Sigh. This poor mission, which has certainly suffered its share of slings and arrows, has had its launch postponed until September. The launch slip last week messed things up a bit to start, of course. And now the launch constraints butt up against the launch of the Phoenix Mars probe in early August. Worse, the orbital path of Dawn is somewhat complicated — it needs to slip into orbit around two separate asteroids, making launch windows tight.
Think of it this way: you are in a car doing laps at a racetrack at 100 kph. You have a bow and arrow, and you have to shoot at a target off to the side. You can wait until the last millisecond and shoot the arrow quickly, or give yourself an extra half-second and shoot the arrow a little more slowly. That range in time is your launch window.
Oh — did I mention the target is moving? And oh — you have to hit a bullseye within a tenth of a millimeter of the exact center of the target. And oh — later on there is a second target you have to hit as well, starting from the first target. That second target is moving too.
Have fun!
That’s why the launch constraints on these missions can be so severe. Things in the solar system have to be just so.
So: next time you want to complain about NASA letting launches slip, or that they are a bunch of boobs, try that little experiment above and see how well you do. Those guys can thread a needle from millions of kilometers away, and they do this sort of thing all the time.
So Dawn’s launch will be in September, when the targets line up well again. Until then, we have Phoenix to look forward too, and that’s a fantastic mission as well.
July 8th, 2007 at 6:15 pm
I never liked the analogies about shooting bullets across the US and hitting the bullseye, since it misses on very important part — spacecraft can make mid-course corrections. Admittedly these can make up for gross errors, but it isn’t like you are stuck with the trajectory you end up with after the launch.
July 8th, 2007 at 6:21 pm
I love the optimistic attitude , after so many years of waiting , what’s a couple more months?
July 8th, 2007 at 7:46 pm
Also, the launch window argument doesn’t apply as well since this spacecraft uses low-thrust ion engines. No typical chemically-maneuvered spacecraft could ’stand down’ for a couple months and come back for a launch in the same year. Because of the flexibility allowed by the ion thrusters, they’ll be able to adjust their thrusting to optimize trajectories that other missions couldn’t.
There’s also some exciting news that they may do a couple other asteroid flybys en route between Vesta and Ceres, but they’ve been keeping it quiet because they won’t know which asteroids are possible until after they launch and ‘wring out’ the spacecraft to know its capabilities.
July 8th, 2007 at 8:20 pm
Those are both good points, but no analogy is perfect! It gets the point across: we’re aiming at moving targets, and you need to be in the right position — or a range of positions — to get to where you want to go.
July 8th, 2007 at 8:56 pm
A bit disappointing to have the delay but I just hope they’re getting all the problems out the way and once launched it all goes brilllantly. (Touch wood.)
I’m really backing this one & wish ‘em the best.
July 8th, 2007 at 10:18 pm
“(Touch Wood.)”
Why?
July 8th, 2007 at 10:42 pm
Ive been trying to figure out what’s more complicated: the math involved in launching probes in our solar system, or the navigating NASA through the politics of the government. At least the rockets don’t need chaos theory…
And Dan Gerhards, perhaps StevoRs wife is out of town?
July 8th, 2007 at 11:20 pm
I’m disappointed, it is a very rocky beginning to visit some very rocky rocks. Actually, I’m much more excited about DAWN than Phoenix. We’re talking about Terra incognito here. Still don’t want to rush the doctor, take time and do it right.
I repeat my original question so more people can read it: Will Dawn still do a visit with Mars? Another question, will DAWN still be the first mission to arrive at the newly defined class of dwarf planet (Ceres) or will Dr. Stern’s New Horizon make it to Pluto first?
July 9th, 2007 at 12:32 am
Jeffrey Simpson Says: “I never liked the analogies about shooting bullets across the US and hitting the bulls-eye, since it misses on very important part — spacecraft can make mid-course corrections. Admittedly these can make up for gross errors, but it isn’t like you are stuck with the trajectory you end up with after the launch.”
That’s true of interplanetary missions, but not with all rocket flights. Many moons ago, I worked for Lockheed on the Trident program (the Mk. 4 and Mk. 500 reentry bodies). The analogy for a ballistic missile flight is more like being in a car sitting on a desert. Your goal is to drive it to a specific location several miles away and roll to a stop exactly on top of the target. The car is very strange since the throttle has only one position, full on. And once you start the car it is going to go a full power until the gas runs out.
The target can be at any range within your gas allotment, but most of them will be much closer, so you have to figure out how to use up on the way. You can do this by driving a zig-zag course on your way.
Two more things I forgot to mention. First, the target is in the middle of a muddy swamp (the atmosphere) that you have to estimate the amount of energy it will suck out of your car rapidly at the very end, and 2) You can look around all you want before you start the car, but once you touch the key, a hood drops down over the windows, and you have to do the whole thing blind! If you don’t roll exactly to a stop within a meter of the target, you’ve failed.
- Jack
July 9th, 2007 at 12:34 am
Hmmm, that sentence in the third paragraph above should read, “figure out how to use up the extra energy on the way.”
- Jack
July 9th, 2007 at 2:36 am
Dan Gerhards
Says:
July 8th, 2007 at 10:18 pm
“(Touch Wood.)â€
Why?
Why not?
Oh yeah - splinters! :-0
… But then again splinters lead to infections which lead to antibodies which lead to improved resistence and a better immune system!
As the proposed reason for touching wood Iain’t gonna diognify that with a comment.
… D’oh Iguess I just did! Ok NO wife at least not yet in my life (sigh) but that wasn’t quite what I was meaning to imply! Which was just wishing them good luck & success.
More seriously I agree with Troy - I too would rather see DAWN (or is it just Dawn) prioritised than Phoenix. The Dawn mission is exploring where we’venever been before as opposed to a planet with several rovers and several orbiters currently studying it. Also too, I think the poor old Dawn people have suffered enough …
its going where
July 9th, 2007 at 2:43 am
Editing capability please .aadd here BA!
NewHorizons reaches Pluto in 2015 DAWn reaches Ceres in 20?? .. Anyone know?
I would expect Dawn to take less time & get to a dwarf planet first - although I actually dispute the whole dwarf / classical distinction & would call both Pluto & Ceres planets along with anything else large enough tobe gravitationally rounded & neither star nor moon.
Mind you the rate Dawn keeps being put back it might not even have launched when NewHorizons resches the Pluto-Charon system …
July 9th, 2007 at 3:11 am
Dawn will be done with its primary mission around the time New Horizon’s reaches Pluto, assuming this mission timeline holds:
http://dawn.jpl.nasa.gov/mission/timeline.asp
I will be curious to see whether this change in launch date effects Dawn’s ability to slingshot past Mars. The above timeline showed it when I checked, listing Dawn’s launch date as “summer 2007.” If it were traditionally propelled using chemicals, I’d say Mars was out, but I’ve found that I can’t intuit ion-propelled trajectories.
July 9th, 2007 at 5:04 am
Perhaps just as interesting as the Dawn mission, NASA has approved new missions for the Stardust and Deep Impact probes, that both already had enormous success with their primary missions. Pretty interesting stuff, they want Stardust to re-visit Tempel1 (if the story has it right), the comet that Deep Impact punched a hole in. And Deep Impact will visit yet another comet. Amazing stuff, none of which was planned when the spacecraft were designed and launched.
Spaceflight Now has the story. (July 5th..old news
)
July 9th, 2007 at 5:51 am
Bugger.
July 9th, 2007 at 7:52 am
[…] “Fire at Kitt Peak Observatory“. Ainda no mesmo blog, “Dawn launch postponed to September“; […]
July 9th, 2007 at 4:39 pm
The satellite I am using for my current research was delayed for over a year from its initial launch time. These things happen to the best of us, I suppose…
July 13th, 2007 at 11:18 pm
Thanks Tom.
From ‘Sky & Space’ magazine July-Aug. ‘07 article : “Journey to an asteroid … then onto a dwarf planet” Page45 :
***
“Beginning in July 2010, Dawn will study Vesta and then beginning in August 2014 the mission will move on to Ceres.”
***
So Dawn will arrive at Vesta 5 years before NewHorizons reaches Pluto and Ceres just ayear befroe beating NewHorizions to 1st dwarf planet by a year - all going to schedule.
July 13th, 2007 at 11:21 pm
Corrected version :
So Dawn will arrive at Vesta 5 years before NewHorizons reaches Pluto and Ceres just a year before - beating NewHorizions to 1st dwarf planet exploration honours by a year - all going to schedule.
& also assuming Pluto, and for that matter, Ceres aren’t restored to proper planet status as they should be by then!