Dawn Cruise Options

[Hungry4info]

It begins in my mind when Dawn's view of Vesta is better than Hubble's.

Agreed (and the same with the Pluto encounter in 2015). Up until that point, the mission doesn't really provide a lot of new information.

[stevesliva]

Vestonian (Vestian?)

Vestal.

[centsworth_II]

...when will the ion propulsion be turned off because "we're there!"?

As I understand this Dawn Journal entry, the ion thrust will be turned off a little over two weeks after entering orbit around Vesta.

"In late July 2011, as the probe follows its approach trajectory to Vesta, their paths will be so similar they will be moving at nearly the same direction and speed around the Sun... That combination of distance and velocity will allow Vesta to take gentle hold of Dawn. The spacecraft will not even notice the difference, but it will be in orbit around its first celestial target, even as it continues ion thrusting to reach the planned orbit more than 2 weeks later.

....Dawn’s first loop around Vesta will be about 10 days, and its second will take 4. It will stop thrusting when it is in 'survey orbit,' where one revolution takes just under 3 days."

[tasp]

Wow, a 10 day orbit around such a low mass (compared to Mars or Mercury) object. That is interesting. I assume while the drive is on maneuvering the craft for 'Kodak moments' won't happen. But if an interesting shot 'drifts by' where ever the camera is pointed at the time (crescent Vesta with Saturn in the background for instance) are there plans to click a few?

Also, are scans for possible satellites scheduled?

[djellison]

It reminds me of NEAR and Eros. Long orbits, very slow etc etc.

[Greg Hullender]

Vestal.

Well, "Vestian" if you want to derive it from the Latin Genitive, like most of the other planets do, but it'll really depend (I think) on what the Dawn team does, since whatever they write will quickly constitute 90%+ of all actual uses in English. "Vestal" ought to refer to the astrological effect of Vesta--whatever that is.

Then we'll see if anyone is brave enough to use "Cererean" when we get to Ceres. Or "Cereal," for those who insist on "Vestal." :-)

--Greg

[ilbasso]

And here's hoping the photos at Ceres won't be grainy.

(ducks and runs)

[brellis]

Ya hear that? That's the sound of a hundred puns left in my head, not in this post, lol

It's fascinating to consider the propulsive decisions made in years past that will result in such a gentle arrival.

[stevesliva]

Ya hear that? That's the sound of a hundred puns left in my head, not in this post, lol

I totally teed up "Vestal" during a conversation about insertion. Really, who cares if it's quite right?

[tanjent]

Perhaps a more interesting stat would be the date when Dawn first goes retrograde with respect to the Sun.

--Greg

Will this ever happen? Back of the envelope calculation:
Vesta's semimajor axis (treat it as the radius of a circle) = 2.361 AU
Orbital circumference will be approximately 15 AU (close enough)
1 AU = about 150 million km.
Vesta's orbital period is listed as 1325 days, or 31800 hours
(15 x 150) million km in 31800 hours gives Vesta a prograde motion of about 70K km/hr.
Unless Dawn moves this fast in its orbit relative to Vesta, it seems it can't move retrograde relative to the sun.
Vesta's escape velocity is listed as 0.35 km/sec, which would be (x3600) 1260 km/hr.
(Sorry Greg, my chances to make a substantive contribution here come so rarely, I just couldn't resist.)

[Greg Hullender]

Unless Dawn moves this fast in its orbit relative to Vesta, it seems it can't move retrograde relative to the sun.
Vesta's escape velocity is listed as 0.35 km/sec, which would be (x3600) 1260 km/hr.

No apologies! :-) It's nice to see someone doing the math--and I definitely said the wrong thing. :-) Let's see if I can fix it. I want the point where Dawn's angular velocity with respect to the Sun is less than Vesta's angular velocity. In other words, Dawn is catching up to Vesta. I want the point at which it turns around and moves behind it.

--Greg

[punkboi]

New Dawn journal is up

http://dawn.jpl.nasa.gov/mission/journal_12_30_10.asp

[Greg Hullender]

I see he included a reference to a previous Dawn Journal with a fairly detailed description of how Dawn will enter Vestian orbit. It also talked about scans for satellites.

http://dawn.jpl.nasa.gov/mission/journal_0....asp#spacecraft

--Greg

[ZLD]

Thought this may be of interest to this topic:
A look into Vesta’s interior

I don't have access to Icarus at the moment but for those that do, here is the link to the source article.

[PDP8E]

Dr. Rayman uses a nice big fat word: Brobdingnagian
(see: Gulliver's Travels)
very entertaining Dawn log