Dawn will be orbiting Ceres for a very long time
Personally I can't wait to see what the lowest orbit reveals.
Once in the lowest orbit Dawn will likely be out of fuel. The views will be stunning.
NASA's Dawn space probe has completed its first mapping orbit of the dwarf planet Ceres and the bright spots spotted on the surface are much more numerous than first thought. In March, as Dawn approached the planet, scientists spotted a bright spot on the surface of Ceres and more appeared as the spacecraft approached. A new …
The mapping orbit allows the spacecraft to photograph Ceres at lowish resolution, and in doing so allows the construction of a broad-brush map. By lowering the orbit scientists can start to look at interesting pictures identified from the map at a much higher resolution.
Oh yes, Dawn uses an ion engine; it has a low thrust but does not use much in the way of consumables. At the moment Dawn has plenty of fuel; don't forget this was all accounted for in the overall mission plan.
The ion engine is for getting from place to place.
Don't forget it uses hydrazine as well for its reaction control system - this gives it the thrust it needs to rotate itself (e.g. between imaging Ceres and repositioning itself to send those images home). The job of maintaining or altering its orientation was to be partly down to 3 of its 4 reaction wheels, but two have stopped working, so it'll be using a bit more hydrazine than planned for orientation control now to compensate for only have 2 working wheels - there should be enough in reserve though.
As you said, the hydrazine thrusters and reaction wheels are purely for orientation; the ion engine would be used to change the orbit.
The loss of the reaction wheels, while a serious issue that requires careful mission management, is hardly a show-stopper. At worse mission control could put Dawn into a slow rotation that matches the orbital period around Ceres; this would minimize the amount of re-orientation that needs to be performed, and hence allow the hydrazine to last that bit longer.
This sort of slow rotation is commonly used on Earth orbiting three-axis stabilised satellites, and was first used on a deep space mission by Voyager 2, so its pretty much a standard manoeuvre.
"That would mean those metals would be quite a bit less precious once mined"
No, it's not metal.
Ceres is a world made of a wonderful, frozen alcoholic beverage. Something along the lines of 'vega vodka', 'betelguise brandy' or perhaps 'alpha centauri calvados'. It was placed there by an ancient, technologically advanced race of distillers. These distillers, realizing that humankind would probs get bored of space travel after playing golf on the moon, wanted to give us something else to shoot for. To paraphrase Kennedy 'We choose to go to ceres, cos there's a load of cheap booze there. Think of it as the Lidl of the asteroid belt'.
I'm quite in agreement with Ceres. Here, on Mars, my Ham Bushes and Blanket trees are ready to harvest. I plan to plant Nubile Space Maiden seeds between the rows and that will be my "bumper" crop. They will keep me busy during the Martian winter. So, you all just stay the hell away. I used to be an Earthling, and know just how you people really are.
The report by NASA that concludes that the bright spots on Ceres are from reflected sunlight fly in the face of the actual video animation posted 2 months ago by NASA. This observation that the bright spots are reflections of sunlight is nothing more then mere conjecture by NASA and is made without any scientific evidence, as no evidence was supplied to support the NASA claim! The video of photos showing the orbit clearly shows the same brightness of the bright objects whether in direct sunlight or coming into the path of the direct sunlight. If the bright spots were from only the reflections of sunlight then NASA never would of suspected the other possibilities and by measuring the intensity of the so called reflected light on each photo as the orbiting bright spots rotate in and out of sunlight NASA can easily calculate the intensity of the reflected sunlight from each photo taken. This process could of been executed two months ago and a factual conclusion of reflected sunlight would of been established at that time. NASA is a scientific research organization that forgets the actual basis of establishing science itself. NASA please show us the factual evidence of the light spectrometer measurements from each photo to establish the claim of 100% reflected light as you claim!
"air your concerns about this obvious failing by NASA"
Frankly I'm not all that convinced that NASA's assessment regarding the origin of of the spots is based on anything more educated than "well what else could they be?" - which doesn't mean they're not exactly just that but isn't an exactly convincing argument either.
I have no pretensions to being a boffin but I do find the ice argument convincing. After all (as you said) what else could it be? Bloody great banks of lights? Massed crowds of Cereans in tinfoil hats as Dawn comes ever closer? Piles of highly reflective and recently dusted unknownium? Frozen carbon dioxide? Occam's razor and all that suggest a boring answer unless closer inspection rules out the ice theory.
(But I won't be really satisfied until there's a rover wandering around on the surface doing measurements).
Re "NASA please show us the factual evidence of the light spectrometer measurements from each photo to establish the claim of 100% reflected light as you claim!" I'm hoping that was rhetorical. I'm fairly sure that the chances of someone from NASA reading a comments post in the Reg, smacking head and thinking "of course, we must publish our figures early on in the mission so as to prove we are proper scientists" are somewhat slim.
NASA, you must stop doing the detailed measurements that you have spent so much time and money getting ready for, abandon the actual mission, and devote everything to making a different set of measurements just to satisfy the conspiracy theories of one person who knows nothing about the subject except what's been in newspaper stories.
Dear frankfsp, please refer to the relevant legal precedent which covers this. The case of Arkell v. Pressdram.
"This observation that the bright spots are reflections of sunlight is nothing more then mere conjecture by NASA and is made without any scientific evidence, as no evidence was supplied to support the NASA claim!"
What about the spectrographic data of light reflecting from the bright spots? I mean, Dawn can't take photographs without capturing spectra since its two imaging systems either use spectral filters (FC) or is an imaging spectrograph (VIR).
That the scientific data, franksp, is not on your computer monitor does not prove NASA lacks it.
(Was that an inappropriate double-negative?)
Rather than just insulting you, how about a little educated guessing?
The bright spots are bright. Really, really bright. Ceres' albedo is below that of our Moon but not by much, and on the moon the reflected sunlight is incredibly bright- that's why there are no stars in photos from the moon, the brightness had to be lowered that far to stop the cameras being swamped that the pinpricks of light became invisible.
Now look at the photo. Its actual brightness would be like looking at the sun through a slight cloud- still retina-searingly bright. It's clearly had its brightness lowered (or more likely the sensitivity of the camera was lowered). That dull-grey looking surface is very bright indeed. The really reflective spots are even brighter as they're reflecting far more of the sunlight.
When the brightness is juuust right for looking at craters etc, the reflective areas are still substantially above the maximum brightness that the camera can record- hence the brilliant white appearance. And they're so much brighter that the camera finds them off-the-scale bright even when they're not in direct sunlight.
Fascinating animation. Quite unlike Luna - no maria, no rays from carters, one "rille" like structure to the left of the two bright spots. I get the impression that the other bright spots and patches are predominantly on one side of the planet. Does this suggest a single event was responsible for all the birght spots and patches? What's the size distribution of the craters, I got an impression that there are more medium-large ones than I'd expect - but am I deluding myself?
I think that's a bit of a puzzling statement with regards reflected light. It almost implies that previously they thought it wasn't reflected?!
What we do have to consider in all of the photos is that the bright spots are massively over exposed and as such, their apparent brightness won't be altering across the sequence of images as it probably is doing in reality.
Absolutely fascinating though! I hope it doesn't turn out to be a chunk of ice. Would love to see a spectrographic interpretation though.
Where did this bit come from, "and the dwarf planet may have picked up its ice from the impacts of water-rich asteroids on its surface."?
Ceres composition is generally reckoned to be a large part ice, at least it's current location is about right for ice, its orbit being being around the ice line. The sort of thing Dawn's investigations will support or reject.
Tax dollars well spent. Go Dawn!
Perhaps both NASA and the non-believers are correct. Maybe the spots are reflected light but it's where the Ceresians (?) have swept the dust away to build the greens for their golf courses ...
Anyway, the lack of the important fact here is obvious - how big are these reflective spots? Presumably much bigger than the Reg-SI unit of a fun-bag but smaller than a blue whale? Or perhaps it's several Olympic sized swimming pools? And do we have an El-Reg unit of reflectivity? Perhaps the light of a 100W bulb reflected of Duncan Moorhouse's bonce = 1 Scalp?
The largest has a diameter of just over 10 km or an area of 69000 Olympic swimming pools.
Ceres' visible albedo is 0.090±0.0033, that is pitchblack. Use your favorite graphics editor to compare R/G/B=0/0/0 with R/G/B=23/23/23 to convince yourself. I do not know how white the "white" spots are.
Beer because Ceres was the goddess of grain crops.
Hmmm ... given that Star Wars was "a long time ago, in a place far, far away", could the Empire parked another Death Star in our back yard and then forgotten where they left it ("I sure I left it in this corner of the asteroid belt, Darth. Can't you blip the keys to flash it's lights."
Just think of the parking fines ....
What's more interesting about the shiny (i.e. reflective: I guess nobody thinks they're actually luminous) spots is not that there are so many, but that there are so few. Ceres must be collecting dust all the time, and that dust must be shoved around by micro-impacts. One would expect an ice surface to be covered rather quickly, so what is it that causes these uncovered ice regions in those specific places?
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