Dawn dead in Ceres orbit, ran out of fuel Oct 2018

[OmCheeto]

Happy 9th anniversary!

DAWN JOURNAL
September 27, 2016

Dear Dawnniversaries,

Nine years ago today, Dawn set sail on an epic journey of discovery and adventure.
...

An indication as to how near we are to the end of the journey; "The spacecraft has used 68 of the 71 gallons (256 of the 270 liters) of xenon it carried when it rode its rocket from Earth into space".

No word on hydrazine reserves.

Another statistic; "Since launch, ... Dawn has traveled ... 3.6 billion miles, or 5.8 billion kilometers".

Which means that Dawn gets about 53,000,000 mpg. (22,700,000 km/liter)

 

[1oldman2]

Three gallons left, wonder what that will be worth in mission time ?

- from Chief Engineer/ Mission Director, Marc Rayman (JPL)
October 12 - Dawn Team Preparing for New Ceres Observations

Orbiting Ceres at an altitude of about 920 miles (1,480 kilometers), Dawn is traveling over the alien landscapes at about 400 mph (645 kilometers per hour). After ion thrusting concluded last week, navigators measured the parameters of the orbit very accurately. The actual orbit is so close to the planned orbit that the expected refinements in the timing of observations are unnecessary. To optimize the quality of the data to be collected, engineers are making small adjustments to the direction the spacecraft will point its sensors for some of the measurements. Science observations will begin on Oct. 16

October 6 - Dawn Completes Ascent Spiral

Dawn concluded its ascent on schedule last night by stopping its ion engine at 11:02:48 p.m. PDT. When it began the spiral climb on Sept. 2, the spacecraft was in a 5.4-hour orbit at an altitude of 240 miles (385 kilometers). Now it is in an 18.9-hour orbit about 920 miles (1,480 kilometers) above Ceres. Navigators will measure its orbital parameters carefully to pin down the details. Mission controllers will use the results to refine the timing of Dawn's new observations of the dwarf planet, which are scheduled to begin on Oct. 16.

Nine years ago today, Dawn thrust with its remarkable ion propulsion in space for the first time. As explained in the latest Dawn Journal, the explorer has used its ion engines extensively in the intervening nine years to accomplish extraordinary feats in its interplanetary expedition.

 

[OmCheeto]

Three gallons left, wonder what that will be worth in mission time ?
...

Well, they claim that when the mission ends, Dawn will be in a permanent stable orbit around Ceres. Which I think implies that they don't really need it anymore. Which I think implies, that they can continue the mission until another reaction wheel fails, and the hydrazine runs out. Of course there's also the problem of Dawn entering Ceres shadow, which, without knowing it's current orbital inclination relative to the sun, I can't even make a guess as to when that will occur. Perhaps I'll go back through the last log and see if I missed that bit of information.

 

[OmCheeto]

...
Perhaps I'll go back through the last log and see if I missed that bit of information.

Marc only mentions; "...The angle to the sun will be smaller...", in the Aug 31 journal entry.

One day, I will kill him.
But then again, he has slipped us some very top secret information about the mission in the past.
Perhaps not.

 

[1oldman2]

One day, I will kill him.
But then again, he has slipped us some very top secret information about the mission in the past.
Perhaps not.

It would be like sacrificing the queen in a close chess game.

 

[OmCheeto]

Was just snooping through twitter, and I discovered that we've missed a planetary science meeting:

Division for Planetary Sciences and the European Planetary Science Congress

in Pasadena, California
16–21 October 2016
Abstract Book 353 page pdf​

As usual James Tuttle Keane [twitter] has some interesting illustrations.

More at #DPSEPSC [twitter]

 

[OmCheeto]

The new journal is out!

DAWN JOURNAL
October 31, 2016

Some interesting things:

The relative size and angle of the 5 orbits, as they would have appeared if looking down at the north pole:

The following paragraph had me gasp:

This fifth Ceres campaign was intricate and intensive, but it stayed right on the tight schedule. Dawn began collecting data as planned on Oct. 16 and finished transmitting its findings to Earth on Oct. 29. And it was exceedingly productive, yielding almost 3,000 photographs plus a great many infrared spectra and visible spectra containing a wealth of new information about Ceres.
[bolding mine]
​

This could mean one of two things:

1. The mission is over, or
2. Something else is about to happen​

Fortunately; "On Nov. 4, the spaceship will once again power on ion engine #2 and start another spiral to a sixth orbital observing post."

Yay!

 

[mfb]

That diagram indicates that shadow won't be an issue for the next months.

 

[OmCheeto]

That diagram indicates that shadow won't be an issue for the next months.

And finally, we've been given an indication where Dawn will be placed, but not the angle...

New Ceres Views as Dawn Moves Higher

"On Nov. 4, Dawn began making its way to a sixth science orbit, which will be over 4,500 miles (7,200 kilometers) from Ceres.
...
Dawn should reach this next orbit in early December.
One goal of Dawn's sixth science orbit is to refine previously collected measurements. The spacecraft 's gamma ray and neutron spectrometer, which has been investigating the composition of Ceres' surface, will characterize the radiation from cosmic rays unrelated to Ceres. This will allow scientists to subtract "noise" from measurements of Ceres, making the information more precise.

The spacecraft is healthy..."​

ps. I've been channeling the spirit of Marcus all morning.

 

[OmCheeto]

The new journal is out!

DAWN JOURNAL
November 28, 2016

It appears that Dawn is being placed in an elliptical orbit, far away from Ceres, to gather background radiation noise, in order to reduce the signal to noise ratio for their ground radiation survey.

Here's a graph I doodled to show its new relative distance. (Orbit 6)

 

[mfb]

You cannot reduce the signal to noise ratio of previous measurements, you can only hope to understand the noise better.

Staying closer would have allowed to see the terminator region under a better angle, possibly improving the 3D mapping a bit. Measuring that background must be really important - but not so important that they would have done the measurements in earlier, higher orbits.

 

[1oldman2]

You know... I used to look at Marcus's avatar and think of Mad magazine, I recently came across an old copy and immediately Marcus came to mind, all I could say was "what me worry ?"
https://www.nasa.gov/feature/jpl/where-is-the-ice-on-ceres-new-nasa-dawn-findings

At first glance, Ceres, the largest body in the main asteroid belt, may not look icy. Images from NASA's Dawn spacecraft have revealed a dark, heavily cratered world whose brightest area is made of highly reflective salts -- not ice. But newly published studies from Dawn scientists show two distinct lines of evidence for ice at or near the surface of the dwarf planet. Researchers are presenting these findings at the 2016 American Geophysical Union meeting in San Francisco.

"These studies support the idea that ice separated from rock early in Ceres’ history, forming an ice-rich crustal layer, and that ice has remained near the surface over the history of the solar system," said Carol Raymond, deputy principal investigator of the Dawn mission, based at NASA's Jet Propulsion Laboratory, Pasadena, California.

 

[1oldman2]

December Journal's out!


http://dawn.jpl.nasa.gov/mission/journal_12_29_16.html

 

[OmCheeto]

Happy 2nd year anniversary of this thread!

 

[1oldman2]

Happy January Journal release. Some very interesting reading and a new mission phase coming up, (XM04)
http://dawn.jpl.nasa.gov/mission/journal_01_31_17.html

 

[1oldman2]

http://news.agu.org/press-release/new-research-shows-ceres-may-have-vanishing-ice-volcanoes/
WASHINGTON, DC - A recently discovered solitary ice volcano on the dwarf planet Ceres may have some hidden older siblings, say scientists who have tested a likely way such mountains of icy rock - called cryovolcanoes - might disappear over millions of years.

"We think we have a very good case that there have been lots of cryovolcanoes on Ceres but they have deformed," said Michael Sori of the Lunar and Planetary Laboratory at the University of Arizona in Tucson, and lead author of the new paper.

Ahuna Mons is a prominent feature on Ceres, rising to about half the height of Mount Everest. Its solitary existence has puzzled scientists since they spied it.

 

[mfb]

From the January journal:

Dawn has already measured the light reflected over a wide range of angles, as is clear from the figure above showing the orbits. But the strongest discrimination among different textures relies on measuring the opposition surge. That is Dawn’s next objective, a bonus in the bonus extended mission.

That requires a plane change by nearly 90 degrees. Initially the fixed orbital plane was though to be a hard limit on the mission lifetime. With the high orbit Dawn now has, a plane change is possible. The high orbit also makes it easier to avoid the shadow while getting close to opposition.

 

[1oldman2]

https://phys.org/news/2017-02-scien...e=menu&utm_medium=link&utm_campaign=item-menu
http://www.sciencedirect.com/science/article/pii/S001910351630731X
http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA21419
This enhanced color composite image, made with data from the framing camera aboard NASA's Dawn spacecraft , shows the area around Ernutet crater. The bright red portions appear redder with respect to the rest of Ceres. In a 2017 study in the journal Science, researchers from the Dawn science team found that these red areas around Ernutet are associated with evidence of organic material.

 

[OmCheeto]

I'm not even ready for this kind of maths...

...from the latest journal.

 

[1oldman2]

...from the latest journal.

My favorite Journal to date.

 

[mfb]

Dawn Identifies Age of Ceres' Brightest Area

The bright material in the center of Occator Crater is about 4 million years old, 30 million years younger than the crater.

 

[OmCheeto]

Dawn Identifies Age of Ceres' Brightest Area

The bright material in the center of Occator Crater is about 4 million years old, 30 million years younger than the crater.

And from the Max Planck piece they referenced:

"Pictures of the crater showing haze when imaged at certain angles seem to speak for the latter. At the end of 2015 already, MPS researchers explained this phenomenon with the sublimation of water.

Recent investigations support this interpretation. The MPS researchers evaluated numerous images of Occator crater from an early phase of the mission taken from a distance of 14,000 kilometers and from low angles. They clearly show variations in brightness following a diurnal rhythm. “The nature of the light scattering at the bottom of Occator differs fundamentally from that at other parts of the Ceres surface," MPS researcher Guneshwar Singh Thangjam describes the result of his analysis. "The most likely explanation is that near the crater floor an optically thin, semi-transparent haze is formed," he adds. The researchers believe that the haze is possibly formed by sublimating water emerging from fractures in the floor of the crater when exposed to sunlight."​

I wonder if this haze has a warming effect. Occator crater is 4 km deep.
[google google google]

Ah ha!

Andrew Dessler and colleagues from Texas A&M University in College Station confirmed that the heat-amplifying effect of water vapor is potent enough to double the climate warming caused by increased levels of carbon dioxide in the atmosphere. [ref: NASA]​

I'll take that as a definite maybe.

 

[mfb]

Andrew Dessler and colleagues from Texas A&M University in College Station confirmed that the heat-amplifying effect of water vapor is potent enough to double the climate warming caused by increased levels of carbon dioxide in the atmosphere. [ref: NASA]

That is the atmosphere on Earth.
Ceres doesn't have a notable atmosphere.

 

[OmCheeto]

That is the atmosphere on Earth.
Ceres doesn't have a notable atmosphere.

Perhaps I should refrain from posting things so soon after waking up in the morning.
After scratching my head for a bit, a couple cups of coffee, and massive googling*, I can find no evidence that the crater is thermally different from its surroundings.

-------------
*Also, reading about the electromagnetic absorption by water, made my head hurt.

 

[1oldman2]

I'll take that as a definite maybe.

Perhaps I should refrain from posting things so soon after waking up in the morning.
After scratching my head for a bit, a couple cups of coffee, and massive googling*, I can find no evidence that the crater is thermally different from its surroundings.

-------------
*Also, reading about the electromagnetic absorption by water, made my head hurt.

More coffee is the answer. (unless the answer is 42)
I believe the process of sublimation will lower the temperature, (citation needed) https://en.wikipedia.org/wiki/Enthalpy_of_sublimation

 

[OmCheeto]

More coffee is the answer. (unless the answer is 42)
I believe the process of sublimation will lower the temperature, (citation needed) https://en.wikipedia.org/wiki/Enthalpy_of_sublimation

I believe you. No citation required from me.

ps. Peculiar thing though, in my googlings this morning, I couldn't find any recent data on Ceres surface temperatures.
Wiki's latest entry on the highest temperature is from 1993. [ref]
I'm not saying the data hasn't been published, but I can't seem to find it.
Pondering now if I should send Marc Rayman another email. It has been 8 months.

 

[mfb]

I believe the process of sublimation will lower the temperature, (citation needed) https://en.wikipedia.org/wiki/Enthalpy_of_sublimation

Completely negligible. Using all the sunlight to sublimate ice, it would go through the surface at a rate of 2.5 meters per year - or 10,000 km in 4 million years. The actual change seems to be lower than 1 km in 4 million years.

 

[1oldman2]

I believe you. No citation required from me.

ps. Peculiar thing though, in my googlings this morning, I couldn't find any recent data on Ceres surface temperatures.
Wiki's latest entry on the highest temperature is from 1993. [ref]
I'm not saying the data hasn't been published, but I can't seem to find it.
Pondering now if I should send Marc Rayman another email. It has been 8 months.

I did some looking around and came up with this info, nothing newer than 2015 but it's probably in the 'ol ballpark.
(Sort of almost relative) http://www.nature.com/nature/journal/v528/n7581/full/nature15754.html

An excerpt from http://www.hou.usra.edu/meetings/lpsc2015/pdf/1745.pdf
(this is rather early in the Ceres phase of Dawns mission so I imagine there is better data to be had at this time.)
"In the 4.5-5.1 μm range,
NESR is dominated by fluctuations of the thermal
emission from the spectrometer, which result in a lowest
measurable temperature of ~170 K, i.e. no temperature
below this threshold can be accurately retrieved by
VIR. This means that VIR cannot measure temperatures
on the nightside of Ceres, as well as in the northern
polar region that will undergo permanent shadowing
conditions throughout Dawn's nominal orbital mission phases."

Ahh... Here we go, not sure of this sites reputation but it appears believable.
https://www.reference.com/science/temperature-ceres-d1b17887e9678a2d#
The quick answer says,
The surface temperature of Ceres averages 130 to 200 degrees Kelvin.

Then there's this, https://www.princeton.edu/~willman/planetary_systems/Sol/Ceres/
It lists a surface temperature of roughly -100 degrees C.

 

[OmCheeto]

The 48th Lunar and Planetary Science Conference is only 4 days away.
Always interesting stuff there:
Program

Ceres specific

Monday
Tuesday​

There may be more that I'm missing. It's a rather full conference.

 

[1oldman2]

A nice piece on the Optics of Opposition in the March Journal.
http://dawn.jpl.nasa.gov/mission/journal_03_30_17.html

 

[1oldman2]

Dawn is now a unicycle ?
https://dawn.jpl.nasa.gov/mission/status.html
The good news is the April journal is out. https://dawn.jpl.nasa.gov/mission/journal_04_25_17.html

 

[1oldman2]

May Journal is out.
https://dawn.jpl.nasa.gov/mission/journal_05_24_17.html
"On the other side of the solar system, invisible by virtue both of the blinding glare of the sun and by the vastness of the distance, Dawn is continuing its remarkable cosmic adventure. Orbiting high above dwarf planet Ceres, the spacecraft is healthy and performing all of its assignments successfully even when confronted with what appears to be adversity."

 

[1oldman2]

An interesting piece on the geology and history of Ceres.
https://www.nasa.gov/image-feature/jpl/pia21409/complex-relationships-in-the-occator-kirnis-region

 

[mfb]

Dawn's extended mission will end June 30. The future is currently discussed.

One of the options discussed: Send it to another asteroid. It was discussed earlier already, but then scientists decided to study Ceres more. Now the idea comes up again. Dawn is in a high orbit already, it wouldn't take too much delta_v to escape and to change the orbit a bit. Firing the ion thrusters also saves hydrazine.

 

[1oldman2]

The future is currently discussed.

A very interesting article, thanks. I can't imagine not squeezing every bit of usefulness from Dawn, shutting it down would be a loss of resources that would be hard to justify. I'm betting they choose a flyby mission to another Asteroid rather than burn the remaining fuel at Ceres, although there seems to be a fair supply remaining the rate of consumption is far lower when not maintaining its current orbit compared to interplanetary travel. Curious to see what NASA decides to do with the program.