determines the actual odds of a strike. I'd like to see the new figures in detail.

We still won't be able to rule out an impact on Mars until a couple of weeks with new, fresh observations of the asteroid.

[ugordan]

We still won't be able to rule out an impact on Mars until a couple of weeks with new, fresh observations of the asteroid.

I'm a pessimist so I'll formulate it this way: we still won't be able to rule out a miss until new observations show up. The fact the predicted path is getting closer to Mars isn't really indicative of anything, it could miss ("overshoot") Mars and go to the other side just as well for all we know. Mars is not some kind of a great attractor here!
Remember back when Apophis (?) was tracked for an Earth impact, there was a slight increase of a chance for a hit at one point only to be ruled out by later measurements. The predicted path is just one point in a large ellipse, not the most probable point at that.

I'm looking forward to new probability estimates and ellipses, but even a 10-fold decrease (probably unlikely with only 3 recently added datapoints) in ellipse semimajor axis still leaves a whopping 100 000 km impact parameter.

[MarsIsImportant]

Mars has gravity. And the current best guess path takes it to only within 2 and 1/2 times the the diameter of Mars to an actual impact. That is extremely close. The closer it gets to Mars, the more Mars' gravity will affect the path of the asteroid. So the trend is significant, because we need to know where this thing is going to go. Afterall, this is a NEO too.

[Stu]

Hey, look on the bright side... if it misses Mars then maybe it'll hit Phobos or Deimos instead, then shower Mars with enough debris to make dozens of new craters...!

(pauses to allow time for killjoy Vulcan "A fascinating theory Captain, but unfortunately the orbital parameters of the bodies involved means such a collison could not happen" posts to flood in...)

[ElkGroveDan]

Hey, look on the bright side... if it misses Mars then maybe it'll hit Phobos or Deimos instead, then shower Mars with enough debris to make dozens of new craters...!

LOL

..and don't forget the rings that would then take shape around Mars.

[MarsIsImportant]

Well, I guess that is one way we could finally get a closer look at Phobos or Deimos!

This maybe a scary thought...despite logic, Captain Kirk tended to be correct with his intuition.

[nprev]

The MERs use the popular LN-200 IMU.

Thanks, Del. That's a nice little unit: FOGs & SSAs, only uses 12W. Still think that it would sense an impact of reasonable energy not TOO far away (say within a few hundred km, or more depending on the kinetic energy conductance of Mars' crust).

To add some pessimism (but, yeah, here's still hopin'), unless MRO can track it inbound I wonder if we'll even know if it hits until it can't be found zooming around anymore. The uncertainty will remain pretty large until shortly before the encounter, and well before that it will become almost unobservable from Earth-based scopes due to growing Marslight washout...hell, it's hard enough to pick up Phobos & Deimos, much less a 50m rock.

[SteveM]

Here's the latest Horizon observational ephemeris for Opportunity -- apparently based on the new observations. The asteroid really tears across the sky and is brighter at closest approach (ninth magnitude) in this revised version. It's interesting how the asteroid sets at about 11:40 UT and rises again about 4 hours later at 15:40. But all the interesting stuff happens in daylight.

CODE

Date__(UT)__HR:MN R.A._(ICRF/J2000.0)_DEC Azi_(a-appr)_Elev APmag delta deldot

2008-Jan-30 08:00 *x 19 14 29.75 -26 06 47.0 44.2763 77.4146 n.a. .001119758994332 -12.4773173
2008-Jan-30 08:20 *x 19 11 04.19 -26 12 38.5 20.3823 80.7437 n.a. .001019834490894 -12.4346540
2008-Jan-30 08:40 *t 19 06 53.38 -26 19 25.0 343.2271 81.3518 n.a. .000920283052273 -12.3838495
2008-Jan-30 09:00 *x 19 01 41.25 -26 27 16.7 312.7583 78.5229 n.a. .000821184099440 -12.3210520
2008-Jan-30 09:20 *x 18 55 03.14 -26 36 22.6 296.0594 73.6897 n.a. .000722658243020 -12.2395393
2008-Jan-30 09:40 *x 18 46 19.28 -26 46 43.5 286.5309 67.7772 n.a. .000624900148017 -12.1268977
2008-Jan-30 10:00 *x 18 34 21.72 -26 57 50.2 280.1632 60.9379 n.a. .000528246662206 -11.9584635
2008-Jan-30 10:20 *x 18 17 05.69 -27 07 29.1 275.1185 52.8907 n.a. .000433331866382 -11.6803905
2008-Jan-30 10:40 *x 17 50 22.63 -27 07 14.3 270.3355 42.8424 n.a. .000341482965162 -11.1601933
2008-Jan-30 11:00 *x 17 05 19.88 -26 24 26.3 264.8198 28.9251 n.a. .000255874104730 -10.0236624
2008-Jan-30 11:20 *x 15 44 06.07 -22 50 37.3 256.9104 6.9177 n.a. .000185204194490 -7.1356436
2008-Jan-30 11:40 *s 13 35 09.46 -11 20 33.4 242.3044 -27.4819 9.68 .000151851190861 -0.5295519
2008-Jan-30 12:00 *x 11 31 52.61 +03 57 57.7 208.3976 -58.0619 8.78 .000178023916770 6.4910393
2008-Jan-30 12:20 *x 10 17 23.64 +12 49 43.0 157.4809 -63.1501 8.90 .000245131156386 9.7235864
2008-Ja-30 12:40 * 09 35 47.43 +17 02 46.4 130.7972 -55.7115 9.23 .000328828851257 10.9623996
2008-Jan-30 13:00 * 09 10 42.46 +19 15 12.6 119.4228 -47.4719 9.57 .000419183472640 11.5004648
2008-Jan-30 13:20 * 08 54 15.03 +20 33 00.3 113.5219 -39.9903 9.88 .000512617446795 11.7689937
2008-Jan-30 13:40 * 08 42 41.91 +21 23 00.6 109.9647 -33.1694 10.16 .000607668173096 11.9182664
2008-Jan-30 14:00 * 08 34 09.47 +21 57 22.6 107.6089 -26.8158 10.41 .000703653878681 12.0084555
2008-Jan-30 14:20 * 08 27 35.06 +22 22 12.4 105.9547 -20.7885 10.63 .000800223304134 12.0668511
2008-Jan-30 14:40 * 08 22 21.66 +22 40 51.2 104.7517 -14.9941 10.84 .000897182111537 12.1071307
2008-Jan-30 15:00 08 18 06.13 +22 55 17.0 103.8622 -9.3707 11.02 .000994417559616 12.1367131
2008-Jan-30 15:20 08 14 33.33 +23 06 43.5 103.2054 -3.8763 11.19 .001091862492983 12.1598826
2008-Jan-30 15:40 r 08 11 32.94 +23 15 58.9 102.7318 1.5184 11.35 .001189476710756 12.1792388
2008-Jan-30 16:00 08 08 57.72 +23 23 35.7 102.4110 6.8339 11.50 .001287236672609 12.1964205

On Spirit's side there's a much more interesting picture with almost everything happening at night. The asteroid rises about 11:40 UT, has closest approach around 12:00, transits around 12:20, and sets around 15:40. I imagine the batteries will be in no condition to even try to observe this.

CODE

Date__(UT)__HR:MN R.A._(ICRF/J2000.0)_DEC Azi_(a-appr)_Elev APmag delta deldot

2008-Jan-30 08:00 19 13 06.32 -26 02 45.7 224.9959 -79.4715 n.a. .001164254698455 -12.4026555
2008-Jan-30 08:20 19 10 33.31 -26 11 43.3 194.9275 -81.8718 n.a. .001064733299115 -12.4093869
2008-Jan-30 08:40 19 07 28.40 -26 22 14.8 157.7088 -81.1152 n.a. .000965173885920 -12.4118425
2008-Jan-30 09:00 19 03 40.14 -26 34 46.4 133.6262 -77.5867 n.a. .000865619649547 -12.4076223
2008-Jan-30 09:20 18 58 51.03 -26 49 54.6 121.0385 -72.7149 n.a. .000766138710915 -12.3927472
2008-Jan-30 09:40 18 52 33.09 -27 08 29.9 113.9679 -67.0866 n.a. .000666842063599 -12.3601497
2008-Jan-30 10:00 18 43 58.67 -27 31 42.3 109.6459 -60.7735 n.a. .000567920270459 -12.2962015
2008-Jan-30 10:20 18 31 40.23 -28 00 58.3 106.9251 -53.5624 n.a. .000469725981687 -12.1718068
2008-Jan-30 10:40 18 12 40.34 -28 37 09.8 105.3570 -44.8778 n.a. .000372983558084 -11.9161452
2008-Jan-30 11:00 17 40 12.18 -29 14 39.7 104.9137 -33.3296 n.a. .000279413463162 -11.3244140
2008-Jan-30 11:20 16 36 49.03 -29 01 36.3 106.1210 -15.2233 n.a. .000193994449112 -9.6676512
2008-Jan-30 11:40 r 14 26 31.32 -22 34 28.8 111.2722 18.5189 10.23 .000133978614495 -4.3040660
2008-Jan-30 12:00 11 41 10.05 -03 28 50.7 135.2281 64.1958 8.40 .000138479769320 5.2727558
2008-Jan-30 12:20 t 10 04 52.40 +09 49 52.2 227.1653 72.0648 8.45 .000203411381899 10.0159916
2008-Jan-30 12:40 09 18 26.72 +15 32 21.1 252.3810 58.5211 8.86 .000290755177909 11.5007828
2008-Jan-30 13:00 08 53 11.66 +18 18 08.3 258.0637 48.1010 9.28 .000385569297056 12.0626098
2008-Jan-30 13:20 x 08 37 42.57 +19 52 00.2 259.9560 39.8333 9.64 .000483491658287 12.3248579
2008-Jan-30 13:40 x 08 27 21.54 +20 51 31.5 260.5320 32.7525 9.95 .000582970674857 12.4668322
2008-Jan-30 14:00 x 08 20 00.16 +21 32 24.8 260.4956 26.3734 10.23 .000683334761876 12.5518423
2008-Jan-30 14:20 x 08 14 32.09 +22 02 10.9 260.1155 20.4411 10.48 .000784246676696 12.6062504
2008-Jan-30 14:40 x 08 10 19.84 +22 24 49.4 259.5117 14.8120 10.70 .000885516500293 12.6424829
2008-Jan-30 15:00 x 08 07 00.73 +22 42 38.3 258.7417 9.4001 10.91 .000987026877464 12.6669807
2008-Jan-30 15:20 *x 08 04 20.26 +22 57 02.3 257.8330 4.1518 11.09 .001088699408410 12.6833433
2008-Jan-30 15:40 *s 08 02 08.75 +23 08 56.0 256.7959 -0.9675 11.26 .001190478107995 12.6937114
2008-Jan-30 16:00 *x 08 00 19.47 +23 18 56.3 255.6302 -5.9802 11.42 .001292320664677 12.6994289

Steve M

This post has been edited by SteveM: Dec 24 2007, 04:38 AM

[Doc]

There is no reason not to try. Remember, these things have been through a lot of what I like to call 'cruel punishment'. What I think they can do(the mission team) is to try and devote an entire day for recharging the batteries or even 2 days (maybe Im asking for too much) then release that energy for a short time in the form of a late night astronomical observation.

When it comes to Spirit Im willing to expose her to the elements. One thing I've noticed about her is that she tends to be the toughest girl in the fleet when you look at her technical record.Need I say more?

By the way, can any body give me extra info/data on the rover batteries?

[djellison]

an entire day for recharging the batteries or even 2 days (maybe Im asking for too much) then release that energy for a short time in the form of a late night astronomical observation.

Lets combine the lessons from the dust storm, with current Whrs. The batteries are roughly 600 Whrs in total when new - and running at something like 80% capacity now, 480 whrs.. The current power is 291 whrs (and decreasing) per Sol

We established that something like 150 Whrs was the minimum survival power when doing nothing ( no comms, no science - nothing ) So currently - the most you could put back in the battery is about 140 Whrs. It would take 4 days to recharge it fully.

To do late night obs ( 0240 AM and on for 2 hours) now would require enormous amounts of actuator heating, put joints and cables thru some nasty stresses and for what? Maybe, a small white streak in an image. Honestly, this is something I'm more than happy for Spirit to pass on.

More info :

http://trs-new.jpl.nasa.gov/dspace/handle/2014/39912
http://trs-new.jpl.nasa.gov/dspace/handle/2014/39793


Doug

[Doc]

Assuming that the asteroid hits the planet not too far away from Opportunity, I am curious to know what we would see.

A humongous plume of dust and rock in the horizon?

Personally, I'd be overjoyed to see the rover get a very unlikely photo of the little speck screaming down to the surface. Just like in the impact scene in the movie 'Deep Impact'. That will probably cause a sensation in the entire human community.

And it will probably cause governments around the world to literally pour their resources into the NEO projects :-)

[Stu]

Welcome to UMSF by the way Doc!

I know what you mean, but I think the cultural impact of an image showing a streak across the martian sky would be somewhere between nothing and absolutely nothing. After all, that very famous (mid 70s?) footage of the asteroid streaking across a clear blue sky above some mountains and a lake (oh come on, you know the one I mean, we've all seen it a gazillion times!) before skipping off the atmosphere and heading back didn't lead people to worry about asteroid impacts, nor has the classic "Peekskill" footage either. And actually, if the footage from Deep Impact and Armageddon hasn't been enough for Govts to take the problem seriously then there's no way on Earth - or Mars - that a grainy image of a streaky...something... taken by one of the rovers will have Govts reaching for their chequebooks...

Like you I'm very curious to know what we'd see if an impact occurred, but unless WD comes down very close to Oppy (which we don't want!) I'm sure we won't see a "humongous plume". Maybe just a vague puff on the horizon? I don't know, we're all just speculating here. But it's fun!

Anyway, I'm sure one of our little rover buddies will get fantastic shots of debris spraying away from either Phobos or Deimos when WD hits it... then the sky will be so full of shooting stars it'll be more like the end of INdependance Day than Deep Impact!

(that was a joke by the way... )

[Stu]

For all those people wanting a "Roving Mars" sequel...





Seriously tho, when will we have a better idea of what's actually going to happen? Will it literally be on the day? If so, that'll be a "don't stray too far from the computer" day, won't it?