11 votes
Accepted

Why was Dawn placed into an orbit that would only be stable for "decades"

Why was Dawn placed into an orbit that would only be stable for “decades” In order to simultaneously obey the rules and maximize science. Maximizing science means staying at Ceres and collecting data ...
uhoh's user avatar
  • 149k
7 votes
Accepted

Which one of these Isp's for the Dawn spacecraft is wrong?

The 3100 s figure is the correct one. Note that a little further along in the same article it says "the engine achieves a specific impulse of one to three thousand seconds." The N·s/kg unit is ...
Russell Borogove's user avatar
6 votes
Accepted

Xenon vs Hydrazine, "Should I Stay or Should I go?" Dawn mission decisions

There is one wheel still operable (at least it was operable the last time they operated it), but Dawn no longer uses it. The third wheel failure was in April of this year (2017 for those reading this ...
Mark Adler's user avatar
  • 58.2k
5 votes

Is Dawn's upcoming low periapsis orbit for XMO7 "resonant"?

This is not a complete answer but I can offer an example of an orbit being in resonance with the rotation rate of a central body. Astrophysicists indeed sometimes use the word "resonant" to describe ...
Tom Spilker's user avatar
  • 18.3k
5 votes

How can a yo-yo de-spin maneuver reverse the rotation?

NASA - and math - to the rescue! 2nd edit: Shorter answer even "firster". Try a Gedankenexperiment. If you are happy with it stopping, then just image the satellite is suddenly much lighter. ...
uhoh's user avatar
  • 149k
5 votes
Accepted

How can a yo-yo de-spin maneuver reverse the rotation?

It would only reduce spin if the weights remained attached. Imagine this: two ropes wrapped on a spinning spool, with weights on the ends. As the weights are released, they spin outwards, extending ...
SF.'s user avatar
  • 55k
5 votes
Accepted

If the Dawn probe visits a third asteroid after Ceres and Vesta, which asteroid could it visit?

Dawn's potential target was asteroid 145 Adeona: On April 20, 2016, New Scientist announced that the Dawn team had sent NASA a proposal for an extended mission. According to the report, the ...
Ginasius's user avatar
  • 920
4 votes

How can a yo-yo de-spin maneuver reverse the rotation?

If the original spin is clockwise: the weights will accelerate a counterclockwise spin as they begin to unwind. This will slow the clockwise spin to a stop (if the cable is long enough; and the ...
Delburt Phend's user avatar
4 votes
Accepted

Ceres gravity from spherical harmonics from Dawn, how to get the coefficients, definitions and potential?

What you're missing is the descriptions of the contents of that file. That's in another file, right next to the one you found. The data for the Ceres gravity model are in JGDWN_CER18C_SHA.TAB and the ...
David Hammen's user avatar
  • 74.8k
3 votes
Accepted

Was DAWN's power-limited propulsion really limited by power used to accelerate the ions?

According to wikipedia each Nustar engine on Dawn used 2100W, and achieved 92mN of thrust with an exhaust velocity around 30 km/s. So from the thrust and the exhaust velocity we can compute the Xenon ...
Steve Linton's user avatar
  • 19.6k
3 votes

Why do New Horizons and Dawn have such different imagers/cameras aboard?

Relative to your 3rd question, a common suite of instruments for every probe doesn't work for several reasons. First, the targets of the missions or their environments may vary considerably. For ...
Vince 49's user avatar
  • 2,611
2 votes

Xenon vs Hydrazine, "Should I Stay or Should I go?" Dawn mission decisions

To answer the question about staying at Ceres or going somewhere else: Dawn does not have enough Xenon propellant left to enter orbit around another asteroid. It can leave Ceres, but can only do a ...
Hobbes's user avatar
  • 128k
2 votes

Xenon vs Hydrazine, "Should I Stay or Should I go?" Dawn mission decisions

I think that your guess addressing the decreasing with the orbital radius $(1/r)^n$, $n=3...\infty$ of the non spherical terms for the gravity potential are probably the clue to the problem. This ...
Julio's user avatar
  • 1,772
2 votes

How can a yo-yo de-spin maneuver reverse the rotation?

All the motion can be returned to the cylinder or rocket but only linear momentum can be transferred from small to large objects; this means that all the motion (linear momentum) of the cylinder is ...
Delburt Phend's user avatar
2 votes

How does one spacecraft best visit multiple asteroids?

CASTAway (PDF) is a mission proposed for ESA that would flyby 10 asteroids in the Main Belt and observe tens thousands telescopically to determine their composition.
LocalFluff's user avatar
1 vote

How long can the dawn probe‘s ion thrusters burn?

Never mind, it‘s 51,385 hours (wow!) From NASA's Dawn by the Numbers: Source: NASA/Jet Propulsion Laboratory-Caltech Published: November 15, 2018 NASA's Dawn mission by the numbers: 51,385 hours of ...
Jake's user avatar
  • 121
1 vote
Accepted

Is Dawn's upcoming low periapsis orbit for XMO7 "resonant"?

What you might be seeing here is language being made. When scientists start studying a new field, they sometimes have to invent words to describe what they see. Here, two sets of scientists ...
Hobbes's user avatar
  • 128k

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