Полет АМС Dawn к Весте и Церере

[Frontm]

Опять эти борозды! Откуда они?

Это следы заметания следов. :wink:

Пришельцев! :shock: У них там база была. :roll:

А не может ли быть вздутие /с пиком на вершине!/ вулканом?

Это насыпь над базой инопланетян

[Salo]

http://www.space.com/12286-vesta-asteroid-dawn-spacecraft-arrival-mase-interview.html

Asteroid Vesta Up Close: Q & A with NASA's Dawn Spacecraft [/size]
Project Manager
by Mike Wall, SPACE.com Senior Writer
Date: 14 July 2011 Time: 03:06 PM ET

After traveling through the the solar system for nearly four years, NASA's Dawn spacecraft is poised to arrive in orbit around Vesta, a huge asteroid the size of Arizona.

The historic event is set to take place at about 10 p.m. PDT Friday, July 15 (1 a.m. EDT July 16), NASA officials said.

But the arrival at Vesta is only one stop in the long road for the Dawn spacecraft.

The spacecraft launched in September 2007 and has logged about 1.7 billion miles (2.7 billion kilometers) since, propelled by its super-efficient ion propulsion system. After spending a year at Vesta, Dawn will head off to study the dwarf planet Ceres, the largest object in the asteroid belt.

Dawn's $466 million mission is aimed at comparing Vesta and Ceres to help scientists learn about the early days of the solar system and the processes that formed and shaped rocky planets like Earth and Mars.

As Dawn's Vesta rendezvous looms, SPACE.com caught up with Dawn project manager Robert Mase of NASA's Jet Propulsion Laboratory in Pasadena, Calif. Mase discussed the upcoming orbital encounter, Dawn's ultimate fate and the challenges of planning a mission to a mostly unknown solar system body.

SPACE.com: Will you be able to tell right away that you're in orbit around Vesta? Or will it take a while to hear from Dawn?
Mase Dawn Vesta
Robert Mase, project manager of NASA's Dawn mission at the agency's Jet Propulsion Laboratory in Pasadena, Calif.
CREDIT: NASA/Paul E. Alers
View full size image

Robert Mase: We're different than your typical mission, and your typical planetary encounter. We spend most of the time thrusting with the ion engine, which means that we're not communicating with the spacecraft. Our antenna is at a fixed position on the spacecraft, and if we're pointed to our thrust attitude, that means we're generally not pointing the antenna at Earth.

We stop for about eight hours once a week to have a communications contact, where we stop thrusting, turn the spacecraft and communicate. [Infographic]

We'll actually be thrusting [Wednesday] night through early Sunday morning. So for all of that time, we will not be in contact with the spacecraft, and then we'll have a planned contact on Sunday morning. That's the first point where we can confirm that we thrusted the way that we expected to, and that we actually are captured [by Vesta].

SPACE.com: So if everything goes according to plan, will you guys have a little party Sunday morning? Or will it just be business as usual?

Mase: It'll be more business as usual for us than you would think. First of all, it's Sunday. While there will be a few people in to check on the spacecraft, the bulk of the team is not going to be working on Sunday. But we'll be back to work on Monday. So perhaps we'll have a small celebration then.

For us, the capture is certainly important, but it's just sort of an event that technically occurs during one of these thrust arcs. [Photos]

In most planetary encounters, the spacecraft comes zipping up to the body, does a propulsive burn that lasts for half an hour or an hour or something like that, then is captured into orbit. It's a critical event — it's gotta happen, or else you just fly right on by.

With us, we're truly rendezvousing with Vesta. Maybe one way to think about it is the way the space shuttle might rendezvous with the space station. We're in an orbit that's very similar to Vesta's now around the sun. We're basically just pacing it at this point.

We're approaching very slowly. We just need to keep thrusting and then eventually we get to the point where technically we're captured.

SPACE.com: So this capture event isn't absolutely critical — if things don't work out, you could just try again soon?

Mase: Yes. And that's the flexiblity that the ion propulsion provides. We do have the ability to catch up if we end up falling behind. We're never at a point where we just fly on by and that's it.
Artist's concept of NASA's Dawn spacecraft, which is closing in on the huge asteroid Vesta.
Artist's concept of NASA's Dawn spacecraft, which is closing in on the huge asteroid Vesta.
CREDIT: NASA/JPL
View full size image

SPACE.com: You've been chasing Vesta down for nearly four years, and now you're almost there. It must feel pretty good.

Mase: Yeah, absolutely. It's been a long journey, but a very worthwhile journey. And the team is very excited.

We've got a team that's not only here at JPL doing the bulk of the engineering operations, but a team of scientists around the country and around the globe. We've got instrument partners in Italy and Germany, so it's truly an international collaboration that has worked on this for a long time.

SPACE.com: What's it like working on these deeper space missions, where it can take years to reach your target? Is there a lot of downtime?

Mase: It would seem that way, but actually we're remarkably busy the whole way. You can kind of split the whole concept into two parts.

There's the part where you're developing, you're building the spacecraft and just getting it to the launch pad. That takes several years, but it's a pretty fast pace all the way.

And then, once you launch it, it's up in space. Then you've got to be continually operating it. It's a different type of activity, but it's not necessarily any less intense. So the things that we've been doing over the last 3 1/2 years — it's not only keeping the spacecraft flying on its way to Vesta, making sure everything's healthy and checking it out. A lot of what we're doing also is planning all the details of what we're going to do when we get to Vesta. [7 Strangest Asteroids in the Solar System]

When we get there, we get into a high altitude, kind of reconnaissance orbit. Then it takes about a month to spiral down into our intermediate altitude orbit, and then about another month and a half to spiral down to our lowest altitude orbit. So we'll be at three altitudes. And then we'll have to spiral back up and out.

Planning out how that's going to happen on a day-by-day, almost hour-by-hour basis for a year — you can imagine there are a lot of details to plan out. That's what we've been doing for the last several years: figuring out exactly what we're going to do, how we're going to do it and what types of contingencies we're going to have in place.

SPACE.com: Three different orbits around a single object seems pretty unusual. Most spacecraft don't get three different looks at a single object from orbit.

Mase: That's right. And again, that's some of the flexibility that we're afforded by the ion propulsion system.

A lot of these planetary encounters, they just fly by, and you get one shot at it and that's about it. Or, some of the ones that do go into orbit — it's pretty expensive, from a propulsion standpoint, just to get into orbit. So typically it's very difficult to carry that much chemical propellant, to be able to change from one orbit to another.

But with the ion propulsion system, you have that capability. And while it takes a while — a month to a month and a half to transition between these orbits — it's not expensive in terms of propellant, so you can afford to do it.

It's a flexibility and a capability that we have that is just not available with other, more conventional chemical systems.

SPACE.com: What are you most looking forward to finding out in this mission, or what is most exciting to you?

Mase: What's exciting for me is that we're going someplace that no one has gone before. We're seeing things that nobody has seen before. We're doing a lot of firsts, and a lot of true exploration. So I find that aspect of it exciting.

I've worked on plenty of other missions that have gone to Mars and other places. Great missions, and they're exciting. But it's going to Mars— a place we know pretty well, and we kind of know what to expect.

But with this one, nobody knows much about Vesta or Ceres. The best images we have are these fuzzy images from Hubble that just sort of hint at what it's going to look like. So being able to go to a place that nobody's seen before, nobody's explored — to me, that's the most exciting part of this mission.

SPACE.com: NASA is aiming to send an astronaut to an asteroid by 2025. Do you see Dawn's mission as helping out in that longer-term goal for manned spaceflight?

Mase: There may be some lessons from Dawn that could be applied to the manned program. Some of the goals of the human program are a little different. They wouldn't be going to the asteroid belt, and they would probably be going to different types or sizes of bodies perhaps than we're going to.

But at the same time, we are learning how to use ion propulsion systems effectively and capably, to be able to rendezvous with these bodies.

SPACE.com: What have some of the biggest challenges with this mission been? You're doing some new things, and going to a new type of object that we haven't seen probes going to in the past.

Mase: Yes. And I think you kind of hit it right on the head. That is one of the biggest challenges: We don't know very much about these bodies, Vesta or Ceres.

Most encounters that we've planned with past missions — like to Mars or Mercury or other planets — we've always had at least a flyby or something that's gone ahead of an orbiter or a lander to be able to do some kind of reconnaissance. If you can fly by, you can pretty well determine the gravity and the spin axis, and all the kinds of things you need to know about the body to be able to operate about it.

That's something that we don't have here. Nobody's ever been by Vesta before, so we don't know all of those things as well as we usually do. And so that's a challenge, in terms of figuring out how to do it and also in putting together a mission plan that can accommodate a range of expected values.

SPACE.com: After a year at Vesta, then it's on to Ceres in July 2012.

Mase: That's right. Next year we spiral out, sort of the opposite of capture. And at that point we're in orbit around the sun again. We thrust for about 2 1/2 years to go a little bit farther away from the sun, to get out to Ceres.

We actually get there in about February of 2015. Then we'll do the same type of operation at Ceres. We'll approach and capture, then spiral in — start at a high altitude orbit, then spiral down to some lower orbits.

The difference there is, once we're at Ceres, we don't have to leave again. We just stay in orbit there.

SPACE.com: Is that Dawn's ultimate fate? Circling Ceres until everything goes dark for the probe?

Mase: Most likely. We certainly have enough of all of our spacecraft consumables to get there. If we have something left, somebody may come up with a bright idea to depart and try to do something else.

But the primary mission as proposed is, we get into orbit around Ceres, do all the good science there and then the mission formally ends in orbit at Ceres.[/size]

[pkl]

Вулкан на небесном теле в 530 км диаметром?
pkl,  такой pkl!
Или вы Экзюпери рассматриваете как научпоп?

Возможно, на ранних стадиях эволюции этого небесного тела, в его недрах могло что-то происходить... нашли же на Весте базальты!

[Salo]

http://www.bbc.co.uk/news/science-environment-14160135

16 July 2011 Last updated at 07:38 GMT

Dawn probe has date with asteroid[/size]
By Jonathan Amos Science correspondent, BBC News

The US space agency says its Dawn probe should now be in orbit around the asteroid Vesta.

The robotic satellite will be spending a year at the 530km-wide body before moving on to the "dwarf planet" Ceres.

New pictures on Dawn's approach to Vesta show the giant rock in unprecedented detail.

The asteroid looks like a punctured football, the result of a colossal collision sometime in its past that knocked off its south polar region.

Confirmation that Dawn is safely circling the rock should come on Sunday (GMT) when the probe is due to return data on its status.

Vesta was discovered in 1807, the fourth asteroid to be identified in the great belt of rocky debris orbiting between Mars and Jupiter.

At the time, its great scale meant it was designated as another planet but it later lost this status as researchers learnt more about the diversity of objects in the Solar System.
Close but careful

Dawn's encounter is occurring about 188 million km (117 million miles) from Earth.

The probe is propelled by an ion engine and engineers put the spacecraft on a course to be captured in the gravitational field of Vesta.

They will not know for sure this has happened until a scheduled communications pass that starts at approximately 0630 GMT on Sunday (2330 PDT on Saturday; 0230 EDT Sunday).

Initially, Dawn will be about 16,000km (9,900 miles) from the asteroid, but this distance will be reduced over time.

Mission scientists hope to get within 200km of the surface but the team do not intend to take any unnecessary risks.

"We would like to get as low as possible but if we crash Dawn, Nasa would understandably be very angry at us," Principal Investigator Chris Russell told BBC News.

Asteroids can tell us about the earliest days of the Solar System. These wandering rocks are often described as the rubble that was left over after the planets proper had formed.

Vesta and Ceres should make for interesting subjects. They are both evolved bodies - objects that have heated up and started to separate into distinct layers.
Surface detail

"We think that Vesta has a metal core in the centre - an iron core - and then silicate rock around it," explained Dr Russell.

"And then, sometime in its history, it got banged on the bottom and a lot of material was liberated. Some of this material gets pulled into the Earth's atmosphere. One in 20 meteorites seen to fall to Earth has been identified with Vesta," he added.

Ceres, which, at 950km in diameter, is by far the largest and most massive body in the asteroid belt, probably did not evolve as much as Vesta.

Scientists think it likely that it retains a lot of water, perhaps in a band of ice deep below the surface.

Dawn's quest at Vesta over the coming months will be to map the asteroid's surface. The probe carries instruments to detect the mineral and elemental abundances in its rocks. It will be looking for evidence of geological processes such as mountain building and rifting. The team is keen to understand how Vesta's surface has been remodelled over time by impacts and even lava flows.[/size]

[Salo]

Пятница, 15 июля 2011
В гости к астероиду[/size]

Американский межпланетный зонд «Заря» готовится зайти на орбиту астероида Веста

Сюзанна Престо

   Американский беспилотный космический аппарат «Заря» («Dawn») направляется к гигантскому астероиду, достичь которого он должен к 16 июля. Ученые НАСА надеются, что экспедиция к поясу астероидов прольет свет на историю солнечной системы.

Веста – необычный астероид. Это небесное тело диаметром 530 км является вторым по величине объектом в поясе астероидов между Марсом и Юпитером. Ученые называют Весту «протопланетой», поскольку по своим характеристикам она напоминает этот класс небесных тел.

И вскоре Весту навестит первый гость с Земли – межпланетный зонд «Заря».
Роберт Мэйс из Лаборатории реактивного движения НАСА рассказал репортерам: «Проведя в космосе почти 4 года, преодолев 2,7 миллиардов километров и дважды обойдя вокруг Солнца, «Заря» наконец приближается к Весте».

Ныне зонд почти достиг цели. По оценкам инженеров, когда «Заря» выйдет на орбиту Весты, расстояние до астероида составит 16 тыс км.

Аппарат сделает снимки Весты, которые будут значительно четче, чем изображения, получаемые с расположенного на орбите Земли космического телескопа «Хаббл».

Исследователи уже отмечали необыкновенное разнообразие структуры поверхности астероида. Однако, как ожидается, сбор научных данных начнется не ранее следующего месяца.

«Заря» питается преимущественно солнечной энергией. Зонд оснащен двумя солнечными батареями общей длиной около 16 метров. Размах их составляет около 20 метров, что, по словам Мэйса, делает «Зарю» самым крупным межпланетным зондом в истории НАСА. Кроме того, у аппарата имеется три ионных двигателя.
Эта технология знакома любителям научной фантастики по американскому сериалу «Звездный путь». Такие двигатели высокоэффективны, поскольку их приводит в действие электрическое поле, а не химические реакции.

Однако, по словам Мэйса, ионные двигатели обладают низкой тягой: «Примерно с такой силой воздействует на вашу руку листок бумаги. Поэтому, чтобы разогнаться от нуля до скорости 95 километров в час, ему необходимо около четырех дней. Зато ионный двигатель может продолжать работу и ускоряться день за днем, месяц за месяцем, постепенно развивая невероятную скорость».

«Заря» проведет на орбите Весты целый год – это будет первой длительной экспедицией к поясу астероидов. Аппарат изучит минеральный состав и характеристики поверхности астероида, соберет информацию о его гравитационном поле и подробно осмотрит гигантский кратер, который может обнажать ядро астероида.

Затем «Заря» отправится к карликовой планете Церера, которая является самым крупным объектом пояса астероидов. Как ожидается, зонд достигнет Цереры к началу 2015 года и проведет на ее орбите несколько месяцев.

Мэйс отмечает, что миссия «Зари» является исключительной, поскольку аппарат посетит сразу два небесных тела за один полет.

Веста не раз посылала Земле свои «приветы» – обломки протопланеты, образовавшиеся при столкновении с другими небесными телами. Ученые полагают, что около 5 процентов метеоритов упали на Землю именно с Весты. [/size]

[Дмитрий Виницкий]

Возможно, на ранних стадиях эволюции этого небесного тела, в его недрах могло что-то происходить... нашли же на Весте базальты!

Вообще-то базальты в метеоритах известны давно. И никак не являются свидетельством вулканизма на астероидах

   :shock:

[pkl]

Я читал, что наличие базальтов является свидетельством доказательством сильного нагрева и плавления пород и, соответственно, вулканических процессов. Базальты в метеоритах объяснялись тем, что оные метеориты - осколки крупных тел, в которых начались геологические процессы. Почему и предположил. Ещё где-то про ранний вулканизм на Весте читал. Вот и предположил! :wink:

Вообще, после Энцелада и Елены я уже ничему не удивляюсь!

[Parf]

Вообще-то, сильный нагрев и плавление - никак не свидетельство вулканических процессов. Вопрос: есть ли на Весте вообще какая-либо тектоническая активность?

Криовулканизм я никак не могу представить. Там же на этапе дифференциации вещества большая часть воды должна была выйти на поверхность и испариться. В общем, весьма загадочная "шишка".

А Веста не могла быть когда-то спутником другой планеты?

[Дмитрий Виницкий]

Вообще-то, сильный нагрев и плавление - никак не свидетельство вулканических процессов. Вопрос: есть ли на Весте вообще какая-либо тектоническая активность?

Вы вообще о чем писали? Вулканические процессы - следствие нагрева и плавления.
Вы, вообще, в курсе, что означают слова "тектоническая активность"?
 :shock:
Сейсмическая активность, разумеется, есть. Другое дело, ей величины.

[Старый]

Криовулканизм я никак не могу представить. Там же на этапе дифференциации вещества большая часть воды должна была выйти на поверхность и испариться.

На таком расстоянии от Солнца могла и не испариться. На спутниках Юпитера же не испарилась.

[Parf]

Вы вообще о чем писали? Вулканические процессы - следствие нагрева и плавления.

Нагрев и плавление пережило большинство тел Солнечной системы. Но вулканические процессы есть далеко не везде.

Вы, вообще, в курсе, что означают слова "тектоническая активность"?
 :shock:
Сейсмическая активность, разумеется, есть. Другое дело, ей величины.

Сорри, я имел в виду как раз сейсмическую активность. А почему "разумеется"? Насколько большим должно быть тело, чтобы у него была сейсмическая активность?

[Parf]

Криовулканизм я никак не могу представить. Там же на этапе дифференциации вещества большая часть воды должна была выйти на поверхность и испариться.

На таком расстоянии от Солнца могла и не испариться. На спутниках Юпитера же не испарилась.

Однако же, спектральный анализ Весты показывает наличие кучи всяких тяжёлых веществ, а воды не показывает.

[Старый]

Однако же, спектральный анализ Весты показывает наличие кучи всяких тяжёлых веществ, а воды не показывает.

Присыпка...

[pkl]

Насколько мне известно, эволюция Весты остановилась как раз между стадиями первоначального "кома" и полного расплавления и дифференциации. Т.е. что-то там начало плавиться, но процесс не пошёл слишком далеко по причине малых размеров "тушки".

А не может быть "шишка" другим астероидом, совершившим, так сказать, "мягкую посадку" и зарывшимся в недра Весты? :roll:

[Дмитрий Виницкий]

Ну, если вам известно, сообщите об этом насавцам.

[pkl]

А смысл? Подозреваю, что насавцам известно в этом вопросе куда больше, чем мне. Да и английский мне ещё учить и учить.

[Дмитрий Виницкий]

Видите, они знают английский, но тем не менее послали сабж.
Всё это только предположения, насчет дифференциации и плавления. Сильно мелко для радиоактивного разогрева.

[pkl]

Ну так и тоже излагаю в предположительном ключе! Есть такая гипотеза... И, надеюсь, скоро мы узнаем, насколько она близка к истине.

P.S.: Хотя... а как мы узнаем? Аппарат ведь заметно бедноват с точки зрения оснащённости научной аппаратурой.

[hlynin]

Вроде бы обещали новости о Дауне часов 12 назад? И что? Не последовал ли он примеру японца?

[us2-star]

hlynin
Зарегистрирован: 25.11.2003
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Откуда: Rostov-Don

...Не последовал ли он примеру японца?

Не имеет права!